Added Audio Recorder. Its working

# Conflicts:
#	app/build.gradle
#	app/src/main/AndroidManifest.xml
#	app/src/main/java/com/example/ueberwachungssystem/MainActivity.java
#	app/src/main/res/layout/activity_main.xml

app/build.gradle

@@ -36,4 +36,22 @@ dependencies {
     testImplementation 'junit:junit:4.13.2'
     androidTestImplementation 'androidx.test.ext:junit:1.1.5'
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'
+
+
+    // OpenCV (from: https://github.com/QuickBirdEng/opencv-android)
+    def opencv_version = "4.5.3.0"
+    implementation "com.quickbirdstudios:opencv:${opencv_version}"
+
+
+    // Required for CameraX
+    def camerax_version = "1.2.2"
+    implementation "androidx.camera:camera-core:${camerax_version}"
+    implementation "androidx.camera:camera-camera2:${camerax_version}"
+    implementation "androidx.camera:camera-lifecycle:${camerax_version}"
+    implementation "androidx.camera:camera-video:${camerax_version}"
+    implementation "androidx.camera:camera-view:${camerax_version}"
+    implementation "androidx.camera:camera-extensions:${camerax_version}"
+
+
+    implementation 'com.jjoe64:graphview:4.2.2'
 }

app/src/main/AndroidManifest.xml

@@ -2,6 +2,15 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools">
 
+    <uses-feature android:name="android.hardware.camera"/>
+    <uses-permission android:name="android.permission.CAMERA"/>
+    <uses-permission android:name="android.permission.RECORD_AUDIO" />
+
+    <!--<uses-permission android:name="android.permission.BLUETOOTH"/>-->
+    <!--<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>-->
+    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
+    <uses-permission android:name="android.permission.INTERNET" />
+
     <application
         android:allowBackup="true"
         android:dataExtractionRules="@xml/data_extraction_rules"

app/src/main/java/com/example/ueberwachungssystem/AudioRecorder.java

@@ -0,0 +1,83 @@
+package com.example.ueberwachungssystem;
+
+import android.content.Context;
+import android.media.MediaPlayer;
+import android.media.MediaRecorder;
+
+import java.io.File;
+import java.io.IOException;
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
+
+public class AudioRecorder {
+    private final Context context;
+    private MediaRecorder mediaRecorder = null;
+    private boolean isRecording = false;
+    private File outputDir;      // Default: in app files directory
+
+
+    public AudioRecorder (Context context) {
+        this.context = context;
+        this.outputDir = context.getFilesDir();
+    }
+
+    public void startRecording() {
+        // Handle logic
+        if (outputDir == null)
+            return;
+        if (isRecording)
+            return;
+        isRecording = true;
+
+        // Setup Audio Recorder for output Format: 3GP
+        mediaRecorder = new MediaRecorder();
+        mediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
+        mediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
+        mediaRecorder.setOutputFile(outputDir + "/" + generateFileName() + ".3gp");
+        mediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
+        try {
+            mediaRecorder.prepare();
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+        mediaRecorder.start();
+    }
+
+    public void stopRecording() {
+        if (mediaRecorder != null) {
+            mediaRecorder.stop();
+            mediaRecorder.reset();
+            mediaRecorder.release();
+            mediaRecorder = null;
+            isRecording = false;
+        }
+    }
+
+    public boolean isRecording(){
+        return isRecording;
+    }
+
+    public void setOutputDir(File outputDir) {
+        this.outputDir = outputDir;
+    }
+
+    private String generateFileName(){
+        // Get the current timestamp
+        LocalDateTime currentTime = LocalDateTime.now();
+        // Define the format for the timestamp
+        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMdd_HHmmss");
+        // Return the timestamp as a string
+        return currentTime.format(formatter);
+    }
+
+    public void playAudio() {
+        MediaPlayer mp = new MediaPlayer();
+        try {
+            mp.setDataSource(context.getFilesDir() + "/audio.3gp");
+            mp.prepare();
+            mp.start();
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+}

app/src/main/java/com/example/ueberwachungssystem/Detection/DetectionReport.java

@@ -0,0 +1,38 @@
+package com.example.ueberwachungssystem.Detection;
+
+import android.util.Log;
+
+import java.util.Calendar;
+
+/** Detection Report Class */
+public class DetectionReport {
+    public String timeStamp;
+    public String detectionType;
+    public float detectedValue;
+    public boolean detectionState;
+
+    public DetectionReport(boolean detectionState, String detectionType, float detectedAmplitude) {
+        this.timeStamp = String.valueOf(Calendar.getInstance().getTime());
+        this.detectionType = detectionType;
+        this.detectedValue = detectedAmplitude;
+        this.detectionState = detectionState;
+
+        //this.detectorID = detectorID;
+    }
+
+
+    /** Get Detection Report in String format */
+    public String toString() {
+        String state = "State: " + "[" + this.detectionState + "]";
+        String time = "Time: " + "[" + this.timeStamp + "]";
+        String type = "Type: " + "[" + this.detectionType + "]";
+        String value = "Value: " + "[" + this.detectedValue + "]";
+
+        return String.join("\t", state, time, type, value);
+    }
+
+    /** Debug Report */
+    public void log(String tag) {
+        Log.d(tag, this.toString());
+    }
+}

app/src/main/java/com/example/ueberwachungssystem/Detection/Detector.java

@@ -0,0 +1,75 @@
+package com.example.ueberwachungssystem.Detection;
+
+import android.os.CountDownTimer;
+
+import androidx.annotation.NonNull;
+
+
+abstract public class Detector {
+    private OnDetectionListener listener;
+    private boolean isDetecting = false;
+    private boolean extendViolation = false;
+
+    // Countdown parameters
+    private final int COUNTDOWN_TIME = 5000;          // milliseconds
+    private final int COUNTDOWN_POLLING_TIME = 100;   // milliseconds
+
+    /** Constructor - takes context of current activity */
+    public Detector() {}
+
+
+    /** On Detection Listener - runs when violation is reported */
+    public interface OnDetectionListener {
+        void onDetection(@NonNull DetectionReport detectionReport);
+    }
+    public void setOnDetectionListener(@NonNull OnDetectionListener listener) {
+        this.listener = listener;
+    }
+
+    /** Triggers onDetectionListener - call this to trigger violation/alarm */
+    public void reportViolation(String detectionType, float amplitude) {
+        if (listener != null) {
+            if (!isDetecting) {
+                isDetecting = true;
+                DetectionReport detectionReport = new DetectionReport(true, detectionType, amplitude);
+                listener.onDetection(detectionReport);
+                startDetectionTimer(detectionType, amplitude);
+            } else {
+                extendViolation = true;
+            }
+        } else {
+            isDetecting = false;
+            extendViolation = false;
+        }
+    }
+
+    private void startDetectionTimer(String detectionType, float amplitude) {
+        isDetecting = true;
+        new CountDownTimer((long) COUNTDOWN_TIME, COUNTDOWN_POLLING_TIME) {
+            @Override
+            public void onTick(long millisUntilFinished) {
+                if (extendViolation) {
+                    extendViolation = false;
+                    startDetectionTimer(detectionType, amplitude);
+                    this.cancel();
+                }
+            }
+            @Override
+            public void onFinish() {
+                isDetecting = false;
+                DetectionReport detectionReport = new DetectionReport(false, detectionType, amplitude);
+                listener.onDetection(detectionReport);
+            }
+        }.start();
+    }
+
+    public void extendViolation(){
+        this.extendViolation = true;
+    }
+
+    /** Starts Detection (abstract method: needs to be overridden in child class) */
+    public abstract void startDetection();
+
+    /** Stops Detection (abstract method: needs to be overridden in child class) */
+    public abstract void stopDetection();
+}

