[Java/Android] Detect the fragment is on focus (User is viewing)

MyFragment.java

// Useful for viewPagers.

public class MyFragment extends Fragment {
  @Override
  public void setUserVisibleHint(boolean isVisibleToUser) {
    super.setUserVisibleHint(isVisibleToUser);
    if (isVisibleToUser) { 
        // User is viewing the fragment,
        // or fragment is inside the screen
        doYourThing();
    }
    else { 
        // User is not viewing the fragment, 
        // or fragment is our of the screen
        doYourThing();
    }
  }
}