this piece of line of code is not allowed in android.
Intent intent = new Intent(null, LandVideoAct.class);
coming to your crash problem. Its mainly because of a above line of code. When full screen of video in webview is called , its gives call to android system ie onShowCustomView(View view, CustomViewCallback callback)
. Where you above line of code is failing.
instead of that use activity context or application context
Intent intent = new Intent(context, LandVideoAct.class);