public IntentService(String name) {
    super();
    mName = name;
}

@WorkerThread
protected abstract void onHandleIntent(@Nullable Intent intent)

@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 + "]");// 创建了HandlerThread来进行异步消息传递
        thread.start();

        mServiceLooper = thread.getLooper();// 传递的是HandlerThread的loop对象;
// (由于looper 对象和 HandlerThread绑定,而HandlerThread又是一个异步线程,把HandlerThread 持有的 looper 传递给 ServiceHandler
这样ServiceHandler就变成了处理异步线程的执行类)
        mServiceHandler = new ServiceHandler(mServiceLooper);// 一个继承了Handler的Handler
    }

/**
     * You should not override this method for your IntentService. Instead,
     * override {@link #onHandleIntent}, which the system calls when the IntentService
     * receives a start request.
     * @see android.app.Service#onStartCommand
     */
    @Override
    public int onStartCommand(@Nullable Intent intent, int flags, int startId) {
        onStart(intent, startId);//实际操作都在onStart
        return mRedelivery ? START_REDELIVER_INTENT : START_NOT_STICKY;
    }

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

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

        @Override
        public void handleMessage(Message msg) {
            onHandleIntent((Intent)msg.obj);
            stopSelf(msg.arg1);// 如果没有参数会立即停止, 如果有参数会等待所有消息都处理完之后才会终止任务
        }
    }
```java
onHandleIntent: 是一个抽象方法, 在创建IntentService时一定要实现该方法(异步方法)
如果执行完会立刻销毁, 当有多个服务时会明确到执行完最后一个服务才会销毁;
stopSelf加参数;

**(Service里不能做耗时操作, 而IntentService可以执行耗时操作)**

```java
/**
     * This method is invoked on the worker thread with a request to process.
     * Only one Intent is processed at a time, but the processing happens on a
     * worker thread that runs independently from other application logic.
     * So, if this code takes a long time, it will hold up other requests to
     * the same IntentService, but it will not hold up anything else.
     * When all requests have been handled, the IntentService stops itself,
     * so you should not call {@link #stopSelf}.
     *
     * @param intent The value passed to {@link
     *               android.content.Context#startService(Intent)}.
     *               This may be null if the service is being restarted after
     *               its process has gone away; see
     *               {@link android.app.Service#onStartCommand}
     *               for details.
     */
    @WorkerThread
    protected abstract void onHandleIntent(@Nullable Intent intent);