Android Camera2 API setRepeatingRequest

Question

I'm making android camera app with camera2. my code is almost same with official camera2 sample but transfer fragment to activity. I plan to set zoom as default parameter so made zoom function in openCamera(w, h). Below is my code for set camera default zoom.

private void openCamera(int width, int height) {
    if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
        requestCameraPermission();
        return;
    }
    setUpCameraOutputs(width, height);
    configureTransform(width, height);
    Activity activity = this;
    CameraManager manager = (CameraManager) activity.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 (CameraAccessException e) {
        e.printStackTrace();
    } catch (InterruptedException e) {
        throw new RuntimeException("Interrupted while trying to lock camera opening.", e);
    }

    try{
        CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
        float maxzoom = (characteristics.get(CameraCharacteristics.SCALER_AVAILABLE_MAX_DIGITAL_ZOOM));
        android.graphics.Rect m = characteristics.get(CameraCharacteristics.SENSOR_INFO_ACTIVE_ARRAY_SIZE);
        float zoomLevel = maxzoom/3;
        float ratio = (float) 1/zoomLevel;
        int cropWidth = m.width() - Math.round((float)m.width()*ratio);
        int cropHeight = m.height() - Math.round((float)m.height()*ratio);
        android.graphics.Rect zoom = new android.graphics.Rect(cropWidth/2, cropHeight/2, m.width() - cropWidth/2, m.height() - cropHeight/2);
        previewRequestBuilder.set(CaptureRequest.SCALER_CROP_REGION, zoom);
        try{
            captureSession.setRepeatingRequest(previewRequestBuilder.build(), captureCallback, null); // Null Exception occur
        } catch (CameraAccessException e) {
            e.printStackTrace();
        } catch (NullPointerException ex) {
            ex.printStackTrace();
        }
    } catch (CameraAccessException e) {
        throw new RuntimeException("can not access camera.", e);
    }

}

There's no problem with zoom and camera. But when I install my app with android studio and run app for the first time, it always break with null point exception at setreapeatingrequest(). After 2 or 3 more try then the app runs ok. I suspect that this exception maybe occurs 'cause there's no preview or something. But I have no idea how can I fix this error. Any opinion must be very helpful. Thanks in advance.

Answer 1

It's bit late but for those who concern, I fixed this error by myself. Check this :

delayHandler.postDelayed(new Runnable() {
        @Override
        public void run() {
            try {
                CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
                float maxzoom = (characteristics.get(CameraCharacteristics.SCALER_AVAILABLE_MAX_DIGITAL_ZOOM));
                android.graphics.Rect m = characteristics.get(CameraCharacteristics.SENSOR_INFO_ACTIVE_ARRAY_SIZE);
                float zoomLevel = maxzoom / 6;
                float ratio = (float) 1 / zoomLevel;
                int cropWidth = m.width() - Math.round((float) m.width() * ratio);
                int cropHeight = m.height() - Math.round((float) m.height() * ratio);
                android.graphics.Rect zoom = new android.graphics.Rect(cropWidth / 2, cropHeight / 2, m.width() - cropWidth / 2, m.height() - cropHeight / 2);
                previewRequestBuilder.set(CaptureRequest.SCALER_CROP_REGION, zoom);
                try {
                    captureSession.setRepeatingRequest(previewRequestBuilder.build(), captureCallback, null);
                } catch (CameraAccessException e) {
                    e.printStackTrace();
                } catch (NullPointerException ex) {
                    ex.printStackTrace();
                }
            } catch (CameraAccessException e) {
                throw new RuntimeException("can not access camera.", e);
            }
        }
    }, 500);

Because I made camea to zoom, so it takes some times to prepare camera. After I made camera opened after 500ms delay it worked perfect without error.