First of all, you got guts to ask a Android question and have a iOS logo ;) (kidding)  
But, I think you can use this:
    DisplayMetrics metrics = new DisplayMetrics(); getWindowManager().getDefaultDisplay().getMetrics(metrics);
    android.widget.LinearLayout.LayoutParams params = (android.widget.LinearLayout.LayoutParams) videoView.getLayoutParams();
    params.width =  metrics.widthPixels;
    params.height = metrics.heightPixels;
    params.leftMargin = 0;
    videoView.setLayoutParams(params);
and to set it back:  
    DisplayMetrics metrics = new DisplayMetrics(); getWindowManager().getDefaultDisplay().getMetrics(metrics);
    android.widget.LinearLayout.LayoutParams params = (android.widget.LinearLayout.LayoutParams) videoView.getLayoutParams();
    params.width =  (int) (400*metrics.density);
    params.height = (int) (300*metrics.density);
    params.leftMargin = 30;
    videoView.setLayoutParams(params);
I assume that you know how to make a OnClickListener.
I got the information here: VideoView Full screen in android application
Edit1
I can think of 2 things quickly.
 1. Add this: getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);
 2. or try this:  
YourButton.setVisibility(View.GONE);
or  
YourButton.setVisibility(View.INVISIBLE);