Zoomable Camera2Preview, but cannot gain focus on 2nd capture after zoomed.

Camear2Preview.java

package cameraview.com.cameraview;

import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.ImageFormat;
import android.graphics.Matrix;
import android.graphics.Point;
import android.graphics.Rect;
import android.graphics.RectF;
import android.graphics.SurfaceTexture;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraCaptureSession;
import android.hardware.camera2.CameraCharacteristics;
import android.hardware.camera2.CameraDevice;
import android.hardware.camera2.CameraManager;
import android.hardware.camera2.CameraMetadata;
import android.hardware.camera2.CaptureRequest;
import android.hardware.camera2.CaptureResult;
import android.hardware.camera2.TotalCaptureResult;
import android.hardware.camera2.params.StreamConfigurationMap;
import android.media.Image;
import android.media.ImageReader;
import android.os.Handler;
import android.os.HandlerThread;
import android.support.annotation.NonNull;
import android.util.AttributeSet;
import android.util.Log;
import android.util.Size;
import android.util.SparseIntArray;
import android.view.MotionEvent;
import android.view.Surface;
import android.view.TextureView;

import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;

/**
 * The Camera Preview, using Camera 2 Engine.
 * I would say Camera 2 is just fxxking hard to understand and implement by yourself.
 * Most of the code here is a copy of https://github.com/googlesamples/android-Camera2Basic
 * But adding the front and back camera switching, as well as configurable aspect ratio.
 */

@SuppressLint("NewApi")
public class Camera2Preview extends TextureView {

    public static final String TAG = "Camera2Preview";

    public static final int BACK_CAMERA = CameraCharacteristics.LENS_FACING_BACK;
    public static final int FRONT_CAMERA = CameraCharacteristics.LENS_FACING_FRONT;

    protected Context context;
    protected float aspectRatio = 0.75f;
    private static final float aspectRatioThreshold = 0.05f;

    private String cameraId;
    private int facing = BACK_CAMERA;
    protected CameraDevice cameraDevice;
    protected CameraCharacteristics cameraCharacteristics;
    protected CameraCaptureSession captureSession;
    protected CaptureRequest previewRequest;
    protected CaptureRequest.Builder previewRequestBuilder;
    protected Size previewSize;
    protected int sensorOrientation;

    //Lock
    private Semaphore cameraOpenCloseLock = new Semaphore(1);
    private int state = STATE_PREVIEW;
    private static final int STATE_PREVIEW = 0;
    private static final int STATE_WAITING_LOCK = 1;
    private static final int STATE_WAITING_PRECAPTURE = 2;
    private static final int STATE_WAITING_NON_PRECAPTURE = 3;
    private static final int STATE_PICTURE_TAKEN = 4;

    //Zooming
    public float fingerSpacing = 0;
    public float zoomLevel = 1f;
    public float maximumZoomLevel;
    public Rect zoom;

    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 ImageReader imageReader;
    private Handler backgroundHandler;
    private HandlerThread backgroundThread;

    protected OnPictureTakenListener onPictureTakenListener;
    protected CameraView.OnCameraErrorListener cameraErrorCallback;
    protected CameraView.OnFocusLockedListener focusLockedCallback;

    private final TextureView.SurfaceTextureListener surfaceTextureListener
            = new TextureView.SurfaceTextureListener() {

        @Override
        public void onSurfaceTextureAvailable(SurfaceTexture texture, int width, int height) {
            openCamera(width, height);
        }

        @Override
        public void onSurfaceTextureSizeChanged(SurfaceTexture texture, int width, int height) {
            configureTransform(width, height);
        }

        @Override
        public boolean onSurfaceTextureDestroyed(SurfaceTexture texture) {
            return true;
        }

        @Override
        public void onSurfaceTextureUpdated(SurfaceTexture texture) {
        }

    };

    private final CameraDevice.StateCallback stateCallback = new CameraDevice.StateCallback() {

