Android实现计时与倒计时

[希尔瓦娜斯]

方法一
Timer与TimerTask（Java实现）

public class timerTask extends Activity{  
  
   private int recLen = 11;  
   private TextView txtView;  
   Timer timer = new Timer();  
  
   public void onCreate(Bundle savedInstanceState){  
   super.onCreate(savedInstanceState);  
   
   setContentView(R.layout.timertask);  
   txtView = (TextView)findViewById(R.id.txttime);  
   
   timer.schedule(task, 1000, 1000);       // timeTask  
   }     
  
   TimerTask task = new TimerTask() {  
   @Override  
   public void run() {  
  
   runOnUiThread(new Runnable() {      // UI thread  
   @Override  
   public void run() {  
   recLen--;  
   txtView.setText(""+recLen);  
   if(recLen < 0){  
   timer.cancel();  
   txtView.setVisibility(View.GONE);  
   }  
   }  
   });  
   }  
   };  
}  

方法二
TimerTask与Handler（不用Timer的改进型）

public class timerTask extends Activity{  
   private int recLen = 11;  
   private TextView txtView;  
   Timer timer = new Timer();  
  
   public void onCreate(Bundle savedInstanceState){  
   super.onCreate(savedInstanceState);  
  
   setContentView(R.layout.timertask);  
   txtView = (TextView)findViewById(R.id.txttime);  
  
   timer.schedule(task, 1000, 1000);       // timeTask  
   }     
  
   final Handler handler = new Handler(){  
   @Override  
   public void handleMessage(Message msg){  
   switch (msg.what) {  
   case 1:  
   txtView.setText(""+recLen);  
   if(recLen < 0){  
   timer.cancel();  
   txtView.setVisibility(View.GONE);  
   }  
   }  
   }  
   };  
  
   TimerTask task = new TimerTask() {  
   @Override  
   public void run() {  
   recLen--;  
   Message message = new Message();  
   message.what = 1;  
   handler.sendMessage(message);  
   }  
   };  
} 

方法三
Handler与Message（不用TimerTask）

public class timerTask extends Activity{  
   private int recLen = 11;  
   private TextView txtView;  
  
   public void onCreate(Bundle savedInstanceState) {    
   super.onCreate(savedInstanceState);    
  
   setContentView(R.layout.timertask);   
   txtView = (TextView)findViewById(R.id.txttime);  
  
   Message message = handler.obtainMessage(1);     // Message  
   handler.sendMessageDelayed(message, 1000);  
   }    
  
   final Handler handler = new Handler(){  
  
   public void handleMessage(Message msg){         // handle message  
   switch (msg.what) {  
   case 1:  
   recLen--;  
   txtView.setText("" + recLen);  
  
   if(recLen > 0){  
   Message message = handler.obtainMessage(1);  
   handler.sendMessageDelayed(message, 1000);      // send message  
   }else{  
   txtView.setVisibility(View.GONE);  
   }  
   }  
  
   super.handleMessage(msg);  
   }  
   };  
}  

方法四
Handler与Thread（不占用UI线程）

public class timerTask extends Activity{  
   private int recLen = 0;  
   private TextView txtView;  
  
   public void onCreate(Bundle savedInstanceState){  
   super.onCreate(savedInstanceState);  
  
   setContentView(R.layout.timertask);  
   txtView = (TextView)findViewById(R.id.txttime);  
   
   new Thread(new MyThread()).start();         // start thread  
   }     
  
   final Handler handler = new Handler(){          // handle  
   public void handleMessage(Message msg){  
   switch (msg.what) {  
   case 1:  
   recLen++;  
   txtView.setText("" + recLen);  
   }  
   super.handleMessage(msg);  
   }  
   };  
  
   public class MyThread implements Runnable{      // thread  
   @Override  
   public void run(){  
   while(true){  
   try{  
   Thread.sleep(1000);     // sleep 1000ms  
   Message message = new Message();  
   message.what = 1;  
   handler.sendMessage(message);  
   }catch (Exception e) {  
   }  
   }  
   }  
   }  
}

方法五
Handler与Runnable（最简单型）

public class timerTask extends Activity{  
   private int recLen = 0;  
   private TextView txtView;  
  
   public void onCreate(Bundle savedInstanceState){  
   super.onCreate(savedInstanceState);  
  
   setContentView(R.layout.timertask);  
   txtView = (TextView)findViewById(R.id.txttime);  
   
   handler.postDelayed(runnable, 1000);  
   }     
  
   Handler handler = new Handler();  
   Runnable runnable = new Runnable() {  
   @Override  
   public void run() {  
   recLen++;  
   txtView.setText("" + recLen);  
   handler.postDelayed(this, 1000);  
   }  
   };  
}  

计时与倒计时
方法1，方法2和方法3，都是倒计时
方法4，方法5，都是计时
计时和倒计时，都可使用上述方法实现（代码稍加改动）

UI线程比较
方法1，方法2和方法3，都是在UI线程实现的计时；
方法4和方法5，是另开Runnable线程实现计时

实现方式比较
方法1，采用的是Java实现，即Timer和TimerTask方式；
其它四种方法，都采用了Handler消息处理

推荐使用
如果对UI线程交互要求不很高，可以选择方法2和方法3
如果考虑到UI线程阻塞，严重影响到用户体验，推荐使用方法4，另起线程单独用于计时和其它的逻辑处理
方法5，综合了前几种方法的优点，是最简的