Handler基本概念

Handler基本概念： Handler主要用于异步消息的处理：当发出一个消息之后，首先进入一个消息队列，发送消息的函数即刻返回，而另外一个部分逐个的在消息队列中将消息取出，然后对消息进行出来，就是发送消息和接收消息不是同步的处理。 这种机制通常用来处理相对耗时比较长的操作。 Handler 常用方法：

post(Runnable)

postAtTime(Runnable,long)

postDelayed(Runnable long)

sendEmptyMessage(int)

sendMessage(Message)

sendMessageAtTime(Message,long)

sendMessageDelayed(Message,long)

以上post类方法允许你排列一个Runnable对象到主线程队列中, sendMessage类方法, 允许你安排一个带数据的Message对象到队列中，等待更新.

Android三种实现定时器的方法 

方法一:Handler+Thread

package com.xunfang.handerDemo;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.TextView;

/**
 * handler定时器
 *
 * @author Smalt
 *
 */
public class HanderDemoActivity extends Activity {
    TextView tvShow;
    private int i = 0;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        tvShow = (TextView) findViewById(R.id.tv_show);
        new Thread(new ThreadShow()).start();
    }

    // handler类接收数据
    Handler handler = new Handler() {
        public void handleMessage(Message msg) {
            if (msg.what == 1) {
                tvShow.setText(Integer.toString(i++));
                System.out.println("receive....");
            }
        };
    };

    // 线程类
    class ThreadShow implements Runnable {

        @Override
        public void run() {
            // TODO Auto-generated method stub
            while (true) {
                try {
                    Thread.sleep(1000);
                    Message msg = new Message();
                    msg.what = 1;
                    handler.sendMessage(msg);
                    System.out.println("send...");
                } catch (Exception e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                    System.out.println("thread error...");
                }
            }
        }
    }
}

package com.xunfang.handerDemo;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.TextView;

/**
 * handler定时器
 * 
 * @author Smalt
 * 
 */
public class HanderDemoActivity extends Activity {
	TextView tvShow;
	private int i = 0;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		tvShow = (TextView) findViewById(R.id.tv_show);
		new Thread(new ThreadShow()).start();
	}

	// handler类接收数据
	Handler handler = new Handler() {
		public void handleMessage(Message msg) {
			if (msg.what == 1) {
				tvShow.setText(Integer.toString(i++));
				System.out.println("receive....");
			}
		};
	};

	// 线程类
	class ThreadShow implements Runnable {

		@Override
		public void run() {
			// TODO Auto-generated method stub
			while (true) {
				try {
					Thread.sleep(1000);
					Message msg = new Message();
					msg.what = 1;
					handler.sendMessage(msg);
					System.out.println("send...");
				} catch (Exception e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
					System.out.println("thread error...");
				}
			}
		}
	}
}

方法二:Handler类自带的postDelyed

package com.xunfang.handerDemo;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.widget.TextView;

/**
 * handler定时器使用postDelyed实现
 *
 * @author Smalt
 *
 */
public class HanderDemoActivity extends Activity {
    TextView tvShow;
    private int i = 0;
    private int TIME = 1000;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        tvShow = (TextView) findViewById(R.id.tv_show);
        handler.postDelayed(runnable, TIME); //每隔1s执行
    }

    Handler handler = new Handler();
    Runnable runnable = new Runnable() {

        @Override
        public void run() {
            // handler自带方法实现定时器
            try {
                handler.postDelayed(this, TIME);
                tvShow.setText(Integer.toString(i++));
                System.out.println("do...");
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
                System.out.println("exception...");
            }
        }
    };

}

package com.xunfang.handerDemo;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.widget.TextView;

/**
 * handler定时器使用postDelyed实现
 * 
 * @author Smalt
 * 
 */
public class HanderDemoActivity extends Activity {
	TextView tvShow;
	private int i = 0;
	private int TIME = 1000;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		tvShow = (TextView) findViewById(R.id.tv_show);
		handler.postDelayed(runnable, TIME); //每隔1s执行
	}

	Handler handler = new Handler();
	Runnable runnable = new Runnable() {

		@Override
		public void run() {
			// handler自带方法实现定时器
			try {
				handler.postDelayed(this, TIME);
				tvShow.setText(Integer.toString(i++));
				System.out.println("do...");
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
				System.out.println("exception...");
			}
		}
	};

}

方法三:

Handler+Timer+TimerTask

package com.xunfang.handerDemo;

import java.util.Timer;
import java.util.TimerTask;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.TextView;

/**
 * 定时器实现:Handler+Timer+TimerTask
 *
 * @author Smalt
 *
 */
public class HanderDemoActivity extends Activity {
    TextView tvShow;
    private int i = 0;
    private int TIME = 1000;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        tvShow = (TextView) findViewById(R.id.tv_show);
        timer.schedule(task, 1000, 1000); // 1s后执行task,经过1s再次执行
    }

    Handler handler = new Handler() {
        public void handleMessage(Message msg) {
            if (msg.what == 1) {
                tvShow.setText(Integer.toString(i++));
            }
            super.handleMessage(msg);
        };
    };
    Timer timer = new Timer();
    TimerTask task = new TimerTask() {

        @Override
        public void run() {
            // 需要做的事:发送消息
            Message message = new Message();
            message.what = 1;
            handler.sendMessage(message);
        }
    };
}