如何在 Xamarin 中获取绑定内容

Question

这是我的代码：

public ChatItemCell()
    {
        TextAlignment Ausrichtung = TextAlignment.Start;

        var lblBody = new Label()
        {
            FontSize = Device.GetNamedSize(NamedSize.Medium, typeof(Label)), 
            HorizontalTextAlignment = Ausrichtung,
            TextColor = Color.Black
        };
        lblBody.SetBinding(Label.TextProperty, "Body");

        var lblSender = new Label()
        {
            FontSize = Device.GetNamedSize(NamedSize.Small, typeof(Label)),
            HorizontalTextAlignment = Ausrichtung,
            TextColor = Color.Gray,
            FontAttributes = FontAttributes.Italic
        };
        lblSender.SetBinding(Label.TextProperty, "Sender");

        var layout = new StackLayout()
        {
            Opacity = 90,
            Orientation = StackOrientation.Vertical,
            Children = {lblSender, lblBody}
        };

        Frame outerFrame = new Frame()
        {
            Padding = new Thickness(5, 5, 5, 5),
            OutlineColor = Color.Accent,
            BackgroundColor = Color.Yellow,
            Content = layout,
        };

        Frame objFrame_Outer = new Frame
        {
            Padding = new Thickness(10, 0, 10, 10),
            Content = outerFrame
        };

        View = objFrame_Outer;

    }

我想要的是，TextAligment 取决于“发件人”。意思是：当发件人是“我”时，对齐应该是左，否则应该是右。那么如何获取“Sender”的内容呢？

非常感谢！ 克里兹

Answer 1

您可以将标签的TextAlignment属性绑定到Sender属性，并编写一个ValueConverter，为Sender的值返回正确的TextAlignment：

public class TextAlignmentConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var s = value as string;
        if (s == null) return TextAlignment.End;
        if (s.ToLower() == "me")
            return TextAlignment.Start;
        return TextAlignment.End;
    }

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