自定义控件，例如带有Xamarin.Forms的StackLayout [英] Custom control like StackLayout with Xamarin.Forms

问题描述

我只想用Xamarin.Forms创建一个自定义控件。此自定义控件应在xaml中获取视图的数组/列表（例如 Stacklayout ）。

I just want to create a custom control with Xamarin.Forms. This custom control should take an array/list of views in the xaml (like the Stacklayout, for example).

我的XAML看起来像这样：

My XAML Looks like this:

<controls:MyLayout>
    <ContentView BackgroundColor="Green">
        <Label Text="Test 1" />
    </ContentView>

    <ContentView BackgroundColor="Red">
        <Label Text="Test 1" />
    </ContentView>
</controls:MyLayout>

以及 MyLayout 的类：

[ContentProperty("Children")]
public class MyLayout: ScrollView, IViewContainer<View>
{
     public IList<View> Children { get; set; }

    // And some more properties and methods ...
}

但是当我编译它并在我的Android手机上运行它时，出现以下错误：

But when I compile this and run it on my Android phone, I get the following error:

已引发异常调用的目标。 --->
Xamarin.Forms.Xaml.XamlParseException：位置29：8。无法分配
属性子项： Xamarin.Forms.ContentView
和 System.Collections.Generic.IList`1 [Xamarin.Forms.View]之间的类型不匹配

Exception has been thrown by the target of an invocation. ---> Xamarin.Forms.Xaml.XamlParseException: Position 29:8. Cannot assign property "Children": type mismatch between "Xamarin.Forms.ContentView" and "System.Collections.Generic.IList`1[Xamarin.Forms.View]"

我该如何解决？我缺少什么？

How can I solve this? What am I missing?

推荐答案

您的财产孩子必须只能获得访问者。我记得这也是一个面临的问题。

Your property Children must to have only get accessor. As I remember this was an issue a faced too. And also that list must be initialized.

[ContentProperty("Children")]
public class MyLayout: ScrollView, IViewContainer<View>
{
     public IList<View> Children { get; } = new List<View>();

    // And some more properties and methods ...
}

I `d宁愿这样

[ContentProperty(nameof(Children))]
public class MyLayout: ScrollView, IViewContainer<View>
{
     private List<View> _children;
     public IList<View> Children => _children;

     public MyLayout()
     {
         _children = new List<View>();
     }
    // And some more properties and methods ...
}

甚至使用ObservableCollection<>而是简单的List<>。 ObservableCollection可以帮助您观察集合何时发生更改，它可以帮助您何时布局的内容子级在布局中添加或删除

Or even use ObservableCollection<> instead simple List<>. ObservableCollection can help you to observe when collection changes an it can help you when layout`s content children adds or removes from layout

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