Hello! when I call startPreview on the onCreate method of an activity or a fragment, the surface becomes black (but my webcam turns on the led indicating it's on) it only works when i call startPreview on a click of a button or something that will happen on a later time.. How can I fix that?

After i open easycamera class, i get preview of the camera but camera is freezing.

public class MakePhotoActivity extends Activity {

SurfaceHolder previewHolder;
SurfaceView mSurfaceView;
private boolean previewIsRunning;
private EasyCamera camera;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mSurfaceView = (SurfaceView) findViewById(R.id.surface);
    previewHolder = mSurfaceView.getHolder();
    previewHolder.addCallback(new SurfaceHolder.Callback() {

        public void surfaceChanged(SurfaceHolder holder, int format,
                int width, int height) {
             if (!previewIsRunning && (camera != null)) {
                 try {
                    camera.startPreview(holder);
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                 previewIsRunning = true;
             }
        }

        public void surfaceCreated(SurfaceHolder holder) {

            camera = DefaultEasyCamera.open(CameraInfo.CAMERA_FACING_FRONT);

        }

        public void surfaceDestroyed(SurfaceHolder holder) { 
            camera.close();
            camera = null;

        }

    });
}

}