当Bool变量变为True时，更改标签 [英] Changing a Label when a Bool variable turns True

问题描述

我不太确定如何解释这个...我要把代码放在psuedo代码中以便于阅读

几乎我想要一个标签改变它的文本，当一个类的bool变量更改...我不知道我需要使用，因为我使用WPF和类不能只是改变我不认为的标签？ p>

我需要某种事件吗？或WPF事件？感谢任何帮助

  public MainWindow（）
 {
 SomeClass temp = new SomeClass（）; 
 
 void ButtonClick（sender，EventArgs e）
 {
 if（temp.Authenticate）
 label.Content =AUTHENTICATED; 
} 
} 
 
 public SomeClass 
 {
 bool _authenticated; 
 
 public bool Authenticate（）
 {
 //发送UDP msg 
 //等待UDP msg进行身份验证
 //相应地返回true或false 
} 
} 
  

解决方案

另一个除了BradledDotNet之外的WPF方法的答案是使用触发器。这将是纯粹基于无转换代码的XAML。

XAML：

 <标签> 
< Label.Style> 
< Style TargetType =Label> 
< Style.Triggers> 
< DataTrigger Binding ={Binding Path = IsAuthenticated}Value =True> 
< Setter Property =ContentValue =Authenticated/> 
< / DataTrigger> 
< /Style.Triggers> 
< / Style> 
< /Label.Style> 
< / Label> 
  

相同的规则适用于BradledDotNet提及的ViewModel，并且IsAuthenticated属性应该引发PropertyChanged事件。

- 按照Gayot Fow的建议添加一些样板代码 -

查看代码后面：

为了简单起见，我将只是将视图的DataContext设置在后面。为了更好的设计，您可以使用ViewModelLocator，如 here 。

  public partial class SampleWindow：Window 
 {
 SampleModel _model = new SampleModel（）; 
 
 public SampleWindow（）{
 InitializeComponent（）; 
 DataContext = _model; //将model / viewmodel附加到DataContext以在XAML中绑定
} 
} 
  

示例模型（应该是ViewModel）：

这里的要点是附加模型/ viewmodel必须实现INotifyPropertyChanged。 / p>

  public class SampleModel：INotifyPropertyChanged 
 {
 bool _isAuthenticated = false; 
 
 public bool IsAuthenticated {
 get {return _isAuthenticated; } 
 set {
 if（_isAuthenticated！= value）{
 _isAuthenticated = value; 
 OnPropertyChanged（IsAuthenticated）; //提高此事件是绑定正常工作的关键
} 
} 
} 
 
公共事件PropertyChangedEventHandler PropertyChanged; 
 
 void OnPropertyChanged（string propName）{
 if（PropertyChanged！= null）{
 PropertyChanged（this，new PropertyChangedEventArgs（propName））; 
} 
} 
} 
  

i'm not really sure how to explain this... i'm going to put the code in psuedo code for easy reading

pretty much I want a label to change it's text when a bool variable of a class changes... i'm not sure what I need to use since i'm using WPF and the class can't just change the label i don't think?

do i need some sort of event? or a WPF event? thanks for any help

public MainWindow()
{
   SomeClass temp = new SomeClass();

   void ButtonClick(sender, EventArgs e)
   {  
      if (temp.Authenticate)
        label.Content = "AUTHENTICATED";
   }
}

public SomeClass
{
  bool _authenticated;

  public bool Authenticate()
  {
    //send UDP msg
    //wait for UDP msg for authentication
    //return true or false accordingly
  }
}

解决方案

Another WPF approach other than BradledDotNet answer is to use triggers. This will be purely XAML based without converter code.

XAML:

<Label>
  <Label.Style>
    <Style TargetType="Label">
      <Style.Triggers>
        <DataTrigger Binding="{Binding Path=IsAuthenticated}" Value="True">
          <Setter Property="Content" Value="Authenticated" />
        </DataTrigger>
      </Style.Triggers>
    </Style>
  </Label.Style>
</Label>

Same rule applies as mentioned by BradledDotNet, ViewModel should be attached and "IsAuthenticated" property should raise the PropertyChanged event.

-- Add some boilerplate code as suggested by Gayot Fow --

View Code Behind:

For simplicity I will just set the DataContext of the view in code behind. For a better design you can use ViewModelLocator as explained here.

public partial class SampleWindow : Window
{
  SampleModel _model = new SampleModel();

  public SampleWindow() {
    InitializeComponent();
    DataContext = _model; // attach the model/viewmodel to DataContext for binding in XAML
  }
}

Example Model (it should really be ViewModel):

The main point here is the attached model/viewmodel has to implement INotifyPropertyChanged.

public class SampleModel : INotifyPropertyChanged
{
  bool _isAuthenticated = false;

  public bool IsAuthenticated {
    get { return _isAuthenticated; }
    set {
      if (_isAuthenticated != value) {
        _isAuthenticated = value;
        OnPropertyChanged("IsAuthenticated"); // raising this event is key to have binding working properly
      }
    }
  }

  public event PropertyChangedEventHandler PropertyChanged;

  void OnPropertyChanged(string propName) {
    if (PropertyChanged != null) {
      PropertyChanged(this, new PropertyChangedEventArgs(propName));
    }
  }
}

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