在View/ImageVIew中显示Drawable

API

View.setBackground(Drawable)
ImageView.setImagDrawable(Drawable)

源码分析

View.mBackground在View.draw(Canvas)中绘制，调用Drawable.draw(Canvas)
ImageView.mDrawable在ImageView.onDraw(Canvas)中绘制，调用Drawable.draw(Canvas)

Drawable对View的更新操作的实现

API

Drawable.invalidateSelf

更新

Drawable.scheduleSelf(Runnable, long)

延时更新

Drawable.unscheduleSelf

取消延时更新

源码分析：委托模式

Drawable.Callback

接口，定义更新相关方法invalidateDrawable、scheduleDrawable、unscheduleDrawable

Drawable