Set full screen this way,
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 back to original size, this way.
DisplayMetrics metrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(metrics);
android.widget.LinearLayout.LayoutParams params = (android.widget.LinearLayout.LayoutParams) videoView.getLayoutParams();
params.width = (int)(300*metrics.density);
params.height = (int)(250*metrics.density);
params.leftMargin = 30;
videoView.setLayoutParams(params);