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Fix for BlazorWebView Back Navigation Issues on Android 13+ After Predictive Back Gesture Changes #33213

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Fix for BlazorWebView Back Navigation Issues on Android 13+ After Predictive Back Gesture Changes #33213

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2600b9c
fix-lifecycleEvent
SuthiYuvaraj Dec 17, 2025
3dc46e8
Added RemoveEvent
SuthiYuvaraj Dec 17, 2025
9283564
remove publicAPI
SuthiYuvaraj Dec 18, 2025
6c66a23
Apply suggestion from @Copilot
SuthiYuvaraj Dec 19, 2025
e86c270
Update BlazorWebViewHandler.Android.cs
SuthiYuvaraj Dec 19, 2025
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47 changes: 47 additions & 0 deletions src/BlazorWebView/src/Maui/Android/BlazorWebViewHandler.Android.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@
using Microsoft.Maui;
using Microsoft.Maui.Dispatching;
using Microsoft.Maui.Handlers;
using Microsoft.Maui.LifecycleEvents;
using static global::Android.Views.ViewGroup;
using AWebView = global::Android.Webkit.WebView;
using Path = System.IO.Path;
Expand All @@ -21,6 +22,7 @@ public partial class BlazorWebViewHandler : ViewHandler<IBlazorWebView, AWebView
private WebChromeClient? _webChromeClient;
private AndroidWebKitWebViewManager? _webviewManager;
internal AndroidWebKitWebViewManager? WebviewManager => _webviewManager;
private AndroidLifecycle.OnBackPressed? _onBackPressedHandler;

private ILogger? _logger;
internal ILogger Logger => _logger ??= Services!.GetService<ILogger<BlazorWebViewHandler>>() ?? NullLogger<BlazorWebViewHandler>.Instance;
Expand Down Expand Up @@ -60,10 +62,55 @@ protected override AWebView CreatePlatformView()
return blazorAndroidWebView;
}

protected override void ConnectHandler(AWebView platformView)
{
base.ConnectHandler(platformView);

// Register OnBackPressed lifecycle event handler to check WebView's back navigation
// This ensures predictive back gesture (Android 13+) checks WebView.CanGoBack() before popping page
var services = MauiContext?.Services;
if (services != null)
{
// Create a weak reference to avoid memory leaks
var weakPlatformView = new WeakReference<AWebView>(platformView);

AndroidLifecycle.OnBackPressed handler = (activity) =>
{
// Check if WebView is still alive and can navigate back
if (weakPlatformView.TryGetTarget(out var webView) && webView.CanGoBack())
{
webView.GoBack();
return true; // Prevent back propagation - handled by WebView
}

return false; // Allow back propagation - let page be popped
};

// Register with lifecycle service - will be invoked by HandleBackNavigation in MauiAppCompatActivity
var lifecycleService = services.GetService<ILifecycleEventService>();
if (lifecycleService is LifecycleEventService concreteService)
{
concreteService.AddEvent(nameof(AndroidLifecycle.OnBackPressed), handler);
_onBackPressedHandler = handler;
}
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Copilot AI Dec 18, 2025

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The code casts ILifecycleEventService to LifecycleEventService to call AddEvent, but RemoveEvent is also internal and requires the same cast. Consider either: (1) Making RemoveEvent part of ILifecycleEventService or ILifecycleBuilder interface for better API design, or (2) Adding a comment explaining why this internal cast is necessary. The current approach creates coupling to the concrete implementation.

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}
}

private const string AndroidFireAndForgetAsyncSwitch = "BlazorWebView.AndroidFireAndForgetAsync";

protected override void DisconnectHandler(AWebView platformView)
{
// Clean up lifecycle event handler to prevent memory leaks
if (_onBackPressedHandler != null && MauiContext?.Services != null)
{
var lifecycleService = MauiContext.Services.GetService<ILifecycleEventService>();
if (lifecycleService is LifecycleEventService concreteService)
{
concreteService.RemoveEvent(nameof(AndroidLifecycle.OnBackPressed), _onBackPressedHandler);
_onBackPressedHandler = null;
}
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Copilot AI Dec 18, 2025

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The same cast pattern (ILifecycleEventService to LifecycleEventService) is repeated in both ConnectHandler and DisconnectHandler. Consider extracting this to a helper method or property to reduce code duplication and make the intent clearer. For example, a private method like TryGetLifecycleEventService() that returns the concrete service or null.

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}
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Copilot AI Dec 18, 2025

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The compound null check can be simplified for better readability. Consider checking MauiContext?.Services first and storing it in a local variable, then checking _onBackPressedHandler separately. This makes the code flow clearer and avoids repeated null-conditional access.

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platformView.StopLoading();

if (_webviewManager != null)
Expand Down
1 change: 1 addition & 0 deletions src/BlazorWebView/src/Maui/PublicAPI/net-android/PublicAPI.Unshipped.txt
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@@ -1 +1,2 @@
#nullable enable
override Microsoft.AspNetCore.Components.WebView.Maui.BlazorWebViewHandler.ConnectHandler(Android.Webkit.WebView! platformView) -> void
9 changes: 9 additions & 0 deletions src/Core/src/LifecycleEvents/LifecycleEventService.cs
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Expand Up @@ -39,5 +39,14 @@ public IEnumerable<TDelegate> GetEventDelegates<TDelegate>(string eventName)

public bool ContainsEvent(string eventName) =>
_mapper.TryGetValue(eventName, out var delegates) && delegates?.Count > 0;

internal void RemoveEvent<TDelegate>(string eventName, TDelegate action)
where TDelegate : Delegate
{
if (_mapper.TryGetValue(eventName, out var delegates) && delegates != null)
{
delegates.Remove(action);
}
}
}
}
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