.NET MAUI Community Toolkit MVVM异步按钮点击后变灰无法恢复

Windows平台下，异步RelayCommand执行时，按钮的Pressed视觉状态不会在异步操作完成后自动重置，导致按钮保持灰色（Pressed状态的默认视觉表现），但命令本身仍处于启用状态，可正常触发。

方案一：强制触发UI线程状态更新 #

在异步命令方法末尾添加一个空的UI线程操作，让UI线程有机会重置按钮的视觉状态：

public partial class MainPageViewModel : ObservableObject
{
    [RelayCommand]
    async Task TestSomethingAsync()
    {
        await Task.Delay(1);
        System.Diagnostics.Debug.WriteLine(nameof(TestSomethingAsync));
        // 触发UI线程处理状态更新，重置按钮视觉状态
        await MainThread.InvokeOnMainThreadAsync(() => {});
    }

    [RelayCommand]
    void TestMore()
    {
        System.Diagnostics.Debug.WriteLine(nameof(TestMore));
    }
}

方案二：绑定命令运行状态控制视觉状态 #

利用CommunityToolkit.MVVM自动生成的{CommandName}IsRunning属性（异步命令专属），通过视觉状态绑定精准控制按钮背景色：

1. 实现布尔值反转转换器：

public class InverseBooleanConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        => !(bool)value;

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        => !(bool)value;
}

2. 在MainPage资源中声明转换器：

<ContentPage.Resources>
    <local:InverseBooleanConverter x:Key="InverseBooleanConverter"/>
</ContentPage.Resources>

3. 修改按钮XAML，添加视觉状态绑定：

<Button
    Text="T1 Async"
    Command="{Binding TestSomethingCommand}"
    HorizontalOptions="Center">
    <VisualStateManager.VisualStateGroups>
        <VisualStateGroup x:Name="CommandExecutionStates">
            <VisualState x:Name="CommandRunning">
                <VisualState.Setters>
                    <Setter Property="BackgroundColor" Value="Gray"/>
                </VisualState.Setters>
            </VisualState>
            <VisualState x:Name="CommandIdle">
                <VisualState.Setters>
                    <Setter Property="BackgroundColor" Value="Blue"/>
                </VisualState.Setters>
            </VisualState>
        </VisualStateGroup>
    </VisualStateManager.VisualStateGroups>
    <VisualStateManager.VisualStateBindings>
        <VisualStateBinding
            VisualStateName="CommandRunning"
            Binding="{Binding TestSomethingCommandIsRunning}"/>
        <VisualStateBinding
            VisualStateName="CommandIdle"
            Binding="{Binding TestSomethingCommandIsRunning, Converter={StaticResource InverseBooleanConverter}}"/>
    </VisualStateManager.VisualStateBindings>
</Button>

方案三：重写按钮Pressed状态样式 #

若不需要保留按钮按下时的视觉反馈，可直接修改样式让Pressed状态背景色与Normal状态一致：

<Button
    Text="T1 Async"
    Command="{Binding TestSomethingCommand}"
    HorizontalOptions="Center">
    <Button.Style>
        <Style TargetType="Button">
            <Setter Property="BackgroundColor" Value="Blue"/>
            <Setter Property="VisualStateManager.VisualStateGroups">
                <VisualStateGroupList>
                    <VisualStateGroup x:Name="CommonStates">
                        <VisualState x:Name="Normal"/>
                        <VisualState x:Name="Pressed">
                            <VisualState.Setters>
                                <Setter Property="BackgroundColor" Value="Blue"/>
                            </VisualState.Setters>
                        </VisualState>
                        <VisualState x:Name="Disabled">
                            <VisualState.Setters>
                                <Setter Property="BackgroundColor" Value="Gray"/>
                            </VisualState.Setters>
                        </VisualState>
                    </VisualStateGroup>
                </VisualStateGroupList>
            </Setter>
        </Style>
    </Button.Style>
</Button>

内容的提问来源于stack exchange，提问作者user3439702