app/src/main/java/com/example/ueberwachungssystem/Detection/VideoDetector.java

@@ -0,0 +1,441 @@
+package com.example.ueberwachungssystem.Detection;
+
+import android.Manifest;
+import android.annotation.SuppressLint;
+import android.app.Activity;
+import android.content.Context;
+import android.content.pm.PackageManager;
+import android.graphics.Bitmap;
+import android.graphics.ImageFormat;
+import android.media.Image;
+import android.os.CountDownTimer;
+import android.util.Log;
+import android.view.Surface;
+import android.widget.ImageView;
+import android.widget.Toast;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.camera.core.CameraSelector;
+import androidx.camera.core.ExperimentalGetImage;
+import androidx.camera.core.ImageAnalysis;
+import androidx.camera.core.ImageProxy;
+import androidx.camera.core.Preview;
+import androidx.camera.core.VideoCapture;
+import androidx.camera.lifecycle.ProcessCameraProvider;
+import androidx.camera.view.PreviewView;
+import androidx.core.app.ActivityCompat;
+import androidx.core.content.ContextCompat;
+import androidx.lifecycle.LifecycleOwner;
+
+import com.google.common.util.concurrent.ListenableFuture;
+
+import org.opencv.android.OpenCVLoader;
+import org.opencv.android.Utils;
+import org.opencv.core.Core;
+import org.opencv.core.CvType;
+import org.opencv.core.Mat;
+import org.opencv.core.MatOfPoint;
+import org.opencv.core.Scalar;
+import org.opencv.core.Size;
+import org.opencv.imgproc.Imgproc;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.ExecutionException;
+
+
+/**
+ * Video Detector inherits some methods from abstract Detector class (more info there)
+ * USE FROM MAIN ACTIVITY:
+ * VideoDetector vd = new VideoDetector(this);
+ * */
+
+
+@ExperimentalGetImage
+public class VideoDetector extends Detector {
+
+    // Calling Activity
+    private final Context context;
+
+    // Permission handling
+    private static final int PERMISSION_REQUEST_CODE = 3691;
+
+    // Camera Provider
+    private ProcessCameraProvider cameraProvider;
+    private final ImageAnalysis imageAnalysis;
+    private final VideoCapture videoCapture;
+    private final Preview preview;
+
+    // Logic
+    private boolean isDetecting = false;
+    private boolean isRecording = false;
+    private boolean allowReportViolation = false;
+
+    // Image Processing
+    private Mat previousImage = null;
+
+    // Debugging
+    private ImageView inputImageView = null;
+    private ImageView outputImageView = null;
+
+
+    // Recording
+    private final String outputName = "video.mp4";
+
+
+    // Parameters
+    private static final float ALARM_THRESHOLD = 0.5f;   // Percent of pixels changed
+    private static final long START_DELAY = 20000;   // milliseconds
+    private static final android.util.Size IMAGE_RES = new android.util.Size(640, 480);
+
+
+    private enum UseCase {
+        ImageAnalysis,
+        Preview,
+        VideoCapture
+    };
+
+
+    /** Constructor */
+    public VideoDetector(Context context) {
+        super();
+        this.context = context;
+        this.imageAnalysis = setupImageAnalysis();
+        this.videoCapture = setupVideoCapture();
+        this.preview = new Preview.Builder().build();
+    }
+
+    /** Get State of the Detector */
+    public boolean isRunning() {
+        return isDetecting;
+    }
+
+
+    /** Starts the Video Detection */
+    @Override
+    public void startDetection() {
+        // Check States
+        if (isDetecting)
+            return;
+        // Return On Request Permissions
+        if (!hasPermissions()) {
+            getPermissions();
+            return;
+        }
+        // Open CV startup check
+        if (!OpenCVLoader.initDebug()) {
+            Log.e("OpenCV", "Unable to load OpenCV!");
+            return;
+        } else
+            Log.d("OpenCV", "OpenCV loaded Successfully!");
+        // Get Process Camera Provider and start
+        final ListenableFuture<ProcessCameraProvider> cameraProviderFuture = ProcessCameraProvider.getInstance(context);
+        cameraProviderFuture.addListener(() -> {
+            try {
+                cameraProvider = cameraProviderFuture.get();
+                isDetecting = true;
+                bindCameraProvider(UseCase.ImageAnalysis);
+            } catch (ExecutionException | InterruptedException e) {}
+        }, ContextCompat.getMainExecutor(context));
+
+        startViolationTimer();
+    }
+
+    /** Stops the Video Detection */
+    @Override
+    public void stopDetection() {
+        if (!isDetecting || imageAnalysis == null)
+            return;
+        cameraProvider.unbind(imageAnalysis);
+        isDetecting = false;
+        allowReportViolation = false;
+    }
+
+    /** Permission handling */
+    private boolean hasPermissions() {
+        return ContextCompat.checkSelfPermission(context, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED &&
+                ContextCompat.checkSelfPermission(context, Manifest.permission.RECORD_AUDIO) == PackageManager.PERMISSION_GRANTED;
+    }
+    private void getPermissions() {
+        if (!hasPermissions())
+            ActivityCompat.requestPermissions((Activity) context, new String[]{android.Manifest.permission.CAMERA, Manifest.permission.RECORD_AUDIO}, PERMISSION_REQUEST_CODE);
+    }
+
+
+
+    /** Binds the Luminosity Analyzer (configure and run Analysis) */
+    private void bindCameraProvider(UseCase useCase) {
+        // Specify which Camera to use
+        CameraSelector cameraSelector = new CameraSelector.Builder().requireLensFacing(CameraSelector.LENS_FACING_BACK).build();
+        cameraProvider.unbindAll();
+        cameraProvider.bindToLifecycle((LifecycleOwner) context, cameraSelector, imageAnalysis, videoCapture);
+    }
+
+
+    /** Start delay until Violation Report is allowed */
+    private void startViolationTimer() {
+        new CountDownTimer((long) (START_DELAY), 100) {
+            @Override
+            public void onTick(long millisUntilFinished) {
+            }
+            @Override
+            public void onFinish() {
+                allowReportViolation = true;
+            }
+        }.start();
+    }
+
+
+    private ImageAnalysis setupImageAnalysis() {
+        // Configure and create Image Analysis
+        ImageAnalysis.Builder builder = new ImageAnalysis.Builder();
+        builder.setTargetResolution(IMAGE_RES);
+        builder.setBackpressureStrategy(ImageAnalysis.STRATEGY_KEEP_ONLY_LATEST);
+        builder.setOutputImageFormat(ImageAnalysis.OUTPUT_IMAGE_FORMAT_YUV_420_888);
+        ImageAnalysis imageAnalysis = builder.build();
+        // Set Analyzer
+        imageAnalysis.setAnalyzer(ContextCompat.getMainExecutor(context), imageProxy -> {
+            if (imageProxy.getFormat() == ImageFormat.YUV_420_888) {
+                Image image = imageProxy.getImage();
+                assert image != null;
+
+                // Violation Handling
+                Mat processed = processImage(imageProxy);
+                int n = OpenCVHelper.countNonZeroPixels(processed);
+                int pixelCount = image.getWidth() * image.getHeight();
+                float percentChanged = (float) n / pixelCount;
+
+                // Violation Condition
+                if (percentChanged * 100 > ALARM_THRESHOLD) {
+                    if (allowReportViolation)
+                        reportViolation("Video", n);
+                }
+            }
+            imageProxy.close();
+        });
+        return imageAnalysis;
+    }
+
+    @SuppressLint("RestrictedApi")
+    private VideoCapture setupVideoCapture() {
+        return new VideoCapture.Builder()
+                .setTargetRotation(Surface.ROTATION_0)
+                .build();
+    }
+
+    @SuppressLint("RestrictedApi")
+    public void startRecording() {
+        // Check States
+        if (isRecording){
+            extendViolation();
+            return;
+        }
+
+        // Return On Request Permissions
+        if (!hasPermissions()) {
+            getPermissions();
+            return;
+        }
+
+        final ListenableFuture<ProcessCameraProvider> cameraProviderFuture = ProcessCameraProvider.getInstance(context);
