ComboBox SelectedItem未更新-Java 学习之路

我正在使用ComboBox（WPF 4.0）来显示编辑器应用程序的用户定义的段落样式 . ComboBox有两列：

（1）段落样式的未格式化名称
（2）文本"abcABC123"，在根据第一列中的段落样式格式化的某些属性中

这些是用户定义的段落样式类的公共属性（其中最后3个不是ResourceKeys，而是包含ResourceKeys的变量）：

_NameInternal
_NameUI
_ResourceKey_background
_ResourceKey_foreground
_ResourceKey_fontFamily

问题：ComboBox显示SelectedItem . 如果我打开一个对话框，更改SelectedItem（Background，Foreground，FontFamily）的三个Binding属性中的一个或多个并关闭对话框，则不会更新ComboBox的SelectedItem . 但是，如果我放下它，它会显示新的格式 .

有没有办法在Xaml而不是C＃中解决这个问题？

<Window.Resources>
    <local2:_2StylesPara x:Key="_2stylesPara" />
    <CollectionViewSource x:Key="_collectionViewSource_stylesPara" Source="{StaticResource _2stylesPara}">
        <CollectionViewSource.SortDescriptions>
            <!-- Requires 'xmlns:scm="clr-namespace:System.ComponentModel;assembly=WindowsBase"' declaration. -->
            <scm:SortDescription PropertyName="_NameUI" Direction="Ascending"/>
        </CollectionViewSource.SortDescriptions>
    </CollectionViewSource>
</Window.Resources>

<ComboBox Name="_cbStylesPara" HorizontalAlignment="Left" 
          ItemsSource="{Binding Source={StaticResource _collectionViewSource_stylesPara}}" 
          SelectedValuePath="_NameInternal" IsSynchronizedWithCurrentItem="True" >
    <ComboBox.Resources>
        <local2:_2ResourceLookupConverter x:Key="_resourceLookupConverter"/>
    </ComboBox.Resources>
    <ComboBox.ItemTemplate>
        <DataTemplate>
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="100"/>
                    <ColumnDefinition Width="100" />
                </Grid.ColumnDefinitions>
                <Grid.RowDefinitions>
                    <RowDefinition />
                </Grid.RowDefinitions>
                <TextBlock Text="{Binding _NameUI}" Grid.Column="0" VerticalAlignment="Center" />
                <TextBlock Grid.Column="1" Text="abcABC123" Margin="3,0,0,0"
                           Background="{Binding _ResourceKey_background, Converter={StaticResource _resourceLookupConverter}}"
                           Foreground="{Binding _ResourceKey_foreground, Converter={StaticResource _resourceLookupConverter}}"
                           FontFamily="{Binding _ResourceKey_fontFamily, Converter={StaticResource _resourceLookupConverter}}"/>
            </Grid>
        </DataTemplate>
    </ComboBox.ItemTemplate>
</ComboBox>

代码背后：

public class _2ResourceLookupConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        return App.Current.TryFindResource(value);
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        return Binding.DoNothing;
    }
}

以下是用户定义的段落样式的2个类：

public class _2StylesPara : ObservableCollection<_2StylePara>
// ObservableCollection implements INotifyPropertyChanged
{
    public _2StylesPara(){}
}

public class _2StylePara
{
    public event PropertyChangedEventHandler PropertyChanged;

    // This method is not reached if Background, Foreground or FontFamily changes
    private void SetValue<T>(ref T property, T value, string propertyName = null)
    {
        if (object.Equals(property, value) == false)
        {
            property = value;

            if (this.PropertyChanged != null)
            {
                this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }

    private string _nameInternal = string.Empty;
    private string _nameUI = string.Empty;
    private string _resourceKey_background = string.Empty;
    private string _resourceKey_foreground = string.Empty;
    private string _resourceKey_fontFamily = string.Empty;
    private string _resourceKey_nameUI = string.Empty; 
    private string _resourceKey_style = string.Empty; 
    private Style _style = null;
    private ResourceDictionary _valuesRD = null;
    private string _pathToValuesRD = string.Empty;


    public string NameInternal
    {
        get { return this._nameInternal; }
        set { SetValue(ref this._nameInternal, value); }
    }

    public string NameUI
    {
        get { return this._nameUI; }
        set { SetValue(ref this._nameUI, value); }
    }

    public string ResourceKey_background
    {
        get { return this._resourceKey_background; }
        set { SetValue(ref this._resourceKey_background, value); }
    }

    public string ResourceKey_foreground
    {
        get { return this._resourceKey_foreground; }
        set { SetValue(ref this._resourceKey_foreground, value); }
    }

    public string ResourceKey_fontFamily
    {
        get { return this._resourceKey_fontFamily; }
        set { SetValue(ref this._resourceKey_fontFamily, value); }
    }

