ListView 中的 UserControl DependencyProperty 绑定

UserControl DependencyProperty binding in ListView(ListView 中的 UserControl DependencyProperty 绑定)
本文介绍了ListView 中的 UserControl DependencyProperty 绑定的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!

问题描述

当我尝试在 ListView 中使用自定义 UserControl 时,它会失败并且只显示空块(以下 TextBlock 可以工作).虽然 ListView 之外的 customControl 工作得很好.有什么问题?

When I try to use a custom UserControl in a ListView, it fails and only empty blocks are displayed (the following TextBlock works though). While the customControl outside the ListView works pretty well. What's the problem?

MainWindow.xaml

MainWindow.xaml

<Grid>
    <StackPanel>
        <controls:CustomControl x:Name="customControl" CustomText="Test"/>
        <ListView x:Name="listView">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <StackPanel>
                        <controls:CustomControl CustomObject="{Binding}"/>
                        <TextBlock Text="{Binding Text}"/>
                    </StackPanel>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
    </StackPanel>
</Grid>

MainWindow.cs

MainWindow.cs

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        InitializeMyComponent();
    }

    public System.Collections.ObjectModel.ObservableCollection<CustomClass> CustomCollection { get; set; }

    private void InitializeMyComponent()
    {
        this.CustomCollection = new System.Collections.ObjectModel.ObservableCollection<CustomClass>();
        this.CustomCollection.Add(new CustomClass() { Number = 1, Text = "a" });
        this.CustomCollection.Add(new CustomClass() { Number = 2, Text = "b" });
        this.CustomCollection.Add(new CustomClass() { Number = 3, Text = "c" });
        this.listView.ItemsSource = this.CustomCollection;
        this.customControl.Custom = new CustomClass() { Number = 0, Text = "customControl" };
    }
}

CustomControl.xaml

CustomControl.xaml

<Grid>
    <StackPanel>
        <TextBlock>
            <Run x:Name="numberRun" Text="{Binding CustomObject.Number}"/>
            <Run x:Name="textRun" Text="{Binding CustomObject.Text}"/>
            <Run Text="{Binding CustomText}"/>
        </TextBlock>
    </StackPanel>
</Grid>

CustomControl.cs

CustomControl.cs

public partial class CustomControl : UserControl
{
    public static readonly DependencyProperty CustomObjectProperty;
    public static readonly DependencyProperty CustomTextProperty;

    static CustomControl()
    {
        CustomObjectProperty = DependencyProperty.Register("CustomObject", typeof(CustomClass), typeof(CustomControl), new PropertyMetadata(default(CustomClass), OnCustomObjectPropertyChanged));
        CustomTextProperty = DependencyProperty.Register("CustomText", typeof(string), typeof(CustomControl), new PropertyMetadata(string.Empty, OnCustomTextPropertyChanged));
    }
    public CustomControl()
    {
        InitializeComponent();
        this.DataContext = this;
    }

    public CustomClass CustomObject
    {
        get
        {
            return (CustomClass)(this.GetValue(CustomObjectProperty));
        }
        set
        {
            this.SetValue(CustomObjectProperty, value);
        }
    }
    public string CustomText
    {
        get
        {
            return (string)(this.GetValue(CustomTextProperty));
        }
        set
        {
            this.SetValue(CustomTextProperty, value);
        }
    }

    private static void OnCustomObjectPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { }
    private static void OnCustomTextPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { }
}

CustomClass.cs

CustomClass.cs

public class CustomClass : INotifyPropertyChanged
{
    private int number;
    private string text;

    public CustomClass()
    {
        this.number = new int();
        this.text = string.Empty;
    }

    public int Number
    {
        get
        {
            return this.number;
        }
        set
        {
            this.number = value;
            this.OnPropertyChanged();
        }
    }
    public string Text
    {
        get
        {
            return this.text;
        }
        set
        {
            this.text = value;
            this.OnPropertyChanged();
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected void OnPropertyChanged([System.Runtime.CompilerServices.CallerMemberName] string name = null)
    {
        PropertyChangedEventHandler handler = this.PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(name));
        }
    }
}

推荐答案

将UserControl的DataContext设置为UserControl实例

Setting a UserControl's DataContext to the UserControl instance like

this.DataContext = this;

有效地防止绑定到外部"继承的 DataContext,正如预期的那样

effectively prevents bindings to an "external", inherited DataContext, as expected in

<controls:CustomControl CustomObject="{Binding}"/>

作为一般规则,从不显式设置 UserControl 的 DataContext.从 UserControl 的构造函数中删除上述行,并在 UserControl 的 XAML 中使用 RelativeSource 编写绑定:

As a general rule, never set a UserControl's DataContext explicitly. Remove the above line from the UserControl's constructor, and write the bindings in the UserControl's XAML with RelativeSource:

<Run x:Name="numberRun" Text="{Binding CustomObject.Number,
    RelativeSource={RelativeSource AncestorType=UserControl}}"/>

这篇关于ListView 中的 UserControl DependencyProperty 绑定的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持编程学习网!

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