Releasing camera object in surfaceChanged causes force close (Null Pointer Exception)

Question

public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {

..........
.......

  public void surfaceCreated(SurfaceHolder holder) {
    ........
    ..........
    // I create camera object with camera.open
  }

  public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
    // I start camera preview successfully and call my function.
   Myfunction();
   //this function does some checking (a separate thread ) n releases camera object immediately and also release the camera preview
  }
}

Now that I am still in onsurfaceChanged() when the control leaves this function I get a Force close(Null Pointer exception) at SurfaceView (564). I know this error is because i released the camera and its suface view. According to the documentation of android the onsurfaceChanged() is called atleast once after surfaceCreated();

So my Query is it wrong that i am releasing the camera object and its preview holder before the control goes out of onsurfaceChanged()?? My requirement is I check some situation n release the camera if its condition is false as soon as create preview i.e startPreview(); do some task ahead inside onsurfaceChanged() itself.

is there any way i can detect the onsurfaceChanged() is called once and then i can trigger Myfunction();

Answer 1

The easy workaround would be to use CameraPreview.post() to release camera after your callback returns:

public class CameraPreview … {

    void Myfunction() {
        …
        this.post(new Runnable() { 
            public void run() {
                mCamera.release();
                mCamera = null;
            }
        }
        …
    }
}