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附加到窗體上時調用該方法。在這時，view有了一個用於顯示的Surface，將開始繪制。註意，此方法要保證在調用onDraw(Canvas) 之前調用，但可能在調用 onDraw(Canvas) 之前的任何時刻，包括調用 onMeasure(int, int) 之前或之後。

看得出次方法在onDraw方法之前調用，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，代碼如下：

1. @Override
2. protected void onAttachedToWindow() {
3. super.onAttachedToWindow();
5. if (Log.LOGV) Log.v("onAttachedToWindow " + this);
7. if (mAttached) return;
8. mAttached = true;
10. if (mAnimate) {
11. setBackgroundResource(R.drawable.animate_circle);
12. /* Start the animation (looped playback by default). */
13. ((AnimationDrawable) getBackground()).start();
14. }
16. if (mLive) {
17. /* monitor time ticks, time changed, timezone */
18. IntentFilter filter = new IntentFilter();
19. filter.addAction(Intent.ACTION_TIME_TICK);
20. filter.addAction(Intent.ACTION_TIME_CHANGED);
21. filter.addAction(Intent.ACTION_TIMEZONE_CHANGED);
22. mContext.registerReceiver(mIntentReceiver, filter, null, mHandler);
23. }
25. /* monitor 12/24-hour display preference */
26. mFormatChangeObserver = new FormatChangeObserver();
27. mContext.getContentResolver().registerContentObserver(
28. Settings.System.CONTENT_URI, true, mFormatChangeObserver);
30. updateTime();
31. }

另外在屏蔽Home鍵的時候也會用到

1. public void 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>

將視圖從窗體上分離的時候調用該方法。這時視圖已經不具有可繪制部分。

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

1. @Override
2. protected void onDetachedFromWindow() {
3. super.onDetachedFromWindow();
5. if (!mAttached) return;
6. mAttached = false;
8. Drawable background = getBackground();
9. if (background instanceof AnimationDrawable) {
10. ((AnimationDrawable) background).stop();
11. }
13. if (mLive) {
14. mContext.unregisterReceiver(mIntentReceiver);
15. }
16. mContext.getContentResolver().unregisterContentObserver(
17. mFormatChangeObserver);
18. }

具體的用法視個人的需求而定了，自己控制重寫就好了。

Android重寫view時onAttachedToWindow () 和 onDetachedFromWindow ()