Binding to Service from Activity or starting service in different process?

I want to do Bluetooth connection in Service. And there needs to be interaction between Activities and Services. The service should be started as soon as the app is started and should be able to communicate with UI Activities on certain situations.

What should be the appropriate way of doing it? If I bind the service from only one Activity then that service will be communicating only with that Activity. So, do I need to take AIDL based approach or is there any other way out for this?

Otherwise, can I have a class that extends Application class and then start the service from there and b开发者_如何转开发ind the Application class instead?

This is quite a broad question, so I'll answer as best as I can. From what I know of services, multiple activities can bind a single service, all having access to it. Only once all activities that bound the service end their connections (by unbinding), does the service actually stop.

The android documentation on services tells us:

... the system will keep the service running as long as either it is started or there are one or more connections to it with the Context.BIND_AUTO_CREATE flag. Once neither of these situations hold, the service's onDestroy() method is called and the service is effectively terminated

So my recommendation would be to bind the service from all activities that need to communicate with it. When binding with a service an IBinder is returned, which you can use to communicate with the service. Again according to the Android documentation on services:

Usually the IBinder returned is for a complex interface that has been written in aidl.

Although if you only need to perform simple communication with the service, you could use the Messenger class instead of writing full AIDL files. A sample of this can be found here.

Hope this answers your question!

You could bind directly to the Service as the above answer states, however there is no need for Messengers. Your service will be running in the same process as your activity 99.9% of the time. Messengers are designed for inter-process communication (IPC). Also no need for AIDL - that was designed for advanced IPC.

Instead, you should use: BroadcastReceivers and Intents. This is what they were designed for (communication between components in an app).