Customizing the UIApplicationDelegate on iOS

Uno Platform provides the ability to provide custom behavior for UIApplicationDelegate on iOS.

The App type does not derive from UIApplicationDelegate. Instead, Uno Platform provides Uno.UI.Runtime.AppleUIKit.UnoUIApplicationDelegate. If you decide to implement your own application lifecycle handling, create a new type that derives from it:

public class MyApplicationDelegate : Uno.UI.Runtime.AppleUIKit.UnoUIApplicationDelegate
{
    // Your own code or overrides
}

You then need to inform Uno Platform to use this custom class instead of the built-in delegate by adjusting the host creation in Main.iOS.cs:

using Uno.UI.Hosting;

var host = UnoPlatformHostBuilder.Create()
    .App(() => new SamplesApp.App())
    .UseAppleUIKit(builder => builder.UseUIApplicationDelegate<MyApplicationDelegate>())
    .Build();

host.Run();

Important

Make sure to call the base methods when you override key application lifecycle methods, so that the internals of Uno Platform are still properly executed.

Scene lifecycle

Apps built with the version 27 SDKs must use the UIKit scene lifecycle, or iOS and tvOS 27 refuse to launch them.

An app that declares a scene manifest (UIApplicationSceneManifest) in Info.plist uses it, with a scene delegate deriving from Uno.UI.Runtime.AppleUIKit.UnoUISceneDelegate, or UnoUISceneDelegate itself when the manifest names no delegate class. Secondary windows require a manifest, see Support for secondary windows.

An app without a manifest gets the scene lifecycle from Uno Platform when it is built with a version 27 SDK or later, whatever its .NET version, or when the SDK version can't be read: UnoUIApplicationDelegate assigns an Uno Platform scene delegate to the app's scene, which hosts the app's single window. Apps built with an older SDK keep the app lifecycle. To choose explicitly, set UnoUseSceneLifecycle in Info.plist:

<key>UnoUseSceneLifecycle</key>
<true/>

Setting it to false keeps the app lifecycle, which only SDKs older than 27 support. The key is ignored when the app declares a scene manifest, or when its value is neither a boolean nor a number.

At startup, Uno Platform logs which lifecycle the app runs and what decided it, at the Information level of the Uno.UI.Runtime.AppleUIKit.AppleUIKitLifecycle logger. The default logging setup only shows warnings from Uno loggers, so add a filter to see it:

builder.AddFilter("Uno.UI.Runtime.AppleUIKit.AppleUIKitLifecycle", LogLevel.Information);

Under the scene lifecycle, UIKit no longer calls the application delegate's URL, user activity, home-screen shortcut, and foreground and background methods:

• In an app without a manifest, Uno Platform forwards them to the application delegate, so overrides such as OpenUrl, ContinueUserActivity, PerformActionForShortcutItem, OnActivated or DidEnterBackground keep working. The URL, shortcut or user activity the app was launched with is no longer in FinishedLaunching's launch options: it reaches OpenUrl, PerformActionForShortcutItem or ContinueUserActivity once the scene connects, after OnLaunched.
• In an app with a manifest, these overrides are not called. Uno Platform reports the activations through AppInstance, see Protocol activation.