Question

我已经创建了一个自定义ViewCell，它应该在我的ListView中使用相同的代码适用于Android，但不适用于UWP（Windows Phone和Windows桌面等）。

该项目是Xamarin Forms。

当我在ListView中使用它时......我只能看到空白单元格。

<?xml version="1.0" encoding="UTF-8"?>
<ViewCell xmlns="http://xamarin.com/schemas/2014/forms" 
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="AAA.Extensions.AttributeViewCell"
            Tapped="AttributeViewCell_OnTapped"
          >
<Grid
    x:Name="AttributeGrid"
    >
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*"/>
        <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>

    <Grid.RowDefinitions>
        <RowDefinition Height="Auto"/>
    </Grid.RowDefinitions>

    <StackLayout
        Grid.Column="0"
        >
        <Label
            Text="{Binding Code}"
            TextColor="#000000"
            />
        <Label
            Text="{Binding Description}"
            TextColor="#000000"
            />
    </StackLayout>

    <StackLayout
        Grid.Column="1"
        x:Name="DynamicContentStackLayout"
        >

    </StackLayout>
</Grid>

我的代码

[XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class AttributeViewCell : ViewCell
    {
        #region Bindable Properties
        public static readonly BindableProperty CodeProperty = BindableProperty.Create(nameof(Code),typeof(string),typeof(AttributeViewCell), defaultBindingMode:BindingMode.TwoWay);
        public static readonly BindableProperty DescriptionProperty = BindableProperty.Create(nameof(Description), typeof(string), typeof(AttributeViewCell), defaultBindingMode:BindingMode.TwoWay);
        #endregion

        #region Properties
        /// <summary>
        /// Attribute Code
        /// </summary>
        public string Code
        {
            get => (string) GetValue(CodeProperty);
            set => SetValue(CodeProperty,value);
        }

        /// <summary>
        /// Attribute's description
        /// </summary>
        public string Description
        {
            get => (string) GetValue(DescriptionProperty);
            set => SetValue(DescriptionProperty, value);
        }
        #endregion

        public AttributeViewCell()
        {
            InitializeComponent ();
            this.BindingContext = this;
        }

        private void AttributeViewCell_OnTapped(object sender, EventArgs e)
        {
            // I CAN SEE BINDINGS here...
        }
    }

整个ViewModel正在进行绑定 POCO看起来如下

public class Attribute
    {
        public string Code { get; set; }
        public string Description { get; set; }
    }

VM public class ProductDetailsPageViewModel：BaseViewModel { #region Fields private readonly AnonymousCheckerService _anonymousCheckerService; private List _attributes;

        #endregion

        #region Properties

        public List<Attribute> Attributes
        {
            get => _attributes;
            set
            {
                _attributes = value; 
                OnPropertyChanged();
            }
        }

        #endregion

        //basic ctor
        public ProductDetailsPageViewModel()
        {
            _aaa= new aaa();
            Attributes = _aaa.GetInfo("123").Attributes;
        }
    }

最后，ListView

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:extensions="clr-namespace:AnonymousCheckerApp.Extensions"
             x:Class="AnonymousCheckerApp.Views.ProductDetailsPage">
    <StackLayout>
        <ListView
            ItemsSource="{Binding Attributes}"
            >
            <ListView.ItemTemplate>
                <DataTemplate>
                    <extensions:AttributeViewCell
                        Code="{Binding Code}"
                        Description="{Binding Description}"
                        AttributeDetails="{Binding AttributeDetails}"
                        />
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
    </StackLayout>
</ContentPage>

and it's codebehind
public ProductDetailsPage()
        {

            var vm = new ProductDetailsPageViewModel();
            this.BindingContext = vm;

            InitializeComponent ();
        }

我在视单元上附加了一个Tapped事件...我可以看到绑定......

修改1

我已经注释掉了Grid代码，因为我发现其他一些开发人员在Grid元素内堆叠的元素上存在绑定问题... 仍然没有工作，奇怪的是，它正确地解析了＃34; XAML元素，但它无法进行绑定....我做错了什么？

这就是Android的外观

Answer 1

我已经测试了您的代码并重现了您的问题。此行this.BindingContext = this;是不必要的。因为AttributeViewCell是继承ViewCell，您可以直接在ListView DataTemplate中使用它。所以请从AttributeViewCell构造函数中删除以下行代码。

 this.BindingContext = this;

Xamarin.UWP自定义ViewCell绑定问题

1 个答案: