Android之Handler详解（四）-优快云博客

本文链接：https://blog.youkuaiyun.com/iteye_11971/article/details/82202101

本文详细介绍了如何在Android应用中利用Handler机制实现主线程与子线程间的双向消息传递，包括创建Looper、发送与接收消息的过程，并通过实例演示了如何在不同线程间传递消息，以及如何在主线程中接收子线程的消息并进行相应处理。

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d、自己创建新的线程，然后在新线程中创建Looper，主线程调用子线程中的发消息方法，将消息发给子线程的消息队列。

package com.dxyh.test;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.util.Log;

public class MainActivity extends Activity {
	private final static String TAG = "HandlerTest";
	
	private final static int TASK_BEGIN	= 1;
	private final static int TASK_1	= 2;
	private final static int TASK_2	= 3;
	private final static int TASK_END	= 4;
	
	private Handler workHandler = null;
	
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Log.i(TAG, "[M_TID:" + Thread.currentThread().getId() + "]" +
        		"This is in main thread.");
        
        LooperThread testThread = new LooperThread();
        testThread.start();
        
        // 注意，这里需要等待一下，防止出现空指针异常
        while (null == workHandler) {
        }
        
        testThread.sendMessageTodoYourWork();
    }
    
    class LooperThread extends Thread {
    	@Override
    	public void run() {
    		Looper.prepare();
    		
    		workHandler = new Handler() {
    			// 现在在每个case之后，你可以做任何耗时的操作了
    	    	@Override
    	    	public void handleMessage(Message msg) {
    	    		switch (msg.what) {
    	    		case TASK_BEGIN:
    	    			Log.i(TAG, "[H_TID:" +
    	    			   Thread.currentThread().getId() + "] Get TASK_BEGIN");
    	    			break;
    	    			
    	    		case TASK_1:
    	    			Log.i(TAG, "[H_TID:" +
    	    			   Thread.currentThread().getId() + "] Get TASK_1");
    	    			break;
    	    			
    	    		case TASK_2:
    	    			Log.i(TAG, "[H_TID:" +
    	    			   Thread.currentThread().getId() + "] Get TASK_2");
    	    			break;
    	    			
    	    		case TASK_END:
    	    			Log.i(TAG, "[H_TID:" +
    	    			   Thread.currentThread().getId() + "] Get TASK_END");
    	    			Looper.myLooper().quit();
    	    			finish();
    	    			break;
    	    		}
    	    		super.handleMessage(msg);
    	    	}
    		};
    		
    		Looper.loop();
    	}
    	
    	public void sendMessageTodoYourWork() {
    		Log.i(TAG, "[S_ID:" + Thread.currentThread().getId() + "]" +
				"Send TASK_START to handler.");
    		// 启动任务（消息只有标识，立即投递）
    		workHandler.sendEmptyMessage(TASK_BEGIN);

    		Log.i(TAG, "[S_ID:" + Thread.currentThread().getId() + "]" +
				"Send TASK_1 to handler.");
    		// 开始任务1（在workHandler的消息队列中获取一个Message对象，避免重复构造）
    		Message msg1 = workHandler.obtainMessage(TASK_1);
    		msg1.obj = "This is task1";
    		workHandler.sendMessage(msg1);
    		
    		Log.i(TAG, "[S_ID:" + Thread.currentThread().getId() + "]" +
				"Send TASK_2 to handler.");    		
    		// 开启任务2（和上面类似）
    		Message msg2 = Message.obtain();
    		msg2.arg1 = 10;
    		msg2.arg2 = 20;
    		msg2.what = TASK_2;
    		workHandler.sendMessage(msg2);

    		Log.i(TAG, "[S_ID:" + Thread.currentThread().getId() + "]" +
				"Send TASK_END to handler.");
    		// 结束任务（空消息体，延时2s投递）
    		workHandler.sendEmptyMessageDelayed(TASK_END, 2000);
    	}
    }
}

运行结果：

e、主/子线程均有一个消息队列，然后相互传递消息（这种方式是最灵活的，双向传递，也不复杂）

package com.dxyh.test;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.util.Log;

public class MainActivity extends Activity {
	private final static String TAG = "HandlerTest";
	
	private final static int TASK_BEGIN		= 1;
	private final static int TASK_1		= 2;
	private final static int TASK_2		= 3;
	private final static int TASK_END		= 4;
	
	private final static int TASK_BEGIN_OVER	= 11;
	private final static int TASK_1_OVER	= 12;
	private final static int TASK_2_OVER	= 13;
	private final static int TASK_END_OVER	= 14;
	
	private Handler workHandler = null;
	
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Log.i(TAG, "[M_TID:" + Thread.currentThread().getId() + "]" +
        		"This is in main thread.");
        
        LooperThread testThread = new LooperThread();
        testThread.start();
        
        // 注意，这里需要等待一下，防止出现空指针异常
        while (null == workHandler) {
        }
        
        testThread.sendMessageTodoYourWork();
    }
  
    Handler mainHandler = new Handler () {
    	// 在每个case之后，不能做耗时的操作
    	@Override
    	public void handleMessage(Message msg) {
    		switch (msg.what) {
    		case TASK_BEGIN_OVER:
    			Log.i(TAG, "[MH_TID:" +
    				Thread.currentThread().getId() + "] TASK_BEGIN_OVER");
    			break;
    			
    		case TASK_1_OVER:
    			Log.i(TAG, "[MH_TID:" +
    				Thread.currentThread().getId() + "] TASK_1_OVER");
    			break;
    			
    		case TASK_2_OVER:
    			Log.i(TAG, "[MH_TID:" +
    				Thread.currentThread().getId() + "] TASK_2_OVER");
    			break;
    			
    		case TASK_END_OVER:
    			Log.i(TAG, "[MH_TID:" +
    				Thread.currentThread().getId() + "] TASK_END_OVER");
    			finish();
    			break;
    		}
    		super.handleMessage(msg);
    	}
    };
    
    class LooperThread extends Thread {
    	@Override
    	public void run() {
    		Looper.prepare();
    		
    		workHandler = new Handler() {
    			// 现在在每个case之后，你可以做任何耗时的操作了
    	    	@Override
    	    	public void handleMessage(Message msg) {
    	    		switch (msg.what) {
    	    		case TASK_BEGIN:
    	    			Log.i(TAG, "[ZH_TID:" +
    	    			   Thread.currentThread().getId() + "] Get TASK_BEGIN");
    	    			// 做完之后报告信息给主线程
    	    			mainHandler.sendEmptyMessage(TASK_BEGIN_OVER);
    	    			break;
    	    			
    	    		case TASK_1:
    	    			Log.i(TAG, "[ZH_TID:" +
    	    			   Thread.currentThread().getId() + "] Get TASK_1");
    	    			// 做完之后报告信息给主线程
    	    			mainHandler.sendEmptyMessage(TASK_1_OVER);
    	    			break;
    	    			
    	    		case TASK_2:
    	    			Log.i(TAG, "[ZH_TID:" +
    	    			   Thread.currentThread().getId() + "] Get TASK_2");
    	    			// 做完之后报告信息给主线程
    	    			mainHandler.sendEmptyMessage(TASK_2_OVER);
    	    			break;
    	    			
    	    		case TASK_END:
    	    			Log.i(TAG, "[ZH_TID:" +
    	    			   Thread.currentThread().getId() + "] Get TASK_END");
    	    			Looper.myLooper().quit();
    	    			// 做完之后报告信息给主线程
    	    			mainHandler.sendEmptyMessage(TASK_END_OVER);
    	    			Looper.myLooper().quit();
    	    			break;
    	    		}
    	    		super.handleMessage(msg);
    	    	}
    		};
    		
    		Looper.loop();
    	}
    	
    	public void sendMessageTodoYourWork() {
    		Log.i(TAG, "[ZS_ID:" + Thread.currentThread().getId() + "]" +
				"Send TASK_START to handler.");
    		// 启动任务（消息只有标识，立即投递）
    		workHandler.sendEmptyMessage(TASK_BEGIN);

    		Log.i(TAG, "[ZS_ID:" + Thread.currentThread().getId() + "]" +
				"Send TASK_1 to handler.");
    		// 开始任务1（在workHandler的消息队列中获取一个Message对象，避免重复构造）
    		Message msg1 = workHandler.obtainMessage(TASK_1);
    		msg1.obj = "This is task1";
    		workHandler.sendMessage(msg1);
    		
    		Log.i(TAG, "[ZS_ID:" + Thread.currentThread().getId() + "]" +
				"Send TASK_2 to handler.");    		
    		// 开启任务2（和上面类似）
    		Message msg2 = Message.obtain();
    		msg2.arg1 = 10;
    		msg2.arg2 = 20;
    		msg2.what = TASK_2;
    		workHandler.sendMessage(msg2);

    		Log.i(TAG, "[ZS_ID:" + Thread.currentThread().getId() + "]" +
				"Send TASK_END to handler.");
    		// 结束任务（空消息体，延时2s投递）
    		workHandler.sendEmptyMessageDelayed(TASK_END, 2000);
    	}
    }
}

以上一到四均摘自：http://blog.youkuaiyun.com/dengxiayehu