Android实现计时与倒计时的几种方法

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