Question

我有一个Xamarin项目，并且我试图在ValueConverter上绑定一个对象。我在UWP项目中完成了此任务，但在Xamarin中却遇到了编译错误：

找不到“ UserData”的属性，可绑定属性或事件，或者值和属性之间的类型不匹配。

这样做的目的是，当您在ListView中选择一个项目时，该条目将读取UserValue属性，当您编辑此条目中的文本时，该项目的属性的内容将更新，并且此更改为在ListView中可见。

有我的代码：

MainPage.XAML：

<input type="radio" name="radio1" id="radio1" required />
<input type="radio" name="radio1" id="radio2" />

<div>Text to be green if radio2 is checked</div>

MainPage.XAML.cs：

<StackLayout>
    <Entry x:Name="Entry_NewValue" TextChanged="Entry_NewValue_TextChanged"/>

    <ListView x:Name="_ListView" ItemSelected="_ListView_ItemSelected">
        <ListView.ItemTemplate>
            <DataTemplate>
                <ViewCell>
                    <Grid>
                        <Grid.Resources>
                            <local:ViewCell_Converter x:Key="ViewCell_Converter" UserData="{Binding}"/>
                        </Grid.Resources>

                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="2*"/>
                            <ColumnDefinition Width="*"/>
                        </Grid.ColumnDefinitions>

                        <Label Grid.Column="0" Text="{Binding UserName}"/>
                        <Label Grid.Column="1" Text="{Binding UserValue, Converter={StaticResource ViewCell_Converter}}"/>
                    </Grid>
                </ViewCell>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>
</StackLayout>

Methods.cs：

public MainPage()
{
    InitializeComponent();

    _ListView.ItemsSource = UserDatas();
}        

private ObservableCollection<UserData> UserDatas()
{
    return new ObservableCollection<UserData>()
    {
        new UserData() { UserName = "Name1", UserValue = 10, ValidatedByUser = true, },
        new UserData() { UserName = "Name2", UserValue = 11, ValidatedByUser = false, },
        new UserData() { UserName = "Name3", UserValue = 12, ValidatedByUser = true, },
        new UserData() { UserName = "Name4", UserValue = 13, ValidatedByUser = false, },
        new UserData() { UserName = "Name5", UserValue = 14, ValidatedByUser = true, },
    };
}

private void _ListView_ItemSelected(object sender, SelectedItemChangedEventArgs e)
{
    if (e.SelectedItem is UserData userData)
    {
        Entry_NewValue.Text = userData.UserValue.ToString();
    }
}

private void Entry_NewValue_TextChanged(object sender, TextChangedEventArgs e)
{
    if (_ListView.SelectedItem is UserData userData)
    {
        if (double.TryParse(Entry_NewValue.Text, out double _double))
        {
            if(userData.UserValue != _double)
            {
                userData.UserValue = _double;
            }                
        }
    }
}

Answer 1

这是重新布置（快速示例）：

    public class ViewCell_Converter : IValueConverter
{

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value is double doubleValue)
        {
            if (value is double _value)
            {
                return string.Format("{0:0.00}", doubleValue);
            }
        }

        return null;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

您不需要更多的Valueconverter。

<StackLayout>
    <Entry x:Name="Entry_NewValue" TextChanged="Entry_NewValue_TextChanged"/>

    <ListView x:Name="_ListView" ItemSelected="_ListView_ItemSelected">
        <ListView.ItemTemplate>
            <DataTemplate>
                <ViewCell>
                    <Grid>
                        <Grid.Resources>
                            <local:ViewCell_Converter x:Key="ViewCell_Converter"/>
                        </Grid.Resources>

                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="2*"/>
                            <ColumnDefinition Width="*"/>
                        </Grid.ColumnDefinitions>

                        <Label Grid.Column="0" Text="{Binding UserName}"/>
                        <Label Grid.Column="1" Text="{Binding UserValue, Converter={StaticResource ViewCell_Converter}}"/>
                    </Grid>
                </ViewCell>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>
</StackLayout>

Xamarin形成具有可绑定属性的ValueConverter

1 个答案: