当用户通过Tab键将焦点放在复选框上时,会出现一个虚线边框以指示该复选框具有焦点。
当代码调用myCheckBox.Focus()
使复选框获得焦点时,不会出现此类指示器(尽管按空格键可以切换状态)。
我如何在程序化地将焦点集中在复选框上时使复选框的焦点边框出现?
KeyboardNavigationEx
文件,我成功解决了这个问题(所有功劳都归功于 punker76)。KeyboardHelper.Focus
方法并传递应该聚焦的 UIElement
(例如 KeyboardHelper.Focus(myCheckBox)
)即可。KeyboardHelper
类的代码:public sealed class KeyboardHelper
{
private static KeyboardHelper _Instance;
private readonly PropertyInfo _AlwaysShowFocusVisual;
private readonly MethodInfo _ShowFocusVisual;
// Explicit static constructor to tell C# compiler
// not to mark type as beforefieldinit
static KeyboardHelper()
{
}
private KeyboardHelper()
{
var type = typeof(KeyboardNavigation);
_AlwaysShowFocusVisual = type.GetProperty("AlwaysShowFocusVisual", BindingFlags.NonPublic | BindingFlags.Static);
_ShowFocusVisual = type.GetMethod("ShowFocusVisual", BindingFlags.NonPublic | BindingFlags.Static);
}
internal static KeyboardHelper Instance => _Instance ?? (_Instance = new KeyboardHelper());
internal void ShowFocusVisualInternal()
{
_ShowFocusVisual.Invoke(null, null);
}
internal bool AlwaysShowFocusVisualInternal
{
get { return (bool)_AlwaysShowFocusVisual.GetValue(null, null); }
set { _AlwaysShowFocusVisual.SetValue(null, value, null); }
}
public static void Focus(UIElement element)
{
element?.Dispatcher.BeginInvoke(DispatcherPriority.Background, new Action(() =>
{
var keybHack = KeyboardHelper.Instance;
var oldValue = keybHack.AlwaysShowFocusVisualInternal;
keybHack.AlwaysShowFocusVisualInternal = true;
try
{
Keyboard.Focus(element);
keybHack.ShowFocusVisualInternal();
}
finally
{
keybHack.AlwaysShowFocusVisualInternal = oldValue;
}
}));
}
}
'initially set chkCheckBox.Appearance = 1
'on Got Focus set appearance = 0 - Flat
Private Sub chkCheckBox_GotFocus()
chkCheckBox.Appearance = 0
End Sub
'on Lost Focus set appearance = 1 - 3D
Private Sub chkCheckBox_LostFocus()
chkCheckBox.Appearance = 1
End Sub