added Functions to VideoDetector:

startDetection(), stopDetection(), isRunning()

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

 import androidx.appcompat.app.AppCompatActivity;
 import androidx.camera.core.Camera;
 import androidx.camera.core.CameraSelector;
-import androidx.camera.core.ImageAnalysis;
-import androidx.camera.core.ImageProxy;
 import androidx.camera.core.Preview;
 import androidx.camera.lifecycle.ProcessCameraProvider;
 import androidx.camera.view.PreviewView;
 
 import android.Manifest;
 import android.content.pm.PackageManager;
-import android.graphics.ImageFormat;
-import android.media.Image;
 import android.os.Bundle;
-import android.util.Log;
-import android.util.Size;
 import android.view.View;
 import android.widget.Button;
 import android.widget.TextView;
 
 import com.google.common.util.concurrent.ListenableFuture;
 
-import java.nio.ByteBuffer;
 import java.util.concurrent.ExecutionException;
 
 @ExperimentalGetImage
     private TextView textView;
     private Button previewButton;
     private Boolean cameraPreviewIsRunning = false;
+    private Boolean isPressed = false;
 
 
     @Override
 
 
         VideoDetector vd = new VideoDetector(this);
+        vd.startDetection();
 
         previewButton.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
                 getCameraAccess();
-                if (isCameraAccessAllowed())
-                    vd.runImageAnalysis();
+                if (isCameraAccessAllowed() && !isPressed)
+                {
+                    vd.stopDetection();
+                    isPressed = true;
+                }
+                else if (isCameraAccessAllowed() && isPressed) {
+                    vd.startDetection();
+                    isPressed = false;
+                }
             }
         });
     }
 
-
-
     private boolean isCameraAccessAllowed() {
         return ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED;
     }

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

 import java.nio.ByteBuffer;
 import java.util.concurrent.ExecutionException;
 
-
 @ExperimentalGetImage
 public class VideoDetector {
 
     private final Context context;
-    private float currentLuminosity;
-
+    private ProcessCameraProvider cameraProvider;
+    private Boolean isDetectionRunning = false;
+    //private float currentLuminosity;
 
+    /** Constructor */
     public VideoDetector(Context context) {
         this.context = context;
     }
 
-    public void runImageAnalysis() {
+    /** Return State of Video Detector */
+    public Boolean isRunning() {
+        return isDetectionRunning;
+    }
+
+    /** Starts Video Detection */
+    public void startDetection() {
+        isDetectionRunning = true;
         // Request Camera Provider
         final ListenableFuture<ProcessCameraProvider> cameraProviderFuture = ProcessCameraProvider.getInstance(context);
         //Check for Camera availability
             @Override
             public void run() {
                 try {
-                    ProcessCameraProvider cameraProvider = cameraProviderFuture.get();
-                    bindImageAnalysis(cameraProvider);
+                    cameraProvider = cameraProviderFuture.get();
+                    bindLuminosityAnalysis(cameraProvider);
                 } catch (ExecutionException | InterruptedException e) {
                     // No errors need to be handled for this Future. This should never be reached.
                 }
         },ContextCompat.getMainExecutor(context));
     }
 
-    private void bindImageAnalysis(@NonNull ProcessCameraProvider cameraProvider) {
+    /** Stops Video Detection */
+    public void stopDetection() {
+        cameraProvider.unbindAll();
+        isDetectionRunning = false;
+    }
+
+    /** 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));
                     Image image = imageProxy.getImage();
                     assert image != null;
 
+                    // Analyze frame
                     float luminosity = calculateLuminosity(image);
-                    currentLuminosity = luminosity;
                     Log.d("Video Detector", String.valueOf(luminosity));
                 }
                 imageProxy.close();
         cameraProvider.bindToLifecycle((LifecycleOwner) context, cameraSelector, imageAnalysis, preview);
     }
 
-
+    /** Return Luminosity from Image */
     private float calculateLuminosity (Image image) {
         int width = image.getWidth();
         int height = image.getHeight();