绑定服务学习

1. In your service, create an instance of Binder that either:
   • contains public methods that the client can call
   • returns the current Service instance, which has public methods theclient can call
   • or, returns an instance of another class hosted by the service with public methods theclient can call
2. Return this instance of Binder from the onBind() callback method.
3. In the client, receive the Binder from the onServiceConnected() callback method andmake calls to the bound service using the methods provided.

public class LocalService extends Service {
    // Binder given to clients
    private final IBinder mBinder = new LocalBinder();
    // Random number generator
    private final Random mGenerator = new Random();

    /**
     * Class used for the client Binder.  Because we know this service always
     * runs in the same process as its clients, we don‘t need to deal with IPC.
     */
    public class LocalBinder extends Binder {
        LocalService getService() {
            // Return this instance of LocalService so clients can call public methods
            return LocalService.this;
        }
    }

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

    /** method for clients */
    public int getRandomNumber() {
      return mGenerator.nextInt(100);
    }
}