Android 中比 Timer 更好方法

电玩女神 2022-10-01 03:46 61阅读 0赞

Android中的Timer一般像下面这样写：

**Timer timer = new Timer( );**

**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）**

**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**