IntentService源码分析以及HandlerThread的用法

最新推荐文章于 2025-11-09 17:04:45 发布

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本文解析了Android中IntentService的工作原理及其实现方式。IntentService继承自Service，通过内部维护的HandlerThread实现任务队列，能够自动处理Intent并最终停止自身。

直接上源码：

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);
            stopSelf(msg.arg1);
        }
    }

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

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

    @Override
    public void onCreate() {

        super.onCreate();
        HandlerThread thread = new HandlerThread("IntentService[" + mName + "]");
        thread.start();

        mServiceLooper = thread.getLooper();
        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();
    }

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

    protected abstract void onHandleIntent(Intent intent);
}

HandlerThread部分源码：

public class HandlerThread extends Thread {
    int mPriority;
    int mTid = -1;
    Looper mLooper;

    public HandlerThread(String name) {
        super(name);
        mPriority = Process.THREAD_PRIORITY_DEFAULT;
    }
	
	---

    @Override
    public void run() {
        mTid = Process.myTid();
        Looper.prepare();
        synchronized (this) {
            mLooper = Looper.myLooper();
            notifyAll();
        }
        Process.setThreadPriority(mPriority);
        onLooperPrepared();
        Looper.loop();
        mTid = -1;
    }
	
	---
	
}

分析：

IntentService继承自Service，是一个抽象类。

调用onCreate()方法时就new了一个HandlerThread和ServiceHandler对象，IntentService不会轻易被系统杀死。

调用startService()方法时，IntentService会把传递来的参数封装成Message并通过ServiceHandler进行发送。

接着ServiceHandler会调用onHandleIntent()方法来处理这个Message，处理完成后就会调用stopSelf()方法来结束自己。

HandlerThread继承自Thread，使用可以参考IntentService使用HandlerThread的用法。