View onDraw、dispatchDraw、invalidate和computeScroll介绍
结合View.Java的源码,在draw方法中:publicvoiddraw(Canvascanvas){/*View的绘制过程分为下面几步:Drawthebackground绘制背景Ifnecessary,savethecanvas’layerstoprepareforfading如有必要,颜色渐变淡之前保存画布层(即锁定原有的画布内容)Drawview’scontent绘制View的内容Dra