TimerTask task = new TimerTask( ) {
public void run ( ) {
Message message = new Message( );
message.what = 1;
handler.sendMessage(message);
}
};

final Handler handler = new Handler( ) {
public void handleMessage(Message msg) {
switch (msg.what) {
case 1:
log.e("Timer","Timer");
update( );
break;
}

super.handleMessage(msg);
}
};

protected void onDestroy ( ) {
if (timer != null) {
timer.cancel( );
timer = null;
}
super.onDestroy( );
}
protected void onCreate (Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.setContentView(R.layout.main);
timer.schedule(task,1000,5000);
}

最重要的一点是 timer.schedule(task,1000,5000),如果设置为 timer.schedule(task,5000)是不会工作的。

因为timer.schedule(task,5000) 是表示执行一次的任务。
timer.schedule(task,1000,5000)表示 1 秒钟后开始 5 秒钟为周期 重复执行，
更好的方法是通过下面的代码 (Handler加Runnable线程，更简洁）

java代码：
private Handler handler = new Handler( );

private Runnable runnable = new Runnable( ) {
public void run ( ) {
update( );

handler.postDelayed(this,1000);
//postDelayed(this,1000)方法安排一个Runnable对象到主线程队列中
}
};

handler.postDelayed(runnable,1000); // 开始Timer
handler.removeCallbacks(runnable); //停止Timer