Multiple activities binding to a service

问题

I have a service component (common task for all my apps), which can be invoked by any of the apps. I am trying to access the service object from the all activities, I noticed that the one which created the service [startService(intent)] has the right informaion. But rest does not get the informaion needed. My Code is as below:

// Activity.java
public void onCreate(Bundle savedInstanceState) {
    ...

    Intent intent = new Intent (this.context, Service.class) ;
    this.context.startService(intent) ;
    this.context.bindService(intent, this, Context.BIND_AUTO_CREATE) ;
    ...
    String result = serviceObj.getData() ;
}

public void onServiceConnected(ComponentName name, IBinder service) {
    serviceObj = ((Service.LocalBinder)service).getService();
    timer.scheduleAtFixedRate(task, 5000, 60000 ) ;
}



// Service.java

private final IBinder mBinder = new LocalBinder();

public class LocalBinder extends Binder {
    Service getService() {
        return Service.this;
    }
}

public void onCreate() {
    super.onCreate();
    context = getApplicationContext() ;
}

public void onStart( Intent intent, int startId ) {

... some processing is done here...

}

public IBinder onBind(Intent intent) {
    return mBinder;
}

If I invoke startService(intent). it creates a new service and runs in parallel to the other service.

If I don't invoke startService(intent), serviceObj.getData() retuns null value.

Can any one enlighten me where have I gone wrong.

Any kind of pointer will be very useful..

Thanks and regards, Vinay

回答1:

If I invoke startService(intent). it creates a new service and runs in parallel to the other service.

No, it does not. There will be at most one instance of your service running.

If I don't invoke startService(intent), serviceObj.getData() retuns null value.

startService() has nothing to do with it, from my reading of your code. You are attempting to use serviceObj in onCreate(). That will never work. bindService() is an asynchronous call. You cannot use serviveObj until onServiceConnected() is called. onServiceConnected() will not be called until sometime after onCreate() returns.

Also:

• While there are cases when you might need both startService() and bindService(), they are not both needed in the normal case.
• Do not use getApplicationContext().

来源：https://stackoverflow.com/questions/3396274/multiple-activities-binding-to-a-service