WPF ListView 不会在 PropertyChanged 上更新

Question

我有一个 WPF 列表视图，它在组合框中显示材质、厚度和厚度单位...xaml 看起来像这样（为了清晰起见，我删除了所有可视化设置）：

    <ListView ItemsSource="{Binding Path=MaterialLayers}" IsSynchronizedWithCurrentItem="True">
        <ListView.Resources>
            <x:Array x:Key="DistanceUnitItems" Type="sys:String" xmlns:sys="clr-namespace:System;assembly=mscorlib">
                <sys:String>cm</sys:String>
                <sys:String>inches</sys:String>
            </x:Array>
            <DataTemplate x:Key="ThicknessUnit">
                <ComboBox ItemsSource="{StaticResource DistanceUnitItems}" SelectedIndex="{Binding ThicknessUnit}" />
            </DataTemplate>
        </ListView.Resources>
        <ListView.View>
            <GridView>
                <GridViewColumn Header="Material Name" DisplayMemberBinding="{Binding MaterialName}"/>
                <GridViewColumn Header="Material Thickness" DisplayMemberBinding="{Binding MaterialThickness}"/>  />
                <GridViewColumn Header="Thickness Unit" CellTemplate="{StaticResource ThicknessUnit}"  />
            </GridView>
        </ListView.View>
    </ListView>

MaterialLayers 是 ObservableCollection<MaterialLayer>

MaterialLayer 具有 MaterialName、MaterialThickness 和 ThicknessUnit 的属性（0 表示厘米，1 表示英寸）。 MaterialThickness 将内部存储的值（以厘米为单位）转换为厚度单位指定的单位。

当ThicknessUnit 改变时，我的DataViewModel 调用PropertyChanged 事件处理程序，属性名称为“MaterialLayers”。

所以，我希望 MaterialThickness 在 ThicknessUnit 更改时自动更新。

我已经对其进行了调试，并且调用了 PropertyChanged("MaterialLayers")。（当调用 ThicknessUnit 设置方法时，它调用父数据类 (MyData) 上的一个事件，该事件调用 DataViewModel 上的一个事件，该事件调用PropertyChanged 处理程序。）

DataViewModel 中的相关代码

    public delegate void DataChangedHandler(String identifier);

    public DataViewModel()
    {
        Data = new MyData();
        Data.DataChanged += new DataChangedHandler(RaisePropertyChanged);
    }

    public ObservableCollection<XTRRAMaterialLayer> MaterialLayers
    {
        get { return _data.MaterialLayers; }
        set { }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    public void RaisePropertyChanged(string propertyName)
    {
        // take a copy to prevent thread issues
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }

MyData 中的相关代码

public class XTRRAData
{
    public ObservableCollection<XTRRAMaterialLayer> MaterialLayers { get; set; }

    public event DataChangedHandler DataChanged;



    public MyData()
    {
        MaterialLayers = new ObservableCollection<MaterialLayer>();
    }

    public void myDataChanged(String identifier)
    {
        DataChanged(identifier);
    }

    public void AddLayer()
    {
        MaterialLayer layer = new MaterialLayer() { MaterialName="Test", MaterialThickness=5, ThicknessUnit=0 };

        layer.DataChanged += new DataChangedHandler(myDataChanged); 
    }
}

MaterialLayer 的相关代码

public class XTRRAMaterialLayer
{
    public XTRRAMaterialLayer()
    {
        _thicknessUnit = 0; // cm
    }
    public event DataChangedHandler DataChanged;

    public String MaterialName { get; set; }

    public double MaterialThickness
    {
        get
        {
            switch (_thicknessUnit)
            {
                default:
                case 0:
                    return DIST;
                case 1:
                    return DIST * 0.393700787;
            }
        }
        set
        {
            switch (_thicknessUnit)
            {
                default:
                case 0:
                    DIST = value;
                    break;
                case 1:
                    DIST = value / 0.393700787;
                    break;
            }

        }
    }

    public int _thicknessUnit;

    public int ThicknessUnit
    {
        get { return(int) _thicknessUnit;  }
        set
        {
            _thicknessUnit = (eThicknessUnits)value;
            FireDataChanged("MaterialLayers");
        }
    }

    public void FireDataChanged(String identifier)
    {
        if(DataChanged!=null)
        {
            DataChanged(identifier);
        }
    }

}

谁能帮忙？

Answer 1

您需要在要更改的属性所在的类中实现INotifyPropertyChanged - 在您的情况下为 XTRRAMaterialLayer，并在属性更改时引发 PropertyChanged 事件。

您的属性应如下所示：

public int ThicknessUnit
{
    get { return(int) _thicknessUnit;  }
    set
    {
        _thicknessUnit = (eThicknessUnits)value;
        NotifyPropertyChanged();
    }
}

NotifyPropertyChanged 事件处理程序：

public event PropertyChangedEventHandler PropertyChanged;

// This method is called by the Set accessor of each property. 
// The CallerMemberName attribute that is applied to the optional propertyName 
// parameter causes the property name of the caller to be substituted as an argument. 
private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
{
    if (PropertyChanged != null)
    {
        PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}