[英]How can I change the Visibility of a TextBlock with a Trigger?
當我嘗試編譯以下代碼時,我得到錯誤“可見性”成員無效,因為它沒有合格的類型名稱。
我需要更改什么才能在Status = off時使TextBlock消失 ?
XAML:
<Window x:Class="TestTrigger123345.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="300" Width="300">
<StackPanel>
<TextBlock Text="This is a sentence.">
<TextBlock.Triggers>
<Trigger Property="{Binding Status}" Value="off">
<Setter Property="Visibility" Value="Collapsed"/>
</Trigger>
</TextBlock.Triggers>
</TextBlock>
<TextBlock Text="{Binding Status}"/>
</StackPanel>
</Window>
代碼背后:
using System.Windows;
namespace TestTrigger123345
{
public partial class Window1 : Window
{
public Window1()
{
InitializeComponent();
DataContext = this;
Status = "off";
}
public string Status { get; set; }
}
}
我改為DataTrigger和Dependency Properties,它得到了同樣的錯誤:
XAML:
<Window x:Class="TestTrigger123345.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="300" Width="300">
<StackPanel HorizontalAlignment="Left">
<TextBlock Text="{Binding Status}">
<TextBlock.Triggers>
<DataTrigger Binding="{Binding Status}" Value="off">
<Setter Property="TextBlock.Background" Value="Tan"/>
</DataTrigger>
</TextBlock.Triggers>
</TextBlock>
</StackPanel>
</Window>
代碼背后:
using System.Windows;
namespace TestTrigger123345
{
public partial class Window1 : Window
{
public Window1()
{
InitializeComponent();
DataContext = this;
Status = "off";
}
#region DependencyProperty: Status
public string Status
{
get
{
return (string)GetValue(StatusProperty);
}
set
{
SetValue(StatusProperty, value);
}
}
public static readonly DependencyProperty StatusProperty =
DependencyProperty.Register("Status", typeof(string), typeof(Window1),
new FrameworkPropertyMetadata());
#endregion
}
}
我使用具有實現INotifyPropertyChanged的屬性Status的ViewModel重新進行此操作,並獲得相同的錯誤:
WindowViewModel.cs:
using System.ComponentModel;
namespace TestTrigger123345
{
class WindowViewModel
{
#region ViewModelProperty: Status
private string _status;
public string Status
{
get
{
return _status;
}
set
{
_status = value;
OnPropertyChanged("Status");
}
}
#endregion
#region PropertChanged Block
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string property)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(property));
}
}
#endregion
}
}
代碼背后:
using System.Windows;
namespace TestTrigger123345
{
public partial class Window1 : Window
{
public Window1()
{
InitializeComponent();
WindowViewModel windowViewModel = new WindowViewModel();
windowViewModel.Status = "off";
DataContext = windowViewModel;
}
}
}
當然有一種方法可以用觸發器以某種方式做到這一點。
您需要指定應在其上設置可見性的類型
<Setter Property="FrameworkElement.Visibility" Value="Visible"/>
嘗試這樣的事情:
<PasswordBox Name="pbxPassword" />
<TextBox Text="{Binding Password,
ElementName=pbxPassword,
UpdateSourceTrigger=PropertyChanged}">
<TextBox.Style>
<Style TargetType="TextBox">
<Setter Property="Visibility" Value="Hidden" />
<Style.Triggers>
<DataTrigger Binding="{Binding IsChecked, ElementName=chbShowPassword}" Value="True">
<Setter Property="Visibility" Value="Visible" />
</DataTrigger>
</Style.Triggers>
</Style>
</TextBox.Style>
</TextBox>
<CheckBox Name="chbShowPassword">
Show password
</CheckBox>
元素的觸發器僅支持EventTrigger,因此您無法使用屬性觸發器(Trigger)。 查看FrameworkElement.Triggers屬性。
也許您需要實現INotifyPropertyChanged並在Status更改時引發PropertyChange?
您可以在Visibility和Status字符串之間使用Converter,而不是使用觸發器。
對於Bindings,使用DataTrigger,對於可以使用Trigger的屬性。還要確保Status屬性通知;)使其成為依賴屬性或使用INotifyPropertyChanged接口。
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