Question

I have a .razor page which takes a lot of time to load. Is it possible to disable/override the hardware Back button in Blazor Hybrid MAUI for a specific .razor page? The primary reason for doing so is to make sure the user doesn t accidentally presses it and have to wait for the loading again. We are working on a more sophisticated cache to handle this better but for now we just want to override the back button to switch tab inside of the page rather than full page back.

Answer 1

You can do that by setting a keylistener for the webview.

Custom a keylistener in the android part:

namespace BlazorApp.Platforms.Android
{
    public class MyListener : Java.Lang.Object, IOnKeyListener
    {
        public bool OnKey(global::Android.Views.View v, [GeneratedEnum] Keycode keyCode, KeyEvent e)
        {
            if(keyCode == Keycode.Back && e.Action == KeyEventActions.Down)
            {
                return true; // this will cancel the back button pressed event
            }
            return false;
        }
    }
}

And in the MainPage.xaml:

<BlazorWebView x:Name="webview" HostPage="wwwroot/index.html">
        <BlazorWebView.RootComponents>
            <RootComponent Selector="#app" ComponentType="{x:Type local:Main}" />
        </BlazorWebView.RootComponents>
    </BlazorWebView>

Override the OnHandlerChanged() method in the MainPage.cs:

protected override void OnHandlerChanged()
    {
        base.OnHandlerChanged();
#if ANDROID
        var web = webview.Handler.PlatformView as Android.Webkit.WebView;
        web.SetOnKeyListener(new Platforms.Android.MyListener());
#endif
    }

Update:

You can add a judgement before you cancel the back button event. Such as:

namespace BlazorApp.Platforms.Android
{
    public class MyListener : Java.Lang.Object, IOnKeyListener
    {
        public bool OnKey(global::Android.Views.View v, [GeneratedEnum] Keycode keyCode, KeyEvent e)
        {
            if(keyCode == Keycode.Back && e.Action == KeyEventActions.Down)
            {
                string url = (v as gloabl::Android.Webkit.WebView).Url;
                if(url.EndsWith("specialpage"));// the razor page s route is @page"/specialpage"
                   return true; // this will cancel the back button pressed event
            }
            return false;
        }
    }
}

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