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

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