Native views
PlatformChannelView hosts an explicitly registered Kotlin/Java or Swift/Objective-C view inside a MAUI layout. Each connection has its own native instance, bridge, and MethodChannel. Two views using the same factory remain independent.
Windows supports WinUI elements through WindowsFactory and WindowsNativeView. See Windows integration.
For a practical integration, see PdfViewer: an embedded PDFKit/PdfRenderer surface with navigation, zoom, and native callbacks. The button below is the small lifecycle fixture used by the framework's verification sample.
Register a factory
Include the adapter AAR or XCFramework just as you would for a native module. UseNativeChannels registers the MAUI handler automatically. Factory registration is separate from Modules; a view factory is created when a view connects.
builder.UseNativeChannels(options =>
{
options.ViewFactories.Add(new NativeViewFactoryRegistration(
"sample.button",
"dev.nativechannels.sample.ButtonViewFactory",
"MCButtonViewFactory",
"NativeChannelsSample"));
});The factory name is case-sensitive and must be unique. Use the full Android class name and the explicit Objective-C class name. Apple framework names omit .framework. Missing registrations, classes, or framework assets fail with an exception; no empty fallback view is supplied.
Use the view
var nativeButton = new PlatformChannelView
{
FactoryName = "sample.button",
HeightRequest = 72,
CreationParameters = new Dictionary<string, object?> { ["title"] = "Tap me" }
};
nativeButton.Connected += (_, _) =>
{
nativeButton.Channel!.SetMethodCallHandler((call, token) =>
{
if (call.Method != "clicked")
throw new MethodNotImplementedException();
// This handler enters on the MAUI UI thread.
statusLabel.Text = $"Native tap {call.GetArgument<int>("count")}";
return ValueTask.FromResult<object?>("managed acknowledgement");
});
};
layout.Children.Add(nativeButton);InstanceId and Channel are null while disconnected. Install handlers in Connected, since every reconnection supplies a new channel. Once connected, invoke the adapter's methods through nativeButton.Channel, for example await nativeButton.Channel!.InvokeAsync("setTitle", "Updated"). The sample's method names are adapter-specific, not built-in view operations.
Creation parameters use JsonMessageCodec and the application's configured serializer metadata and limits. DTOs need source-generated metadata for trimming/AOT. Creation parameters are encoded once per connection. Replacing either configuration property while connected throws. To change configuration, await DisconnectAsync(), update the properties, then call Reconnect(). Mutating an existing parameters collection does not update the native view; use a method call. Set a MAUI size or layout constraint explicitly; native intrinsic-size measurement is not provided.
Implement the native factory
On Android, implement NativeViewFactory with a public parameterless constructor. Its create method receives an Android context, NativeBridge, instance ID, channel name, and copied argument bytes. Return a NativeViewInstance whose getView() returns one new unattached Android view. Its close() removes listeners and releases adapter-owned resources.
On Apple, export an NSObject subclass with an explicit @objc name and implement NativeViewFactory (MCNativeViewFactory). createView receives the bridge, instance ID, channel name, and argument Data; return a NativeViewInstance (MCNativeViewInstance) with a stable UIView and close(). The bridge loads the registered adapter framework before looking up its class.
Decode arguments with the native JsonMessageCodec, and construct a native MethodChannel using exactly the supplied name and bridge. Configure its handler with onMainThread = true (Kotlin) or onMainThread: true (Swift) before touching UI. Do not invoke managed callbacks during factory construction; install them after the managed Connected event has had a chance to register a handler.
The working factories show creation parameters, updating a native button, click callbacks, and cleanup:
Only generic view-host operations are bound to C#. Keep your adapter class reachable: the Android bridge ships a consumer rule for NativeViewFactory implementors, and Apple factories need their explicit Objective-C names in the packaged framework.
Lifecycle and threading
Creation, attachment, disconnection, and reconnection require the UI thread. Managed incoming view handlers enter on that thread. Native UI handlers must opt into the native main-thread dispatcher; channel calls never make arbitrary native SDK operations thread-safe automatically.
Unloading the MAUI view or disconnecting its handler invalidates the channel immediately, removes native content, calls the adapter's close(), and drains its isolated bridge. Outstanding calls fail with ObjectDisposedException. Owned managed registrations are removed and late responses are ignored. Cleanup of one view cannot dispose another view's bridge or the app-wide channel service. The native adapter must cancel its own timers, observers, and SDK operations in close().
Loading the view again creates a new instance. Reconnect() also recreates it immediately when a MAUI handler is available. Both operations assign a fresh instance ID and channel name; cached old channels remain disposed. DisconnectAsync() permits deterministic cleanup while retaining the MAUI wrapper. A later MAUI load or explicit Reconnect() connects it again.
Callers own neither the exposed channel nor its bridge. Let the view manage their lifetime; do not cache the channel across connection changes. The view does not persist native state across detach, activity recreation, or process death. Backgrounding alone is not a guarantee of disconnection.
Verification
The package-only sample hosts two native buttons and exercises isolated state, creation parameters, bidirectional callbacks, UI dispatch, reconnect, pending-call cancellation, and stale-channel rejection. Run it using the sample commands. The verification record separates compiled targets from actual execution and physical-device coverage.