android服务如何与活动交互

Question

I'm developing a subway guide app, when reaching a new station, a notification will pop up, and the map shown in the main activity will refresh. I put the guide code in a service so that users can run other apps while being guided. But the main activity needs to be refreshed when reaching a new station, how can the service make some changes to the view in the main activity?

Answer 1

In your activity, you should register a receiver

Declare the receiver first

public class ReceiverTest extends BroadcastReceiver
{
  @Override
  public void onReceive(Context context, Intent intent)
  {
     // extras from service
     int key = intent.getIntExtra("key", 0);

     //do things here
  }
}

Register it in OnCreate of your activity

ReceiverTest mReceiver = new ReceiverTest();
IntentFilter filter;
filter = new IntentFilter("packagename.dosomething");
registerReceiver(mReceiver, filter);

Then, in your service, broadcast the event

Intent i = new Intent("packagename.dosomething");
// You could put the information in extras, then get the value in receiver
i.putExtra("key", 123);
context.sendBroadcast(i);

Answer 2

There are a couple of ways to do this. You can bind the service with the activity. You can send broadcast messages to the activity (the activity need to register with the Broadcast Reciever) There are lot of discussions on this topic. You can go through them.

Answer 3

The best way to share data between the Service S and Activity A

Use the local binding pattern and have Activity A bind to Service S, then call the service's exposed API to retrieve whatever is needed.

How can the external activity B communicate with the Service S to determine if it has completed with all its preprocessing, and the Activity A is ready to be invoked?

Use the remote binding pattern and AIDL. Activity B would register an AIDL-defined callback with Service S, which the service would invoke when appropriate. See here and here for an example.