        @Override
        public void onOpened(@NonNull CameraDevice cameraDevice) {
            // This method is called when the camera is opened.  We start camera preview here.
            cameraOpenCloseLock.release();
            Camera2Preview.this.cameraDevice = cameraDevice;
            createCameraPreviewSession();
        }

        @Override
        public void onDisconnected(@NonNull CameraDevice cameraDevice) {
            cameraOpenCloseLock.release();
            cameraDevice.close();
            Camera2Preview.this.cameraDevice = null;
        }

        @Override
        public void onError(@NonNull CameraDevice cameraDevice, int error) {
            cameraOpenCloseLock.release();
            cameraDevice.close();
            Camera2Preview.this.cameraDevice = null;
        }

    };

    private final ImageReader.OnImageAvailableListener onImageAvailableListener
            = new ImageReader.OnImageAvailableListener() {
        @SuppressLint("NewApi")
        @Override
        public void onImageAvailable(ImageReader reader) {
            Image image = null;
            try {
                if (onPictureTakenListener == null) return;
                image = reader.acquireLatestImage();
                ByteBuffer buffer = image.getPlanes()[0].getBuffer();
                byte[] bytes = new byte[buffer.capacity()];
                buffer.get(bytes);
                onPictureTakenListener.onPictureTaken(bytes);
                image.close();
            } catch (final Exception e) {
                if (cameraErrorCallback != null) {
                    post(new Runnable() {
                        @Override
                        public void run() {
                            cameraErrorCallback.onCameraError(e);
                        }
                    });
                }
            }
        }

    };


    private CameraCaptureSession.CaptureCallback captureCallback
            = new CameraCaptureSession.CaptureCallback() {

        private void process(CaptureResult result) {
            switch (state) {
                case STATE_PREVIEW: {
                    // We have nothing to do when the camera preview is working normally.
                    break;
                }
                case STATE_WAITING_LOCK: {
                    Integer afState = result.get(CaptureResult.CONTROL_AF_STATE);
                    Log.i("cameraFocus", "" + afState);
                    if (afState == null) {
                        captureStillPicture();
                    } else if (CaptureResult.CONTROL_AF_STATE_FOCUSED_LOCKED == afState ||
                            CaptureResult.CONTROL_AF_STATE_NOT_FOCUSED_LOCKED == afState ||
                            CaptureResult.CONTROL_AF_STATE_INACTIVE == afState /*add this*/) {
                        // CONTROL_AE_STATE can be null on some devices
                        Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);
                        if (aeState == null ||
                                aeState == CaptureResult.CONTROL_AE_STATE_CONVERGED) {
                            state = STATE_PICTURE_TAKEN;
                            captureStillPicture();
                        } else {
                            runPrecaptureSequence();
                        }
                    }
                    break;
                }
                case STATE_WAITING_PRECAPTURE: {
                    // CONTROL_AE_STATE can be null on some devices
                    Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);
                    if (aeState == null ||
                            aeState == CaptureResult.CONTROL_AE_STATE_PRECAPTURE ||
                            aeState == CaptureRequest.CONTROL_AE_STATE_FLASH_REQUIRED) {
                        state = STATE_WAITING_NON_PRECAPTURE;
                    }
                    break;
                }
                case STATE_WAITING_NON_PRECAPTURE: {
                    // CONTROL_AE_STATE can be null on some devices
                    Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);
                    if (aeState == null || aeState != CaptureResult.CONTROL_AE_STATE_PRECAPTURE) {
                        state = STATE_PICTURE_TAKEN;
                        captureStillPicture();
                    }
                    break;
                }
            }
        }

        @Override
        public void onCaptureProgressed(@NonNull CameraCaptureSession session,
                                        @NonNull CaptureRequest request,
                                        @NonNull CaptureResult partialResult) {
            process(partialResult);
        }

        @Override
        public void onCaptureCompleted(@NonNull CameraCaptureSession session,
                                       @NonNull CaptureRequest request,
                                       @NonNull TotalCaptureResult result) {
            process(result);
        }

