Question

我希望能够更改自定义ViewCell上的绑定属性并更新ListView项 - 但它似乎只用于初始化视图，并且不会反映更改。请告诉我我错过了什么！

在这里，我选择了tapped事件并尝试更改ViewCell的字符串但未成功：

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; }
    }
}

我添加的值如下：

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

我缺少的是在绑定到INotifyPropertyChanged的数据类上实现ViewCell接口。

在我的原始实现中，DocumentType类只有string Name { get; set; }之类的简单属性，但要将其值反映在ViewCell中，您需要实现INotifyPropertyChanged，以便在更改时属性它通知绑定的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"); } } 

        ...
    }
}

如何在创建列表后更新Xamarin Forms ListView的ViewCell属性？

1 个答案: