学步园

 在重写View的时候，会遇到这两个方法

protected void onAttachedToWindow()

Description copied from class: View

This is called when the view is attached to a window. At this point it has a Surface and will start drawing. Note that this function is guaranteed to be called before View.onDraw(android.graphics.Canvas), however it may be called
any time before the first onDraw -- including before or after View.onMeasure(int, int).
Overrides: 
onAttachedToWindow in class View

当此view附加到窗体上时调用该方法。在这时，view有了一个用于显示的Surface，将开始绘制。注意，此方法要保证在调用onDraw(Canvas) 之前调用，但可能在调用 onDraw(Canvas) 之前的任何时刻，包括调用 onMeasure(int,
int) 之前或之后。

看得出次方法在onDraw方法之前调用，也就是view还没有画出来的时候，可以在此方法中去执行一些初始化的操作，google的AlarmClock动态时钟View就是在这个方法中进行广播的注册，代码如下：

另外在屏蔽Home键的时候也会用到

public void onAttachedToWindow ()
Since: API Level 5
Called when the main window associated with the activity has been attached to the window manager. See View.onAttachedToWindow() for more information.
See Also
    * onAttachedToWindow()
private boolean catchHomeKey = false;
    @Override
        public void onAttachedToWindow() {
                // TODO Auto-generated method stub
            if(catchHomeKey) {
                    this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD);
            }
          super.onAttachedToWindow();
        }
        @Override
        public boolean onKeyDown(int keyCode, KeyEvent event) {
                // TODO Auto-generated method stub
                if(keyCode == KeyEvent.KEYCODE_HOME) {
                        Log.e(TAG, "Home key down");
                }
                return super.onKeyDown(keyCode, event);
        }

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protected void onDetachedFromWindow()

Description copied from class: View
This is called when the view is detached from a window. At this point it no longer has a surface for drawing.
Overrides: 
onDetachedFromWindow in class AdapterView<ListAdapter>

将视图从窗体上分离的时候调用该方法。这时视图已经不具有可绘制部分。

onDetachedFromWindow()正好与onAttachedToWindow()的用法相对应，在destroy view的时候调用，所以可以加入取消广播注册等的操作，还是google的闹钟代码：