Xamarin Android辅助功能--我们如何通过编程方式将辅助功能焦点设置为UI元素(如按钮)

Question

在我的Xamarin Android应用程序中，用户需要从旋转器(下拉菜单)中选择一项。从旋转器中选择任何项之后，可访问性焦点将转移到屏幕的开始，而不是下一个可调焦点元素，这不是预期的行为。因此，试图找到一种方式，以编程方式设置焦点按钮，但似乎没有办法在Xamarin Android。

我试过了

Button1.RequestFocus();

Button1.RequestFocusFromTouch();

Button1.SendAccessibilityEvent(EventTypes.ViewAccessibilityFocused);

但什么都没用！！

下面的代码示例与Xamarin iOS相关：

    UIAccessibility.PostNotification(UIAccessibilityPostNotification.ScreenChanged, myFirstElement);

这种方法在Xamarin iOS中可用，工作良好，因此需要类似的方式让Xamarin以编程方式聚焦。

在这里，我张贴样例代码。

我的.axml文件代码：

<?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">
    <Spinner
        android:id="@+id/spinner"
        android:layout_width="200dp"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"   android:focusable="true"    android:focusableInTouchMode="true"/>
    <Button
        android:text="Add"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/btnAdd" 
        android:focusable="true"
        android:focusableInTouchMode="true"/>
</LinearLayout> </LinearLayout>

我的活动档案

protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);

        // Set our view from the "main" layout resource
        this.SetContentView (Resource.Layout.Main);
Spinner spinner = this.FindViewById<Spinner>(Resource.Id.spinner);
        Button btnAdd = this.FindViewById<Button>(Resource.Id.btnAdd);
var adapter = ArrayAdapter.CreateFromResource(this, Resource.Array.planets_array, Android.Resource.Layout.SimpleSpinnerItem);

            adapter.SetDropDownViewResource(Android.Resource.Layout.SimpleSpinnerDropDownItem);
            spinner.Adapter = adapter;
            btnAdd.Click += (s, e) =>
              {
                  string toasts = string.Format("Add button got focus");
                  Toast.MakeText(this, toasts, ToastLength.Long).Show();
              };

        }

        private void spinner_ItemSelected(object sender, AdapterView.ItemSelectedEventArgs e)
        {
            Spinner spinner = (Spinner)sender;

            string toast = string.Format("The planet is {0}", spinner.GetItemAtPosition(e.Position));
            Toast.MakeText(this, toast, ToastLength.Long).Show();
            //btnAdd.RequestFocus();
            btnAdd.RequestFocusFromTouch();
            btnAdd.RequestFocus();
            if (btnAdd.IsFocused)
            {
                string toasts = string.Format("Add button got focus");
                Toast.MakeText(this, toasts, ToastLength.Long).Show();                
            }
            skillSeleted = "selected";
        }

        protected override void OnResume()
        {
            base.OnResume();
            if (skillSeleted == "selected")
            {
                btnAdd.RequestFocusFromTouch();
                btnAdd.RequestFocus();
            }
        }


//Add this to String file under values folder:
<string-array name="planets_array">
<item>Mercury</item>
<item>Venus</item>
<item>Earth</item>
<item>Mars</item>
<item>Jupiter</item>
<item>Saturn</item>
<item>Uranus</item>
<item>Neptune</item>

​

请在三星移动( Samsung )的Marshmallow版本中查看此场景。

提前谢谢。

Answer 1

public class MainPage : ContentPage {
    public MainPage() => Content = BuildView().CreateView();

    void SetState() => BuildView().Apply(Content);

    int _counter;

    Command _push => new Command(() => {
        _counter++;
        SetState();
    });

    ViewModel BuildView() =>
        new StackLayoutModel(
            children: new ViewModel[] {
                new LabelModel(text: _counter.ToString(), fontSize: 42),
                new ButtonModel(text: "Increment", command: _push),
            },
            padding: new Thickness(42));
}