c# - Xamarin 表单 UWP 工具提示

Question

我想通过使用 native View 和 Windows.UI.Xaml Nuget 包在 Xamarin for UWP 中添加工具提示。我已将以下引用添加到 xaml 页面以获取 Windows native View :

<ContentPage 

             xmlns:win="clr-namespace:Windows.UI.Xaml.Controls;assembly=Windows, Version=255.255.255.255, Culture=neutral, PublicKeyToken=null, ContentType=WindowsRuntime;targetPlatform=Windows"   

</ContentPage>

我可以成功访问 native Windows 控件，例如一个文本 block :

<    win: TextBlock Text="S"/>

但是，当我尝试将工具提示添加到控件时:

<win:TextBlock Text="S" ToolTipService.ToolTip="Service agreement"/>

我在编译过程中得到以下异常:

"Xamarin.Forms.Xaml.XamlParseException: 'Position 56:45. Type ToolTipService not found in xmlns http://xamarin.com/schemas/2014/forms'"

系统是否混淆了标准 Windows.UI.Xaml.Controls 命名空间和 Nuget 包中的扩展命名空间？

Answer 1

ToolTipService 是附加属性，它不会在Forms客户端中找到ToolTipService组件，更好的方法是使用Effect创建您自己的小费服务并将其呈现在 UWP 平台中。您可以引用以下步骤。

• Create a subclass of the PlatformEffect class.

• Override the OnAttached method and write logic to customize the control.

• Override the OnDetached method and write logic to clean up the control customization, if required.

• Add a ResolutionGroupName attribute to the effect class. This attribute sets a company wide namespace for effects, preventing collisions with other effects with the same name. Note that this attribute can only be applied once per project.

• Add an ExportEffect attribute to the effect class. This attribute registers the effect with a unique ID that's used by Xamarin.Forms, along with the group name, to locate the effect prior to applying it to a control. The attribute takes two parameters – the type name of the effect, and a unique string that will be used to locate the effect prior to applying it to a control.

UWP 代码部分

[assembly: ResolutionGroupName("Microsoft")]
[assembly: ExportEffect(typeof(UWPToolTipEffect), nameof(TooltipEffect))]

namespace NativeSwitch.UWP
{
    public class UWPToolTipEffect : PlatformEffect
    {
        protected override void OnAttached()
        {
            var control = Control ?? Container;

            if (control is DependencyObject)
            {
                ToolTip toolTip = new ToolTip();
                toolTip.Content = TooltipEffect.GetText(Element);
                switch (TooltipEffect.GetPosition(Element))
                {
                    case TooltipPosition.Bottom:
                        toolTip.Placement = Windows.UI.Xaml.Controls.Primitives.PlacementMode.Bottom;
                        break;
                    case TooltipPosition.Top:
                        toolTip.Placement = Windows.UI.Xaml.Controls.Primitives.PlacementMode.Top;
                        break;
                    case TooltipPosition.Left:
                        toolTip.Placement = Windows.UI.Xaml.Controls.Primitives.PlacementMode.Left;
                        break;
                    case TooltipPosition.Right:
                        toolTip.Placement = Windows.UI.Xaml.Controls.Primitives.PlacementMode.Right;
                        break;
                    default:
                        return;
                }
                ToolTipService.SetToolTip(control, toolTip);
            }

        }

        protected override void OnDetached()
        {

        }
    }
}

表单代码部分

public static class TooltipEffect
{

    public static readonly BindableProperty TextProperty =
      BindableProperty.CreateAttached("Text", typeof(string), typeof(TooltipEffect), string.Empty, propertyChanged: OnTextChanged);

    public static readonly BindableProperty PositionProperty =
      BindableProperty.CreateAttached("Position", typeof(TooltipPosition), typeof(TooltipEffect), TooltipPosition.Bottom);


    public static string GetText(BindableObject view)
    {
        return (string)view.GetValue(TextProperty);
    }

    public static void SetText(BindableObject view, string value)
    {
        view.SetValue(TextProperty, value);
    }

    public static TooltipPosition GetPosition(BindableObject view)
    {
        return (TooltipPosition)view.GetValue(PositionProperty);
    }

    public static void SetPosition(BindableObject view, TooltipPosition value)
    {
        view.SetValue(PositionProperty, value);
    }

    static void OnTextChanged(BindableObject bindable, object oldValue, object newValue)
    {
        var view = bindable as View;
        if (view == null)
        {
            return;
        }

        string text = (string)newValue;
        if (!string.IsNullOrEmpty(text))
        {
            view.Effects.Add(new ControlTooltipEffect());
        }
        else
        {
            var toRemove = view.Effects.FirstOrDefault(e => e is ControlTooltipEffect);
            if (toRemove != null)
            {
                view.Effects.Remove(toRemove);
            }
        }
    }

}

public enum TooltipPosition
{
    Bottom,

    Right,

    Left,

    Top
}

class ControlTooltipEffect : RoutingEffect
{
    public ControlTooltipEffect() : base($"Microsoft.{nameof(TooltipEffect)}")
    {

    }
}

用法

// forms project namesapce
xmlns:effects="clr-namespace:ToolTipTestApp"
......

<win:TextBlock
    effects:TooltipEffect.Position="Right"
    effects:TooltipEffect.Text="Hello"
    Text="Hello Wrold"
    />