    };


    public Camera2Preview(Context context) {
        super(context);
        init(context);
    }


    public Camera2Preview(Context context, float aspectRatio) {
        super(context);
        this.aspectRatio = aspectRatio;
        init(context);
    }

    public Camera2Preview(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context);
    }

    public Camera2Preview(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(context);
    }

    private void init(Context context) {
        this.context = context;
    }


    private static Size chooseOptimalSize(Size[] choices, int textureViewWidth,
                                          int textureViewHeight, int maxWidth, int maxHeight, Size aspectRatio) {

        // Collect the supported resolutions that are at least as big as the preview Surface
        List<Size> bigEnough = new ArrayList<>();
        // Collect the supported resolutions that are smaller than the preview Surface
        List<Size> notBigEnough = new ArrayList<>();
        int w = aspectRatio.getWidth();
        int h = aspectRatio.getHeight();
        for (Size option : choices) {
            if (option.getWidth() <= maxWidth && option.getHeight() <= maxHeight &&
                    option.getHeight() == option.getWidth() * h / w) {
                if (option.getWidth() >= textureViewWidth &&
                        option.getHeight() >= textureViewHeight) {
                    bigEnough.add(option);
                } else {
                    notBigEnough.add(option);
                }
            }
        }

        // Pick the smallest of those big enough. If there is no one big enough, pick the
        // largest of those not big enough.
        if (bigEnough.size() > 0) {
            return Collections.min(bigEnough, new CompareSizesByArea());
        } else if (notBigEnough.size() > 0) {
            return Collections.max(notBigEnough, new CompareSizesByArea());
        } else {
            Log.e(TAG, "Couldn't find any suitable preview size");
            return choices[0];
        }
    }

    private void setUpCameraOutputs(int width, int height) {
        CameraManager manager = (CameraManager) context.getSystemService(Context.CAMERA_SERVICE);
        String cameraId = null;
        try {
            for (String each : manager.getCameraIdList()) {
                if (this.facing == manager.getCameraCharacteristics(each).get(CameraCharacteristics.LENS_FACING)) {
                    cameraId = each;
                    break;
                }
            }
            if (cameraId == null) throw new Exception("No correct facing camera is found.");
            CameraCharacteristics characteristics
                    = manager.getCameraCharacteristics(cameraId);
            cameraCharacteristics = characteristics;

            maximumZoomLevel = (characteristics.get(CameraCharacteristics.SCALER_AVAILABLE_MAX_DIGITAL_ZOOM));

            StreamConfigurationMap map = characteristics.get(
                    CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
            if (map == null) {
                throw new Exception("configuration map is null.");
            }

            // For still image captures, we use the largest available size.
            Size largest;
            ArrayList<Size> sizes = new ArrayList<>();
            for (Size each : map.getOutputSizes(ImageFormat.JPEG)) {
                float thisAspect = (float) each.getHeight() / each.getWidth();
                if ((Math.abs(thisAspect - aspectRatio)) < aspectRatioThreshold) {
                    sizes.add(each);
                }
            }
            if (sizes.size() == 0) return;
            largest = Collections.max(sizes, new CompareSizesByArea());
            imageReader = ImageReader.newInstance(largest.getWidth(), largest.getHeight(),
                    ImageFormat.JPEG, /*maxImages*/3);
            imageReader.setOnImageAvailableListener(
                    onImageAvailableListener, backgroundHandler);

            // Find out if we need to swap dimension to get the preview size relative to sensor
            // coordinate.
            int displayRotation = getDisplay().getRotation();
            //noinspection ConstantConditions
            sensorOrientation = characteristics.get(CameraCharacteristics.SENSOR_ORIENTATION);
            boolean swappedDimensions = false;
            switch (displayRotation) {
                case Surface.ROTATION_0:
                case Surface.ROTATION_180:
                    if (sensorOrientation == 90 || sensorOrientation == 270) {
                        swappedDimensions = true;
                    }
                    break;
                case Surface.ROTATION_90:
                case Surface.ROTATION_270:
                    if (sensorOrientation == 0 || sensorOrientation == 180) {
                        swappedDimensions = true;
                    }
                    break;
                default:
                    Log.e(TAG, "Display rotation is invalid: " + displayRotation);
            }

