在重寫View的時候，會遇到這兩個方法

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

當此view附加到窗體上時呼叫該方法。在這時，view有了一個用於顯示的Surface，將開始繪製。注意，此方法要保證在呼叫onDraw(Canvas) 之前呼叫，但可能在呼叫 onDraw(Canvas) 之前的任何時刻，包括呼叫 onMeasure(int, int)之前或之後。

看得出次方法在onDraw方法之前呼叫，也就是view還沒有畫出來的時候，可以在此方法中去執行一些初始化的操作，google的AlarmClock動態時鐘View就是在這個方法中進行廣播的註冊，程式碼如下：

1. @Override
2.     protectedvoid onAttachedToWindow() {  
3.         super.onAttachedToWindow();  
4.         if (Log.LOGV) Log.v("onAttachedToWindow " + this);  
5.         if (mAttached) return;  
6.         mAttached = true;  
7.         if (mAnimate) {  
8.             setBackgroundResource(R.drawable.animate_circle);  
9.             /* Start the animation (looped playback by default). */
10.             ((AnimationDrawable) getBackground()).start();  
11.         }  
12.         if (mLive) {  
13.             /* monitor time ticks, time changed, timezone */
14.             IntentFilter filter = new IntentFilter();  
15.             filter.addAction(Intent.ACTION_TIME_TICK);  
16.             filter.addAction(Intent.ACTION_TIME_CHANGED);  
17.             filter.addAction(Intent.ACTION_TIMEZONE_CHANGED);  
18.             mContext.registerReceiver(mIntentReceiver, filter, null, mHandler);  
19.         }  
20.         /* monitor 12/24-hour display preference */
21.         mFormatChangeObserver = new FormatChangeObserver();  
22.         mContext.getContentResolver().registerContentObserver(  
23.                 Settings.System.CONTENT_URI, true, mFormatChangeObserver);  
24.         updateTime();  
25.     }  

另外在遮蔽Home鍵的時候也會用到

1. publicvoid onAttachedToWindow() {  
2. this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD);  
3. super.onAttachedToWindow();  
4. }  

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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>

將檢視從窗體上分離的時候呼叫該方法。這時檢視已經不具有可繪製部分。

onDetachedFromWindow()正好與onAttachedToWindow()的用法相對應，在destroy view的時候呼叫，所以可以加入取消廣播註冊等的操作，還是google的鬧鐘程式碼：

1. @Override
2.     protectedvoid onDetachedFromWindow() {  
3.         super.onDetachedFromWindow();  
4.         if (!mAttached) return;  
5.         mAttached = false;  
6.         Drawable background = getBackground();  
7.         if (background instanceof AnimationDrawable) {  
8.             ((AnimationDrawable) background).stop();  
9.         }  
10.         if (mLive) {  
11.             mContext.unregisterReceiver(mIntentReceiver);  
12.         }  
13.         mContext.getContentResolver().unregisterContentObserver(  
14.                 mFormatChangeObserver);  
15.     }  

具體的用法視個人的需求而定了，自己控制重寫就好了。