+        cameraProviderFuture.addListener(() -> {
+            try {
+                cameraProvider = cameraProviderFuture.get();
+                isRecording = true;
+                bindCameraProvider(UseCase.VideoCapture);
+
+                File vidFile = new File(context.getFilesDir() + "/" + outputName);
+                if (ActivityCompat.checkSelfPermission(context, Manifest.permission.RECORD_AUDIO) != PackageManager.PERMISSION_GRANTED) {
+                    return;
+                }
+                videoCapture.startRecording(
+                        new VideoCapture.OutputFileOptions.Builder(vidFile).build(),
+                        context.getMainExecutor(),
+                        new VideoCapture.OnVideoSavedCallback() {
+                            @Override
+                            public void onVideoSaved(@NonNull VideoCapture.OutputFileResults outputFileResults) {
+                                isRecording = false;
+                                Toast.makeText(context, "recording saved", Toast.LENGTH_SHORT).show();
+                            }
+                            @Override
+                            public void onError(int videoCaptureError, @NonNull String message, @Nullable Throwable cause) {
+                                isRecording = false;
+                                Toast.makeText(context, "recording failed", Toast.LENGTH_SHORT).show();
+                            }
+                        }
+                );
+            } catch (ExecutionException | InterruptedException e) {}
+        }, ContextCompat.getMainExecutor(context));
+    }
+
+    @SuppressLint("RestrictedApi")
+    public void stopRecording(){
+        videoCapture.stopRecording();
+        cameraProvider.unbind(videoCapture);
+        isRecording = false;
+    }
+
+    /** Process Image to be used for Motion Detection */
+    private Mat processImage(ImageProxy imageProxy){
+        if (imageProxy == null)
+            return null;
+
+        // Image Transformation
+        Mat imageMat = OpenCVHelper.extractYChannel(imageProxy);
+
+        // Show Input Image
+        if (inputImageView != null)
+            OpenCVHelper.debugMat(imageMat, inputImageView);
+
+        // Preprocess Image
+        Mat preprocessed = imageMat;
+        preprocessed = OpenCVHelper.addGaussianBlur(preprocessed, new Size(21, 21));
+        preprocessed = OpenCVHelper.addBlur(preprocessed, new Size(3, 3));
+
+        if (previousImage == null) {
+            previousImage = preprocessed;
+            return null;
+        }
+
+        // Process Image
+        Mat processed = preprocessed.clone();
+        processed = OpenCVHelper.thresholdPixels(processed, previousImage, 25);
+        processed = OpenCVHelper.dilateBinaryMat(processed, new Size(3,3));
+        processed = OpenCVHelper.dilateBinaryMat(processed, new Size(3,3));
+        processed = OpenCVHelper.thresholdContourArea(processed, 500);
+
+        // Output
+        previousImage = preprocessed.clone();
+        // Show Output Image
+        if (outputImageView != null)
+            OpenCVHelper.debugMat(processed, outputImageView);
+        return processed;
+    }
+
+    public void debugProcessing(@NonNull ImageView inputImageView, @NonNull ImageView outputImageView){
+        this.inputImageView = inputImageView;
+        this.outputImageView = outputImageView;
+    }
+
+    public void setPreviewView(@NonNull PreviewView previewView) {
+        // Create Preview
+        if (this.preview != null)
+            this.preview.setSurfaceProvider(previewView.getSurfaceProvider());
+    }
+
+
+
+    private static class OpenCVHelper{
+        private OpenCVHelper() {}
+
+        /** OpenCV helper methods **/
+        private static Mat addGaussianBlur(Mat inputMat, Size kernelSize){
+            Mat outputMat = new Mat();
+            Imgproc.GaussianBlur(inputMat, outputMat, kernelSize, 0);
+            return outputMat;
+        }
+
+        private static Mat addBlur(Mat inputMat, Size kernelSize){
+            Mat outputMat = new Mat();
+            Imgproc.blur(inputMat, outputMat, kernelSize);
+            return outputMat;
+        }
+
+        private static Mat extractYChannel(@NonNull ImageProxy imgProxy) {
+            Image img = imgProxy.getImage();
+
+            assert img != null;
+            ByteBuffer yBuffer = img.getPlanes()[0].getBuffer();
+            byte[] yData = new byte[yBuffer.remaining()];
+            yBuffer.get(yData);
+
+            Mat yMat = new Mat(img.getHeight(), img.getWidth(), CvType.CV_8UC1);
+            yMat.put(0, 0, yData);
+
+            return yMat;
+        }
+
+        private static Mat thresholdPixels(Mat inputMat, Mat previousImage, int threshold){
+            Mat diffImage = new Mat();
+            Core.absdiff(inputMat, previousImage, diffImage);
+            Mat binaryMat = new Mat();
+            Imgproc.threshold(diffImage, binaryMat, threshold, 255, Imgproc.THRESH_BINARY);
+            return binaryMat;
+        }
+
+        private static Mat imageProxyToGrayscaleMat(ImageProxy imageProxy) {
+            // Step 1: Extract the image data from ImageProxy
+            ImageProxy.PlaneProxy[] planes = imageProxy.getPlanes();
+            ByteBuffer yBuffer = planes[0].getBuffer();
+            byte[] yData = new byte[yBuffer.remaining()];
+            yBuffer.get(yData);
+
+            // Step 2: Convert the image data to NV21 format
+            int width = imageProxy.getWidth();
+            int height = imageProxy.getHeight();
+            byte[] nv21Data = new byte[width * height * 3 / 2];
+            // Assuming the image format is YUV_420_888
+            System.arraycopy(yData, 0, nv21Data, 0, yData.length);
+            for (int i = yData.length; i < nv21Data.length; i += 2) {
+                nv21Data[i] = yData[i + 1];
+                nv21Data[i + 1] = yData[i];
+            }
+
+            // Step 3: Create a grayscale Mat from the NV21 data
+            Mat grayscaleMat = new Mat(height, width, CvType.CV_8UC1);
+            grayscaleMat.put(0, 0, nv21Data);
+
+            return grayscaleMat;
+        }
+
+
+        private static Mat thresholdContourArea(Mat inputMat, float areaThreshold){
+            List<MatOfPoint> contours = new ArrayList<>();
+            Mat hierarchy = new Mat();
+            Imgproc.findContours(inputMat, contours, hierarchy, Imgproc.RETR_EXTERNAL, Imgproc.CHAIN_APPROX_SIMPLE);
+
+            Mat outputMat = new Mat(inputMat.size(), inputMat.type(), new Scalar(0));
+            // Iterate over the contours and draw only the larger contours on the outputMat
+            for (MatOfPoint contour : contours) {
+                double contourArea = Imgproc.contourArea(contour);
+                if (contourArea > areaThreshold) {
+                    Imgproc.drawContours(outputMat, Collections.singletonList(contour), 0, new Scalar(255), -1);
+                }
+            }
+            // Apply the outputMat as a mask to the dilatedImage
+            Mat maskedImage = new Mat();
+            inputMat.copyTo(maskedImage, outputMat);
+            return outputMat;
+        }
+
+        private static Mat dilateBinaryMat(Mat inputMat, Size kernelSize){
+            Mat dilatedMat = new Mat();
+            Mat kernel = Imgproc.getStructuringElement(Imgproc.MORPH_ELLIPSE, kernelSize);
+            Imgproc.dilate(inputMat, dilatedMat, kernel);
+            return dilatedMat;
+        }
+
+        private static int countNonZeroPixels(Mat inputImage) {
+            if (inputImage != null)
+                return Core.countNonZero(inputImage);
+            else
+                return 0;
+        }
+
+
+        private static void debugMat(Mat mat, ImageView imageView) {
+            if (imageView == null || mat == null)
+                return;
+
+            Bitmap bitmap = Bitmap.createBitmap(mat.cols(), mat.rows(), Bitmap.Config.ARGB_8888);
+            Utils.matToBitmap(mat, bitmap);
+
+            // Display the bitmap in an ImageView
+            imageView.setImageBitmap(bitmap);
+        }
+    }
+}