            Point displaySize = new Point();
            getDisplay().getSize(displaySize);
            int rotatedPreviewWidth = width;
            int rotatedPreviewHeight = height;
            int maxPreviewWidth = displaySize.x;
            int maxPreviewHeight = displaySize.y;

            if (swappedDimensions) {
                rotatedPreviewWidth = height;
                rotatedPreviewHeight = width;
                maxPreviewWidth = displaySize.y;
                maxPreviewHeight = displaySize.x;
            }

            // Danger, W.R.! Attempting to use too large a preview size could  exceed the camera
            // bus' bandwidth limitation, resulting in gorgeous previews but the storage of
            // garbage capture data.
            previewSize = chooseOptimalSize(map.getOutputSizes(SurfaceTexture.class),
                    rotatedPreviewWidth, rotatedPreviewHeight, maxPreviewWidth,
                    maxPreviewHeight, largest);

            this.cameraId = cameraId;
        } catch (final Exception e) {
            if (cameraErrorCallback != null) {
                post(new Runnable() {
                    @Override
                    public void run() {
                        cameraErrorCallback.onCameraError(e);
                    }
                });
            }
        }
    }

    @SuppressLint("MissingPermission")
    private void openCamera(int width, int height) {
        setUpCameraOutputs(width, height);
        configureTransform(width, height);
        CameraManager manager = (CameraManager) context.getSystemService(Context.CAMERA_SERVICE);
        try {
            if (!cameraOpenCloseLock.tryAcquire(2500, TimeUnit.MILLISECONDS)) {
                throw new RuntimeException("Time out waiting to lock camera opening.");
            }
            manager.openCamera(cameraId, stateCallback, backgroundHandler);
        } catch (final Exception e) {
            if (cameraErrorCallback != null) {
                post(new Runnable() {
                    @Override
                    public void run() {
                        cameraErrorCallback.onCameraError(e);
                    }
                });
            }
        }
    }

    private void closeCamera() {
        try {
            cameraOpenCloseLock.acquire();
            if (null != captureSession) {
                captureSession.close();
                captureSession = null;
            }
            if (null != cameraDevice) {
                cameraDevice.close();
                cameraDevice = null;
            }
            if (null != imageReader) {
                imageReader.close();
                imageReader = null;
            }
        } catch (InterruptedException e) {
            throw new RuntimeException("Interrupted while trying to lock camera closing.", e);
        } finally {
            cameraOpenCloseLock.release();
        }
    }

    private void createCameraPreviewSession() {
        try {
            SurfaceTexture texture = getSurfaceTexture();
            assert texture != null;

            // We configure the size of default buffer to be the size of camera preview we want.
            texture.setDefaultBufferSize(previewSize.getWidth(), previewSize.getHeight());

            // This is the output Surface we need to start preview.
            Surface surface = new Surface(texture);

            // We set up a CaptureRequest.Builder with the output Surface.
            previewRequestBuilder
                    = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
            previewRequestBuilder.addTarget(surface);

            // Here, we create a CameraCaptureSession for camera preview.
            cameraDevice.createCaptureSession(Arrays.asList(surface, imageReader.getSurface()),
                    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.
                            captureSession = cameraCaptureSession;
                            try {
                                // Auto focus should be continuous for camera preview.
                                previewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE,
                                        CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);

                                // Finally, we start displaying the camera preview.
                                previewRequest = previewRequestBuilder.build();
                                captureSession.setRepeatingRequest(previewRequest,
                                        captureCallback, backgroundHandler);
                            } catch (final CameraAccessException e) {
                                if (cameraErrorCallback != null) {
                                    post(new Runnable() {
                                        @Override
                                        public void run() {
                                            cameraErrorCallback.onCameraError(e);
                                        }
                                    });
                                }
                            }
                        }

