Monday, August 26, 2013

android camera.open() freeze

weirdest thing happened while i was experimenting with android.hardware.camera api.
i was testing on a 2.2 device and of course there were the problems with
Camera.getNumberOfCameras() missing etc, but when i got to the point to get a handle to the camera with a simple camera.open() - nothing happened!

literally, because the app froze and nothing would unfroze it. it even blocked other applications trying to use the camera, and that until reboot of the device.

i thought maybe it happened because i was on the ui thread, but even as i pushed the camera code to an AsyncTask,doInBackground(), while the ui thread was responsive there was never response from the async portion

weird, a?

i read this was only fixed about API 5 releases and 3 years later. wow!

the obvious workaround is to use intent as i was originally planning, but is this really such a big, unsolvable problem? certainly there are apps that are using the hardware.camera api so how do they manage to workaround it? or maybe the problem is gone in the camera.open(int) method, which is introduced in 2.3

in any case, android is fun. i wonder if you'd agree with this statement if you we're working on it for money under strict client requirements...

UPDATE 2013/09/06:

So there is a way to get handle of the camera, as i suspected in involves SurfaceView which i didn't want to get much into at the time of the previous writing as i was planning to use intent, but actually there are many examples for using SurfaceView out there and here is the code that worked for me:

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        getWindow().setFormat(PixelFormat.TRANSLUCENT);

        surface_view = new SurfaceView(getApplicationContext());
        addContentView(surface_view, new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));

        if (surface_holder == null) {
            surface_holder = surface_view.getHolder();
            surface_holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);//http://stackoverflow.com/a/6793598/1419136
        }

        sh_callback = my_callback();
        surface_holder.addCallback(sh_callback);
    }
   
    SurfaceHolder.Callback my_callback() {     
        SurfaceHolder.Callback ob1 = new SurfaceHolder.Callback() {

            @Override
            public void surfaceDestroyed(SurfaceHolder holder) {
                  mCamera.stopPreview();
                  mCamera.release();
                  mCamera = null;
            }

            @Override
            public void surfaceCreated(SurfaceHolder holder) {
                mCamera = Camera.open();

                  try {
                       mCamera.setPreviewDisplay(holder); 
                  } catch (IOException exception) { 
                        mCamera.release(); 
                        mCamera = null; 
                  }
            }

            @Override
            public void surfaceChanged(SurfaceHolder holder, int format, int width,
                    int height) {
                mCamera.startPreview();
            }
        };
        return ob1;
}

this is all from the wonderful post at http://stackoverflow.com/a/10482872/1419136 by Bharat Sharma

a very nice example of actually taking a picture is here: http://stackoverflow.com/a/16399425/1419136, by user jiahao

so stackoverflow has been getting huge over the view years, i still remember one of its founders writing a post about dreaming about such a hub of help for developers/admins and all kinds of people looking for qualified answers - well done!

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