Real time zoom in Camera2

Question

I am a bit of a newbie and trying to build an app based on https://inducesmile.com/android/android-camera2-api-example-tutorial/ to assist a hard of sight individual. I need to use a Bluetooth game controller to control the zoom level in real time- when a button is pressed, the zoom level changes. I have removed the "Take Picture" button and top banner so that I can use full screen. I have tried to change the zoom level in different methods: createCameraPreview, updatePreview and dispatchKeyEvent but its not working. Where should I apply the new captureRequestBuilder with the updated zoom Rect? Thanks.

+import ...

public class AndroidCameraApi extends AppCompatActivity {
    private static final String TAG = "AndroidCameraApi";
    private TextureView textureView;
    private static final SparseIntArray ORIENTATIONS = new SparseIntArray();
    static {
        ORIENTATIONS.append(Surface.ROTATION_0, 90);
        ORIENTATIONS.append(Surface.ROTATION_90, 0);
        ORIENTATIONS.append(Surface.ROTATION_180, 270);
        ORIENTATIONS.append(Surface.ROTATION_270, 180);
    }
    private String cameraId;
    protected CameraDevice cameraDevice;
    protected CameraCaptureSession cameraCaptureSessions;
    protected CaptureRequest captureRequest;
    protected CaptureRequest.Builder captureRequestBuilder;
    private Size imageDimension;
    private ImageReader imageReader;
    private File file;
    private static final int REQUEST_CAMERA_PERMISSION = 200;
    private boolean mFlashSupported;
    private Handler mBackgroundHandler;
    private HandlerThread mBackgroundThread;

    private int kc;    //kc is keyCode from bluetooth controller
    Rect zoomCropPreview = new Rect(1094, 822, 2186, 1642);    //zoomed in
    //Rect zoomCropPreview = new Rect(0,0,4032,3024);   //full screen

    @Override
    protected void onCreate(Bundle savedInstanceState) {              //onCreate set up layout, texture, take pciture button
        super.onCreate(savedInstanceState);
        //this.requestWindowFeature(Window.FEATURE_NO_TITLE);    //remove title bar
        this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);   //remove notification mar
        setContentView(R.layout.activity_android_camera_api);
        textureView = (TextureView) findViewById(R.id.texture);    //set up texture
        assert textureView != null;
        textureView.setSurfaceTextureListener(textureListener);
    }

    TextureView.SurfaceTextureListener textureListener = new TextureView.SurfaceTextureListener() {
        @Override
        public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
            //open your camera here
            openCamera();
        }
    };

    private void openCamera() {
        CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
        Log.e(TAG, "is camera open");
        try {
            cameraId = manager.getCameraIdList()[0];
            CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
            Float maxDigitalZoom = characteristics.get(CameraCharacteristics.SCALER_AVAILABLE_MAX_DIGITAL_ZOOM);    //get maximum digital zoom (=8)
            Rect asd = characteristics.get(CameraCharacteristics.SENSOR_INFO_ACTIVE_ARRAY_SIZE);
            StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
            assert map != null;
            imageDimension = map.getOutputSizes(SurfaceTexture.class)[0];
            // Add permission for camera and let user grant the permission
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(AndroidCameraApi.this, new String[]{Manifest.permission.CAMERA, Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_CAMERA_PERMISSION);
                return;
            }
            manager.openCamera(cameraId, stateCallback, null);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
        Log.e(TAG, "openCamera X");
    }

    private final CameraDevice.StateCallback stateCallback = new CameraDevice.StateCallback() {
        @Override
        public void onOpened(CameraDevice camera) {
            //This is called when the camera is open
            Log.e(TAG, "onOpened");
            cameraDevice = camera;
            createCameraPreview();
        }

        @Override
        public void onDisconnected(CameraDevice camera) {
            cameraDevice.close();
        }