                        @Override
                        public void onConfigureFailed(
                                @NonNull CameraCaptureSession cameraCaptureSession) {
                        }
                    }, null
            );
        } catch (final CameraAccessException e) {
            if (cameraErrorCallback != null) {
                post(new Runnable() {
                    @Override
                    public void run() {
                        cameraErrorCallback.onCameraError(e);
                    }
                });
            }
        }
    }

    private void configureTransform(int viewWidth, int viewHeight) {
        if (null == previewSize) {
            return;
        }
        int rotation = getDisplay().getRotation();
        Matrix matrix = new Matrix();
        RectF viewRect = new RectF(0, 0, viewWidth, viewHeight);
        RectF bufferRect = new RectF(0, 0, previewSize.getHeight(), previewSize.getWidth());
        float centerX = viewRect.centerX();
        float centerY = viewRect.centerY();
        if (Surface.ROTATION_90 == rotation || Surface.ROTATION_270 == rotation) {
            bufferRect.offset(centerX - bufferRect.centerX(), centerY - bufferRect.centerY());
            matrix.setRectToRect(viewRect, bufferRect, Matrix.ScaleToFit.FILL);
            float scale = Math.max(
                    (float) viewHeight / previewSize.getHeight(),
                    (float) viewWidth / previewSize.getWidth());
            matrix.postScale(scale, scale, centerX, centerY);
            matrix.postRotate(90 * (rotation - 2), centerX, centerY);
        } else if (Surface.ROTATION_180 == rotation) {
            matrix.postRotate(180, centerX, centerY);
        }
        setTransform(matrix);
    }

    public void takePicture() {
        lockFocus();
    }

    private void lockFocus() {
        try {
            // This is how to tell the camera to lock focus.
            previewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER,
                    CameraMetadata.CONTROL_AF_TRIGGER_START);
            // Tell #captureCallback to wait for the lock.
            state = STATE_WAITING_LOCK;
            captureSession.capture(previewRequestBuilder.build(), captureCallback,
                    backgroundHandler);
        } catch (final CameraAccessException e) {
            if (cameraErrorCallback != null) {
                post(new Runnable() {
                    @Override
                    public void run() {
                        cameraErrorCallback.onCameraError(e);
                    }
                });
            }
        }
    }

    private void unlockFocus() {
        try {
            // Reset the auto-focus trigger
            previewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER,
                    CameraMetadata.CONTROL_AF_TRIGGER_CANCEL);
            captureSession.capture(previewRequestBuilder.build(), captureCallback,
                    backgroundHandler);
            // After this, the camera will go back to the normal state of preview.
            state = STATE_PREVIEW;
            //resume Zoom effect after taking a picture
            previewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE,
                    CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
            if (zoom != null) previewRequestBuilder.set(CaptureRequest.SCALER_CROP_REGION, zoom);
            captureSession.setRepeatingRequest(previewRequestBuilder.build(), captureCallback,
                    backgroundHandler);
        } catch (final CameraAccessException e) {
            if (cameraErrorCallback != null) {
                post(new Runnable() {
                    @Override
                    public void run() {
                        cameraErrorCallback.onCameraError(e);
                    }
                });
            }
        }
    }

    private void runPrecaptureSequence() {
        try {
            // This is how to tell the camera to trigger.
            previewRequestBuilder.set(CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER,
                    CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER_START);
            // Tell #captureCallback to wait for the precapture sequence to be set.
            state = STATE_WAITING_PRECAPTURE;
            captureSession.capture(previewRequestBuilder.build(), captureCallback,
                    backgroundHandler);
        } catch (final CameraAccessException e) {
            if (cameraErrorCallback != null) {
                post(new Runnable() {
                    @Override
                    public void run() {
                        cameraErrorCallback.onCameraError(e);
                    }
                });
            }
        }
    }

    private void captureStillPicture() {
        try {
            if (null == cameraDevice) {
                return;
            }
            // This is the CaptureRequest.Builder that we use to take a picture.
            final CaptureRequest.Builder captureBuilder =
                    cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
            captureBuilder.addTarget(imageReader.getSurface());