app/src/main/java/com/example/ueberwachungssystem/DetectionReport.java

@@ -0,0 +1,36 @@
+package com.example.ueberwachungssystem;
+
+import android.util.Log;
+
+import java.util.Calendar;
+
+/** Detection Report Class */
+public class DetectionReport {
+    public String timeStamp;
+    public String detectionType;
+    public float detectedValue;
+    public String detectorID;
+
+    public DetectionReport(String detectorID, String detectionType, float detectedAmplitude) {
+        this.timeStamp = String.valueOf(Calendar.getInstance().getTime());
+        this.detectionType = detectionType;
+        this.detectedValue = detectedAmplitude;
+        this.detectorID = detectorID;
+    }
+
+
+    /** Get Detection Report in String format */
+    public String toString() {
+        String time = "Time: " + "[" + this.timeStamp + "]";
+        String type = "Type: " + "[" + this.detectionType + "]";
+        String value = "Value: " + "[" + this.detectedValue + "]";
+        String id = "ID: " + "[" + this.detectorID + "]";
+
+        return String.join("\t", time, type, value, id);
+    }
+
+    /** Debug Report */
+    public void log(String tag) {
+        Log.d(tag, this.toString());
+    }
+}

app/src/main/java/com/example/ueberwachungssystem/Detector.java

@@ -0,0 +1,40 @@
+package com.example.ueberwachungssystem;
+
+import android.app.Activity;
+import android.content.Context;
+import androidx.annotation.NonNull;
+
+
+abstract public class Detector {
+    private OnDetectionListener listener;
+
+    /** Constructor - takes context of current activity */
+    public Detector(Context context) {};
+
+
+    /** On Detection Listener - runs when violation is reported */
+    public interface OnDetectionListener {
+        void onDetection(@NonNull DetectionReport detectionReport);
+    }
+    public void setOnDetectionListener(@NonNull OnDetectionListener listener) {
+        this.listener = listener;
+    }
+
+
+    /** Triggers onDetectionListener - call this to trigger violation/alarm */
+    private void reportViolation(String detectorID, String detectionType, float amplitude) {
+        if (listener != null) {
+            DetectionReport detectionReport = new DetectionReport(detectorID, detectionType, amplitude);
+            listener.onDetection(detectionReport);
+        } else {
+            throw new IllegalStateException("No listener set for violation reporting");
+        }
+    }
+
+
+    /** Starts Detection (abstract method: needs to be overridden in child class) */
+    public abstract void startDetection();
+
+    /** Stops Detection (abstract method: needs to be overridden in child class) */
+    public abstract void stopDetection();
+}

app/src/main/java/com/example/ueberwachungssystem/MainActivity.java

@@ -1,15 +1,78 @@
 package com.example.ueberwachungssystem;
 
+import androidx.annotation.NonNull;
 import androidx.appcompat.app.AppCompatActivity;
+import androidx.camera.core.ExperimentalGetImage;
+import androidx.camera.view.PreviewView;
 
 import android.os.Bundle;
+import android.util.Log;
+import android.view.View;
+import android.widget.ImageView;
+import android.widget.TextView;
+import android.widget.ToggleButton;
 
+import com.example.ueberwachungssystem.Detection.DetectionReport;
+import com.example.ueberwachungssystem.Detection.Detector;
+import com.example.ueberwachungssystem.Detection.VideoDetector;
+import com.example.ueberwachungssystem.logger.Logger;
+import com.jjoe64.graphview.GraphView;
+
+@ExperimentalGetImage
 public class MainActivity extends AppCompatActivity {
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
-        //
+
+
+        ImageView inputImageView = findViewById(R.id.inputImageView);
+        ImageView outputImageView = findViewById(R.id.outputImageView);
+        PreviewView previewView = findViewById(R.id.previewView);
+
+
+        // Mic stuff
+        TextView textView= (TextView) findViewById(R.id.textView); //Set textview for showing logged content
+        Logger logger = new Logger(this.getClass().getSimpleName(), textView, "");
+        GraphView graph = (GraphView) findViewById(R.id.graph);
+        MicrophoneDetector mic = new MicrophoneDetector(this, logger, graph);
+        mic.startDetection();
+
+
+
+        AudioRecorder audioRecorder = new AudioRecorder(this);
+
+        // video Stuff
+        VideoDetector vd = new VideoDetector(this);
+        //vd.setPreviewView(previewView);
+        vd.debugProcessing(inputImageView, outputImageView);
+        vd.setOnDetectionListener(new Detector.OnDetectionListener() {
+            @Override
+            public void onDetection(@NonNull DetectionReport detectionReport) {
+                Log.d("onDetection", detectionReport.toString());
+            }
+        });
+        vd.startDetection();
+
+
+        ToggleButton toggleButton = findViewById(R.id.toggleButton);
+        toggleButton.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                if (toggleButton.isChecked())
+                {
+                    //vd.startDetection();
+                    vd.startRecording();
+                    audioRecorder.startRecording();
+
+                }
+                else {
+                    //vd.stopDetection();
+                    vd.stopRecording();
+                    audioRecorder.stopRecording();
+                }
+            }
+        });
     }
 }

