Refactor

startDetection(), stopDetection(), isRunning()

app/build.gradle

@@ -36,4 +36,13 @@ dependencies {
     testImplementation 'junit:junit:4.13.2'
     androidTestImplementation 'androidx.test.ext:junit:1.1.5'
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'
+
+    // 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}"
 }

app/src/main/AndroidManifest.xml

@@ -2,6 +2,9 @@
 <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"/>
+
     <application
         android:allowBackup="true"
         android:dataExtractionRules="@xml/data_extraction_rules"

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 +1,38 @@
+package com.example.ueberwachungssystem;
+
+import androidx.annotation.NonNull;
+
+
+abstract public class Detector {
+    private OnDetectionListener listener;
+
+    /** 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 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

@@ -1,14 +1,86 @@
 package com.example.ueberwachungssystem;
 
+import androidx.annotation.NonNull;
 import androidx.appcompat.app.AppCompatActivity;
+import androidx.camera.view.PreviewView;
+import androidx.core.app.ActivityCompat;
+import androidx.core.content.ContextCompat;
+import androidx.camera.core.ExperimentalGetImage;
 
+import android.Manifest;
+import android.content.pm.PackageManager;
 import android.os.Bundle;
+import android.view.View;
+import android.widget.TextView;
+import android.widget.Toast;
+import android.widget.ToggleButton;
 
+import com.example.ueberwachungssystem.VideoDetection.VideoDetector;
+
+@ExperimentalGetImage
 public class MainActivity extends AppCompatActivity {
 
+    private static final int CAMERA_PERMISSION_REQUEST_CODE = 101;
+
+
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
+
+        TextView textView = findViewById(R.id.textView);
+        PreviewView previewView = findViewById(R.id.previewView);
+
+
+        VideoDetector vd = new VideoDetector(this);
+        vd.setPreviewView(previewView);
+        vd.setOnDetectionListener(new VideoDetector.OnDetectionListener() {
+            @Override
+            public void onDetection(@NonNull DetectionReport detectionReport) {
+                detectionReport.log("OnDetection");
+                textView.setText(detectionReport.toString());
+            }
+        });
+        //vd.startDetection();
+
+
+        ToggleButton toggleButton = findViewById(R.id.previewButton);
+        toggleButton.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                getCameraAccess();
+                if (isCameraAccessAllowed() && toggleButton.isChecked())
+                {
+                    vd.startDetection();
+                }
+                else {
+                    vd.stopDetection();
+                    textView.setText("");
+                }
+            }
+        });
+    }
+
+    private boolean isCameraAccessAllowed() {
+        return ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED;
+    }
+
+    private void getCameraAccess() {
+        if (!isCameraAccessAllowed())
+            ActivityCompat.requestPermissions(this, new String[]{android.Manifest.permission.CAMERA}, CAMERA_PERMISSION_REQUEST_CODE);
+    }
+
+    @Override
+    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
+        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
+
+        if (requestCode == CAMERA_PERMISSION_REQUEST_CODE && grantResults.length > 0) {
+            boolean cameraRights = grantResults[0] == PackageManager.PERMISSION_GRANTED;
+            if (cameraRights) {
+                Toast.makeText(this, "camera permission granted", Toast.LENGTH_LONG).show();
+            } else {
+                Toast.makeText(this, "camera permission denied", Toast.LENGTH_LONG).show();
+            }
+        }
     }
 }

