Xamarin Forms Dependency Service：单击按钮后更改可访问性焦点

Question

我想要的是能够在单击按钮后将可访问性焦点设置到特定元素。我尝试使用依赖服务来实现这一点，但它不起作用，我认为是因为我尝试将 Forms.View 转换为 Android.View，但我不确定这是否是问题所在，也许我我做错了什么。你知道怎么做吗，使用依赖服务或其他什么？

我尝试了什么，（目前仅在 Android 上）：

主页：

public partial class MainPage : ContentPage

{
    Button b1;
    Button b2;
    IAccessibilityFocusService service;

    public MainPage()
    {
    InitializeComponent();

            service = DependencyService.Get<IAccessibilityFocusService(DependencyFetchTarget.NewInstance);

            b1 = new Button
            {
                Text = "BUTTON 1",
                BackgroundColor = Color.Blue,
            };

            b2 = new Button
            {
                Text = "BUTTON 2",
            };
            stacklayout.Children.Add(b1);
            stacklayout.Children.Add(b2);
            b1.Clicked += Mybutton_Clicked;
     }

     private async void Mybutton_Clicked(object sender, EventArgs e)
     {
           Console.WriteLine("PIPPO clicked");
           service.ChangeAccessibilityFocus(b2);
     }
}

IAccessibilityFocusService：

public interface IAccessibilityFocusService { void ChangeAccessibilityFocus(View v);
}

AndroidAccessibilityFocus：

[assembly: Dependency(typeof(CustomViewAccessibility.Droid.AccessibilityFocus))]
public class AndroidAccessibilityFocus : IAccessibilityFocusService
{

    public void ChangeAccessibilityFocus(View v)
    {
            //first I convert the Forms.Veiw to the native android view, so that I can invoke sendAccessibilityEvent on that view.
            Platform.CreateRendererWithContext(v, Android.App.Application.Context).View.SendAccessibilityEvent(EventTypes.ViewFocused); 

    }
}

Answer 1

您需要先注册您的服务才能解决它。

using Xamarin.Forms;

[assembly: Dependency(typeof(AndroidAccessibilityFocus ))]
namespace DependencyServiceDemos.iOS
{
    public class AndroidAccessibilityFocus : IAccessibilityFocusService
    {
        public void ChangeAccessibilityFocus(View v)
        {
            ...
        }
    }
}

注册工作正在[assembly: Dependency(typeof(AndroidAccessibilityFocus ))]完成。

更多详情请见Microsoft's documentation。