app/src/main/java/com/example/ueberwachungssystem/MicrophoneDetector.java

@@ -0,0 +1,445 @@
+package com.example.ueberwachungssystem;
+
+import static java.lang.Math.*;
+
+import android.Manifest;
+import android.app.Activity;
+import android.content.Context;
+import android.content.pm.PackageManager;
+import android.media.AudioFormat;
+import android.media.AudioRecord;
+import android.media.MediaRecorder;
+import android.os.AsyncTask;
+
+import androidx.core.app.ActivityCompat;
+import androidx.core.content.ContextCompat;
+
+import com.example.ueberwachungssystem.Signalverarbeitung.Complex;
+import com.example.ueberwachungssystem.Signalverarbeitung.FFT;
+import com.example.ueberwachungssystem.logger.Logger;
+import com.jjoe64.graphview.GraphView;
+import com.jjoe64.graphview.series.DataPoint;
+import com.jjoe64.graphview.series.LineGraphSeries;
+
+public class MicrophoneDetector extends Detector {
+    /**
+     * Constructor - takes context of current activity
+     *
+     * @param context
+     */
+
+    private static final int RECHTEANFORDERUNG_MIKROFON = 1;
+
+    private AufnahmeTask aufnahmeTask;
+    public boolean armed = false;
+    public int Schwellwert_Alarm = 100;
+    GraphView graph;
+
+    Logger logger;
+    private Activity MainActivityForClass;
+
+    public MicrophoneDetector(Context context, Logger MainLogger, GraphView MainGraph) {
+        super(context);
+        MainActivityForClass = (Activity) context;
+        logger = MainLogger; //Class uses the same logger as the MainActivity
+        logger.log(this.getClass().getSimpleName() + ".onCreate");
+        graph = MainGraph;
+
+        if (!istZugriffAufMikrofonErlaubt()) {
+            zugriffAufMikrofonAnfordern();
+        }
+    }
+
+    @Override
+    public void startDetection() {
+        logger.log(this.getClass().getSimpleName() + ".startDetection");
+
+        if (!istZugriffAufMikrofonErlaubt()) {
+            zugriffAufMikrofonAnfordern();
+        }
+        if (istZugriffAufMikrofonErlaubt()) {
+            aufnahmeTask = new AufnahmeTask();
+            aufnahmeTask.execute();
+        }
+    }
+
+    @Override
+    public void stopDetection() {
+        logger.log(this.getClass().getSimpleName() + ".stopDetection");
+        if (aufnahmeTask != null) {
+            aufnahmeTask.cancel(true);
+            // aufnahmeTask = null; // if aufnahmeTask = null, break in for loop would not work (Nullpointer Exception)
+        }
+    }
+
+    private boolean istZugriffAufMikrofonErlaubt() {
+        if (ContextCompat.checkSelfPermission(MainActivityForClass, android.Manifest.permission.RECORD_AUDIO) != PackageManager.PERMISSION_GRANTED) {
+            logger.log("Zugriff auf Mikrofon ist verboten.");
+            return false;
+        } else {
+            logger.log("Zugriff auf Mikrofon ist erlaubt.");
+            return true;
+        }
+    }
+
+    private void zugriffAufMikrofonAnfordern() {
+        ActivityCompat.requestPermissions(MainActivityForClass, new String[]{Manifest.permission.RECORD_AUDIO}, RECHTEANFORDERUNG_MIKROFON);
+    }
+
+    class AufnahmeTask extends AsyncTask<Long, Verarbeitungsergebnis, Void> {
+        private AudioRecord recorder;
+        private final int sampleRateInHz = 44100;
+        private final int channelConfig = AudioFormat.CHANNEL_IN_MONO;
+        private final int audioFormat = AudioFormat.ENCODING_PCM_16BIT;
+        private int minPufferGroesseInBytes;
+        private int pufferGroesseInBytes;
+        private RingPuffer ringPuffer = new RingPuffer(10);
+        private float kalibierWert;
+        private DetectionReport detectionReport;
+
+        AufnahmeTask() {
+            minPufferGroesseInBytes = AudioRecord.getMinBufferSize(sampleRateInHz, channelConfig, audioFormat);
+            pufferGroesseInBytes = minPufferGroesseInBytes * 2;
+            if (ActivityCompat.checkSelfPermission(MainActivityForClass, Manifest.permission.RECORD_AUDIO) != PackageManager.PERMISSION_GRANTED) {
+                // TODO: Consider calling
+                //    ActivityCompat#requestPermissions
+                // here to request the missing permissions, and then overriding
+                //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
+                //                                          int[] grantResults)
+                // to handle the case where the user grants the permission. See the documentation
+                // for ActivityCompat#requestPermissions for more details.
+                ActivityCompat.requestPermissions(MainActivityForClass, new String[]{Manifest.permission.RECORD_AUDIO}, RECHTEANFORDERUNG_MIKROFON);
+            }
+
+            recorder = new AudioRecord(MediaRecorder.AudioSource.MIC, sampleRateInHz, channelConfig, audioFormat, pufferGroesseInBytes);
+
+//            textViewMinPufferGroesseInBytes.setText("" + minPufferGroesseInBytes);
+//            textViewPufferGroesseInBytes.setText("" + pufferGroesseInBytes);
+//            textViewAbtastrate.setText("" + recorder.getSampleRate());
+//            textViewAnzahlKanaele.setText("" + recorder.getChannelCount());
+
+            logger.log("Puffergroeße: "+ minPufferGroesseInBytes + " " + pufferGroesseInBytes);
+            logger.log("Recorder (SR, CH): "+ recorder.getSampleRate() + " " + recorder.getChannelCount());
+
+            int anzahlBytesProAbtastwert;
+            String s;
+            switch (recorder.getAudioFormat()) {
+                case AudioFormat.ENCODING_PCM_8BIT:
+                    s = "8 Bit PCM ";
+                    anzahlBytesProAbtastwert = 1;
+                    break;
+                case AudioFormat.ENCODING_PCM_16BIT:
+                    s = "16 Bit PCM";
+                    anzahlBytesProAbtastwert = 2;
+                    break;
+                case AudioFormat.ENCODING_PCM_FLOAT:
+                    s = "Float PCM";
+                    anzahlBytesProAbtastwert = 4;
+                    break;
+                default:
+                    throw new IllegalArgumentException();
+            }
+//            textViewAudioFormat.setText(s);
+
+            switch (recorder.getChannelConfiguration()) {
+                case AudioFormat.CHANNEL_IN_MONO:
+                    s = "Mono";
+                    break;
+                case AudioFormat.CHANNEL_IN_STEREO:
+                    s = "Stereo";
+                    anzahlBytesProAbtastwert *= 2;
+                    break;
+                case AudioFormat.CHANNEL_INVALID:
+                    s = "ungültig";
+                    break;
+                default:
+                    throw new IllegalArgumentException();
+            }
+//            textViewKanalKonfiguration.setText(s);
+            logger.log("Konfiguration: "+ s);
+
+            int pufferGroesseInAnzahlAbtastwerten = pufferGroesseInBytes / anzahlBytesProAbtastwert;
+            int pufferGroesseInMillisekunden = 1000 * pufferGroesseInAnzahlAbtastwerten / recorder.getSampleRate();
+
+//            textViewPufferGroesseInAnzahlAbtastwerte.setText("" + pufferGroesseInAnzahlAbtastwerten);
+//            textViewPufferGroesseInMillisekunden.setText("" + pufferGroesseInMillisekunden);
+        }
+
+        @Override
+        protected Void doInBackground(Long... params) {
+            recorder.startRecording();
+            short[] puffer = new short[pufferGroesseInBytes / 2];
+            long lastTime = System.currentTimeMillis();
+            float verarbeitungsrate = 0;
+            final int maxZaehlerZeitMessung = 10;
+            int zaehlerZeitMessung = 0;
+            int anzahlVerarbeitet = 0;
+            GleitenderMittelwert gleitenderMittelwert = new GleitenderMittelwert(0.3f);
+
+            //Kalibrierung
+            try {
+                Thread.sleep(3000);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+            int i = 0;
+            for (i = 0; i < 20; i++) {
+                int n = recorder.read(puffer, 0, puffer.length);
+                Verarbeitungsergebnis kalibrierErgebnis = verarbeiten(puffer, n);
+                kalibierWert += kalibrierErgebnis.maxAmp;
+                try {
+                    Thread.sleep(50);
+                } catch (InterruptedException e) {
+                    e.printStackTrace();
+                }
+            }
+            kalibierWert = kalibierWert/i;
+
+//            Complex[] zeitSignal = new Complex[puffer.length];
+//            for (int j = 0; j < puffer.length; j++) {
+//                zeitSignal[j] = new Complex(puffer[j], 0);
+//            }
+//            Complex[] spektrum = FFT.fft(zeitSignal);
+            double[] spektrum = calculateFFT(puffer);
+            DataPoint AddPoint;
+//            LineGraphSeries<DataPoint> series = new LineGraphSeries<DataPoint>(new DataPoint[]{});
+//            for (i = 0; i < spektrum.length; i++) {
+//                AddPoint = new DataPoint(i, spektrum[i]);
+//                series.appendData(AddPoint, true, spektrum.length);
+//            }
+//            graph.addSeries(series);
+            // logger.log(spektrum.toString());
+
+            for (; ; ) {
+                if (aufnahmeTask.isCancelled()) {
+                    break;
+                } else {
+                    int n = recorder.read(puffer, 0, puffer.length);
+                    Verarbeitungsergebnis ergebnis = verarbeiten(puffer, n);
+                    anzahlVerarbeitet += n;
+
+                    spektrum = calculateFFT(puffer);
+                    LineGraphSeries<DataPoint> newseries = new LineGraphSeries<DataPoint>(new DataPoint[]{});
+                    for (i = 0; i < spektrum.length; i++) {
+                        AddPoint = new DataPoint(i, spektrum[i]);
+                        newseries.appendData(AddPoint, true, spektrum.length);
+                    }
+                    graph.removeAllSeries();
+                    graph.addSeries(newseries);
+                    zaehlerZeitMessung++;
+                    if (zaehlerZeitMessung == maxZaehlerZeitMessung) {
+                        long time = System.currentTimeMillis();
+                        long deltaTime = time - lastTime;
+                        verarbeitungsrate = 1000.0f * anzahlVerarbeitet / deltaTime;
+                        verarbeitungsrate = gleitenderMittelwert.mittel(verarbeitungsrate);
+                        zaehlerZeitMessung = 0;
+                        anzahlVerarbeitet = 0;
+                        lastTime = time;
+                    }
+
+
+                    ergebnis.verarbeitungsrate = (int) verarbeitungsrate;
+                    publishProgress(ergebnis);
+
+                    try {
+                        Thread.sleep(100);
+                    } catch (InterruptedException e) {
+                        e.printStackTrace();
+                    }
+                }
+            }
+            recorder.release();
+            return null;
+        }
+
+        private Verarbeitungsergebnis verarbeiten(short[] daten, int n) {
+            String status;
+            short maxAmp = -1;
+            if (n == AudioRecord.ERROR_INVALID_OPERATION) {
+                status = "ERROR_INVALID_OPERATION";
+            } else if (n == AudioRecord.ERROR_BAD_VALUE) {
+                status = "ERROR_BAD_VALUE";
+            } else {
+                status = "OK";
+                short max = 0;
+                for (int i = 0; i < n; i++) {
+                    if (daten[i] > max) {
+                        max = daten[i];
+                        //max = 20 * log10(abs(daten[i]) / 32768);
+                    }
+                }
+
+                ringPuffer.hinzufuegen(max);
+                maxAmp = ringPuffer.maximum();
+                if (maxAmp <= Schwellwert_Alarm+kalibierWert) {
+                    armed = true;
+                }
+            }
+
+            return new Verarbeitungsergebnis(status, maxAmp, 0);
+        }
+
+        @Override
+        protected void onProgressUpdate(Verarbeitungsergebnis... progress) {
+            super.onProgressUpdate(progress);
+//            textViewMaxAmp.setText("" + progress[0].maxAmp);
+//            textViewVerarbeitungsrate.setText("" + progress[0].verarbeitungsrate);
+            float maxAmpPrint = round(20*log10(abs(progress[0].maxAmp/1.0)));
+            float kalibierWertPrint = round(20*log10(abs(kalibierWert)));
+            logger.overwriteLastlog("VR, Max, Kal:" + progress[0].verarbeitungsrate + ", " + maxAmpPrint
+            + " dB, " + kalibierWertPrint + " dB");
+
+            if (progress[0].maxAmp >= Schwellwert_Alarm+kalibierWert && armed == true) {
+                armed = false;
+                detectionReport = new DetectionReport("Mic1", "Audio", maxAmpPrint);
+                logger.log("");
+                logger.log("Alarm!");
+                logger.log(detectionReport.toString());
+                logger.log("");
+            }
+        }
+    }
+
+    private double[] calculateFFT(short[] zeitsignal)
+    {
+        byte signal[] = new byte[zeitsignal.length];
+        // loops through all the values of a Short
+        for (int i = 0; i < zeitsignal.length-1; i++) {
+            signal[i] = (byte) (zeitsignal[i]);
+            signal[i+1] = (byte) (zeitsignal[i] >> 8);
+        }
+
+        final int mNumberOfFFTPoints =1024;
+        double mMaxFFTSample;
+
+        double temp;
+        Complex[] y;
+        Complex[] complexSignal = new Complex[mNumberOfFFTPoints];
+        double[] absSignal = new double[mNumberOfFFTPoints/2];
+
+        for(int i = 0; i < mNumberOfFFTPoints; i++){
+            temp = (double)((signal[2*i] & 0xFF) | (signal[2*i+1] << 8)) / 32768.0F;
+            complexSignal[i] = new Complex(temp,0.0);
+        }
+
+        y = FFT.fft(complexSignal);
+
+        mMaxFFTSample = 0.0;
+        // mPeakPos = 0;
+        for(int i = 0; i < (mNumberOfFFTPoints/2); i++)
+        {
+            absSignal[i] = y[i].abs();
+//            absSignal[i] = Math.sqrt(Math.pow(y[i].re(), 2) + Math.pow(y[i].im(), 2));
+//            if(absSignal[i] > mMaxFFTSample)
+//            {
+//                mMaxFFTSample = absSignal[i];
+//                // mPeakPos = i;
+//            }
+        }
+
+        return absSignal;
+
+    }
+
+    class Verarbeitungsergebnis {
+        String status;
+        short maxAmp;
+        int verarbeitungsrate;
+        Verarbeitungsergebnis(String status, short maxAmp, int verarbeitungsrate) {
+            this.status = status;
+            this.maxAmp = maxAmp;
+            this.verarbeitungsrate = verarbeitungsrate;
+        }
+    }
+
+    class RingPuffer {
+        private short[] puffer;
+        private final int laenge;
+        private int anzahlEnthaltenerDaten;
+        private int position;
+
+        public RingPuffer(int n) {
+            laenge = n;
+            anzahlEnthaltenerDaten = 0;
+            position = 0;
+            puffer = new short[laenge];
+        }
+
+        public void hinzufuegen(short wert) {
+            puffer[position] = wert;
+            position++;
+            if (position >= laenge) {
+                position = 0;
+            }
+            if (anzahlEnthaltenerDaten < laenge) {
+                anzahlEnthaltenerDaten++;
+            }
+        }
+
+        public void hinzufuegen(short[] daten) {
+            for (short d : daten) {
+                puffer[position] = d;
+                position++;
+                if (position >= laenge) {
+                    position = 0;
+                }
+            }
+            if (anzahlEnthaltenerDaten < laenge) {
+                anzahlEnthaltenerDaten += daten.length;
+                if (anzahlEnthaltenerDaten >= laenge) {
+                    anzahlEnthaltenerDaten = laenge;
+                }
+            }
+        }
+
+        public short maximum() {
+            short max = 0;
+            for (int i = 0; i < anzahlEnthaltenerDaten; i++) {
+                if (puffer[i] > max) {
+                    max = puffer[i];
+                }
+            }
+            return max;
+        }
+
+        public float mittelwert() {
+            float summe = 0;
+            for (int i = 0; i < anzahlEnthaltenerDaten; i++) {
+                summe += puffer[i];
+            }
+            return summe / anzahlEnthaltenerDaten;
+        }
+    }
+
+    class GleitenderMittelwert {
+        private final float wichtungNeuerWert;
+        private final float wichtungAlterWert;
+        private float mittelwert = 0;
+        private boolean istMittelwertGesetzt = false;
+
+        GleitenderMittelwert(float wichtungNeuerWert) {
+            this.wichtungNeuerWert = wichtungNeuerWert;
+            this.wichtungAlterWert = 1 - this.wichtungNeuerWert;
+        }
+
+        float MittelwertPuffer(short[] puffer) {
+
+            for (int i = 0; i < puffer.length; i++) {
+                mittelwert = Math.abs(puffer[i]);
+            }
+            mittelwert = mittelwert/puffer.length;
+
+            return mittelwert;
+        }
+
+        float mittel(float wert) {
+            if (istMittelwertGesetzt) {
+                mittelwert = wert * wichtungNeuerWert + mittelwert * wichtungAlterWert;
+            } else {
+                mittelwert = wert;
+                istMittelwertGesetzt = true;
+            }
+            return mittelwert;
+        }
+    }
+}

