这个问题与如何在 XAML 中设置上边距相同?但关于 Xamarin 而不是 WPF。
如何在 XAML 的视图上设置单个边距?
链接的问答指示默认实现始终将所有未指定的边距设置为 0,即使来自代码也是如此。
除非我遗漏了什么,否则只需指定边距,如下所示:
<Label
Margin = "0,20,0,0"
Text = "Hello World!" />
边距指定为左、上、右、下值。
解决方案是创建一个 AttachedProperty:
using System;
using Xamarin.Forms;
namespace Sample.Utils
{
/// <summary>
/// Allows setting Top,Left,Right,Bottom Margin independently from each other.
/// The default implementation does not allow that, even from code. This
/// attached property remembers the previously set margins and only modifies what you intend to modify.
/// </summary>
public static class Margin
{
public static readonly BindableProperty LeftProperty = BindableProperty.CreateAttached(
propertyName: "Left",
returnType: typeof(double),
declaringType: typeof(Margin),
propertyChanged: LeftPropertyChanged,
defaultValue: 0.0d);
private static void LeftPropertyChanged(BindableObject bindable, object oldValue, object newValue)
{
SetLeft(bindable, (double)newValue);
}
public static void SetLeft(BindableObject element, double value)
{
var view = element as View;
if (view != null)
{
Thickness currentMargin = (Xamarin.Forms.Thickness)view.GetValue(View.MarginProperty);
view.Margin = new Thickness(value, currentMargin.Top, currentMargin.Right, currentMargin.Bottom);
}
}
public static double GetLeft(BindableObject element)
{
View view = element as View;
if (view != null)
{
Thickness margin = (Xamarin.Forms.Thickness)view.GetValue(View.MarginProperty);
return margin.Left;
}
return (double)LeftProperty.DefaultValue;
}
}
}
以相同的方式声明 Bottom
、 Top
和 Right
。然后在 XAML 中使用它,如下所示:
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:utils="using:Sample.Utils"
x:Class="Sample.MyContentPage">
<StackLayout
Orientation="Vertical"
utils:Margin.Left="{StaticResource InnerPageContentMarginLeft}">
</StackLayout>
</ContentPage>
来源:
* https://forums.xamarin.com/discussion/66026/use-attached-bindable-property-in-xaml
* https://stackoverflow.com/a/32408461/2550406
也许尝试一个 valueConverter,您可以在其中通过绑定将值发送到转换器并返回一个 Thickness 对象。有点像
Margin ={{Binding Marginleft, Converter={StaticResource stringToThicknessConverter}}
你传递一个字符串并取回一个厚度对象的地方,例如 new thickness(0,marginleft,0,0)
.
您也可以直接绑定到视图模型中的厚度类型对象,但这是一种不好的做法,因为它会在视图模型中创建一个视图依赖项,这违背了 MVVM 的目的