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

@@ -0,0 +1,165 @@
+package com.example.ueberwachungssystem.VideoDetection;
+
+import android.content.Context;
+import android.graphics.ImageFormat;
+import android.media.Image;
+import android.util.Size;
+
+import androidx.annotation.NonNull;
+import androidx.camera.core.CameraSelector;
+import androidx.camera.core.ExperimentalGetImage;
+import androidx.camera.core.ImageAnalysis;
+import androidx.camera.core.Preview;
+import androidx.camera.lifecycle.ProcessCameraProvider;
+import androidx.camera.view.PreviewView;
+import androidx.core.content.ContextCompat;
+import androidx.lifecycle.LifecycleOwner;
+
+import com.example.ueberwachungssystem.Detector;
+import com.google.common.util.concurrent.ListenableFuture;
+
+import java.nio.ByteBuffer;
+import java.util.concurrent.ExecutionException;
+
+@ExperimentalGetImage
+public class VideoDetector extends Detector {
+
+    // Calling Activity
+    private final Context context;
+    // Camera Provider
+    private ProcessCameraProvider cameraProvider;
+    private Boolean isDetectionRunning = false;
+    // Preview Camera Image
+    private PreviewView previewView = null;
+    // Detect Violation
+    private static final float PIXEL_THRESHOLD = 30f;  // Luminosity (brightness channel of YUV_420_888)
+    private static final float ALARM_THRESHOLD = 1f;   // Percent of pixels changed
+    private ByteBuffer previousBuffer = null;
+
+
+
+    /** Constructor */
+    public VideoDetector(Context context) {
+        super();
+        this.context = context;
+    }
+
+
+    /** Starts Video Detection */
+    @Override
+    public void startDetection() {
+        if (isDetectionRunning)
+            return;
+        // Request Camera Provider
+        final ListenableFuture<ProcessCameraProvider> cameraProviderFuture = ProcessCameraProvider.getInstance(context);
+        //Check for Camera availability
+        cameraProviderFuture.addListener(() -> {
+            try {
+                cameraProvider = cameraProviderFuture.get();
+                bindLuminosityAnalysis(cameraProvider);
+                isDetectionRunning = true;
+                previousBuffer = null;
+            } catch (ExecutionException | InterruptedException e) {
+                // No errors need to be handled for this Future. This should never be reached.
+            }
+        },ContextCompat.getMainExecutor(context));
+    }
+
+
+    /** Stops Video Detection */
+    @Override
+    public void stopDetection() {
+        if (!isDetectionRunning)
+            return;
+        cameraProvider.unbindAll();
+        isDetectionRunning = false;
+    }
+
+
+    /** Set PreviewView to show Image */
+    public void setPreviewView(PreviewView previewView) {
+        this.previewView = previewView;
+    }
+
+
+    /** Binds the Luminosity Analyzer (configure and run Analysis) */
+    private void bindLuminosityAnalysis(@NonNull ProcessCameraProvider cameraProvider) {
+        // Configure and create Image Analysis
+        ImageAnalysis.Builder builder = new ImageAnalysis.Builder();
+        builder.setTargetResolution(new Size(640, 480));
+        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;
+
+                // Changed Pixel Detection
+                int pixelChanged = getChangedPixelCount(image);
+                int width = image.getWidth();
+                int height = image.getHeight();
+
+                float percentPixelChanged = (float) 100f * pixelChanged / (width * height);
+
+                if (percentPixelChanged > ALARM_THRESHOLD)
+                    reportViolation("0", "Video", percentPixelChanged);
+            }
+            imageProxy.close();
+        });
+        // Create Preview
+        Preview preview = new Preview.Builder().build();
+        // Specify which Camera to use
+        CameraSelector cameraSelector = new CameraSelector.Builder().requireLensFacing(CameraSelector.LENS_FACING_BACK).build();
+        // Update PreviewView if set
+        if (previewView != null)
+            preview.setSurfaceProvider(previewView.getSurfaceProvider());
+
+        cameraProvider.bindToLifecycle((LifecycleOwner) context, cameraSelector, imageAnalysis, preview);
+    }
+
+
+
+    /** Calculate Amount of Pixels changed */
+    private int getChangedPixelCount(Image image) {
+        Image.Plane[] planes = image.getPlanes();
+        ByteBuffer buffer = planes[0].getBuffer();
+
+        if (previousBuffer == null) {
+            previousBuffer = ByteBuffer.allocate(buffer.capacity());
+            buffer.rewind();
+            previousBuffer.put(buffer);
+            previousBuffer.rewind();
+            return 0;
+        }
+
+        int width = image.getWidth();
+        int height = image.getHeight();
+
+        int yRowStride = image.getPlanes()[0].getRowStride();
+        int yPixelStride = image.getPlanes()[0].getPixelStride();
+
+        int changedPixelCount = 0;
+
+        // Count changed pixels
+        for (int y = 0; y < height; ++y) {
+            for (int x = 0; x < width; x++) {
+                int index = (y * yRowStride) + (x * yPixelStride);
+                int luminosity = (buffer.get(index) & 0xff);
+                int previousLuminosity = (previousBuffer.get(index) & 0xff);
+                int diff = Math.abs(luminosity - previousLuminosity);
+                if (diff > PIXEL_THRESHOLD)
+                    changedPixelCount++;
+            }
+        }
+
+        // Reset and copy Byte Buffer
+        buffer.rewind();
+        previousBuffer.rewind();
+        previousBuffer.put(buffer);
+
+        return changedPixelCount;
+    }
+}

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

@@ -1,18 +1,37 @@
 <?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="center"
+    android:orientation="vertical"
     tools:context=".MainActivity">
 
     <TextView
+        android:id="@+id/textView"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:text="Hello World!"
+        android:text=""
+        android:textSize="20dp"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent"
         app:layout_constraintTop_toTopOf="parent" />
 
-</androidx.constraintlayout.widget.ConstraintLayout>
+
+    <ToggleButton
+        android:id="@+id/previewButton"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:text="ToggleButton" />
+
+
+    <androidx.camera.view.PreviewView
+        android:id="@+id/previewView"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:backgroundTint="@android:color/black"/>
+
+</LinearLayout>