app/src/main/java/com/example/ueberwachungssystem/Signalverarbeitung/Complex.java

@@ -0,0 +1,148 @@
+package com.example.ueberwachungssystem.Signalverarbeitung;
+
+import java.util.Objects;
+
+public class Complex {
+    private final double re;   // the real part
+    private final double im;   // the imaginary part
+
+    // create a new object with the given real and imaginary parts
+    public Complex(double real, double imag) {
+        re = real;
+        im = imag;
+    }
+
+    // return a string representation of the invoking com.example.ueberwachungssystem.Signalverarbeitung.Complex object
+    public String toString() {
+        if (im == 0) return re + "";
+        if (re == 0) return im + "i";
+        if (im < 0) return re + " - " + (-im) + "i";
+        return re + " + " + im + "i";
+    }
+
+    // return abs/modulus/magnitude
+    public double abs() {
+        return Math.hypot(re, im);
+    }
+
+    // return angle/phase/argument, normalized to be between -pi and pi
+    public double phase() {
+        return Math.atan2(im, re);
+    }
+
+    // return a new com.example.ueberwachungssystem.Signalverarbeitung.Complex object whose value is (this + b)
+    public Complex plus(Complex b) {
+        Complex a = this;             // invoking object
+        double real = a.re + b.re;
+        double imag = a.im + b.im;
+        return new Complex(real, imag);
+    }
+
+    // return a new com.example.ueberwachungssystem.Signalverarbeitung.Complex object whose value is (this - b)
+    public Complex minus(Complex b) {
+        Complex a = this;
+        double real = a.re - b.re;
+        double imag = a.im - b.im;
+        return new Complex(real, imag);
+    }
+
+    // return a new com.example.ueberwachungssystem.Signalverarbeitung.Complex object whose value is (this * b)
+    public Complex times(Complex b) {
+        Complex a = this;
+        double real = a.re * b.re - a.im * b.im;
+        double imag = a.re * b.im + a.im * b.re;
+        return new Complex(real, imag);
+    }
+
+    // return a new object whose value is (this * alpha)
+    public Complex scale(double alpha) {
+        return new Complex(alpha * re, alpha * im);
+    }
+
+    // return a new com.example.ueberwachungssystem.Signalverarbeitung.Complex object whose value is the conjugate of this
+    public Complex conjugate() {
+        return new Complex(re, -im);
+    }
+
+    // return a new com.example.ueberwachungssystem.Signalverarbeitung.Complex object whose value is the reciprocal of this
+    public Complex reciprocal() {
+        double scale = re * re + im * im;
+        return new Complex(re / scale, -im / scale);
+    }
+
+    // return the real or imaginary part
+    public double re() {
+        return re;
+    }
+
+    public double im() {
+        return im;
+    }
+
+    // return a / b
+    public Complex divides(Complex b) {
+        Complex a = this;
+        return a.times(b.reciprocal());
+    }
+
+    // return a new com.example.ueberwachungssystem.Signalverarbeitung.Complex object whose value is the complex exponential of this
+    public Complex exp() {
+        return new Complex(Math.exp(re) * Math.cos(im), Math.exp(re) * Math.sin(im));
+    }
+
+    // return a new com.example.ueberwachungssystem.Signalverarbeitung.Complex object whose value is the complex sine of this
+    public Complex sin() {
+        return new Complex(Math.sin(re) * Math.cosh(im), Math.cos(re) * Math.sinh(im));
+    }
+
+    // return a new com.example.ueberwachungssystem.Signalverarbeitung.Complex object whose value is the complex cosine of this
+    public Complex cos() {
+        return new Complex(Math.cos(re) * Math.cosh(im), -Math.sin(re) * Math.sinh(im));
+    }
+
+    // return a new com.example.ueberwachungssystem.Signalverarbeitung.Complex object whose value is the complex tangent of this
+    public Complex tan() {
+        return sin().divides(cos());
+    }
+
+    // a static version of plus
+    public static Complex plus(Complex a, Complex b) {
+        double real = a.re + b.re;
+        double imag = a.im + b.im;
+        Complex sum = new Complex(real, imag);
+        return sum;
+    }
+
+    // See Section 3.3.
+    public boolean equals(Object x) {
+        if (x == null) return false;
+        if (this.getClass() != x.getClass()) return false;
+        Complex that = (Complex) x;
+        return (this.re == that.re) && (this.im == that.im);
+    }
+
+    // See Section 3.3.
+    public int hashCode() {
+        return Objects.hash(re, im);
+    }
+
+    // sample client for testing
+    public static void main(String[] args) {
+        Complex a = new Complex(5.0, 6.0);
+        Complex b = new Complex(-3.0, 4.0);
+
+        System.out.println("a            = " + a);
+        System.out.println("b            = " + b);
+        System.out.println("Re(a)        = " + a.re());
+        System.out.println("Im(a)        = " + a.im());
+        System.out.println("b + a        = " + b.plus(a));
+        System.out.println("a - b        = " + a.minus(b));
+        System.out.println("a * b        = " + a.times(b));
+        System.out.println("b * a        = " + b.times(a));
+        System.out.println("a / b        = " + a.divides(b));
+        System.out.println("(a / b) * b  = " + a.divides(b).times(b));
+        System.out.println("conj(a)      = " + a.conjugate());
+        System.out.println("|a|          = " + a.abs());
+        System.out.println("tan(a)       = " + a.tan());
+    }
+}

