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RxLifecycle

This library allows one to automatically complete sequences based on a second lifecycle stream.

This capability is useful in Android, where incomplete subscriptions can cause memory leaks.

Usage

You must start with an Observable<T> representing a lifecycle stream. Then you use RxLifecycle to bind a sequence to that lifecycle.

You can bind when the lifecycle emits anything:

myObservable
    .compose(RxLifecycle.bind(lifecycle))
    .subscribe();

Or you can bind to when a specific lifecyle event occurs:

myObservable
    .compose(RxLifecycle.bindUntilEvent(lifecycle, ActivityEvent.DESTROY))
    .subscribe();

Alternatively, you can let RxLifecycle determine the appropriate time to end the sequence:

myObservable
    .compose(RxLifecycleAndroid.bindActivity(lifecycle))
    .subscribe();

It assumes you want to end the sequence in the opposing lifecycle event - e.g., if subscribing during START, it will terminate on STOP. If you subscribe after PAUSE, it will terminate at the next destruction event (e.g., PAUSE will terminate in STOP).

Providers

Where do lifecycles come from? Generally, they are provided by an appropriate LifecycleProvider<T>. But where are those implemented?

You have a few options for that:

  1. Use rxlifecycle-components and subclass the provided RxActivity, RxFragment, etc. classes.
  2. Use Android's lifecycle + rxlifecycle-android-lifecycle to generate providers.
  3. Write the implementation yourself.

If you use rxlifecycle-components, just extend the appropriate class, then use the built-in bindToLifecycle() (or bindUntilEvent()) methods:

public class MyActivity extends RxActivity {
    @Override
    public void onResume() {
        super.onResume();
        myObservable
            .compose(bindToLifecycle())
            .subscribe();
    }
}

If you use rxlifecycle-android-lifecycle, then you just pass your LifecycleOwner to AndroidLifecycle to generate a provider:

public class MyActivity extends LifecycleActivity {
    private final LifecycleProvider<Lifecycle.Event> provider
        = AndroidLifecycle.createLifecycleProvider(this);

    @Override
    public void onResume() {
        super.onResume();
        myObservable
            .compose(provider.bindToLifecycle())
            .subscribe();
    }
}

Unsubscription

RxLifecycle does not actually unsubscribe the sequence. Instead it terminates the sequence. The way in which it does so varies based on the type:

  • Observable, Flowable and Maybe - emits onCompleted()
  • Single and Completable - emits onError(CancellationException)

If a sequence requires the Subscription.unsubscribe() behavior, then it is suggested that you manually handle the Subscription yourself and call unsubscribe() when appropriate.

Kotlin

The rxlifecycle-kotlin module provides built-in extensions to the base RxJava types:

myObservable
    .bindToLifecycle(myView)
    .subscribe { }

myObservable
    .bindUntilEvent(myRxActivity, STOP)
    .subscribe { }

There is an additional rxlifecycle-android-lifecycle-kotlin module to provider extensions to work with LifecycleOwner's.

myObservable
    .bindUntilEvent(myLifecycleActivity, ON_STOP)
    .subscribe { }

Installation

implementation 'com.trello.rxlifecycle4:rxlifecycle:4.0.2'

// If you want to bind to Android-specific lifecycles
implementation 'com.trello.rxlifecycle4:rxlifecycle-android:4.0.2'

// If you want pre-written Activities and Fragments you can subclass as providers
implementation 'com.trello.rxlifecycle4:rxlifecycle-components:4.0.2'

// If you want pre-written support preference Fragments you can subclass as providers
implementation 'com.trello.rxlifecycle4:rxlifecycle-components-preference:4.0.2'

// If you want to use Android Lifecycle for providers
implementation 'com.trello.rxlifecycle4:rxlifecycle-android-lifecycle:4.0.2'

// If you want to use Kotlin syntax
implementation 'com.trello.rxlifecycle4:rxlifecycle-kotlin:4.0.2'

// If you want to use Kotlin syntax with Android Lifecycle
implementation 'com.trello.rxlifecycle4:rxlifecycle-android-lifecycle-kotlin:4.0.2'

License

Copyright (C) 2016 Trello

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.