Invalidate the whole view on Android

Invalidate the whole view. If the view is visible, onDraw(android.graphics.Canvas) will be called at some point in the future.

This must be called from a UI thread. To call from a non-UI thread, call postInvalidate().

gauge.invalidate();

References
https://developer.android.com/reference/android/view/View.html#invalidate()
http://stackoverflow.com/questions/10647558/when-its-necessary-to-execute-invalidate-on-a-view