Looper物件之角色(Demo 3)

这个例子是为了更进一步的理解Demo2
这个例子跟Demo2只是有些小的改动,大家可以对比的看下
Java代码 
 
package com.example.Looper_03;  
 
import android.app.Activity;  
import android.content.Context;  
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 Looper_03 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;  
    EventHandler h;  
    Context ctx;  
 
    public void onCreate(Bundle icicle) {  
        super.onCreate(icicle);  
        ctx = this;  
        LinearLayout layout = new LinearLayout(this);  
        layout.setOrientation(LinearLayout.VERTICAL);  
        btn = new Button(this);  
        btn.setId(101);  
        btn.setBackgroundResource(R.drawable.icon);  
        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.setBackgroundResource(R.drawable.icon);  
        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:  
            // 此h是屬於main線程的(用來存取主線程的MessageQueue)  
            //h = new EventHandler(Looper.myLooper());//@  
              
            //或者可以写成这样;  
            h = new EventHandler();  
              
            t = new myThread();  
            t.start();  
            break;  
        case 102:  
            finish();  
            break;  
        }  
    }  
      
    //或者可以写成这样;  
    public class EventHandler extends Handler {  
        @Override 
        public void handleMessage(Message msg) {  
            ((Activity) ctx).setTitle((String) msg.obj);  
        }  
    }  
 
    // ------------------------------------------------  
    /*public class EventHandler extends Handler {//@ 
        public EventHandler(Looper looper) { 
            super(looper); 
        } 

        @Override 
        public void handleMessage(Message msg) { 
            ((Activity) ctx).setTitle((String) msg.obj); 
        } 
    }*/ 
 
    // ------------------------------------------------------  
    class myThread extends Thread {  
        public void run() {  
            String obj = "from myThread";  
            Message m = h.obtainMessage(1, 1, 1, obj);  
            //这里还是通过主线程的handler来传送消息  
            //所以还是由主线程的Looper来接受消息  
            h.sendMessage(m);  
        }  
    }  
}  
// ------------------------------------------------------