Looper物件之角色(Demo 4)

这个例子主要演示了主,子线程之间的信息交互
Java代码 
package com.example.Looper_04;  
 
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_04 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;  
    private Handler h;  
    private 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);  
        // 这里执行了子线程  
        t = new myThread();  
        t.start();  
    }  
 
    public void onClick(View v) {  
        switch (v.getId()) {  
        case 101:  
            String obj = "mainThread";  
            Message m = h.obtainMessage(1, 1, 1, obj);  
            // 发送的消息由子线程的handler来进行处理  
            h.sendMessage(m);  
            break;  
        case 102:  
            h.getLooper().quit();  
            finish();  
            break;  
        }  
    }  
 
    // ------------------------------------------------  
    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() {  
            // 初始化当前子线程的Looper物件之管理对象  
            Looper.prepare();  
            h = new Handler() {  
                public void handleMessage(Message msg) {  
                    //又建立了主线程的handler对象  
                    EventHandler ha = new EventHandler(Looper.getMainLooper());  
                    String obj = (String) msg.obj + ", myThread";  
                    Message m = ha.obtainMessage(1, 1, 1, obj);  
                    ha.sendMessage(m);  
                }  
            };  
            Looper.loop();  
        }  
    }  
}