我想在我的Button上设置多个DataTriggers.我做了一些研究,发现MultiDataTrigger允许你这样做.如果CCTVPath == string.Empty OR PermissionsFlag == false,我希望我的Button的Visibility属性设置为false.这就是我到目前为止所拥有的;
<Button Grid.Column="3" x:Name="cctvFeedButton" Content="Live Feed" Width="100" FontSize="16" HorizontalAlignment="Right" Margin="5" Click="OnCCTVButtonClick"> <Button.Style> <Style TargetType="Button"> <Style.Triggers> <MultiDataTrigger> <MultiDataTrigger.Conditions> <Condition Binding="{Binding CCTVPath}" Value=""/> <Condition Binding="{Binding PermissionsFlag}" Value="False"/> </MultiDataTrigger.Conditions> <Setter Property="Visibility" Value="Hidden"/> </MultiDataTrigger> </Style.Triggers> </Style> </Button.Style> </Button>
在我的代码隐藏中,我设置PermissionsFlag就像这样;
public bool PermissionsFlag { get; set; }
private void OnPageLoaded(object sender,RoutedEventArgs e)
{
PermissionsFlag = false;
}
正如你所看到的PermissionsFlag肯定是假的,并且肯定是空CCTVPath但是Button永远不会被隐藏.我究竟做错了什么？
更新：
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this,new PropertyChangedEventArgs(propertyName));
}
private bool _permissionsFlag;
public bool Flag
{
get { return _permissionsFlag; }
set
{
_permissionsFlag = value;
OnPropertyChanged("PermissionsFlag");
}
}
private void OnPageLoaded(object sender,RoutedEventArgs e)
{
Flag = false;
CCTVImageCollection = GetImages();
imageListBox.ItemsSource = CCTVImageCollection;
DataContext = this;
}
在我的XAML中：
<Button.Style>
<Style TargetType="Button">
<Style.Triggers>
<DataTrigger Binding="{Binding PermissionsFlag}" Value="False">
<Setter Property="Visibility" Value="Hidden"/>
</DataTrigger>
</Style.Triggers>
</Style>
</Button.Style>
解决方法
将条件转换为两个独立的DataTriggers
<Style.Triggers>
<DataTrigger Binding="{Binding CCTVPath}" Value="">
<Setter Property="Visibility" Value="Hidden"/>
</DataTrigger>
<DataTrigger Binding="{Binding PermissionsFlag}" Value="False">
<Setter Property="Visibility" Value="Hidden"/>
</DataTrigger>
</Style.Triggers>
确保绑定路径正确(检查VS Output窗口是否有可能的异常消息)
另外：不要只依赖Button的隐藏状态,在代码中正确实现权限(OnCCTVButtonClick).在这里阅读原因：
How to Snoop proof your wpf application?
auto-property PermissionsFlag(public bool PermissionsFlag {get; set;})不会通知视图有关更改.
可以实现INotifyPropertyChanged接口(在我的测试窗口中它是这样完成的：公共部分类Window3：Window,INotifyPropertyChanged)然后在属性更改时引发事件.
这是一个完整的工作示例,我用于测试
public partial class Window3 : Window,INotifyPropertyChanged
{
public Window3()
{
InitializeComponent();
this.DataContext = this;
//PermissionsFlag = true;
CCTVPath = "youtube.com";
}
private bool _permissionsFlag = false;
private string _cctvPath;
public bool PermissionsFlag
{
get { return _permissionsFlag; }
set
{
_permissionsFlag = value;
OnPropertyChanged("PermissionsFlag");
}
}
public string CCTVPath
{
get { return _cctvPath; }
set
{
_cctvPath = value;
OnPropertyChanged("CCTVPath");
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this,new PropertyChangedEventArgs(propertyName));
}
}
窗口xaml：
<Window x:Class="WpfDemos.Views.Window3"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window3" Height="300" Width="300">
<StackPanel>
<CheckBox Name="chkPermissionsFlag"
Content="PermissionsFlag"
IsChecked="{Binding Path=PermissionsFlag,UpdateSourceTrigger=PropertyChanged}"/>
<TextBox Text="{Binding Path=CCTVPath,UpdateSourceTrigger=PropertyChanged}"/>
<Button x:Name="cctvFeedButton" Content="Live Feed"
Width="100" FontSize="16" HorizontalAlignment="Right" Margin="5">
<Button.Style>
<Style TargetType="Button">
<Style.Triggers>
<DataTrigger Binding="{Binding Path=CCTVPath}" Value="">
<Setter Property="Visibility" Value="Hidden"/>
</DataTrigger>
<DataTrigger Binding="{Binding Path=PermissionsFlag}" Value="False">
<Setter Property="Visibility" Value="Hidden"/>
</DataTrigger>
</Style.Triggers>
</Style>
</Button.Style>
</Button>
</StackPanel>
</Window>
