Handler消息傳遞機制Demo

說明：

要想在非主線程中，建立Handler對象，首先須要使用Looper類的prepare方法來初始化一個Looper對象，而後建立這個Handler對象，再使用Looper類的loop方法，啓動looper，從消息隊列裏獲取和處理消息　。

public void run(){

super.run();

Looper.prepare();

//實例化一個Handler對象

//....................

Looper.loop();

}

下面用一個Demo(圖片隨機展現)

AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.demohandler"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="10"
        android:targetSdkVersion="19" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.demohandler.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >
    
    <ImageView android:id="@+id/imageView1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <TextView android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

</RelativeLayout>

MainActivity.java:

package com.example.demohandler;

import java.util.Random;

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

public class MainActivity extends Activity implements Runnable{
	
	private ImageView iv ;
	private Handler handler;
	private int[] path= new int[]{R.drawable.img1,R.drawable.img3,R.drawable.img3,R.drawable.img4};
	
	private String[] title = new String[]{"高清壁紙1","高清壁紙2","高清壁紙3","高清壁紙4"};

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		iv = (ImageView)findViewById(R.id.imageView1);
		
		Thread t = new Thread(this);
		t.start();
		
		handler = new Handler(){
			public void handleMessage(Message msg){
				TextView tv = (TextView)findViewById(R.id.textView1);
				if(msg.what ==0x101){
					tv.setText(msg.getData().getString("title"));
					iv.setImageResource(path[msg.arg1]);
				}
				super.handleMessage(msg);
			}
		};
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

	@Override
	public void run() {
		// TODO Auto-generated method stub
		int index =0;
		while(!Thread.currentThread().isInterrupted()){
			index = new Random().nextInt(path.length);//產生一個隨機數
			Message m = handler.obtainMessage();//獲取一個Message
			m.arg1 = index;//保存要顯示廣告圖片的索引值
			Bundle bundle = new Bundle();//
			m.what = 0x101;//設置消息標識
			bundle.putString("title", title[index]);//保存標題
			m.setData(bundle);//將Bundle對象保存到Message中
			
			handler.sendMessage(m);//發送消息
			try{
				Thread.sleep(2000);
			}catch(InterruptedException e){
				e.printStackTrace();
			}
		}
	}

}