Android cameraSource.stop() causing app to freeze

Question

I am building an app that has a qr scanner using the google vision api. I am having trouble stopping the camera after the qr code is read. the flow is MainActivity -> QrActivity once the qr-code received a detection the app should return to the main activity.

If i do not call cameraSource.release() it works fine but the device heats up a lot and has a significant impact on battery drain. however if i release the camera source the mainActivity becomes un-responsive and the app will crash.

Why is it becoming unresponsive? and where is the correct place to release the camera source?

QrActivity

@Override
protected void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_qr);
    cancelBtn = (Button) findViewById(R.id.cancel_button);
    cancelBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            onBackPressed();
        }
    });

    new QrReader(this);
}

QrReader Class

public class QrReader {

    private static final String TAG = "QrReader";

    private SurfaceView cameraView;
    private TextView barcodeInfo;
    private BarcodeDetector barcodeDetector;
    private CameraSource cameraSource;
    private Activity mActivity;
    private AccessPointCredentials barCodeData;

    public QrReader(Activity activity) {
        this.mActivity = activity;

        cameraView = (SurfaceView) mActivity.findViewById(R.id.camera_view);
        barcodeInfo = (TextView) mActivity.findViewById(R.id.code_info);

        barcodeDetector =
                new BarcodeDetector.Builder(mActivity)
                        .setBarcodeFormats(Barcode.QR_CODE)
                        .build();

        cameraSource = new CameraSource
                .Builder(mActivity, barcodeDetector)
                .setAutoFocusEnabled(true)
                .build();

        cameraView.getHolder().addCallback(new SurfaceHolder.Callback() {

            @Override
            public void surfaceCreated(SurfaceHolder holder) {

                cameraSource = new CameraSource
                        .Builder(mActivity, barcodeDetector)
                        .setAutoFocusEnabled(true)
                        .setFacing(0)
                        .build();
                try {                  
                    cameraSource.start(cameraView.getHolder());

                } catch (Exception ioe) {
                    ioe.printStackTrace();
                }
            }

            @Override
            public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
            }

            @Override
            public void surfaceDestroyed(SurfaceHolder holder) {
                  // Log.i(TAG, "surfaceDestroyed: stopping camera Source");

                  // cameraSource.release();
            }
        });

        barcodeDetector.setProcessor(new Detector.Processor<Barcode>() {
            @Override
            public void release() {
                Log.i(TAG, "release: ");
            }

            @Override
            public void receiveDetections(Detector.Detections<Barcode> detections) {
                final SparseArray<Barcode> barCodes = detections.getDetectedItems();

                if (barCodes.size() != 0) {

                    Log.i(TAG, "received a Barcode");
                    barcodeInfo.post(new Runnable() {    // Use the post method of the TextView
                        public void run() {
                            barcodeInfo.setText(barCodes.valueAt(0).displayValue);

                        }
                    });
                    Gson g = new Gson();
                    try {
                        barCodeData = g.fromJson(barCodes.valueAt(0).rawValue, AccessPointCredentials.class);
                    } catch (Exception e) {
                        barCodeData = new AccessPointCredentials();
                        barCodeData.setSsid(barCodes.valueAt(0).rawValue);
                        barCodeData.setPass(null);
                        e.printStackTrace();
                    }

                    connectToWifi(barCodeData);

                    // CameraSource.release causes app to freeze

                    // cameraSource.release();
                }
            }
        });
    }

    private void connectToWifi(final AccessPointCredentials credentials) {

                //wificonnect code

    }

}

Answer 1

it's been 3 months but I just stumbled on the same problem and figure it out. The code inside the receiveDetections method is running on a different thread so if you want to do something that needs the ui thread you need to post it from a handler:

Handler handler = new Handler(Looper.getMainLooper());
handler.post(new Runnable() {
     @Override
     public void run() {
         cameraSource.release();
     }
});