使用mvvm在启动时将键盘焦点设置在文本框上

Question

我的UI表单加载时无法将键盘焦点设置在文本框控件上。我正在使用MVVM模式和我 尝试解决以下link，但这没有帮助。当表单加载时，有一个插入符号 在我的文本框中，但它没有闪烁，我不能在其中写文字。我使用时会发生同样的事情 FocusManager.focused元素在XAML中。我也尝试过使用Keyboard.Focus（MytextBox），但同样的事情发生了......请帮助任何人，我被困2天......

这是我创建依赖项属性IsFocused的类，并使用它在我的viewmodel中与isFocused属性绑定：

public  static class Attached
{

    public static DependencyProperty IsFocusedProperty = DependencyProperty.RegisterAttached("IsFocused", typeof(bool), typeof(Attached), new UIPropertyMetadata(false, OnIsFocusedChanged));

    public static bool GetIsFocused(DependencyObject dependencyObject)
    {
        return (bool)dependencyObject.GetValue(IsFocusedProperty);
    }

    public static void SetIsFocused(DependencyObject dependencyObject, bool value)
    {
        dependencyObject.SetValue(IsFocusedProperty, value);
    }

    public static void OnIsFocusedChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
    {
        TextBox textBox = dependencyObject as TextBox;
        bool newValue = (bool)dependencyPropertyChangedEventArgs.NewValue;
        bool oldValue = (bool)dependencyPropertyChangedEventArgs.OldValue;
        Keyboard.Focus(textBox);
        if (newValue && !oldValue && !textBox.IsFocused)  textBox.Focus();
    }

}

这是我的XAML：

  <TextBox a:Attached.IsFocused="{Binding IsFocused, UpdateSourceTrigger=PropertyChanged, NotifyOnSourceUpdated=True}.../>"