app/src/main/java/com/example/ueberwachungssystem/Signalverarbeitung/FFT.java

@@ -0,0 +1,248 @@
+package com.example.ueberwachungssystem.Signalverarbeitung;
+// Source: https://introcs.cs.princeton.edu/java/97data/FFT.java.html
+
+import android.util.Log;
+
+/******************************************************************************
+ *  Compilation:  javac FFT.java
+ *  Execution:    java FFT n
+ *  Dependencies: com.example.ueberwachungssystem.Signalverarbeitung.Complex.java
+ *
+ *  Compute the FFT and inverse FFT of a length n complex sequence
+ *  using the radix 2 Cooley-Tukey algorithm.
+ *  Bare bones implementation that runs in O(n log n) time and O(n)
+ *  space. Our goal is to optimize the clarity of the code, rather
+ *  than performance.
+ *
+ *  This implementation uses the primitive root of unity w = e^(-2 pi i / n).
+ *  Some resources use w = e^(2 pi i / n).
+ *
+ *  Reference: https://www.cs.princeton.edu/~wayne/kleinberg-tardos/pdf/05DivideAndConquerII.pdf
+ *
+ *  Limitations
+ *  -----------
+ *   -  assumes n is a power of 2
+ *
+ *   -  not the most memory efficient algorithm (because it uses
+ *      an object type for representing complex numbers and because
+ *      it re-allocates memory for the subarray, instead of doing
+ *      in-place or reusing a single temporary array)
+ *
+ *  For an in-place radix 2 Cooley-Tukey FFT, see
+ *  https://introcs.cs.princeton.edu/java/97data/InplaceFFT.java.html
+ *
+ ******************************************************************************/
+
+public class FFT {
+
+    // compute the FFT of x[], assuming its length n is a power of 2
+    public static Complex[] fft(Complex[] x) {
+        int n = x.length;
+
+        // base case
+        if (n == 1) return new Complex[]{x[0]};
+
+        // radix 2 Cooley-Tukey FFT
+        if (n % 2 != 0) {
+            throw new IllegalArgumentException("n is not a power of 2");
+        }
+
+        // compute FFT of even terms
+        Complex[] even = new Complex[n / 2];
+        for (int k = 0; k < n / 2; k++) {
+            even[k] = x[2 * k];
+        }
+        Complex[] evenFFT = fft(even);
+
+        // compute FFT of odd terms
+        Complex[] odd = even;  // reuse the array (to avoid n log n space)
+        for (int k = 0; k < n / 2; k++) {
+            odd[k] = x[2 * k + 1];
+        }
+        Complex[] oddFFT = fft(odd);
+
+        // combine
+        Complex[] y = new Complex[n];
+        for (int k = 0; k < n / 2; k++) {
+            double kth = -2 * k * Math.PI / n;
+            Complex wk = new Complex(Math.cos(kth), Math.sin(kth));
+            y[k] = evenFFT[k].plus(wk.times(oddFFT[k]));
+            y[k + n / 2] = evenFFT[k].minus(wk.times(oddFFT[k]));
+        }
+        return y;
+    }
+
+
+    // compute the inverse FFT of x[], assuming its length n is a power of 2
+    public static Complex[] ifft(Complex[] x) {
+        int n = x.length;
+        Complex[] y = new Complex[n];
+
+        // take conjugate
+        for (int i = 0; i < n; i++) {
+            y[i] = x[i].conjugate();
+        }
+
+        // compute forward FFT
+        y = fft(y);
+
+        // take conjugate again
+        for (int i = 0; i < n; i++) {
+            y[i] = y[i].conjugate();
+        }
+
+        // divide by n
+        for (int i = 0; i < n; i++) {
+            y[i] = y[i].scale(1.0 / n);
+        }
+
+        return y;
+
+    }
+
+    // compute the circular convolution of x and y
+    public static Complex[] cconvolve(Complex[] x, Complex[] y) {
+
+        // should probably pad x and y with 0s so that they have same length
+        // and are powers of 2
+        if (x.length != y.length) {
+            throw new IllegalArgumentException("Dimensions don't agree");
+        }
+
+        int n = x.length;
+
+        // compute FFT of each sequence
+        Complex[] a = fft(x);
+        Complex[] b = fft(y);
+
+        // point-wise multiply
+        Complex[] c = new Complex[n];
+        for (int i = 0; i < n; i++) {
+            c[i] = a[i].times(b[i]);
+        }
+
+        // compute inverse FFT
+        return ifft(c);
+    }
+
+
+    // compute the linear convolution of x and y
+    public static Complex[] convolve(Complex[] x, Complex[] y) {
+        Complex ZERO = new Complex(0, 0);
+
+        Complex[] a = new Complex[2 * x.length];
+        for (int i = 0; i < x.length; i++) a[i] = x[i];
+        for (int i = x.length; i < 2 * x.length; i++) a[i] = ZERO;
+
+        Complex[] b = new Complex[2 * y.length];
+        for (int i = 0; i < y.length; i++) b[i] = y[i];
+        for (int i = y.length; i < 2 * y.length; i++) b[i] = ZERO;
+
+        return cconvolve(a, b);
+    }
+
+    // compute the DFT of x[] via brute force (n^2 time)
+    public static Complex[] dft(Complex[] x) {
+        int n = x.length;
+        Complex ZERO = new Complex(0, 0);
+        Complex[] y = new Complex[n];
+        for (int k = 0; k < n; k++) {
+            y[k] = ZERO;
+            for (int j = 0; j < n; j++) {
+                int power = (k * j) % n;
+                double kth = -2 * power * Math.PI / n;
+                Complex wkj = new Complex(Math.cos(kth), Math.sin(kth));
+                y[k] = y[k].plus(x[j].times(wkj));
+            }
+        }
+        return y;
+    }
+
+    // display an array of com.example.ueberwachungssystem.Signalverarbeitung.Complex numbers to standard output
+    public static void show(Complex[] x, String title) {
+        System.out.println(title);
+        System.out.println("-------------------");
+        for (int i = 0; i < x.length; i++) {
+            System.out.println(x[i]);
+        }
+        System.out.println();
+    }
+
+    /***************************************************************************
+     *  Test client and sample execution
+     *
+     *  % java FFT 4
+     *  x
+     *  -------------------
+     *  -0.03480425839330703
+     *  0.07910192950176387
+     *  0.7233322451735928
+     *  0.1659819820667019
+     *
+     *  y = fft(x)
+     *  -------------------
+     *  0.9336118983487516
+     *  -0.7581365035668999 + 0.08688005256493803i
+     *  0.44344407521182005
+     *  -0.7581365035668999 - 0.08688005256493803i
+     *
+     *  z = ifft(y)
+     *  -------------------
+     *  -0.03480425839330703
+     *  0.07910192950176387 + 2.6599344570851287E-18i
+     *  0.7233322451735928
+     *  0.1659819820667019 - 2.6599344570851287E-18i
+     *
+     *  c = cconvolve(x, x)
+     *  -------------------
+     *  0.5506798633981853
+     *  0.23461407150576394 - 4.033186818023279E-18i
+     *  -0.016542951108772352
+     *  0.10288019294318276 + 4.033186818023279E-18i
+     *
+     *  d = convolve(x, x)
+     *  -------------------
+     *  0.001211336402308083 - 3.122502256758253E-17i
+     *  -0.005506167987577068 - 5.058885073636224E-17i
+     *  -0.044092969479563274 + 2.1934338938072244E-18i
+     *  0.10288019294318276 - 3.6147323062478115E-17i
+     *  0.5494685269958772 + 3.122502256758253E-17i
+     *  0.240120239493341 + 4.655566391833896E-17i
+     *  0.02755001837079092 - 2.1934338938072244E-18i
+     *  4.01805098805014E-17i
+     *
+     ***************************************************************************/
+
+    public static void main(String[] args) {
+        int n = Integer.parseInt(args[0]);
+        Complex[] x = new Complex[n];
+
+        // original data
+        for (int i = 0; i < n; i++) {
+            x[i] = new Complex(i, 0);
+        }
+        show(x, "x");
+
+        // FFT of original data
+        Complex[] y = fft(x);
+        show(y, "y = fft(x)");
+
+        // FFT of original data
+        Complex[] y2 = dft(x);
+        show(y2, "y2 = dft(x)");
+
+        // take inverse FFT
+        Complex[] z = ifft(y);
+        show(z, "z = ifft(y)");
+
+        // circular convolution of x with itself
+        Complex[] c = cconvolve(x, x);
+        show(c, "c = cconvolve(x, x)");
+
+        // linear convolution of x with itself
+        Complex[] d = convolve(x, x);
+        show(d, "d = convolve(x, x)");
+    }
+}
+
+

app/src/main/java/com/example/ueberwachungssystem/logger/Logger.java

@@ -0,0 +1,61 @@
+package com.example.ueberwachungssystem.logger;
+
+import android.util.Log;
+import android.widget.TextView;
+
+import java.io.PrintWriter;
+import java.io.StringWriter;
+
+public class Logger {
+    private TextView textView; 
+    private StringBuffer sb = new StringBuffer(); 
+    private String tag;
+    private int lengthOfLastLog = 0;
+    private boolean overwrite = false;
+
+    public Logger(String tag, TextView textView, String logInitText)  {
+        this.tag = tag;
+        this.textView = textView;
+        sb.append(logInitText);
+    }
+
+    public void log(String s)  {
+        overwrite = false;
+        Log.d(tag, s);
+        sb.append(s).append("\n");
+        if (textView != null) {
+            textView.setText(sb.toString());
+        }
+    }
+
+    public void overwriteLastlog(String s)  {
+        Log.d(tag, s);
+        lengthOfLastLog = s.length();
+        if (overwrite)
+        {
+            sb.setLength(sb.length() - (lengthOfLastLog + 1));
+        }
+        sb.append(s).append("\n");
+        overwrite = true;
+        if (textView != null) {
+            textView.setText(sb.toString());
+        }
+    }
+
+    public void log(Exception e)  {
+        StringWriter sw = new StringWriter();
+        e.printStackTrace(new PrintWriter(sw));
+        log(sw.toString());
+    }
+
+    public void clearLog()  {
+        sb.setLength(0);
+        if (textView != null) {
+            textView.setText("");
+        }
+    }
+
+    public String getLoggedText()  {
+        return sb.toString();
+    }
+}

app/src/main/res/layout/activity_main.xml

@@ -1,18 +1,56 @@
 <?xml version="1.0" encoding="utf-8"?>
-<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
+    android:layout_gravity="center"
+    android:gravity="top"
+    android:orientation="vertical"
     tools:context=".MainActivity">
 
+
     <TextView
-        android:layout_width="wrap_content"
+        android:id="@+id/textView"
+        android:layout_width="match_parent"
+        android:layout_height="100dp"
+        android:text="TextView" />
+
+    <androidx.camera.view.PreviewView
+        android:id="@+id/previewView"
+        android:layout_width="match_parent"
         android:layout_height="wrap_content"
-        android:text="Hello World!"
+        android:backgroundTint="@android:color/black"/>
+
+    <ToggleButton
+        android:id="@+id/toggleButton"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:text="ToggleButton" />
+
+    <ImageView
+        android:id="@+id/inputImageView"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        tools:srcCompat="@tools:sample/avatars" />
+
+    <ImageView
+        android:id="@+id/outputImageView"
+        android:layout_width="match_parent"
+        android:layout_height="1dp"
+        tools:srcCompat="@tools:sample/avatars" />
+
+    <com.jjoe64.graphview.GraphView
+        android:id="@+id/graph"
+        android:layout_width="match_parent"
+        android:layout_height="200dip"
+        android:layout_marginStart="16dp"
+        android:layout_marginEnd="16dp"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toTopOf="parent" />
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintVertical_bias="0.499" />
 
-</androidx.constraintlayout.widget.ConstraintLayout>
+
+</LinearLayout>

gradle.properties

@@ -18,4 +18,5 @@ android.useAndroidX=true
 # Enables namespacing of each library's R class so that its R class includes only the
 # resources declared in the library itself and none from the library's dependencies,
 # thereby reducing the size of the R class for that library
-android.nonTransitiveRClass=true
+android.nonTransitiveRClass=true
+android.enableJetifier=true