Xamarin Forms Dependency Service：單擊按鈕后更改可訪問性焦點

Question

我想要的是能夠在單擊按鈕后將可訪問性焦點設置為特定元素。 我試圖使用依賴服務來實現這一點，但它不起作用，我想是因為我嘗試將 Forms.View 轉換為 Android.View，但我不確定這是否是問題所在，也許我我做錯了什么。 你知道怎么做嗎，使用依賴服務或其他什么？

我嘗試過的（目前僅在 Android 上）：

主頁：

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

您需要先注冊您的服務，然后才能解決。

using Xamarin.Forms;

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

注冊工作正在使用[assembly: Dependency(typeof(AndroidAccessibilityFocus ))] 。

有關更多詳細信息，請參閱Microsoft 的文檔。