参考: https://www.cnblogs.com/tiger-wang-ms/p/6592189.html
https://blog.csdn.net/a553181867/article/details/51583060
结论: view调用invalidate将导致当前view的重绘(draw调用),view的父类将不会执行draw方法;viewGroup调用invalidate会使viewGroup的子view调用draw,也就是viewGroup内部的子view进行重绘;
而requestLayout方法只会导致当前view的measure和layout。
invalidate:
requestLayout: