[英]Xamarin.Forms - Binding on ContextMenu
I have a list with songs as items.我有一个以歌曲为项目的列表。 A long press on the element should display a context menu.长按元素应显示上下文菜单。
<DataTemplate x:Key="SongTemplate">
<ViewCell>
<ViewCell.ContextActions>
<MenuItem Text="Edit" />
<MenuItem Text="Delete"/>
</ViewCell.ContextActions>
<StackLayout Padding="15,5" VerticalOptions="Center">
<Label Text="{Binding Title}"
FontSize="16"/>
<Label Text="{Binding Performer}"
FontSize="12"/>
</StackLayout>
</ViewCell>
</DataTemplate>
This works well, but I need to bind now so that the context menu opens depending on bool IsAdmin, which lies in AllSongsViewModel这很好用,但我现在需要绑定,以便根据布尔 IsAdmin 打开上下文菜单,它位于 AllSongsViewModel
public bool IsAdmin => _authService.LoggedUser.Role == "Admin";
But I don't know how to bind this property to the context menu但我不知道如何将此属性绑定到上下文菜单
Unfortunately you can't do this on your ViewModel.不幸的是,您不能在 ViewModel 上执行此操作。 But you can set a BindingContextChange event on your View Cell and change it there like this:但是您可以在 View Cell 上设置一个 BindingContextChange 事件并在此处进行更改,如下所示:
XAML: XAML:
<DataTemplate x:Key="SongTemplate">
<ViewCell BindingContextChanged="OnBindingContextChanged">
<StackLayout Padding="15,5" VerticalOptions="Center">
<Label Text="{Binding Title}"
FontSize="16"/>
<Label Text="{Binding Performer}"
FontSize="12"/>
</StackLayout>
</ViewCell>
In your code behind:在您后面的代码中:
private void OnBindingContextChanged(object sender, EventArgs e)
{
base.OnBindingContextChanged();
if (BindingContext == null)
return;
ViewCell theViewCell = ((ViewCell)sender);
var viewModel = this.BindingContext.DataContext as AllSongsViewModel;
theViewCell.ContextActions.Clear();
if (viewModel.IsAdmin)
{
theViewCell.ContextActions.Add(new MenuItem()
{
Text = "Delete",
});
theViewCell.ContextActions.Add(new MenuItem()
{
Text = "Edit",
});
}
}
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