title: How to read OPEN CV camera frames in background Android
body: <p>i am new to android and i am working on an application for face expression recognitions.
  i am using open cv camera.
  it taskes camera frame and display the results.
  but i want camera to read expressions after some time.
  i added the following code in preview frame:
  long releaseTime = SystemClock.currentThreadTimeMillis() + 200;
  SystemClock.sleep(releaseTime- SystemClock.currentThreadTimeMillis());
  but it is not working properly. it puts my app on sleep. i want a code that reads the expressions after few seconds without any pause.</p>