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September 2, 2015 16:00
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/* | |
* 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 | |
* | |
* http://www.apache.org/licenses/LICENSE-2.0 | |
* | |
* 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; | |
/** | |
* IntentService is a base class for {@link Service}s that handle asynchronous | |
* requests (expressed as {@link Intent}s) on demand. Clients send requests | |
* through {@link android.content.Context#startService(Intent)} calls; the | |
* service is started as needed, handles each Intent in turn using a worker | |
* thread, and stops itself when it runs out of work. | |
* | |
* <p>This "work queue processor" pattern is commonly used to offload tasks | |
* from an application's main thread. The IntentService class exists to | |
* simplify this pattern and take care of the mechanics. To use it, extend | |
* IntentService and implement {@link #onHandleIntent(Intent)}. IntentService | |
* will receive the Intents, launch a worker thread, and stop the service as | |
* appropriate. | |
* | |
* <p>All requests are handled on a single worker thread -- they may take as | |
* long as necessary (and will not block the application's main loop), but | |
* only one request will be processed at a time. | |
* | |
* <div class="special reference"> | |
* <h3>Developer Guides</h3> | |
* <p>For a detailed discussion about how to create services, read the | |
* <a href="{@docRoot}guide/topics/fundamentals/services.html">Services</a> developer guide.</p> | |
* </div> | |
* | |
* @see android.os.AsyncTask | |
*/ | |
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); | |
} | |
} | |
/** | |
* 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; | |
} | |
/** | |
* Sets intent redelivery preferences. Usually called from the constructor | |
* with your preferred semantics. | |
* | |
* <p>If enabled is true, | |
* {@link #onStartCommand(Intent, int, int)} will return | |
* {@link Service#START_REDELIVER_INTENT}, so if this process dies before | |
* {@link #onHandleIntent(Intent)} returns, the process will be restarted | |
* and the intent redelivered. If multiple Intents have been sent, only | |
* the most recent one is guaranteed to be redelivered. | |
* | |
* <p>If enabled is false (the default), | |
* {@link #onStartCommand(Intent, int, int)} will return | |
* {@link Service#START_NOT_STICKY}, and if the process dies, the Intent | |
* dies along with it. | |
*/ | |
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 + "]"); | |
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); | |
} | |
/** | |
* 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(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; | |
} | |
/** | |
* 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)}. | |
*/ | |
protected abstract void onHandleIntent(Intent intent); | |
} |
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