AndroidX (.NET for Android)¶

Run the complete page example.

AndroidX support targets a native .NET for Android application. If you want a cross-platform UI stack instead, .NET MAUI also has full ReactiveUI support.

Add ReactiveUI.AndroidX to your .NET for Android application project. It brings ReactiveUI and, through it, ReactiveUI.Binding.

dotnet add package ReactiveUI.AndroidX

ReactiveUI.AndroidX also ships as ReactiveUI.AndroidX.Reactive, built from the same source, for an app that uses System.Reactive.

Configure ReactiveUI at startup¶

Call WithAndroidX on the app builder once, in your Application's OnCreate. WithAndroidXScheduler sets only the main-thread sequencer, for a host that already registers platform services elsewhere.

IReactiveUIBuilder builder = RxAppBuilder.CreateReactiveUIBuilder();
_ = builder.WithAndroidX().BuildApp();

WithAndroidX registers AndroidX's activation fetcher and its main-thread sequencer, backed by the main looper. RxAppBuilder covers the builder itself.

Bind an activity to its view model¶

ReactiveAppCompatActivity<TViewModel> gives an Activity a ViewModel property and runs WhenActivated for you. WireUpControls wires every writable View-typed property to the like-named resource in the activity's layout, so you skip FindViewById calls.

public sealed class MainActivity : AndroidX.ReactiveAppCompatActivity<TimetableViewModel>
{

    protected override async void OnCreate(Bundle? savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        SetContentView(Resource.Layout.activity_main);

        // Implicit strategy: every writable View-typed property (LessonsRecyclerView, BadgeContainer,
        // DetailContainer) is wired to the like-named resource in activity_main.xml.
        this.WireUpControls();

Show a collection in a RecyclerView¶

ReactiveRecyclerViewAdapter<TViewModel, TCollection> binds an ObservableCollection<TViewModel> to a RecyclerView, adding, removing and replacing rows as the collection changes. ReactiveRecyclerViewViewHolder<TViewModel> is the view holder each row uses; it has a ViewModel property and its own WireUpControls.

public sealed class LessonsRecyclerAdapter(ObservableCollection<LessonViewModel> lessons) : ReactiveRecyclerViewAdapter<LessonViewModel, ObservableCollection<LessonViewModel>>(lessons)
{

        // Implicit strategy: any writable View-typed property (SubjectLabel, RoomLabel) is wired to the
        // like-named resource in the inflated row layout.
        this.WireUpControls();

A view holder's Selected and SelectedWithViewModel streams deliver when its row is tapped, and Activated and Deactivated deliver as the row attaches to and detaches from the window.

Android covers the rest of the package: activities, fragments, lists, view hosts, service binding and saving state. Routing covers navigating with a router, and RxAppBuilder covers the builder in depth. There is no ReactiveUI.Validation code in this installation's example project; see Validation for validation rules on a view model. The compelling example walks through a first view model and view on a platform-neutral console app.