Android重寫view時onAttachedToWindow () 和 onDetachedFromWindow ()

  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。注意，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注冊，代碼如下： [java]   @Override       protected void onAttachedToWindow() {           super.onAttachedToWindow();              if (Log.LOGV) Log.v("onAttachedToWindow " + this);              if (mAttached) return;           mAttached = true;              if (mAnimate) {               setBackgroundResource(R.drawable.animate_circle);               /* Start the animation (looped playback by default). */               ((AnimationDrawable) getBackground()).start();           }              if (mLive) {               /* monitor time ticks, time changed, timezone */               IntentFilter filter = new IntentFilter();               filter.addAction(Intent.ACTION_TIME_TICK);               filter.addAction(Intent.ACTION_TIME_CHANGED);               filter.addAction(Intent.ACTION_TIMEZONE_CHANGED);               mContext.registerReceiver(mIntentReceiver, filter, null, mHandler);           }              /* monitor 12/24-hour display preference */           mFormatChangeObserver = new FormatChangeObserver();           mContext.getContentResolver().registerContentObserver(                   Settings.System.CONTENT_URI, true, mFormatChangeObserver);              updateTime();       }   另外在屏蔽Home鍵的時候也會用到 [java]   public void onAttachedToWindow() {   this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD);   super.onAttachedToWindow();   }     -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------   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注冊等的操作，還是google的鬧鐘代碼： [java]   @Override       protected void onDetachedFromWindow() {           super.onDetachedFromWindow();              if (!mAttached) return;           mAttached = false;              Drawable background = getBackground();           if (background instanceof AnimationDrawable) {               ((AnimationDrawable) background).stop();           }   www.2cto.com            if (mLive) {               mContext.unregisterReceiver(mIntentReceiver);           }           mContext.getContentResolver().unregisterContentObserver(                   mFormatChangeObserver);       }     具體的用法視個人的需求而定了，自己控制重寫就好了。