c# - 创建列表后如何更新 Xamarin Forms ListView 的 ViewCell 属性？

Question

我希望能够更改自定义 ViewCell 上的绑定(bind)属性，并更新 ListView 项 - 但它似乎仅用于初始化 View 并且变化没有反射(reflect)出来。请告诉我我缺少什么!

在这里，我拾取了点击事件并尝试更改 ViewCell 的字符串，但没有成功:

private void DocChooser_ItemTapped(object sender, ItemTappedEventArgs e)
{
    var tappedItem = e.Item as DocumentChooserList.DocumentType;
    tappedItem.Name = "Tapped"; // How can I change what a cell displays here? - this doesn't work
}

这是我的 ViewCell 代码:

class DocumentCellView : ViewCell
{
    public DocumentCellView()
    {
        var OuterStack = new StackLayout()
        {
            Orientation = StackOrientation.Horizontal,
            HorizontalOptions = LayoutOptions.FillAndExpand,
        };

        Label MainLabel;
        OuterStack.Children.Add(MainLabel = new Label() { FontSize = 18 });
        MainLabel.SetBinding(Label.TextProperty, "Name");

        this.View = OuterStack;
    }
}

这是我的 ListView 类:

public class DocumentChooserList : ListView
{
    public List<DocumentType> SelectedDocuments { get; set; }

    public DocumentChooserList()
    {
        SelectedDocuments = new List<DocumentType>();
        this.ItemsSource = SelectedDocuments;
        this.ItemTemplate = new DataTemplate(typeof(DocumentCellView));
    }

    // My data-binding class used to populate ListView and hopefully change as we go
    public class DocumentType
    {
        public string Name { get; set; }
    }
}

我添加了这样的值:

DocChooser.SelectedDocuments.Add(new DocumentChooserList.DocumentType(){
    Name = "MyDoc"
});

使用这个简单的数据类:

public class DocumentType
{
    public string Name { get; set; }
}

Answer 1

我缺少的是在绑定(bind)到 ViewCell 的数据类上实现 INotifyPropertyChanged 接口(interface)。

在我最初的实现中，DocumentType 类只有简单的属性，例如 string Name { get;放; }，但要将它们的值反射(reflect)在 ViewCell 中，您需要实现 INotifyPropertyChanged，以便当您更改属性时它会通知绑定(bind)的 ViewCell :

    public class DocumentType : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        private void OnPropertyChanged(string nameOfProperty)
        {
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(nameOfProperty));
        }

        private string _Name;
        public string Name { get { return _Name; } set { _Name = value; OnPropertyChanged("Name"); } } 

        ...
    }
}