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CodingOctocat avatar CodingOctocat commented on June 25, 2024 1

@drasticactions Thanks! In my sample I did forget to set BindingContext, I didn't actually forget this in my actual project, the main problem was that I forgot to add [NotifyCanExecuteChangedFor(nameof(DoWorkCommand))].

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drasticactions avatar drasticactions commented on June 25, 2024 1

I'm glad you solved it! I'm also pleased that NotifyCanExecuteChangedFor exists; since my solution was kind of janky, that one makes more sense.

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github-actions avatar github-actions commented on June 25, 2024

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RoiChen001 avatar RoiChen001 commented on June 25, 2024

Can repro this issue at Android platform on the latest 17.11.0 Preview 1.0(8.0.7/8.0.10/8.0.21).
BindingBreaksStyle.zip

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mattleibow avatar mattleibow commented on June 25, 2024

This looks related: #9753

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CodingOctocat avatar CodingOctocat commented on June 25, 2024

This looks related: #9753

Not quite the same, #9753 case is that the visual of the button has not changed, but in my case the button cannot be enabled/disabled based on the CanExecute change.

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drasticactions avatar drasticactions commented on June 25, 2024

FWIW I was able to get it working just fine

https://github.com/drasticactions/MauiRepros/tree/main/MvvmTestCanExecute

スクリーンショット 2024-05-28 16 08 48 スクリーンショット 2024-05-28 16 08 59

It may be that you didn't set up your model correctly? Maybe the library you are using is at fault? If you make a sample showing what you're doing that could help, or maybe run what I wrote above and see if it doesn't work for you?

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CodingOctocat avatar CodingOctocat commented on June 25, 2024

@drasticactions Hi, I made a sample, I use Mvvm Toolkit, and the [RelayCommand] feature.

public partial class MainViewModel : ObservableObject
{
    [ObservableProperty]
    private bool _canDoWork;  // binding to Switch button

    [RelayCommand(CanExecute = nameof(CanDoWork))]
    private static void DoWork()  // binding to 'Click me' button
    {
        Debug.WriteLine("DoWork");
    }
}

动画

MauiIssue22652.zip

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drasticactions avatar drasticactions commented on June 25, 2024

Thank you for the sample! I believe you set up your view model incorrectly.

First, in your app page, your View Model isn't set as the BindingContext, it's null, so it will never work.

Then, in your ViewModel,

public partial class MainViewModel : ObservableObject
{
    [ObservableProperty]
    private bool _canDoWork;

    [RelayCommand(CanExecute = nameof(CanDoWork))]
    private static void DoWork()
    {
        Debug.WriteLine("DoWork");
    }
}

I am not well versed in the CommunityToolkit MVVM, but I believe you didn't set it up correctly. CanExecute gets called whenever someone calls for it to be raised, it's not done automatically. So when CanDoWork gets updated, you then need to raise the event on DoWork to be able to call CanExecute.

Changing it to this:

public partial class MainViewModel : ObservableObject
{
    [ObservableProperty]
    private bool _canDoWork;
    
    partial void OnCanDoWorkChanged(bool value)
    {
       this.DoWorkCommand.NotifyCanExecuteChanged();
    }

    [RelayCommand(CanExecute = nameof(CanDoWork))]
    private async void DoWork()
    {
        Debug.WriteLine("DoWork");
    }
}

Allows it to work. Likewise, DoWork can't be static, or else you can't call on the command for NotifyCanExecuteChanged. I would encourage you to read their documentation for more about it, but I do not believe this is a MAUI bug.

スクリーンショット 2024-05-28 17 23 59 スクリーンショット 2024-05-28 17 23 53

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