Android 的消息机制（3）

当然我们也可以隐式的指定Looper ，代码如下：

^?[Copy to clipboard] Download zuiniuwang.java

 

/**
 * MessageQueue2.java
 * com.test
 *
 * Function： TODO
 *
 *   ver     date           author
 * ──────────────────────────────────
 *           2011-3-20      Leon
 *
 * Copyright (c) 2011, TNT All Rights Reserved.
*/

package com.test.messagequeue;
/**
 * ClassName:MessageQueue2
 * Function: TODO ADD FUNCTION
 * Reason:   TODO ADD REASON
 *
 * @author   Leon
 * @version
 * @since    Ver 1.1
 * @Date     2011-3-20
 */
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.TextView;

public class MessageQueue3 extends Activity implements OnClickListener {
    private final int WC = LinearLayout.LayoutParams.WRAP_CONTENT;
    private final int FP = LinearLayout.LayoutParams.FILL_PARENT;
    public TextView tv;
    private myThread t;
    private Button btn, btn2, btn3;
    private EHandler mHandler;

    public void onCreate(Bundle icicle) {
                super.onCreate(icicle);
                LinearLayout layout = new LinearLayout(this);
                layout.setOrientation(LinearLayout.VERTICAL);

                btn = new Button(this);
                btn.setId(101);
                btn.setText("test looper");
                btn.setOnClickListener(this);
                LinearLayout.LayoutParams param =
                    new LinearLayout.LayoutParams(100,50);
                param.topMargin = 10;
                layout.addView(btn, param);

                btn2 = new Button(this);
                btn2.setId(102);
                btn2.setText("exit");
                btn2.setOnClickListener(this);
                layout.addView(btn2, param);

                tv = new TextView(this);
                tv.setTextColor(Color.WHITE);
                tv.setText("");
                LinearLayout.LayoutParams param2 =
                   new LinearLayout.LayoutParams(FP, WC);
                param2.topMargin = 10;
                layout.addView(tv, param2);
                setContentView(layout);
               }
        public void onClick(View v) {
        switch(v.getId()){
        case 101:
//           mHandler = new EHandler(Looper.myLooper());
             //可以隐式的制定Looper,和上面的效果是一样的
             mHandler = new EHandler();
             t = new myThread();
             t.start();
             break;
        case 102:
            finish();
            break;
        }
    }
//------------------------------------------------------
class EHandler extends Handler {
            public EHandler(Looper looper) {
                super(looper);
            }
            public EHandler(){

            }
            @Override
            public void handleMessage(Message msg) {
               tv.setText((String)msg.obj);
        }
    }
//------------------------------------------------------
class myThread extends Thread{

     public void run() {

         String obj = "This message is from new thread.";
         mHandler.removeMessages(0);
         Message m = mHandler.obtainMessage(1, 1, 1, obj);
         mHandler.sendMessage(m);
      }
  }

 

 

在此代码中，指令：h = new EventHandler()；就等于：h = new EventHandler(Looper.myLooper())；
它建立了当前线程(Current Thread)的EventHandler对象。由于是由main线程执行此指令的，所以此EventHandler对象是用来存取main线程的Message Queue的。