xamarin - 如何创建具有属性的自定义控件

Question

我需要创建一个带有属性的自定义控件。

这是我的自定义控件:

public class ExpandableStackLayout : StackLayout
{
    public String Title{get;set;}

    public ContentView View { set; get; }

    public String Image{set;get;}


    public ExpandableStackLayout(string title, string image, ContentView view)
    {
        Title = title;
        Image = image;
        View = view;
    }
}

但是当我尝试在 xaml 中使用它时说:“找不到默认构造函数”，如果我创建默认构造函数调用它而不是调用带参数的构造函数。

这是我的 xaml:

<control:ExpandableStackLayout Title="Title" Image="imag.png">
            <control:ExpandableStackLayout.View>
                <ContentView>
                    <OtherView/>
                </ContentView>
            </control:ExpandableStackLayout.View>
        </control:ExpandableStackLayout>

更新

我尝试了您的提示，但还有其他问题:

public static readonly BindableProperty TitleProperty = BindableProperty.Create(
        propertyName: "Title",
        returnType: typeof(String),
        declaringType: typeof(String),
        defaultValue: String.Empty);

    public String Title
    {
        get => (String)GetValue(TitleProperty); 
        set => SetValue(TitleProperty, value); 
    }

    public ContentView View { set; get; }

    public static readonly BindableProperty ImageProperty = BindableProperty.Create(
        propertyName: "Image",
        returnType: typeof(String),
        declaringType: typeof(String),
        defaultValue: string.Empty);

    public String Image
    {
        get => (String)GetValue(TitleProperty);
        set => SetValue(ImageProperty, value);
    }

    public ExpandableStackLayout()
    {
        //Do somethings whith parameters but are null
        usemyParameters();
    }

Answer 1

无需创建构造函数。以下是如何实现 Title 和 Image 属性的解决方案。

public class ExpandableStackLayout : StackLayout
{
    public static readonly BindableProperty TitleProperty =
        BindableProperty.Create<ExpandableStackLayout, string>(p => p.Title, string.Empty, BindingMode.TwoWay);

    public string Title
    {
        get { return (string)base.GetValue(TitleProperty); }
        set { base.SetValue(TitleProperty, value); }
    }

    public static readonly BindableProperty ImageProperty =
        BindableProperty.Create<ExpandableStackLayout, string>(p => p.Image, string.Empty, BindingMode.TwoWay);

    public string Image
    {
        get { return (string)base.GetValue(ImageProperty); }
        set { base.SetValue(ImageProperty, value); }
    }
}

我不知道你想用 View 实现什么。作为开始，我建议您学习 these controls和 Stacklayout implementation .