Android中Handler

本文通过例子来验证和说明使用Handler对象开启的线程是否和主线程为在同一线程中。

程序结构图如下：

[1] HandlerActivity.java中的源码如下：

package com.andyidea.handlerdemo2;

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

public class HandlerActivity extends Activity {

private Handler handler = new Handler();

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//handler.post(r);
setContentView(R.layout.main);
Log.e("activity-->" ,Thread.currentThread().getId() + "");
Log.e("activityname-->" ,Thread.currentThread().getName() + "");

//与主线程同一线程
handler.post(r);

//与主线程不同线程
HandlerThread handlerThread = new HandlerThread("handler_thread");
handlerThread.start();
//HandlerThread线程对象要启动后，
//通过handlerThread.getLooper()方法才能获得Looper对象
MyHandler myHandler = new MyHandler(handlerThread.getLooper());
Message msg  = myHandler.obtainMessage();
msg.sendToTarget();  //发送消息的方式
}

//创建一个线程对象
Runnable r = new Runnable() {

@Override
public void run() {
Log.e("handler-->" ,Thread.currentThread().getId() + "");
Log.e("handlername-->" ,Thread.currentThread().getName() + "");
try{
Thread.sleep(10*1000);
}catch(InterruptedException e){
e.printStackTrace();
}
}
};

//创建Handler对象
class MyHandler extends Handler{

public MyHandler(){

}

public MyHandler(Looper looper){
super(looper);
}

@Override
public void handleMessage(Message msg) {
Log.e("handler-->" ,Thread.currentThread().getId() + "");
Log.e("handler-->" ,Thread.currentThread().getName() + "");
}

}
}

package com.andyidea.handlerdemo2; import android.app.Activity; import android.os.Bundle; import android.os.Handler; import android.os.HandlerThread; import android.os.Looper; import android.os.Message; import android.util.Log; public class HandlerActivity extends Activity { private Handler handler = new Handler(); @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); //handler.post(r); setContentView(R.layout.main); Log.e("activity-->" ,Thread.currentThread().getId() + ""); Log.e("activityname-->" ,Thread.currentThread().getName() + ""); //与主线程同一线程 handler.post(r); //与主线程不同线程 HandlerThread handlerThread = new HandlerThread("handler_thread"); handlerThread.start(); //HandlerThread线程对象要启动后， //通过handlerThread.getLooper()方法才能获得Looper对象 MyHandler myHandler = new MyHandler(handlerThread.getLooper()); Message msg = myHandler.obtainMessage(); msg.sendToTarget(); //发送消息的方式 } //创建一个线程对象 Runnable r = new Runnable() { @Override public void run() { Log.e("handler-->" ,Thread.currentThread().getId() + ""); Log.e("handlername-->" ,Thread.currentThread().getName() + ""); try{ Thread.sleep(10*1000); }catch(InterruptedException e){ e.printStackTrace(); } } }; //创建Handler对象 class MyHandler extends Handler{ public MyHandler(){ } public MyHandler(Looper looper){ super(looper); } @Override public void handleMessage(Message msg) { Log.e("handler-->" ,Thread.currentThread().getId() + ""); Log.e("handler-->" ,Thread.currentThread().getName() + ""); } } }

运行程序后，我们通过Logcat控制台的log.e输出可以看到结果如下：

通过验证，可以看到如果只是通过Handler对象的post()方法，只是把一个子线程对象放到主线程队列中，并不是开启了一个子线程。通过HandlerThread对象方式才是开启了一个新的线程去执行程序。