Uno.Microsoft.UI.Reactor 0.1.0-dev.115

Uno.Microsoft.UI.Reactor

Microsoft.UI.Reactor, the functional, declarative UI framework for WinUI 3, on Uno Platform. You write components and hooks in C#, with no XAML, and the same code runs on desktop (Windows, macOS, Linux), WebAssembly, Android and iOS.

For a Windows App SDK app, use Microsoft's Microsoft.UI.Reactor package instead. This package doesn't target the Windows App SDK.

Requirements

• The .NET SDK 10.0.400 or later.
• Uno.Sdk 7.0.0-dev.104 or later, with the Skia renderer. You don't reference this package yourself: add Reactor to UnoFeatures and the Uno.Sdk brings in the version it was released with.

A new app

Install the Uno templates and create an app from unoapp-reactor:

dotnet new install Uno.Templates@7.0.0-dev.104
dotnet new unoapp-reactor -n MyApp
cd MyApp
dotnet run -f net10.0-desktop

Any later Uno.Templates works too; a plain dotnet new install Uno.Templates installs the latest stable templates, which don't have unoapp-reactor yet.

The app targets desktop, WebAssembly, Android and iOS. Pick fewer with -platforms, for example -platforms desktop wasm.

A single-file app

Save this as Counter.cs and run dotnet run Counter.cs:

#:sdk Uno.Sdk@7.0.0-dev.113
#:property TargetFramework=net10.0-desktop
#:property OutputType=Exe
#:property UnoSingleProject=true
#:property UnoFeatures=SkiaRenderer;Reactor
#:property PublishAot=false
#:property PackAsTool=false

using Microsoft.UI.Reactor;
using Microsoft.UI.Reactor.Core;
using static Microsoft.UI.Reactor.Factories;

ReactorApp.Run<CounterApp>("Counter", width: 480, height: 360);

class CounterApp : Component
{
    public override Element Render()
    {
        var (count, setCount) = UseState(0);

        return VStack(12,
            Heading($"Count: {count}"),
            HStack(8,
                Button("-", () => setCount(count - 1)),
                Button("+", () => setCount(count + 1))
            )
        ).Padding(24);
    }
}

The #:sdk line pins the Uno.Sdk, and with it the Reactor version: a lone file has no global.json to do it. Single-file apps run on desktop only for now.

In an existing Uno project

Add Reactor to UnoFeatures in a single Uno project that uses the Skia renderer:

<UnoFeatures>
  SkiaRenderer;
  Reactor;
</UnoFeatures>

Pin Uno.Sdk 7.0.0-dev.104 or later in its global.json. The feature first shipped in 7.0.0-dev.97; an Uno.Sdk older than that ignores it without a warning, and the build then fails with CS0234 on Microsoft.UI.Reactor.

Remove the Windows target framework (net10.0-windows10.0.x) from the project: with Reactor in UnoFeatures, that target fails with UNOB0031, since this package doesn't target the Windows App SDK.

Every target starts the app with ReactorApp.Run<TRoot>(...), as above, Android included: Android never calls Main on its own, so the package adds the Android Application and launcher Activity that run it, with the app's icon and splash screen. An app that keeps its own NativeApplication sets <ReactorAndroidEntry>false</ReactorAndroidEntry> and returns ReactorApp.CreateHost<TRoot>(...) from its CreateHost.

Another Reactor version

To use a different version of this package than the one your Uno.Sdk brings in, set UnoReactorVersion: <UnoReactorVersion>x.y.z</UnoReactorVersion> in the project, or #:property UnoReactorVersion=x.y.z in a single file.

Learn more

• Reactor on Uno Platform: what works on each target, and what Uno doesn't implement yet.
• Reactor guide: components, hooks, layout and controls. It is written for Windows, but the API is the same.