core/java/android/app/IntentService.java

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;

/**
 * An abstract {@link Service} that serializes the handling of the Intents passed upon service
 * start and handles them on a handler thread.
 *
 * <p>To use this class extend it and implement {@link #onHandleIntent}. The {@link Service} will
 * automatically be stopped when the last enqueued {@link Intent} is handled.
 */
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;
    }

    /**
     * Control redelivery of intents.  If called with true,
     * {@link #onStartCommand(Intent, int, int)} will return
     * {@link Service#START_REDELIVER_INTENT} instead of
     * {@link Service#START_NOT_STICKY}, so that if this service's process
     * is called while it is executing the Intent in
     * {@link #onHandleIntent(Intent)}, then when later restarted the same Intent
     * will be re-delivered to it, to retry its execution.
     */
    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;
    }

    /**
     * Invoked on the Handler thread with the {@link Intent} that is passed to {@link #onStart}.
     * Note that this will be invoked from a different thread than the one that handles the
     * {@link #onStart} call.
     */
    protected abstract void onHandleIntent(Intent intent);
}