    public string ResourceKey_nameUI
    {
        get { return this._resourceKey_nameUI; }
        set { SetValue(ref this._resourceKey_nameUI, value); }
    }

    public string ResourceKey_style
    {
        get { return this._resourceKey_style; }
        set { SetValue(ref this._resourceKey_style, value); }
    }

    public Style Style
    {
        get { return this._style; }
        set { SetValue(ref this._style, value); }
    }

    public ResourceDictionary ValuesRD
    {
        get { return this._valuesRD; }
        set { SetValue(ref this._valuesRD, value); }
    }

    public string PathToValuesRD
    {
        get { return this._pathToValuesRD; }
        set { SetValue(ref this._pathToValuesRD, value); }
    }


    // Constructor
    public _2StylePara(Style sty, string styleNameInternal, string styleNameUI, string resourceKey_style, string resourceKey_nameUI,
                      string resourceKey_foreground, string resourceKey_background, string resourceKey_fontFamily,
                      ResourceDictionary valuesRD, string pathToValuesRD)
    {
        _style = sty;
        _nameInternal = styleNameInternal;                  // [ "_sty001" ]
        _nameUI = styleNameUI;                              // [ "Standard" ]

        _resourceKey_style = resourceKey_style;             // [ "_stylePara001" ]
        _resourceKey_nameUI = resourceKey_nameUI;           // [ "_nameUi001 ]
        _resourceKey_foreground = resourceKey_foreground;   // [ "_brush_textcolor001" ]
        _resourceKey_background = resourceKey_background;   // [ "_brush_backcolor001" ]
        _resourceKey_fontFamily = resourceKey_fontFamily;   // [ "_fontFamily001" ]

        _valuesRD = valuesRD;                               // This ResourceDictionary contains all style values
        _pathToValuesRD = pathToValuesRD;                   // [ "...\Resources\1ParaStyleValuesRD001.xaml" ]
    }
}

1 回答

0
如果我理解正确，_ResourceKey_background和其他属性是您的_2sytlesPara集合中包含的用户定义的段落样式类的属性 . 您遇到的行为是在后台更改这些属性时，视图不会更新 .

在这种情况下，如果您更新模型（也就是UDF样式类实例之一），则应通知绑定有关更新的信息 . 它由应由模型触发的INotifyPropertyChanged.PropertyChanged事件完成 .

绑定自动以相反的方式工作，因此当您在视图上更改某些内容时，您的模型会更新 .

通知的标准属性模式是：
```
class Model : INotifyPropertyChanged
{
    private int _Name = default(int);
    public int Name
    {
        get { return _Name; }
        set
        {
            SetValue(ref this._Name, value);
        }
    }

    private void SetValue<T>(ref T property, T value, [CallerMemberName]string propertyName = null)
    {
        if (object.Equals(property, value) == false)
        {
            property = value;

            if (this.PropertyChanged != null)
            {
                this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
}
```
我希望我理解你的问题，我可以提供帮助 .

UPDATE:

IObservableCollection仅通过绑定机制通知集合中的添加和删除 . 项目的嵌套属性值的更改仍然不会自动反映 .

关于您的代码，我建议您尝试以下修改：

首先，我不建议用下划线开始公共 property 名称 . 根据MS命名约定，以下划线开头的名称通常是私有支持字段 .

所以，改变相应的属性，如：
```
private string _ResourceKey_nameUI = string.Empty;
public string ResourceKey_nameUI
{
    get { return this._ResourceKey_nameUI; }
    set { SetValue(ref this._ResourceKey_nameUI, value); }
}
```
还可以更改属性的绑定：
```
<TextBlock Grid.Column="1" Text="abcABC123" Margin="3,0,0,0" 
Background="{Binding ResourceKey_background, Converter={StaticResource _resourceLookupConverter}}" 
Foreground="{Binding ResourceKey_foreground, Converter={StaticResource _resourceLookupConverter}}"
FontFamily="{Binding ResourceKey_fontFamily, Converter={StaticResource _resourceLookupConverter}}"/>
```
UPDATE 2

WPF绑定检查绑定的模型实例是否实现了INotifyPropertyChanged接口 . 请将您的 class 声明修改为：
```
public class _2StylePara : INotifyPropertyChanged
{
//...
}
```
此外，在后台更改值时，应使用属性而不是支持字段 . 因此，当您更改NameUI时，将调用SetValue方法，它将通知绑定刷新TextBlock . 绑定还应指向属性，而不是支持字段 .

因此：Text =“”NOT Text =“”Plese，如果有帮助则标记为答案 . 谢谢 .
回复于 2024-05-02T08:17:32+08:00

ComboBox SelectedItem未更新

1 回答

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