这个面试的时候，相信是面试官最爱的问题之一。简单的来说，IntentService继承至Service，Service和Acitivity一样是依附于应用主进程的，，它本身不是一个进程或者一个线程。一些耗时的操作可能会引起ANR的bug，（本文测试的时候，Service执行20秒没有报ANR），而IntentService，看它的源代码，onCreate()其实是创建了一个新的线程。
<span style="font-size:14px;">/* * Copyright (C) 2008 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package android.app;import android.content.Intent;import android.os.Handler;import android.os.HandlerThread;import android.os.IBinder;import android.os.Looper;import android.os.Message;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);}@Overridepublic void handleMessage(Message msg) {onHandleIntent((Intent)msg.obj);stopSelf(msg.arg1);}}public IntentService(String name) {super();mName = name;}public void setIntentRedelivery(boolean enabled) {mRedelivery = enabled;}@Overridepublic void onCreate() {super.onCreate();HandlerThread thread = new HandlerThread("IntentService[" + mName + "]");thread.start();mServiceLooper = thread.getLooper();mServiceHandler = new ServiceHandler(mServiceLooper);}@Overridepublic void onStart(Intent intent, int startId) {Message msg = mServiceHandler.obtainMessage();msg.arg1 = startId;msg.obj = intent;mServiceHandler.sendMessage(msg);}@Overridepublic int onStartCommand(Intent intent, int flags, int startId) {onStart(intent, startId);return mRedelivery ? START_REDELIVER_INTENT : START_NOT_STICKY;}@Overridepublic void onDestroy() {mServiceLooper.quit();}@Overridepublic IBinder onBind(Intent intent) {return null;}protected abstract void onHandleIntent(Intent intent);}</span> Looper对象会每次从MessageQueue中获取Intent对象，然后Handler处理消息，调用void onHandleIntent(Intent intent)，在这里可以执行一些耗时的比如下载文件等操作。每次调用IntentService都会生成新的HandlerThread，所以不会阻塞UI主线程。如果需要在一个Service里执行耗时操作，那么IntentService是一个很好的选择，不用在Service里面new Thread()或者New AsyncTask()了那么麻烦了。
都在努力为你驱逐烦恼焦躁，