            // Use the same AE and AF modes as the preview.
            captureBuilder.set(CaptureRequest.CONTROL_AF_MODE,
                    CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);

            // Orientation
            int rotation = getDisplay().getRotation();
            captureBuilder.set(CaptureRequest.JPEG_ORIENTATION, getOrientation(rotation));

            //Zoom
            if (zoom != null) {
                captureBuilder.set(CaptureRequest.SCALER_CROP_REGION, zoom);
            }

            CameraCaptureSession.CaptureCallback captureCallback
                    = new CameraCaptureSession.CaptureCallback() {

                @Override
                public void onCaptureCompleted(@NonNull CameraCaptureSession session,
                                               @NonNull CaptureRequest request,
                                               @NonNull TotalCaptureResult result) {
                    unlockFocus();
                }
            };

            captureSession.stopRepeating();
            captureSession.abortCaptures();
            if (focusLockedCallback != null) {
                post(new Runnable() {
                    @Override
                    public void run() {
                        focusLockedCallback.onFocusLocked();
                    }
                });
            }
            captureSession.capture(captureBuilder.build(), captureCallback, null);
        } catch (final CameraAccessException e) {
            if (cameraErrorCallback != null) {
                post(new Runnable() {
                    @Override
                    public void run() {
                        cameraErrorCallback.onCameraError(e);
                    }
                });
            }
        }
    }

    private int getOrientation(int rotation) {
        // Sensor orientation is 90 for most devices, or 270 for some devices (eg. Nexus 5X)
        // We have to take that into account and rotate JPEG properly.
        // For devices with orientation of 90, we simply return our mapping from ORIENTATIONS.
        // For devices with orientation of 270, we need to rotate the JPEG 180 degrees.
        return (ORIENTATIONS.get(rotation) + sensorOrientation + 270) % 360;
    }

    static class CompareSizesByArea implements Comparator<Size> {

        @Override
        public int compare(Size lhs, Size rhs) {
            // We cast here to ensure the multiplications won't overflow
            return Long.signum((long) lhs.getWidth() * lhs.getHeight() -
                    (long) rhs.getWidth() * rhs.getHeight());
        }

    }

//    @SuppressLint("NewApi")
//    private int getJpegOrientation(CameraCharacteristics characteristics, int deviceOrientation) {
//        if (deviceOrientation == android.view.OrientationEventListener.ORIENTATION_UNKNOWN)
//            return 0;
//        int sensorOrientation = characteristics.get(CameraCharacteristics.SENSOR_ORIENTATION);
//
//        // Round device orientation to a multiple of 90
//        deviceOrientation = (deviceOrientation + 45) / 90 * 90;
//
//        // Reverse device orientation for front-facing cameras
//        boolean facingFront = characteristics.get(CameraCharacteristics.LENS_FACING) == CameraCharacteristics.LENS_FACING_FRONT;
//        if (facingFront) deviceOrientation = -deviceOrientation;
//
//        // Calculate desired JPEG orientation relative to camera orientation to make
//        // the image upright relative to the device orientation
//        int jpegOrientation = (sensorOrientation + deviceOrientation + 360) % 360;
//
//        return jpegOrientation;
//    }

    protected void startBackgroundThread() {
        backgroundThread = new HandlerThread("Camera2 Background");
        backgroundThread.start();
        backgroundHandler = new Handler(backgroundThread.getLooper());
    }