        @Override
        public void onError(CameraDevice camera, int error) {
            cameraDevice.close();
            cameraDevice = null;
        }
    };

    protected void createCameraPreview() {
        try {
            SurfaceTexture texture = textureView.getSurfaceTexture();
            assert texture != null;
            texture.setDefaultBufferSize(imageDimension.getWidth(), imageDimension.getHeight());
            Surface surface = new Surface(texture);
            captureRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
            captureRequestBuilder.addTarget(surface);
            //try to change zoom- didn't work
            //captureRequestBuilder.set(CaptureRequest.SCALER_CROP_REGION, zoomCropPreview);
            cameraDevice.createCaptureSession(Arrays.asList(surface), new CameraCaptureSession.StateCallback() {
                @Override
                public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {
                    //The camera is already closed
                    if (null == cameraDevice) {
                        return;
                    }
                    // When the session is ready, we start displaying the preview.
                    //try to change zoom here- didn't work
                    //captureRequestBuilder.set(CaptureRequest.SCALER_CROP_REGION, zoomCropPreview);
                    cameraCaptureSessions = cameraCaptureSession;
                    updatePreview();                    //update preview screen
                }

                @Override
                public void onConfigureFailed(@NonNull CameraCaptureSession cameraCaptureSession) {
                    Toast.makeText(AndroidCameraApi.this, "Configuration change", Toast.LENGTH_SHORT).show();
                }
            }, null);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    protected void updatePreview() {
        if (null == cameraDevice) {
            Log.e(TAG, "updatePreview error, return");
        }
// Original
        //captureRequestBuilder.set(CaptureRequest.CONTROL_MODE, CameraMetadata.CONTROL_MODE_AUTO);
//Modified
        captureRequestBuilder.set(CaptureRequest.SCALER_CROP_REGION, zoomCropPreview);
        try {
            cameraCaptureSessions.setRepeatingRequest(captureRequestBuilder.build(), null, mBackgroundHandler);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

//********************************
// Change zoom based on Bluetooth controller
//********************************
    @Override
    public boolean dispatchKeyEvent(KeyEvent event) {
        kc = event.getKeyCode();
        Log.i("key pressed", String.valueOf(kc));
//as a test, just change from zoomed in to full screen
        zoomCropPreview.set(0,0,4032,3024);     //change to full screen
        Log.i("zoomCropPreview", (zoomCropPreview).flattenToString());
        //try to change zoom- didn't work
        captureRequestBuilder.set(CaptureRequest.SCALER_CROP_REGION, zoomCropPreview);
        return super.dispatchKeyEvent(event);
    }

    final CameraCaptureSession.CaptureCallback captureCallbackListener = new CameraCaptureSession.CaptureCallback() {
        @Override
        public void onCaptureCompleted(CameraCaptureSession session, CaptureRequest request, TotalCaptureResult result) {
            super.onCaptureCompleted(session, request, result);
            Toast.makeText(AndroidCameraApi.this, "Saved:" + file, Toast.LENGTH_SHORT).show();
            createCameraPreview();
        }
    };

    protected void startBackgroundThread() {
        mBackgroundThread = new HandlerThread("Camera Background");
        mBackgroundThread.start();
        mBackgroundHandler = new Handler(mBackgroundThread.getLooper());
    }

    protected void stopBackgroundThread() {
        mBackgroundThread.quitSafely();
        try {
            mBackgroundThread.join();
            mBackgroundThread = null;
            mBackgroundHandler = null;
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    private void closeCamera() {
        if (null != cameraDevice) {
            cameraDevice.close();
            cameraDevice = null;
        }
        if (null != imageReader) {
            imageReader.close();
            imageReader = null;
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if (requestCode == REQUEST_CAMERA_PERMISSION) {
            if (grantResults[0] == PackageManager.PERMISSION_DENIED) {
                // close the app
                Toast.makeText(AndroidCameraApi.this, "Sorry!!!, you can't use this app without granting permission", Toast.LENGTH_LONG).show();
                finish();
            }
        }
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.e(TAG, "onResume");
        startBackgroundThread();
        if (textureView.isAvailable()) {
            openCamera();
        } else {
            textureView.setSurfaceTextureListener(textureListener);
        }
    }

    @Override
    protected void onPause() {
        Log.e(TAG, "onPause");
        //closeCamera();
        stopBackgroundThread();
        super.onPause();
    }
}    

Answer 1

You need to call cameraCaptureSessions.setRepeatingRequest again after you've updated all the settings in captureRequestBuilder.

Just updating the builder does nothing on its own, it's just modifying a bundle of settings. You need to tell the camera to actually use the new bundle for anything to happen.