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我有一个表单,我想在某些用户操作发生时将焦点设置到文本框。我知道 MVVM 的处理方式是绑定到 VM 属性,但是 TextBox 没有允许这种情况发生的属性。从 VM 设置焦点的最佳方法是什么?

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1 回答 1

8

我创建了一个 IResult 实现,它可以很好地实现这一目标。您可以从 IResult 的 ActionExecutionContext 中获取视图,然后您可以搜索(我按名称搜索)要关注的控件。

public class GiveFocusByName : ResultBase
{
    public GiveFocusByName(string controlToFocus)
    {
        _controlToFocus = controlToFocus;
    }

    private string _controlToFocus;

    public override void Execute(ActionExecutionContext context)
    {
        var view = context.View as UserControl;


        // add support for further controls here
        List<Control> editableControls =
                view.GetChildrenByType<Control>(c => c is CheckBox ||
                                                      c is TextBox ||
                                                      c is Button);

        var control = editableControls.SingleOrDefault(c =>
                                                 c.Name == _controlToFocus);

        if (control != null)
        control.Dispatcher.BeginInvoke(() =>
        {
            control.Focus();

            var textBox = control as TextBox;
            if (textBox != null)
                textBox.Select(textBox.Text.Length, 0);
        });

        RaiseCompletedEvent();
    }
}

如果您需要,我已经省略了一些额外的代码来获取viewcontext可以提供view的时间。ChildWindow

GetChildrenByType 也是一个扩展方法,这里是许多可用的实现之一:

public static List<T> GetChildrenByType<T>(this UIElement element,
                          Func<T, bool> condition) where T : UIElement
{
    List<T> results = new List<T>();
    GetChildrenByType<T>(element, condition, results);
    return results;
}

private static void GetChildrenByType<T>(UIElement element,
                          Func<T, bool> condition, List<T> results) where T : UIElement
{
    for (int i = 0; i < VisualTreeHelper.GetChildrenCount(element); i++)
    {
        UIElement child = VisualTreeHelper.GetChild(element, i) as UIElement;
        if (child != null)
        {
            T t = child as T;
        if (t != null)
        {
            if (condition == null)
                results.Add(t);
            else if (condition(t))
            results.Add(t);
        }
        GetChildrenByType<T>(child, condition, results);
        }
    }
}

然后,您的操作将类似于以下内容(以 Caliburn.Micro ActionMessage 样式调用)。

public IEnumerable<IResult> MyAction()
{
    // do whatever
    yield return new GiveFocusByName("NameOfControlToFocus");
}
于 2011-02-02T22:49:15.593 回答