WPF - 使用MVVM基于模型的不同状态禁用和启用不同控件的优雅方法

Question

我正在为以下问题寻找一个优雅的解决方案.

假设我们有一个具有以下布尔属性的(View)模型:

• Α
• Beta版
• 伽玛
• 三角洲

接下来,我在表面上有5个控件,只有在满足基于这些属性的条件时才能看到它们.当然,只要更新其中一个属性,就应该立即传播更改:

• ControlA - > Alpha &&(Beta || Gamma)
• ControlB - > Delta
• ControlC - > Delta || Beta版
• ControlD - > Gamma && Alpha && Delta
• ControlE - > Alpha || 伽玛

到目前为止我提出的唯一解决方案是使用MultiValueConverters.

ControlA的示例:

<ControlA>
   <ControlA.Visibility>
      <MultiBinding Converter={StaticResource ControlAVisibilityConverter}>
          <Binding Path="Alpha"/>
          <Binding Path="Beta"/>
          <Binding Path="Gamma"/>
      </MultiBinding>
   </ControlA.Visibility>
</ControlA>

此ControlAVisibilityConverter检查条件"Alpha &&(Beta || Gamma)"并返回适当的值.

它确实有用......好吧..但也许你可以想出一个更优雅的解决方案？

谢谢TwinHabit

Answer 1

为每个规则编写转换器会在这种情况下将业务逻辑放在两个位置(在转换器和视图模型中).我建议使用INotifyPropertyChanged事件为ViewModel中的每个控件创建一个属性/标志,以确定控件是否可见(或其他行为).

请注意,当您查看我的viewmodel(下面)时,您将看到我公开了bool和Visibilty类型的属性.

如果您需要使用该属性作为一般规则,请使用bool和DataTrigger.

public bool ControlD

如果您只需要控制可见性,则可以直接绑定到Visibility:

public Visibility ControlA

更新:由于@Wallstreet程序员的评论,我添加了另一个选项来使用BooleanVisibilityConverter.我更新了下面的第五个控件,以反映如何使用转换器.我在底部添加了转换器的代码.

这是XAML中的测试窗口:

<Window x:Class="ControlVisibleTrigger.Views.MainView"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  Title="Main Window" Height="400" Width="800">
  <Window.Resources>
    <Style x:Key="DropDownStyle" TargetType="TextBox">
        <Setter Property="Visibility" Value="Hidden"/>
        <Style.Triggers>
            <DataTrigger Binding="{Binding ControlC}" Value="True">
                <Setter Property="Visibility" Value="Visible"/>
            </DataTrigger>
        </Style.Triggers>
    </Style>
  </Window.Resources>
  <DockPanel>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <StackPanel Grid.Row="0">
            <CheckBox IsChecked="{Binding Path=Alpha,Mode=TwoWay}" Content="Alpha"/>
            <CheckBox IsChecked="{Binding Path=Beta,Mode=TwoWay}" Content="Beta"/>
            <CheckBox IsChecked="{Binding Path=Gamma,Mode=TwoWay}" Content="Gamma"/>
            <CheckBox IsChecked="{Binding Path=Delta,Mode=TwoWay}" Content="Delta"/>
        </StackPanel>
        <TextBox Grid.Row="1" Visibility="{Binding Path=ControlA}" Text="Binding to visibility"/>
        <Button Grid.Row="2" Visibility="{Binding Path=ControlB}" Content="Binding to visibility"/>
        <TextBox Grid.Row="3" Style="{StaticResource DropDownStyle}" Text="Using WindowResource DataTrigger"/>
        <TextBox Grid.Row="4" Text="Using Local DataTrigger">
            <TextBox.Style>
              <Style TargetType="TextBox">
                <Setter Property="Visibility" Value="Hidden"/>
                <Style.Triggers>
                    <DataTrigger Binding="{Binding ControlD}" Value="True">
                        <Setter Property="Visibility" Value="Visible"/>
                    </DataTrigger>
                </Style.Triggers>
              </Style>
            </TextBox.Style>
        </TextBox>
        <Button Grid.Row="5" 
                Content="Press me" 
                Visibility="{Binding Path=ControlE, Converter={StaticResource booleanVisibilityConverter}, ConverterParameter=True, Mode=OneWay}">
    </Grid>
  </DockPanel>
</Window>

这是ViewModel:

public class MainViewModel : ViewModelBase
{
  public MainViewModel()
  {
  }

  private bool _alpha = true;
  public bool Alpha
  {
     get
     {
        return _alpha;
     }
     set
     {
        _alpha = value;
        OnPropertyChanged("ControlA");
        OnPropertyChanged("ControlB");
        OnPropertyChanged("ControlC");
        OnPropertyChanged("ControlD");
        OnPropertyChanged("ControlE");
     }
  }

  private bool _beta = true;
  public bool Beta
  {
     get
     {
        return _beta;
     }
     set
     {
        _beta = value;
        OnPropertyChanged("ControlA");
        OnPropertyChanged("ControlB");
        OnPropertyChanged("ControlC");
        OnPropertyChanged("ControlD");
        OnPropertyChanged("ControlE");
     }
  }

  private bool _gamma = true;
  public bool Gamma
  {
     get
     {
        return _gamma;
     }
     set
     {
        _gamma = value;
        OnPropertyChanged("ControlA");
        OnPropertyChanged("ControlB");
        OnPropertyChanged("ControlC");
        OnPropertyChanged("ControlD");
        OnPropertyChanged("ControlE");
     }
  }

  private bool _delta = true;
  public bool Delta
  {
     get
     {
        return _delta;
     }
     set
     {
        _delta = value;
        OnPropertyChanged("ControlA");
        OnPropertyChanged("ControlB");
        OnPropertyChanged("ControlC");
        OnPropertyChanged("ControlD");
        OnPropertyChanged("ControlE");
     }
  }

  public Visibility ControlA
  {
     get
     {
        Visibility result = Visibility.Hidden;
        if ( Alpha && (Beta || Gamma))
        {
           result = Visibility.Visible;
        }
        return result;
     }
  }

  public Visibility ControlB
  {
     get
     {
        Visibility result = Visibility.Hidden;
        if ( Delta )
        {
           result = Visibility.Visible;
        }
        return result;
     }
  }

  private bool _controlC = false;
  public bool ControlC
  {
     get
     {
        return Delta || Beta;
     }
  }

  private bool _controlD = false;
  public bool ControlD
  {
     get
     {
        return Gamma && Alpha && Delta;
     }
  }

  private bool _controlE = false;
  public bool ControlE
  {
     get
     {
        return Alpha || Gamma;
     }
  }
}

这是转换器:

public class BooleanVisibilityConverter : IValueConverter
{
  public object Convert( object value, Type targetType, object parameter, System.Globalization.CultureInfo culture )
  {
    if( ( value == null ) || ( !( value is bool ) ) )
      return Binding.DoNothing;

    Visibility elementVisibility;
    bool shouldCollapse = ( ( bool )value );

    if( parameter != null )
    {
      try
      {
        bool inverse = System.Convert.ToBoolean( parameter );

        if( inverse )
          shouldCollapse = !shouldCollapse;
      }
      catch
      {
      }
    }

    elementVisibility = shouldCollapse ? Visibility.Collapsed : Visibility.Visible;
    return elementVisibility;
  }

  public object ConvertBack( object value, Type targetType, object parameter, System.Globalization.CultureInfo culture )
  {
    throw new NotImplementedException();
  }
}