Question

我对xaml和xamarin.forms很新，我在使用Data Binding时遇到了一些麻烦。我知道有很多类似的问题，但我发现似乎没有任何效果。我的实际目标是在打开和关闭开关时更改背景颜色。但是现在我只想进行绑定工作，所以我在示例中使用了一个字符串。我的Page.xaml.cs看起来像这样

[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class CounterMainPage : ContentPage
{
    public CounterMainPage ()
    {
        InitializeComponent ();
        BindingContext = new CounterMainPageViewModel();
    }

我的viewmodel看起来像这样：

       class CounterMainPageViewModel
{
    public Color BackGroundColor = Color.Red;
    public string Testning = "Urgent";
}

My Converter类看起来像这样：

public class BoolToColorConverter : IValueConverter
{

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var valueAsString = value.ToString();

        switch (valueAsString)
        {
            case ("Urgent"):
                {

                    return Color.FromHex("#EF3D60");
                }
            case ("Not urgent"):
                {
                    return Color.FromHex("#231F20");
                }
            default:
                {
                    return Color.FromHex("#231F20");
                }
        }



    }

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

最后但并非最不重要的是我的page.xaml看起来像这样：

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
         xmlns:c="clr-namespace:BlankClient"
         xmlns:local="clr-namespace:BlankClient"
         xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
         x:Class="BlankClient.View.CounterMainPage">
<!--Style="{StaticResource PageStyle}">-->
<ContentPage.Resources>
    <ResourceDictionary>
        <c:BoolToColorConverter x:Key="colorConverter"></c:BoolToColorConverter>
    </ResourceDictionary>
</ContentPage.Resources>

<ContentPage.Content>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="50" />
            <RowDefinition Height="50" />
            <RowDefinition Height="50" />
            <RowDefinition Height="50" />
            <RowDefinition Height="50" />
            <RowDefinition Height="50" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="Auto"/>
        </Grid.ColumnDefinitions>
        <Label x:Name="ReceivedFromServer" Text="" Grid.Row="0" Grid.Column="0" Grid.ColumnSpan="3"/>
        <Button Text="A" StyleId="0" Clicked="Button_Clicked" Grid.Row="1" Grid.Column="0"/>
        <Button Text="2" StyleId="1" Clicked="Button_Clicked" Grid.Row="1" Grid.Column="1" />
        <Button Text="3" StyleId="2" Clicked="Button_Clicked" Grid.Row="1" Grid.Column="2"/>
        <Button Text="4" StyleId="3" Clicked="Button_Clicked" Grid.Row="2" Grid.Column="0"/>
        <Button Text="5" StyleId="4" Clicked="Button_Clicked" Grid.Row="2" Grid.Column="1"/>
        <Button Text="6" StyleId="5" Clicked="Button_Clicked" Grid.Row="2" Grid.Column="2"/>
        <Button Text="7" StyleId="6" Clicked="Button_Clicked" Grid.Row="3" Grid.Column="0"/>
        <Button Text="8" StyleId="7" Clicked="Button_Clicked" Grid.Row="3" Grid.Column="1"/>
        <Button Text="9" StyleId="8" Clicked="Button_Clicked" Grid.Row="3" Grid.Column="2"/>
        <Button Text="10" StyleId="9" Clicked="Button_Clicked" Grid.Row="4" Grid.Column="0" BackgroundColor="{Binding Testning,Converter={StaticResource colorConverter}}"/>
        <Button Text="Undo" StyleId="Undo" Clicked="Button_Clicked" Grid.Row="4" Grid.Column="1" IsEnabled="False" />
        <Button Text="Redo" StyleId="Undo " Clicked="Button_Clicked" Grid.Row="4" Grid.Column="2" IsEnabled="False"/>
        <Switch Grid.Row="5" Grid.Column="0" />
    </Grid>


    <!--<StackLayout>
        <Label Text="Counter Main Page" />
        <Button Text="5" StyleId="5" Clicked="Button_Clicked"/>
        <Button Text="10" StyleId="10" />
        <Label x:Name="ReceivedFromServer" Text="ewq"/>
    </StackLayout>-->
</ContentPage.Content>

Answer 1

首先“公共字符串测试=”紧急“;”应该是将其绑定到视图的属性。读取输出，您将看到存在未找到“Testning”属性的异常。

第二：你需要实现INotifyPropertyChanged接口（或使用类似Prism的框架）才能更改属性值并通知UI有关该更改

数据绑定Xamarin表单

1 个答案: