RxServiceBinding: observe the binding of a service

RxServiceBinding.java

/*
 * Copyright (c) 2017 PlanGrid, Inc. All rights reserved.
 */

package com.plangrid.android.services.rx;

import android.app.Service;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Binder;
import android.os.IBinder;

import rx.Observable;
import rx.Subscriber;

public class RxServiceBinding<T extends Binder> implements Observable.OnSubscribe<T> {
    private final Context context;
    private final Intent intent;

    public RxServiceBinding(final Context context, final Intent serviceIntent) {
        this.context = context;
        this.intent = serviceIntent;
    }

    @Override public void call(Subscriber<? super T> subscriber) {
        final ServiceConnection callback = new ServiceCallback<T>(subscriber);
        Observable.<T>create(sub -> {
            context.bindService(intent, callback, Service.BIND_AUTO_CREATE);
        }).doOnUnsubscribe(() -> context.unbindService(callback))
          .subscribe(subscriber);
    }

    private static class ServiceCallback<T extends Binder> implements ServiceConnection {
        final Subscriber<? super T> subscriber;

        ServiceCallback(Subscriber<? super T> subscriber) {
            this.subscriber = subscriber;
        }

        @Override public void onServiceConnected(ComponentName name, IBinder service) {
            if (!subscriber.isUnsubscribed()) {
                //noinspection unchecked
                subscriber.onNext((T)service);
            }
        }

        @Override public void onServiceDisconnected(ComponentName name) {
            subscriber.onCompleted();
        }
    }
}