How to fix Auto focus in Camera2api android

Question

Hi I am using Camera2 api, I am adding a preview to it. issue is Autofocus does not work. and the picture is blurry.

Can you please suggest where I am getting it wrong.

I have added captureRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_START); in updatePreview but not sure if that is the right place.

Can you suggest how to get Autofocus to work please.

Thanks R

private void openCamera() {
    Activity activity = getActivity();
    CameraManager manager = (CameraManager) activity.getSystemService(Context.CAMERA_SERVICE);
    Log.e(TAG, "is camera open");
    try {
        cameraId = manager.getCameraIdList()[0];
        CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
        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(getContext(), Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED
                && ActivityCompat.checkSelfPermission(getContext(), Manifest.permission.WRITE_EXTERNAL_STORAGE)
                != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(getActivity(), 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);
        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.
                cameraCaptureSessions = cameraCaptureSession;
                updatePreview();
                Log.e(TAG, "createCaptureSession -  onConfigured");
            }
            @Override
            public void onConfigureFailed(@NonNull CameraCaptureSession cameraCaptureSession) {
                //Toast.makeText(TakePhotoFragmentCamera2.this, "Configuration change", Toast.LENGTH_SHORT).show();
                Log.e(TAG, "createCaptureSession -  onConfigureFailed");
            }
        }, null);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

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

Answer 1

Please take a look at the sample app Camera2Basic as an example of doing autofocus.

You shouldn't add AF_TRIGGER to a repeating request - that means you're restarting autofocus on every frame. It should be set for a single capture request only, and you can then watch the value of AF_STATE in CaptureResults to see when autofocus completes.

Also in general, you want to set the AF_MODE to CONTINUOUS_PICTURE if the device supports it (most do), so that you can get continuously focusing behavior, not just focusing when AF_TRIGGER is fired in AF_MODE_AUTO. If you use CONTINUOUS_PICTURE, you don't really even need AF_TRIGGER unless for some reason you want to lock focus for an extended period.