android Handler.post定时器

Runnable 并不一定是新开一个线程，比如下面的调用方法就是运行在UI主线程中的：

     Handler mHandler=new Handler();      mHandler.post(new Runnable(){         @Override public void run()         { // TODO Auto-generated method stub          }      });

官方对这个方法的解释如下，注意其中的：“The runnable will be run on the user interface thread. ”

boolean android.view.View .post(Runnable action)

Causes the Runnable to be added to the message queue. The runnable will be run on the user interface thread.

Parameters:

action The Runnable that will be executed.

Returns:

Returns true if the Runnable was successfully placed in to the message queue. Returns false on failure, usually because the looper processing the message queue is exiting.

我们可以通过调用handler的post方法，把Runnable对象（一般是Runnable的子类）传过去；handler会在looper中调用这个Runnable的Run方法执行。

Runnable是一个接口，不是一个线程，一般线程会实现Runnable。所以如果我们使用匿名内部类是运行在UI主线程的，如果我们使用实现这个Runnable接口的线程类，则是运行在对应线程的。

final Handler mHandler=new Handler();
mHandler.post(new Runnable() {
    @Override
    public void run() {
        updateTitle();
        mHandler.postDelayed(this,1000);
    }
});




private void updateTitle() {
    Date date = new Date();
    int hour, minute, second;
    String shour, sminute, ssecond;
    hour = (date.getHours() + 8) % 24;
    minute = date.getMinutes();
    second = date.getSeconds();


    if (hour < 10) {
        shour = "0" + hour;
    } else {
        shour = "" + hour;
    }


    if (minute < 10) {
        sminute = "0" + minute;
    } else {
        sminute = "" + minute;
    }


    if (second < 10) {
        ssecond = "0" + second;
    } else {
        ssecond = "" + second;
    }


    textView.setText("当前时间：" + shour + ":" + sminute + ":" + ssecond);
}