RxAndroid: Reactive Extensions for Android

Android specific bindings for RxJava.

This module adds a number of classes to RxJava that make writing reactive components in Android applications easy and hassle free. More specifically, it

• provides a Scheduler that schedules an Observable on a given Android Handler thread, particularly the main UI thread
• provides base Observer implementations that make guarantees w.r.t. to reliable and thread-safe use throughout Fragment and Activity life-cycle callbacks (coming soon)
• provides reusable, self-contained reactive components for common Android use cases and UI concerns (coming soon)

Communication

Since RxAndroid is part of the RxJava family the communication channels are similar:

• Google Group: RxJava
• Twitter: @RxJava
• GitHub Issues

Versioning

RxAndroid 0.21 and beyond are published under the io.reactivex GroupID and depend on RxJava 1.0.x. Versions 0.20 and earlier were rxjava-android and published along with rxjava-core under the com.netflix.rxjava GroupID.

RxAndroid is staying on the 0.x versioning for now despite RxJava hitting 1.0 as it is not yet felt that the RxAndroid APIs are stabilized.

All usage of 0.20.x and earlier under com.netflix.rxjava should eventually be migrated to RxJava 1.x and io.reactivex. This was done as part of the migration of the project from Netflix/RxJava to ReactiveX/RxJava and ReactiveX/RxAndroid.

During the transition it will be possible for an application to resolve both the com.netflix.rxjava and io.reactivex artifacts. This is unfortunate but was accepted as a reasonable cost for adopting the new name as we hit version 1.0.

The RxJava 0.20.x branch is being maintained with bug fixes on the com.netflix.rxjava GroupId until version 1.0 Final is released to allow time to migrate between the artifacts.

Binaries

Binaries and dependency information for Maven, Ivy, Gradle and others can be found at http://search.maven.org.

Example for Maven:

<dependency>
    <groupId>io.reactivex</groupId>
    <artifactId>rxandroid</artifactId>
    <version>0.24.0</version>
</dependency>

and for Ivy:

<dependency org="io.reactivex" name="rxandroid" rev="0.24.0" />

and for Gradle:

compile 'io.reactivex:rxandroid:0.24.0'

Build

To build:

$ git clone git@github.com:ReactiveX/RxAndroid.git
$ cd RxAndroid/
$ ./gradlew build

Futher details on building can be found on the RxJava Getting Started page of the wiki.

Sample usage

We are working on a samples project which provides runnable code samples that demonstrate common Rx patterns and their use in Android applications.

Observing on the UI thread

One of the most common operations when dealing with asynchronous tasks on Android is to observe the task's result or outcome on the main UI thread. Using vanilla Android, this would typically be accomplished with an AsyncTask. With RxJava instead you would declare your Observable to be observed on the main thread:

public class ReactiveFragment extends Fragment {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Observable.from("one", "two", "three", "four", "five")
                .subscribeOn(Schedulers.newThread())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(/* an Observer */);
    }

This will execute the Observable on a new thread, and emit results through onNext on the main UI thread.

Observing on arbitrary threads

The previous sample is merely a specialization of a more general concept, namely binding asynchronous communication to an Android message loop using the Handler class. In order to observe an Observable on an arbitrary thread, create a Handler bound to that thread and use the AndroidSchedulers.handlerThread scheduler:

new Thread(new Runnable() {
    @Override
    public void run() {
        final Handler handler = new Handler(); // bound to this thread
        Observable.from("one", "two", "three", "four", "five")
                .subscribeOn(Schedulers.newThread())
                .observeOn(AndroidSchedulers.handlerThread(handler))
                .subscribe(/* an Observer */)

        // perform work, ...
    }
}, "custom-thread-1").start();

This will execute the Observable on a new thread and emit results through onNext on "custom-thread-1". (This example is contrived since you could as well call observeOn(Schedulers.currentThread()) but it shall suffice to illustrate the idea.)

Bugs and Feedback

For bugs, questions and discussions please use the Github Issues.

LICENSE

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.