Handler的使用--如何实现Android计时功能

Handler实现计时效果:

 private TextView tv;
    private int time = 11;
    private Handler mHandler = new Handler();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        initView();
        mHandler.post(myRunnale);
    }

    private void initView() {
        tv = (TextView) findViewById(R.id.tv);
    }

    private Runnable myRunnale = new Runnable() {
        @Override
        public void run() {
            time--;
            if(time>0){
                mHandler.postDelayed(myRunnale,1000);
                tv.setText("剩余"+time+"s");
            }else{
                tv.setText("完毕");
            }
        }
    };

其他方式:

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