Xamarin.Forms buttons become disabled after touched

Question

I use Xamarin.Forms and MvvmCross, but I've encountered a problem in applications. Buttons become disabled sometimes after touched and running the commands.

I added IsEnabled="True" to button but nothing changed

<Button 
    WidthRequest="36" 
    HeightRequest="36" 
    CornerRadius="18" 
    BorderWidth="2" 
    FontSize="18" 
    Text="{Binding OptionText}" 
    Command="{Binding OptionSelectedCommand}" 
    CommandParameter="{Binding .}" 
    IsEnabled="True" 
    VerticalOptions="Center" 
    HorizontalOptions="Center"/>

I want this button to be enabled always.

My Command code is:

new MvxAsyncCommand(async () => 
{ 
    if (option.IsSelected) 
    { 
        option.IsSelected = false; 
    } 
    else 
    { 
        option.OptionGroup.Options.ForEach(c => c.IsSelected = false);
        option.IsSelected = true; 
    } 

    return Task.CompletedTask; 
})

Heraldry

What does the code for your Command look like? – Confabulation

Just to expand on Gerald's comment, what is the code you have in OptionSelectedCommand? – Undergarment

this is my OptionSelectedCommand new MvxAsyncCommand(async () => { if (option.IsSelected) { option.IsSelected = false; } else { option.OptionGroup.Options.ForEach(c=>c.IsSelected=false); option.IsSelected = true; } return Task.CompletedTask; }); @GeraldVersluis – Heraldry

This may be related: github.com/MvvmCross/MvvmCross/issues/1589. – Undergarment

Answer 1

Finally I found a solution about this problem. Problem is related to MvxAsyncCommand, solved by using Command instead of MvxAsyncCommand.

I think MvvmCross MvxAsyncCommand has a bug about running asynchronous methods

Heraldry

Not sure why your answer was downvoted. I had the same issues. The button becomes disabled, not always, but most of the time after executing. Thanks for the tip, changing from MvxAsyncCommand to MvxCommand fixed it for me too. – Madura

Unfortunately, the issue is still actual even as of MvvmCross 6.4.0, which is quite embarrassing. – Nave

And workaround just eliminates the issue, however, the command becomes un-async then, and it doesn't lock the button which can be pressed again. – Nave

Still an issue with 6.4.1. – Schema

Answer 2

Mehmet is correct that the root of this issue is in MvxAsyncCommand. I found that my MvxAsyncCommand's CanExecute() method always returned false. When CanExecute() returns false the Xamarin Forms button becomes disabled, which is the intended behavior. But why does CanExecute() always return false? I dug into the source code and I found that the MvxAsyncCommand's CanExecute() method will return false if it thinks the task is running. If you set allowConcurrentExecutions to true in the constructor for MvxAsyncCommand, it will bypass that check and the button will become enabled again.

This needs to be fixed in MvxAsyncCommand, but setting allowConcurrentExecution = true is a temporary work-around.

MvxAsyncCommand on Github:

public bool CanExecute(object parameter)
{
    if (!_allowConcurrentExecutions && IsRunning)
        return false;
    else
        return CanExecuteImpl(parameter);
}

Orsola