在DataTemplate UWP中绑定ComboBoxItem的IsSelected属性

问题描述

我正在尝试绑定ComboBoxItem的IsSelected属性，以便显示正确的图标，如果选择了Item，应该会显示红色图标，否则打开的列表的睡觉会显示灰色。下面的代码显示了我如何尝试实现该功能。

<ComboBox
    ItemsSource="{Binding Icons}"
    SelectedItem="{Binding SelectedIcon, Mode=TwoWay}"
    Style="{ThemeResource DefaultComboBoxStyle}"
    <ComboBox.ItemTemplate>
        <DataTemplate>
            <StackPanel Orientation="Horizontal">
                    <Image
                        Width="20"
                        Height="20"
                        Source="{Binding IconId, Mode=TwoWay, Converter={StaticResource IconConverter}, ConverterParameter={StaticResource True}}"
                        Visibility="{Binding Path=IsSelected,RelativeSource={RelativeSource Mode=TemplatedParent}, Converter={StaticResource BoolToVisibilityConverter}}" />
                    <Image
                        Width="20"
                        Height="20"
                        Source="{Binding IconId, Mode=TwoWay, Converter={StaticResource IconConverter}}"
                        Visibility="{{Binding Path=IsSelected,RelativeSource={RelativeSource Mode=TemplatedParent} Converter={StaticResource BoolToVisibilityInverted}}" />
            </StackPanel>
        </DataTemplate>
    </ComboBox.ItemTemplate>
</ComboBox>

一个项目的图标id对于两个图像是相同的，转换器将根据传递的参数返回正确的图像链接。我已尝试获取父数据上下文并尝试使用comboBoxItem(SelectorItem)的IsSelected属性，但不起作用。

我不想在要迭代的ViewModel中添加IsSelected属性，我假设存在某些语法，但我找不到它。我只想获取属性IsSelected的值，并在不更改ViewModel中的代码的情况下绑定到XAML中。

实现了类似以下代码中的内容，但实现了硬编码元素。根据ComboBoxItem的IsSelected Item属性，会显示正确的图标。我希望使用ItemsSource和DataTemplate实现相同的功能。

 <ComboBox
    SelectedIndex="{Binding IconType, Mode=TwoWay, Converter={StaticResource IconTypeIndexToIconConverter}}"
    Style="{ThemeResource DefaultComboBoxStyle}">
    <ComboBoxItem x:Name="SwitchIcon">
        <StackPanel Orientation="Horizontal">
                <Image
                    Source="{Binding Source=1, Converter={StaticResource IconConverter}}"
                    Style="{ThemeResource DeviceTypeImageBlockStyle}"
                    Visibility="{Binding IsSelected, ElementName=SwitchIcon, Converter={StaticResource BoolToVisibilityInverted}}" />
                <Image
                    Source="{Binding Source=1, Converter={StaticResource IconConverter}, ConverterParameter={StaticResource True}}"
                    Style="{ThemeResource DeviceTypeImageBlockStyle}"
                    Visibility="{Binding IsSelected, ElementName=SwitchIcon, Converter={StaticResource BoolToVisibilityConverter}}" />
        </StackPanel>
    </ComboBoxItem>
    <ComboBoxItem x:Name="LightDimmingIcon">
        <StackPanel Orientation="Horizontal">
                <Image
                    Source="{Binding Source=2, Converter={StaticResource IconConverter}}"
                    Style="{ThemeResource DeviceTypeImageBlockStyle}"
                    Visibility="{Binding IsSelected, ElementName=LightDimmingIcon, Converter={StaticResource BoolToVisibilityInverted}}" />
                <Image
                    Source="{Binding Source=2, Converter={StaticResource IconConverter}, ConverterParameter={StaticResource True}}"
                    Style="{ThemeResource DeviceTypeImageBlockStyle}"
                    Visibility="{Binding IsSelected, ElementName=LightDimmingIcon, Converter={StaticResource BoolToVisibilityConverter}}" />
        </StackPanel>
    </ComboBoxItem>
</ComboBox>

有什么想法吗？解决方案？

推荐答案

恐怕您无法绑定DataTemplateUWP中ComboBoxItem的IsSelected属性。因为TemplatedParent RelativeSource是ContentPresenter而不是ComboBoxItem，您可以使用下面的XAML进行验证。

<ComboBox.ItemTemplate>
    <DataTemplate>
        <StackPanel Orientation="Horizontal">
            <Border DataContext="{Binding RelativeSource={RelativeSource Mode=TemplatedParent}}">
                <TextBlock x:Name="Print" Text="{Binding}"/>
            </Border>
            <TextBlock Text="{Binding}" />
        </StackPanel>
    </DataTemplate>
</ComboBox.ItemTemplate>

它将在Print文本块中显示Windows.UI.Controls.ContentPresenter。

通常，我们通过将IsSlected添加到模型类来处理该场景。并获得选择项，修改IsSelected值以影响UI。下面我做了完整的样品。

代码隐藏

public sealed partial class MainPage : Page, INotifyPropertyChanged
{
    public List<CBContent> Items { get; set; } = new List<CBContent>();
    public MainPage()
    {
        this.InitializeComponent();
        Items.Add(new CBContent { Content = "Item1", IsSelected = false });
        Items.Add(new CBContent { Content = "Item2", IsSelected = false });
        Items.Add(new CBContent { Content = "Item3", IsSelected = false });
        Items.Add(new CBContent { Content = "Item4", IsSelected = false });
        Items.Add(new CBContent { Content = "Item5", IsSelected = false });
        Items.Add(new CBContent { Content = "Item6", IsSelected = false });
        this.DataContext = this;
    }

    public event PropertyChangedEventHandler PropertyChanged;

    private void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
    private CBContent _selectItem;

    private CBContent _previousSelectItem;
    public CBContent SelectItem
    {
        get
        {
            return _selectItem;
        }
        set
        {
            _selectItem = value;
            value.IsSelected = true;
            if(_previousSelectItem != null)
            {
                _previousSelectItem.IsSelected = false;
            }
            _previousSelectItem = _selectItem;
            OnPropertyChanged();
        }
    }
}
public class CBContent : INotifyPropertyChanged
{
    public string Content { get; set; }
    private bool _isSelect;
    public bool IsSelected
    {
        get
        {
            return _isSelect;
        }
        set
        {
            _isSelect = value;
            OnPropertyChanged();
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    private void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

XAML

<Grid>
    <ComboBox ItemsSource="{Binding Items, Mode=OneWay}" SelectedItem="{Binding SelectItem,Mode=TwoWay}">
        <ComboBox.ItemTemplate>
            <DataTemplate>
                <StackPanel Orientation="Horizontal">

                    <Rectangle
                        Width="20"
                        Height="20"
                        Fill="Red"
                        Visibility="{Binding IsSelected, Mode=TwoWay}"
                        />
                    <TextBlock Text="{Binding Content}" />
                </StackPanel>

            </DataTemplate>
        </ComboBox.ItemTemplate>
    </ComboBox>
</Grid>

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