How to prompt a confirm message upon quiting the UWP Xamarin Forms?

user_8830978 0
Viewed 1081

Objective to achieve:
- Prompt confirm message "Are you confirm to exit?", with the options "Yes" and "Cancel"

I have been finding a way to to achieve the objective written above. I have tried the following code:

Windows.UI.Core.Preview.SystemNavigationManagerPreview.GetForCurrentView().CloseRequested += async (sender, args) =>
{
        args.Handled = true;
        var dialog = new MessageDialog("Are you confirm to exit?", "Exit");
        System.Diagnostics.Debug.WriteLine("CLOSE");            
};

the above code i writtin in MainPage.xaml.cs, but this code seem like not working for me, i don't see the "CLOSE" print out in the debug output.

xamarin.forms uwp dialog
1 Answers

After a bit of digging I have found out that app close confirmation is actually a restricted capability that you have to declare in you application manifest. Right-click the Package.appxmanifest file in Solution Explorer and choose View code.

In the opened XML file first add the following namespace in the root Package element:

xmlns:rescap="http://schemas.microsoft.com/appx/manifest/foundation/windows10/restrictedcapabilities"

And now find the Capabilities section where you add the confirmAppClose capability:

<Capabilities>
   <Capability Name="internetClient" />
   <rescap:Capability Name="confirmAppClose" />
</Capabilities>

Also, be aware that if you will want to display the MessageDialog, you will have to use the deferral, so that the system waits for the await to finish before checking the Handled property:

var deferral = e.GetDeferral();           
var dialog = new MessageDialog("Are you sure you want to exit?", "Exit");
var confirmCommand = new UICommand("Yes");
var cancelCommand = new UICommand("No");
dialog.Commands.Add( confirmCommand);            
dialog.Commands.Add(cancelCommand);
dialog.CancelCommandIndex = 1;
dialog.DefaultCommandIndex = 1;
if (await dialog.ShowAsync() == cancelCommand)
{
    //cancel close by handling the event
    e.Handled = true;                
}
deferral.Complete();

The advantage of this approach compared to just terminating the app manually and setting the event as Handled every time is that in this case the app first goes through the suspension lifetime event, which allows you to save any unsaved changes, whereas Application.Terminate() for example would mean an immediate "hard-kill" of the app.

user_7322210
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