    @SuppressLint("NewApi")
    protected void stopBackgroundThread() {
        if (backgroundThread == null) {
            backgroundHandler = null;
            return;
        }
        backgroundThread.quitSafely();
        try {
            backgroundThread.join();
            backgroundThread = null;
            backgroundHandler = null;
        } catch (final InterruptedException e) {
            if (cameraErrorCallback != null) {
                post(new Runnable() {
                    @Override
                    public void run() {
                        cameraErrorCallback.onCameraError(e);
                    }
                });
            }
        }
    }

    public void resume() {
        zoom = null;
        startBackgroundThread();
        if (isAvailable()) {
            openCamera(getWidth(), getHeight());
        } else {
            setSurfaceTextureListener(surfaceTextureListener);
        }
    }

    public void pause() {
        closeCamera();
        stopBackgroundThread();
    }

    public void setOnPictureTakenListener(OnPictureTakenListener callback) {
        this.onPictureTakenListener = callback;
    }

    public void setFacing(boolean isTurningToFront) {
        facing = isTurningToFront ? FRONT_CAMERA : BACK_CAMERA;
        pause();
        resume();
    }

    public void resetFacing () {
        facing = BACK_CAMERA;
    }

    public void setOnCameraErrorListener(CameraView.OnCameraErrorListener callback) {
        cameraErrorCallback = callback;
    }

    public void setOnFocusLockedListener (CameraView.OnFocusLockedListener callback) {
        focusLockedCallback = callback;
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        try {
            Rect rect = cameraCharacteristics.get(CameraCharacteristics.SENSOR_INFO_ACTIVE_ARRAY_SIZE);
            if (rect == null) return false;
            float currentFingerSpacing;

            if (event.getPointerCount() == 2) { //Multi touch.
                currentFingerSpacing = getFingerSpacing(event);
                float delta = 0.05f;
                if (fingerSpacing != 0) {
                    if (currentFingerSpacing > fingerSpacing) {
                        if ((maximumZoomLevel - zoomLevel) <= delta) {
                            delta = maximumZoomLevel - zoomLevel;
                        }
                        zoomLevel = zoomLevel + delta;
                    } else if (currentFingerSpacing < fingerSpacing){
                        if ((zoomLevel - delta) < 1f) {
                            delta = zoomLevel - 1f;
                        }
                        zoomLevel = zoomLevel - delta;
                    }
                    float ratio = (float) 1 / zoomLevel;
                    int croppedWidth = rect.width() - Math.round((float)rect.width() * ratio);
                    int croppedHeight = rect.height() - Math.round((float)rect.height() * ratio);
                    zoom = new Rect(croppedWidth/2, croppedHeight/2,
                            rect.width() - croppedWidth/2, rect.height() - croppedHeight/2);
                    previewRequestBuilder.set(CaptureRequest.SCALER_CROP_REGION, zoom);
                }
                fingerSpacing = currentFingerSpacing;
            } else { //Single touch point, needs to return true in order to detect one more touch point
                return true;
            }
            captureSession.setRepeatingRequest(previewRequestBuilder.build(), captureCallback, backgroundHandler);
            return true;
        } catch (final Exception e) {
            if (BuildConfig.DEBUG) e.printStackTrace();
            if (cameraErrorCallback != null) {
                post(new Runnable() {
                    @Override
                    public void run() {
                        cameraErrorCallback.onCameraError(e);
                    }
                });
            }
            return true;
        }
    }

    private float getFingerSpacing(MotionEvent event) {
        float x = event.getX(0) - event.getX(1);
        float y = event.getY(0) - event.getY(1);
        return (float) Math.sqrt(x * x + y * y);
    }

    public interface OnPictureTakenListener {
        void onPictureTaken(byte[] data);
    }

}

IMO you to replace

zoom = new Rect(croppedWidth/2, croppedHeight/2, rect.width() - croppedWidth/2, rect.height() - croppedHeight/2);

with

int left = (rect.width() - croppedWidth) / 2;
int top = (rect.height() - croppedHeight) / 2;
zoom = new Rect(
    left,
    top,
    left + croppedWidth,
    top + croppedHeight);

to zoom into the center of the screen. Or I'm wrong?