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

参考推荐：

Android之多线程工作-AsyncTask与handler