Android with RxJava

Remarks#

RxAndroid used to be a library with lot of features. It has been splitted in many different libraries moving from version 0.25.0 to 1.x.

A list of libraries that implement the features available before the 1.0 is maintained here.

RxAndroid - AndroidSchedulers

This is literally the only thing you need to start using RxJava on Android.

Include RxJava and RxAndroid in your gradle dependencies:

 // use the last version
compile 'io.reactivex.rxjava2:rxjava:2.1.1'
compile 'io.reactivex.rxjava2:rxandroid:2.0.1'

RxAndroid main addition to RxJava is a Scheduler for the Android Main Thread or UI Thread.

In your code:

Observable.just("one", "two", "three", "four", "five")
        .subscribeOn(Schedulers.newThread())
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe(
            data -> doStuffOnMainThread(),
            error -> handleErrorOnMainThread()
        )

Or you can create a Scheduler for a custom Looper:

Looper backgroundLooper = // ...
Observable.just("one", "two", "three", "four", "five")
        .subscribeOn(Schedulers.newThread())
        .observeOn(AndroidSchedulers.from(backgroundLooper))
        .subscribe(
            data -> doStuffOnMainThread(),
            error -> handleErrorOnMainThread()
        )

For most everything else you can refer to standard RxJava documentation.

RxLifecycle components

The RxLifecycle library makes it easier binding observable subscriptions to Android activities and fragment lifecycle.

Keep in mind that forgetting to unsubscribe an Observable can cause memory leaks and keeping your activity / fragment alive event after it has been destroyed by the system.

Add the library to the dependencies:

// use the last version available
compile 'com.trello:rxlifecycle:0.6.1'
compile 'com.trello:rxlifecycle-components:0.6.1'

Then extends Rx* classes:

RxActivity / support.RxFragmentActivity / support.RxAppCompatActivity
RxFragment / support.RxFragment
RxDialogFragment / support.RxDialogFragment
support.RxAppCompatDialogActivity

You are all set, when you subscribe to an Observable you can now:

someObservable
    .compose(bindToLifecycle())
    .subscribe();

If you execute this in the onCreate() method of the activity it will automatically unsubscribed in the onDestroy().

Tha same happens for:

onStart() -> onStop()
onResume() -> onPause()
onAttach() -> onDetach() (fragment only)
onViewCreated() -> onDestroyView() (fragment only)

As an alternative you can specify the event when you want the unsubscription to happen:

From an activity:

someObservable
    .compose(bindUntilEvent(ActivityEvent.DESTROY))
    .subscribe();

From a Fragment:

someObservable
    .compose(bindUntilEvent(FragmentEvent.DESTROY_VIEW))
    .subscribe();

You can also obtain the lifecycle observable using the method lifecycle() to listen lifecycle events directly.

RxLifecycle can also be used directly passing to it the lifecycle observable:

.compose(RxLifecycleAndroid.bindActivity(lifecycle))

If you need to handle Single or Completable you can do it by just adding respectively forSingle() or forCompletable after the bind method:

someSingle
    .compose(bindToLifecycle().forSingle())
    .subscribe();

It can also be used with Navi library.

Rxpermissions

This library allows the usage of RxJava with the new Android M permission model.

Add the library to the dependencies:

Rxjava

dependencies {
    compile 'com.tbruyelle.rxpermissions:rxpermissions:0.8.0@aar'
}

Rxjava2

dependencies {
    compile 'com.tbruyelle.rxpermissions2:rxpermissions:0.8.1@aar'
}

Usage

Example (with Retrolambda for brevity, but not required):

// Must be done during an initialization phase like onCreate
RxPermissions.getInstance(this)
    .request(Manifest.permission.CAMERA)
    .subscribe(granted -> {
        if (granted) { // Always true pre-M
           // I can control the camera now
        } else {
           // Oups permission denied
        }
    });