无法绑定 XAML uwp [英] Trouble binding XAML uwp
问题描述
我正在学习本教程,http://blogs.u2u.be/diederik/post/2011/11/14/null.aspx,将元素的可见性绑定到布尔属性.该程序不起作用.代码如下:
Hi I am following this tutorial,http://blogs.u2u.be/diederik/post/2011/11/14/null.aspx, to bind the visibility of an element to a Boolean property. The program is not working. Here is the code:
<Page.Resources>
<local:BooleanToVisibilityConverter x:Key="TrueToVisibleConverter"/>
</Page.Resources>
<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
<StackPanel>
<TextBlock Text=" Hello World"
Visibility="{Binding Path=Show_element, Converter={StaticResource TrueToVisibleConverter}}"/>
<Button Click="Button_Click">press button</Button>
</StackPanel>
</Grid>
public sealed partial class MainPage : Page , INotifyPropertyChanged
{
private bool show_element ;
public bool Show_element
{
get { return show_element; }
set
{
show_element = value;
this.OnPropertyChanged();
Debug.WriteLine("Show_element value changed");
}
}
public MainPage()
{
this.InitializeComponent();
}
private void Button_Click(object sender, RoutedEventArgs e)
{
Show_element = !Show_element;
}
public event PropertyChangedEventHandler PropertyChanged = delegate { };
public void OnPropertyChanged(string propertyName = null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
public class BooleanToVisibilityConverter : IValueConverter
{
public bool IsReversed { get; set; }
public object Convert(object value, Type typeName, object parameter, string language)
{
var val = System.Convert.ToBoolean(value);
if (this.IsReversed)
{
val = !val;
}
if (val)
{
return Visibility.Visible;
}
return Visibility.Collapsed;
}
public object ConvertBack(object value, Type targetType, object parameter, string language)
{
throw new NotImplementedException();
}
}
可见性不随属性而改变.由于智能感知(错误 Xaml 命名空间),我遇到了错误已解决.不确定这段代码有什么问题.
The visibility does not change with the property. I was having an error due to intellisense (Error Xaml namespace) which was resolved. Not sure what is wrong with this code.
谢谢.
推荐答案
change
this.OnPropertyChanged();
到
this.OnPropertyChanged("Show_element");
除此之外,您没有 ViewModel(抱歉,我在检查您的代码时错过了),因此您需要创建一个并将其设置为 DataContext:
edit: besides that, you don't have a ViewModel (sorry, missed that when I was checking your code), so you need to create one and set it as DataContext:
ViewModel.cs:
ViewModel.cs:
public class ViewModel : INotifyPropertyChanged
{
private bool show_element;
public bool Show_element
{
get { return show_element; }
set
{
show_element = value;
this.OnPropertyChanged("Show_element");
Debug.WriteLine("Show_element value changed");
}
}
public ViewModel()
{
}
public void ButtonClicked()
{
Show_element = !Show_element;
}
public event PropertyChangedEventHandler PropertyChanged = delegate { };
public void OnPropertyChanged(string propertyName = null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
你的 MainPage.xaml.cs 应该看起来像这样:
and your MainPage.xaml.cs should look somehow like that:
public sealed partial class MainPage : Page
{
private ViewModel _viewModel;
public MainPage()
{
this.InitializeComponent();
_viewModel = new ViewModel();
DataContext = _viewModel;
}
private void Button_Click(object sender, RoutedEventArgs e)
{
_viewModel.ButtonClicked();
}
}
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