2018-06-17 15:31:04 +02:00
|
|
|
**Note:** This page is out-of-date. See [the RxAndroid wiki](https://github.com/ReactiveX/RxAndroid/wiki) for more up-to-date instructions.
|
|
|
|
|
|
|
|
|
|
***
|
|
|
|
|
|
|
|
|
|
The `rxjava-android` module contains Android-specific bindings for RxJava. It adds a number of classes to RxJava to assist in writing reactive components in Android applications.
|
|
|
|
|
|
|
|
|
|
- It provides a `Scheduler` that schedules an `Observable` on a given Android `Handler` thread, particularly the main UI thread.
|
|
|
|
|
- It provides operators that make it easier to deal with `Fragment` and `Activity` life-cycle callbacks.
|
|
|
|
|
- It provides wrappers for various Android messaging and notification components so that they can be lifted into an Rx call chain
|
|
|
|
|
- It provides reusable, self-contained, reactive components for common Android use cases and UI concerns. _(coming soon)_
|
|
|
|
|
|
|
|
|
|
# Binaries
|
|
|
|
|
|
|
|
|
|
You can find binaries and dependency information for Maven, Ivy, Gradle and others at [http://search.maven.org](http://search.maven.org/#search%7Cga%7C1%7Ca%3A%22rxandroid%22).
|
|
|
|
|
|
|
|
|
|
Here is an example for [Maven](http://search.maven.org/#search%7Cga%7C1%7Ca%3A%22rxandroid%22):
|
|
|
|
|
|
|
|
|
|
```xml
|
|
|
|
|
<dependency>
|
|
|
|
|
<groupId>io.reactivex</groupId>
|
|
|
|
|
<artifactId>rxandroid</artifactId>
|
|
|
|
|
<version>0.23.0</version>
|
|
|
|
|
</dependency>
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
…and for Ivy:
|
|
|
|
|
|
|
|
|
|
```xml
|
|
|
|
|
<dependency org="io.reactivex" name="rxandroid" rev="0.23.0" />
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
The currently supported `minSdkVersion` is `10` (Android 2.3/Gingerbread)
|
|
|
|
|
|
|
|
|
|
# Examples
|
|
|
|
|
|
|
|
|
|
## Observing on the UI thread
|
|
|
|
|
|
|
|
|
|
You commonly deal with asynchronous tasks on Android by observing the task’s result or outcome on the main UI thread. Using vanilla Android, you would typically accomplish this with an `AsyncTask`. With RxJava you would instead declare your `Observable` to be observed on the main thread by using the `observeOn` operator:
|
|
|
|
|
|
|
|
|
|
```java
|
|
|
|
|
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 executes the Observable on a new thread, which emits results through `onNext` on the main UI thread.
|
|
|
|
|
|
|
|
|
|
## Observing on arbitrary threads
|
|
|
|
|
The previous example is a specialization of a more general concept: binding asynchronous communication to an Android message loop by 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:
|
|
|
|
|
|
|
|
|
|
```java
|
|
|
|
|
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 executes the Observable on a new thread and emits results through `onNext` on `custom-thread-1`. (This example is contrived since you could as well call `observeOn(Schedulers.currentThread())` but it illustrates the idea.)
|
|
|
|
|
|
|
|
|
|
## Fragment and Activity life-cycle
|
|
|
|
|
|
|
|
|
|
On Android it is tricky for asynchronous actions to access framework objects in their callbacks. That’s because Android may decide to destroy an `Activity`, for instance, while a background thread is still running. The thread will attempt to access views on the now dead `Activity`, which results in a crash. (This will also create a memory leak, since your background thread holds on to the `Activity` even though it’s not visible anymore.)
