Android杂货摊：Handlerpost和Viewpost的区别，android开发游戏加入时间限制

}

// 仔细阅读下面这段注释！！！
// Postpone the runnable until we know on which thread it needs to run.
// Assume that the runnable will be successfully placed after attach.
getRunQueue().post(action);
return true;
}

从上面的源码，我们大概可以看出mAttachInfo字段在这里比较关键，当其有值时，其实和普通的Handler.post就没区别了，但
有时它是没值的，比如我们上面示例代码里的onCreate阶段，那么这时执行到了getRunQueue().post(action);这行代码，从这段注释也大概可以看出来真正的执行会被延迟（这里的Postpone注释）；我们接着往下看看getRunQueue相关的代码，如下：

/** 其实这段注释已经说的很清楚明了了！！！

• Queue of pending runnables. Used to postpone calls to post() until this
• view is attached and has a handler.
  */
  private HandlerActionQueue mRunQueue;

private HandlerActionQueue getRunQueue() {
if (mRunQueue == null) {
mRunQueue = new HandlerActionQueue();
}
return mRunQueue;
}

从上面我们可以看出，mRunQueue就是View用来处理它还没attach到window（还没对应的handler）时，客户代码发起的post调用的，起了一个临时缓存的作用。不然总不能丢弃吧，这样开发体验就太差了！！！
紧接着，我们继续看下HandlerActionQueue类型的定义，代码如下：

public class HandlerActionQueue {
private HandlerAction[] mActions;
private int mCount;

public void post(Runnable action) {
postDelayed(action, 0);
}

public void postDelayed(Runnable action, long delayMillis) {
final HandlerAction handlerAction = new HandlerAction(action, delayMillis);

synchronized (this) {
if (mActiOns== null) {
mActiOns= new HandlerAction[4];
}
mActiOns= GrowingArrayUtils.append(mActions, mCount, handlerAction);
mCount++;
}
}

public void executeActions(Handler handler) {
synchronized (this) {
final HandlerAction[] actiOns= mActions;
for (int i = 0, count = mCount; i final HandlerAction handlerAction = actions[i];
handler.postDelayed(handlerAction.action, handlerAction.delay);
}

mActiOns= null;
mCount = 0;
}
}

private static class HandlerAction {
final Runnable action;
final long delay;

public HandlerAction(Runnable action, long delay) {
this.action = action;
this.delay = delay;
}

public boolean matches(Runnable otherAction) {
return otherAction == null && action == null
|| action != null && action.equals(otherAction);
}
}
}

注意：这里的源码部分，我们只摘录了部分关键代码，其余不太相关的直接略去了。
从这里可以看出，我们前面的View.post调用里的Runnable最终会被存储在这里的mActions数组里，这里最关键的一点就是其executeActions方法，因为这个方法里我们之前post的Runnable才真正通过handler.postDelayed方式使其进入handler对应的消息队列里等待执行；

到此为止，我们还差知道View里的mAttachInfo字段何时被赋值以及这里的executeActions方法是什么时候被触发的，答案就是在View的dispatchAttachedToWindow方法，其关键源码如下：

void dispatchAttachedToWindow(AttachInfo info, int visibility) {
mAttachInfo = info;
…
// Transfer all pending runnables.
if (mRunQueue != null) {
mRunQueue.executeActions(info.mHandler);
mRunQueue = null;
}
performCollectViewAttributes(mAttachInfo, visibility);
onAttachedToWindow();
…
Queue = null;
}
performCollectViewAttributes(mAttachInfo, visibility);
onAttachedToWindow();
…