Android定时器：实现定时的几种方法

当需要更新UI时都需要用到Handler类，否则可以直接处理。

1、用Timer和TimerTask实现

Timer里面有几个比较重要的方法：

void cancel() //取消timer还有任务
Cancels the Timer and all scheduled tasks

void schedule(TimerTask task, long delay, long period) //循环调用可以用此方法，一次调用则是调用另外一个
Schedule a task for repeated fixed-delay execution after a specific delay. //没有最后一个参数的重载方法

void schedule(TimerTask task, Date when, long period) //同上
Schedule a task for repeated fixed-delay execution after a specific time has been reached.

而TimerTask最重要的就是重写run方法

实例：

public class MainActivity extends ActionBarActivity {TextView textView;Button button;Handler handler = new Handler() {     //处理消息的handlerpublic void handleMessage(android.os.Message msg) {textView.setText(msg.obj.toString() + " have excute the task for "+ msg.what + " seconds");}};Timer timer = new Timer();           //实例化一个TimerTimerTask task = new TimerTask() {   //实例化一个TimerTask重写run方法
<span style="white-space:pre">	</span>	private int i = 1;@Overridepublic void run() {// TODO Auto-generated method stubMessage message = Message.obtain();message.obj = "leelit";message.what = i++;handler.sendMessage(message);if (i > 10)timer.cancel();}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);textView = (TextView) findViewById(R.id.textview);button = (Button) findViewById(R.id.button);button.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View arg0) {// TODO Auto-generated method stubtimer.schedule(task, 1000, 1000);      //让task以一秒为周期执行}});}
}

2、用线程的sleep

public class MainActivity extends ActionBarActivity {TextView textView;Button button;Handler handler = new Handler() {public void handleMessage(Message msg) {textView.setText(msg.obj.toString() + " has excuted the task for "+ msg.what + " seconds");}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);textView = (TextView) findViewById(R.id.textview);button = (Button) findViewById(R.id.button);button.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View arg0) {// TODO Auto-generated method stubnew Thread(new TimeTaskThread()).start();   //点击让线程开始}});}private class TimeTaskThread implements Runnable {private int i = 1;private boolean flag = true;@Overridepublic void run() {// TODO Auto-generated method stubwhile (flag) {Message message = Message.obtain();message.obj = "leelit";message.what = i++;handler.sendMessage(message);if (i > 10)                            //终结线程的标志flag = false;                 try {                                  //发送完消息，就让他休眠Thread.sleep(1000);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}}
}

3、用Handler类

final boolean postDelayed(Runnable r, long delayMillis) //特定时间后执行Runnable对象的run方法，要实现循环则在run方法里面再次执行这个方法
Causes the Runnable r to be added to the message queue, to be run after the specified amount of time elapses.

final void removeCallbacks(Runnable r) //将这个Runnable对象移除出消息队列
Remove any pending posts of Runnable r that are in the message queue.

public class MainActivity extends ActionBarActivity {TextView textView;Button button;Handler handler = new Handler() {public void handleMessage(android.os.Message msg) {textView.setText(msg.obj.toString() + " have excute the task for "+ msg.what + " seconds");}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);textView = (TextView) findViewById(R.id.textview);button = (Button) findViewById(R.id.button);button.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View arg0) {// TODO Auto-generated method stubhandler.postDelayed(new TimeTaskThread(), 1000);}});}private class TimeTaskThread implements Runnable {private int i = 1;@Overridepublic void run() {// TODO Auto-generated method stubMessage message = Message.obtain();message.obj = "leelit";message.what = i++;handler.sendMessage(message);handler.postDelayed(this, 1000);      //实现循环执行任务if (i > 10)handler.removeCallbacks(this);}}}

小结：用Timer的 void  schedule(TimerTask task, long delay, long period)方法，用Handler的 final boolean  postDelayed(Runnable r, long delayMillis)方法可以实现定时执行任何，也可以让其循环执行。此外也可以用线程睡眠的方法。