Reactive Programming on Android - RxAndroid - RxJava
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RxJava is a reactive extension for the Java virtual machine that facilitates programming with asynchronous data streams, utilizing functional reactive programming. The document outlines RxJava's basic components, including observables, subscribers, and data manipulation operators, and describes its Android-specific extension, RxAndroid, which provides bindings for Android lifecycle and views. It also addresses potential issues such as backpressure and memory leaks when using RxJava in Android applications.
Reactive Programming on Android - RxAndroid - RxJava
- 1. ReactiveX for Android Ali Muzaffar http://alimuzaffar.com
- 2. What is RxJava RxJava is a reactive extension for the java virtual machine. What is reactive programming. “In computing, reactive programming is a programming paradigm oriented around data flows and the propagation of change. This means that it should be possible to express static or dynamic data flows with ease in the programming languages used, and that the underlying execution model will automatically propagate changes through the data flow.” – Wikipeda Reactive programming is programming with asynchronous data streams. Functional Reactive Programming combines reactive programming and functional programming. We will be using functional reactive programming.
- 3. RxJava Basic Building Blocks Observables Contains all the heavy processing. Emit items (Objects, Strings, Integers etc.). Does not start emitting till someone subscribes. Subscribers Consumes data. Manipulation operators (this is the “functional programming” part) Transforms Filters Etc. Similar to the observer pattern. Except, doesn’t start emitting till there is a subscriber.
- 4. Observers Create a Observer Optional Which thread to compute on. Which thread to return result on.
- 5. Subscribers Create a subscriber
- 6. Simplify Code! Reduce boilerplate code. Chain method calls. Use lambdas.
- 7. Data Manipulation Operators Used to transform or filter data. Keep as much processing on the background thread as possible. Goal is to clean up data and simplify data processing and code.
- 8. Transform Example Map() is one of dozens of operators that let you transform data. Map does not have to return the same type as the one passed in.
- 9. Transform some more… What if our observer returns lists of data? Just an example, this could be an API call returning a JSON array.
- 10. First Approach We could just look through the data in our subscriber. Problem: There is a loop and processing is on the main thread.
- 11. Second Approach Problem: Loop is gone, but we are still doing a lot of processing on the main thread and the nested code is ugly.
- 12. Third approach using flatMap FlatMap takes in data and returns an other Observable. The end subscriber does not know anything about the data transformation going on. Minimal processing on the main thread, simpler code.
- 13. RxAndroid An extension for RxJava built just for Android
- 14. RxAndroid RxAndroid provides bindings for Android. ViewObservable & WidgetObservable provides bindings for views, clicks, scroll, input etc. AndroidObservable provides facilities for working within the Android lifecycle. Bind to activity, fragment or even broadcasts. AndroidSchedulers provides ready for use with the Android multi-threading system.
- 15. ViewObservable & WidgetObservable WidgetObservable.text() to capture text change. ViewObservable.clicks() to capture clicks. Look at Widget and View Example in demo app
- 16. AndroidObservable Provides bindActivity and bindFragment which automatically use the main thread for observing. Provides fromBroacast which allows you to create an Observable that works like a BroadcastReceiver. They also stop emitting automatically when the activity and fragment are finishing.
- 17. AndroidObservable Cache & replay calls continue execution even after we unsubscribe. When you subscribe with a new subscriber, they receive all the emitted data. Hello World Lifecycle Example in demo app
- 18. RxJava has its own issues Backpressure Android – Memory leaks by Observables because they retain references to Context. Continuing subscription during orientations changes can be difficult. Error Handling. NotRxAndroid by Jake Wharton A from-scratch, re-implementation of RxAndroid with a consistent, opinionated API. This library will not have releases and is subject to deletion at any time.
- 19. Links Demo app source https://github.com/alphamu/RxAndroidDemo RxJava https://github.com/ReactiveX/RxJava RxAndroid https://github.com/ReactiveX/RxAndroid Gradle Retro Lambda https://github.com/evant/gradle-retrolambda Allows you to use Java 8 features with Android Retrofit https://github.com/square/retrofit Type-safe REST client for Android and Java by Square, Inc.