Android：如何实现可旋转半圆？

Question

I want to rotate the semi-circular as the upper picture(maybe the view's backgroud). How to implement it?

It should be rotated by the gesture . It maybe like the rotatable circular, but only display the half of the one. I had implemented the rotatable circular using the matrix , but I have no idea about the semi-circular.

Answer 1

I had solved the problem, like these:

Rect rect = new Rect(0, 0, w, h/2);
canvas.clipRect(rect);
canvas.save();