Android View生命周期

1. onFinishInflate() 当View中所有的子控件均被映射成xml后触发

2. onMeasure(int, int) 确定所有子元素的大小

3. onLayout(boolean, int, int, int, int) 当View分配所有的子元素的大小和位置时触发

4. onSizeChanged(int, int, int, int) 当view的大小发生变化时触发

5. onDraw(Canvas) view渲染内容的细节

6. onKeyDown(int, KeyEvent) 有按键按下后触发

7. onKeyUp(int, KeyEvent) 有按键按下后弹起时触发

8. onTrackballEvent(MotionEvent) 轨迹球事件

9. onTouchEvent(MotionEvent) 触屏事件

10. onFocusChanged(boolean, int, Rect) 当View获取或失去焦点时触发

11. onWindowFocusChanged(boolean) 当窗口包含的view获取或失去焦点时触发

12. onAttachedToWindow() 当view被附着到一个窗口时触发

13. onDetachedFromWindow() 当view离开附着的窗口时触发，Android123提示该方法和 onAttachedToWindow() 是相反的

14. onWindowVisibilityChanged(int) 当窗口中包含的可见的view发生变化时触发

Implementing a Custom View

To implement a custom view, you will usually begin by providing overrides for some of the standard methods that the framework calls on all views. You do not need to override all of these methods. In fact, you can start by just overriding onDraw(android.graphics.Canvas).