|
|
|
|
|
|
|
|
|
|
This is still a concern when using RxJava on Android, but you can deal with the problem in a more elegant way by using `Subscription`s and a number of Observable operators. In general, when you run an `Observable` inside an `Activity` that subscribes to the result (either directly or through an inner class), you must unsubscribe from the sequence in `onDestroy`, as shown in the following example:
|
|
|
|
|
|
|
|
|
|
```java
|
|
|
|
|
// MyActivity
|
|
|
|
|
private Subscription subscription;
|
|
|
|
|
|
|
|
|
|
protected void onCreate(Bundle savedInstanceState) {
|
|
|
|
|
this.subscription = observable.subscribe(this);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
...
|
|
|
|
|
|
|
|
|
|
protected void onDestroy() {
|
|
|
|
|
this.subscription.unsubscribe();
|
|
|
|
|
super.onDestroy();
|
|
|
|
|
}
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
This ensures that all references to the subscriber (the `Activity`) will be released as soon as possible, and no more notifications will arrive at the subscriber through `onNext`.
|
|
|
|
|
|
|
|
|
|
One problem with this is that if the `Activity` is destroyed because of a change in screen orientation, the Observable will fire again in `onCreate`. You can prevent this by using the `cache` or `replay` Observable operators, while making sure the Observable somehow survives the `Activity` life-cycle (for instance, by storing it in a global cache, in a Fragment, etc.) You can use either operator to ensure that when the subscriber subscribes to an Observable that’s already “running,” items emitted by the Observable during the span when it was detached from the `Activity` will be “played back,” and any in-flight notifications from the Observable will be delivered as usual.
|
|
|
|
|
|
|
|
|
|
# See also
|
|
|
|
|
* [How the New York Times is building its Android app with Groovy/RxJava](http://open.blogs.nytimes.com/2014/08/18/getting-groovy-with-reactive-android/?_php=true&_type=blogs&_php=true&_type=blogs&_r=1&) by Mohit Pandey
|
|
|
|
|
* [Functional Reactive Programming on Android With RxJava](http://mttkay.github.io/blog/2013/08/25/functional-reactive-programming-on-android-with-rxjava/) and [Conquering concurrency - bringing the Reactive Extensions to the Android platform](https://speakerdeck.com/mttkay/conquering-concurrency-bringing-the-reactive-extensions-to-the-android-platform) by Matthias Käppler
|
|
|
|
|
* [Learning RxJava for Android by example](https://github.com/kaushikgopal/Android-RxJava) by Kaushik Gopal
|
|
|
|
|
* [Top 7 Tips for RxJava on Android](http://blog.futurice.com/top-7-tips-for-rxjava-on-android) and [Rx Architectures in Android](http://www.slideshare.net/TimoTuominen1/rxjava-architectures-on-android-8-android-livecode-32531688) by Timo Tuominen
|
|
|
|
|
* [FRP on Android](http://slid.es/yaroslavheriatovych/frponandroid) by Yaroslav Heriatovych
|
|
|
|
|
* [Rx for .NET and RxJava for Android](http://blog.futurice.com/tech-pick-of-the-week-rx-for-net-and-rxjava-for-android) by Olli Salonen
|
|
|
|
|
* [RxJava in Xtend for Android](http://blog.futurice.com/android-development-has-its-own-swift) by Andre Medeiros
|
|
|
|
|
* [RxJava and Xtend](http://mnmlst-dvlpr.blogspot.de/2014/07/rxjava-and-xtend.html) by Stefan Oehme
|
|
|
|
|
* Grokking RxJava, [Part 1: The Basics](http://blog.danlew.net/2014/09/15/grokking-rxjava-part-1/), [Part 2: Operator, Operator](http://blog.danlew.net/2014/09/22/grokking-rxjava-part-2/), [Part 3: Reactive with Benefits](http://blog.danlew.net/2014/09/30/grokking-rxjava-part-3/), [Part 4: Reactive Android](http://blog.danlew.net/2014/10/08/grokking-rxjava-part-4/) - published in Sep/Oct 2014 by Daniel Lew
|
