service与IntentService 区别

关系：

　　IntentService继承service

区别：

　　IntentService 是一个带有HandlerThread的线程的service，把任务执行完成以后IntentService自动销毁。

　　Service要手动 调用stopSelf（）来销毁。

　　IntentService 运行在子线程中，Service运行在主线程中

作用：

　　 IntentService 用于执行一次复杂的场景使用IntentService相对好一点

　　Service 用于重复执行的场景

代码分析：

　　IntentService 运行在子线程中，Service运行在主线程中

　　MyService 继承Service

package com.example.activitynate;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;

public class MyService extends Service {

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        System.out.println("MyService ===== 所在的线程   "+Thread.currentThread());
        return super.onStartCommand(intent, flags, startId);
    }
}

MyIntentService 继承IntentService

package com.example.activitynate;

import android.app.IntentService;
import android.content.Intent;

public class MyIntentService extends IntentService {

    public MyIntentService(String name) {
        super(name);
    
    }
    public MyIntentService() {
        this("lihao");
    }

    @Override
    protected void onHandleIntent(Intent intent) {
        System.out.println("MyIntentService ===== 所在的线程   "+Thread.currentThread());
    }

    

}

运行结果：

04-07 00:41:58.245: I/System.out(5107): MyService ===== 所在的线程 Thread[main,5,main]
04-07 00:41:58.255: I/System.out(5107): MyIntentService ===== 所在的线程 Thread[IntentService[lihao],5,main]

为什么MyIntentService  会在IntentService[lihao]这个线程中

public abstract class IntentService extends Service {
    private volatile Looper mServiceLooper;
    private volatile ServiceHandler mServiceHandler;
    private String mName;
    private boolean mRedelivery;

    private final class ServiceHandler extends Handler {
        public ServiceHandler(Looper looper) {
            super(looper);
        }

        @Override
        public void handleMessage(Message msg) {
            onHandleIntent((Intent)msg.obj);
15             stopSelf(msg.arg1);
        }
    }

    /**
     * Creates an IntentService.  Invoked by your subclass's constructor.
     *
     * @param name Used to name the worker thread, important only for debugging.
     */
    public IntentService(String name) {
        super();
        mName = name;
    }

 
    public void setIntentRedelivery(boolean enabled) {
        mRedelivery = enabled;
    }

    @Override
    public void onCreate() {
        // TODO: It would be nice to have an option to hold a partial wakelock
        // during processing, and to have a static startService(Context, Intent)
        // method that would launch the service & hand off a wakelock.

        super.onCreate();
        HandlerThread thread = new HandlerThread("IntentService[" + mName + "]");
42         thread.start();
43 
44         mServiceLooper = thread.getLooper();
45         mServiceHandler = new ServiceHandler(mServiceLooper);
    }

    @Override
    public void onStart(Intent intent, int startId) {
        Message msg = mServiceHandler.obtainMessage();
        msg.arg1 = startId;
        msg.obj = intent;
        mServiceHandler.sendMessage(msg);
    }

  
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        onStart(intent, startId);
        return mRedelivery ? START_REDELIVER_INTENT : START_NOT_STICKY;
    }

    @Override
    public void onDestroy() {
        mServiceLooper.quit();
    }

    /**
     * Unless you provide binding for your service, you don't need to implement this
     * method, because the default implementation returns null. 
     * @see android.app.Service#onBind
     */
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

  
    protected abstract void onHandleIntent(Intent intent);
}

从源代码的41-45行中 IntentService 中维护了一个HandlerThread 和一个Handler 很容易看到我们继承的IntentService的线程的名字

由于HandlerThread是个子线程start以后生成了loop传给Handler所以Handler运行在子线程里面然后，Handler发送消息，，接收到消息以后

会调用handleMessage（）方法这个方法里面又调用了onHandleIntent（），这个方法执行完成后调用stopSelf() 13-14行代码，Service将自动销毁。