一般使用
1.自定义一个耗时的IntentService
public class MyIntentService extends IntentService {
/**
* Creates an IntentService. Invoked by your subclass's constructor.
* @param name Used to name the worker thread, important only for debugging.
*/
public MyIntentService(String name) {
super(name);
}
...
@Override
protected void onHandleIntent(Intent intent) {
Log.e("MyIntentService--", Thread.currentThread().getName() + "--" + intent.getStringExtra("info") );
for(int i = 0; i < 100; i++){ //耗时操作
Log.i("onHandleIntent--", i + "--" + Thread.currentThread().getName());
}
}
}
2.启动IntentService
Intent intent = new Intent(this, MyIntentService.class);
intent.putExtra("info", "test");
startService(intent);
源码分析
public abstract class IntentService extends Service {
private volatile Looper mServiceLooper;
private volatile ServiceHandler mServiceHandler;
private String mName;
private boolean mRedelivery;
/**
* 创建一个Handler 来接受处理onHandleIntent
* 处理完耗时onHandleIntent后调用stopSelf停止掉Service
* 所以IntentService 的执行时一次性的
*/
private final class ServiceHandler extends Handler {
public ServiceHandler(Looper looper) {
super(looper);
}
@Override
public void handleMessage(Message msg) {
//处理onHandleIntent
onHandleIntent((Intent)msg.obj);
//停止掉Service
stopSelf(msg.arg1);
}
}
public IntentService(String name) {
super();
mName = name;
}
public void setIntentRedelivery(boolean enabled) {
mRedelivery = enabled;
}
@Override
public void onCreate() {
super.onCreate();
//创建一个HandlerThread
HandlerThread thread = new HandlerThread("IntentService[" + mName + "]");
//开启HandlerThread线程
thread.start();
//获取到HandlerThread的Looper
mServiceLooper = thread.getLooper();
//创建一个ServiceHandler
mServiceHandler = new ServiceHandler(mServiceLooper);
}
/**
*开始时候像mServiceHandler发送一个message
*/
@Override
public void onStart(@Nullable Intent intent, int startId) {
Message msg = mServiceHandler.obtainMessage();
msg.arg1 = startId;
msg.obj = intent;
mServiceHandler.sendMessage(msg);
}
@Override
public int onStartCommand(@Nullable Intent intent, int flags, int startId) {
onStart(intent, startId);
return mRedelivery ? START_REDELIVER_INTENT : START_NOT_STICKY;
}
/**
* 销毁service时候 停止掉mServiceLooper
*/
@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
@Nullable
public IBinder onBind(Intent intent) {
return null;
}
/**
* 模板设计模式的思想 通过子类去实现该方法来执行子类耗时操作
*/
@WorkerThread
protected abstract void onHandleIntent(@Nullable Intent intent);
}
通过源码可以很清楚看出: 通过调用startService 启动 IntentService,调用IntentService的onStart方法,向mServiceHandler发送一个消息,然后处理子类的onHandleIntent 然后调用stopSelf停止掉service然后调用onDestroy 然后mServiceLooper.quit()停止掉HandlerThread的looper
总结
IntentService是继承并处理异步请求的一个类,在IntentService内有一个工作线程来处理耗时操作,启动IntentService的方式和启动传统的Service一样,同时,当任务执行完后,IntentService会自动停止,而不需要我们手动去控制或stopSelf()。另外,可以启动IntentService多次,而每一个耗时操作会以工作队列的方式在IntentService的onHandleIntent回调方法中执行,并且,每次只会执行一个工作线程,执行完第一个再执行第二个。