这个问题让我非常疯狂。我有一个ListPicker,动态填充几个项目。我已经在我的页面的Loaded事件中声明了我的SelectionChanged事件处理程序。当用户单击页面上的某个项目时,ListPicker可见性将从Collpased切换为Visible,并设置ListPicker的值。问题是,ListPicker的索引将基于用户设置,因此当前索引中的三个项目可能是1,而不是默认值为0。我需要在ListPicker中显示1作为当前项而不激活SelectionChanged事件(它根据当前索引执行操作)。然后,只有当用户自己更改所选项目时,才需要触发SelectionChanged事件。
这样做的主要原因不仅是用户在显示时需要在ListPicker中查看他或她当前的设置,而是在SelectionChanged事件操作中发生覆盖当前存在的操作,这非常令人困惑且不应该除非用户指定,否则会发生。
我目前拥有的内容如下
XAML
<toolkit:ListPicker x:Name="lp" Visibility="Collapsed" Margin="12" Width="300"/>
XAML.CS
private void Page_Loaded(object sender, RoutedEventArgs e)
{
lp.SelectionChanged += lp_SelectionChanged;
}
void EditableEllipse_Tap(object sender, System.Windows.Input.GestureEventArgs e)
{
if (sender != null)
{
DependencyObject tappedElement = e.OriginalSource as UIElement;
// find parent UI element of type PhotoThumbnail
//PhotoThumbnail i = this.FindParentOfType<PhotoThumbnail>(tappedElement);
i = this.FindParentOfType<PhotoThumbnail>(tappedElement);
if (i != null)
{
BuildControl(i);
}
}
}
private void BuildControl(PhotoThumbnail pp)
{
switch(pp.NName)
{
case "flip":
List<ListPickerItem> l = new List<ListPickerItem>();
l.Add(new ListPickerItem { Name = "Flip_Vertical", Content = AppResources.App_Flip_Vertical });
l.Add(new ListPickerItem { Name = "Flip_Horizontal", Content = AppResources.App_Flip_Horizontal });
l.Add(new ListPickerItem { Name = "Flip_Both", Content = AppResources.App_Flip_Both });
lp.ItemsSource = l; //Code execution jumps from here to ValueChanged event immediately
lp.Visibility = Visibility.Visible;
lp.SelectedIndex = Settings.Flip.Value - 1;
break;
..
}
}
private async void lp_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if (lp.SelectedIndex != -1) //always defaults to = 0
{
var item = (sender as ListPicker).SelectedItem;
string name = ((ListPickerItem)item).Name;
if (name != null)
{
switch (name)
{
case "Flip_Vertical":
Settings.Flip.Value = 1;
..perform process based on current Setting.Flip.Value.. break;
case "Flip_Horizontal":
Settings.Flip.Value = 2;
..perform process based on current Setting.Flip.Value..
break;
case "Flip_Both":
Settings.Flip.Value = 3;
..perform process based on current Setting.Flip.Value..
break;
...
}
}
}
答案 0 :(得分:0)
尝试使用操作顺序(通过解除钩子并重新加入事件)
private void BuildControl(PhotoThumbnail pp)
{
switch(pp.NName)
{
case "flip":
// unhook event
lp.SelectionChanged -= lp_SelectionChanged;
List<ListPickerItem> l = new List<ListPickerItem>();
l.Add(new ListPickerItem { Name = "Flip_Vertical", Content = AppResources.App_Flip_Vertical });
l.Add(new ListPickerItem { Name = "Flip_Horizontal", Content = AppResources.App_Flip_Horizontal });
l.Add(new ListPickerItem { Name = "Flip_Both", Content = AppResources.App_Flip_Both });
lp.ItemsSource = l; //Code execution jumps from here to ValueChanged event immediately
lp.Visibility = Visibility.Visible;
lp.SelectedIndex = Settings.Flip.Value - 1;
// after setting the index, rehook the event
lp.SelectionChanged += lp_SelectionChanged;
break;
..
}
}