sendMessageDelay()大家都明白，说是延时多少才发送。而sendMessageAtTime()意思也明白，那么怎么用呢？这里的关键，在于怎么取时间。正确做法是：

    long mLastDisplayTime = 0;

    @Override
    protected void onNewIntent(Intent intent)
    {
        String text = intent.getStringExtra("message");
        Message msg = mHandler.obtainMessage(MESSAGE_NEW_ARRIVED, text);

        # 正确取时间的代码。
        long current = SystemClock.uptimeMillis();
        if (mLastDisplayTime == 0)
        {
            mLastDisplayTime = current;
        }
        else
        {
            if (current > mLastDisplayTime+2000)
            {
                mLastDisplayTime = current;
            }
            else
            {
                mLastDisplayTime += 5000;
            }
        }
        mHandler.sendMessageAtTime(msg, mLastDisplayTime);
    }

　　从上述代码中可以看到，关键在于取时间的代码：SystemClock.uptimeMillis()