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:
@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键的时候也会用到
public void onAttachedToWindow() { this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD); super.onAttachedToWindow(); }