我的WPF应用程序在使用INotifyPropertyChanged接口时没有更新xaml textblock文本

Question

我是WPF的初学者，所以请裸机。我有一个有几个属性的类（AlertMsg.cs），它使用INotifyPropertyChanged接口。使用xaml我将该类的命名空间包含在我的窗口（MainWindow.xaml）中。 Intellisense帮助我添加一个数据上下文，并使用xaml将这些属性绑定到我的窗口元素。所以我知道我的窗户知道属性。当我在Visual Studio中运行应用程序时，textblock会从类中加载我的构造函数值。所以我觉得它被绑定到财产上很不错。

我有另一个类（PubNubAlerts.cs），它监听传入的json，它解析json并将这些值设置为我的属性类（AlertMsg.cs）。这部分也工作得很好，因为我可以看到在我的输出窗口中更改的属性。当属性改变它甚至通过PropertyChanged方法时，但当我去看我的窗口（MainWindow）的UI时，在初始化时加载的构造函数值仍然存在。我希望他们使用传入的json数据进行更新。我在执行INotifyPropertyChanged时错过了什么？

MainWindow.xaml

<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
     xmlns:Models="clr-namespace:MyApplication.Models" 
     x:Name="AlertPopup" x:Class="MyApplication.MainWindow" 
     Title="AlertMsg" Height="350" Width="525" WindowState="Normal"> 
    <Window.DataContext> 
     <Models:AlertMsg /> 
    </Window.DataContext> 
    <Grid Background="White" Opacity="0.8"> 
     <TabItem Width="500" Height="300" VerticalAlignment="Center" HorizontalAlignment="Center" HorizontalContentAlignment="Center" VerticalContentAlignment="Center"> 
      <Frame Source="MainPage.xaml" MinWidth="100" MinHeight="100" HorizontalAlignment="Center" HorizontalContentAlignment="Center" VerticalContentAlignment="Center" VerticalAlignment="Center" Width="500" Height="297" FontSize="20" /> 
     </TabItem> 
     <Border Background="{Binding Path=PopUpBackGroundColor, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" BorderBrush="Red" BorderThickness="2" CornerRadius="4" Opacity="0.8" Width="300" Height="80"> 
      <TextBlock HorizontalAlignment="Center" VerticalAlignment="Center" FontSize="22" Text="{Binding Path=MainMessage, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Foreground="Black"></TextBlock> 
     </Border> 
    </Grid> 
</Window> 

MainWindow.xaml.cs

using System.Windows; 


namespace MyApplication 
{ 
    /// <summary> 
    /// Interaction logic for MainWindow.xaml 
    /// </summary> 
    public partial class MainWindow : Window 
    { 
     public MainWindow() 
     { 
      InitializeComponent(); 
      WindowState = WindowState.Normal; 
      WindowStyle = WindowStyle.ThreeDBorderWindow; 
      Height = 400; 
      Width = 400; 

     } 
    } 
} 

AlertMsg.cs

using System.ComponentModel; 
using System; 

namespace MyApplication.Models 
{ 
    // interface 
    class AlertMsg : INotifyPropertyChanged 
    { 

     public event PropertyChangedEventHandler PropertyChanged = delegate { }; 

     //// constructor, some default values 
     public AlertMsg() 
     { 
      this.MainMessage = "TEXT GOES HERE"; 
      this.PopUpBackGroundColor = "Red"; 
     } 


     // main message property 
     private string mainMessage; 
     public string MainMessage 
     { 
      get 
      { 
       return this.mainMessage; 
      } 
      set 
      { 
       if (value != this.mainMessage) 
       { 
        this.mainMessage = value; 

        System.Diagnostics.Debug.WriteLine("MainMessage is now = " + value); 

        OnPropertyChanged("MainMessage"); 

       } 
      } 
     } 
     //background color property of message 
     private string popupBackGroundColor; 
     public string PopUpBackGroundColor 
     { 
      get 
      { 
       return this.popupBackGroundColor; 
      } 
      set 
      { 

       if (value != this.popupBackGroundColor) 
       { 
        this.popupBackGroundColor = value; 
        System.Diagnostics.Debug.WriteLine("popupbackgroundcolor is now = " + value); 
        OnPropertyChanged("PopUpBackGroundColor"); 
       } 
      } 
     } 


     // call this method on the setter of every property 
     // should change the text of the view 
     private void OnPropertyChanged(string propertyName) 
     { 
      try 
      { 
       // change property 
       if (PropertyChanged != null) 
       { 

        PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); 
        System.Diagnostics.Debug.WriteLine("Property " + propertyName + " changed."); 

       } 
      } 
      catch (InvalidAsynchronousStateException e) 
      { 
       System.Diagnostics.Debug.WriteLine("Invalid Asynchrounous State Exception" + e.Message); 
      } 
      catch (Exception generalException) 
      { 
       System.Diagnostics.Debug.WriteLine("Error OnPropertyChanged: " + propertyName + " " + generalException.Message); 
      } 

     } 

    } 
} 

PubNubAlerts.cs（第三方喂我的JSON。你可以不用担心这一点，因为我知道它更新了我的房产，但为了以防万一，我将它包括在内）。

using System; 
using Newtonsoft.Json.Linq; 
using PubnubApi; 
using MyApplication.Models; 


namespace MyApplication 
{ 
    public class PubNubAlerts 
    { 
     static public Pubnub pubnub; 
// hardcoded values for testing 
     static public string channel = "TestChannel"; 
     static public string authKey = "xxxxxxxxxx"; 
     static public string subscribeKey = "xxxxx-xxxxxx-xxxxx-xxxxxxxx"; 
     static public string channelGroup = ""; 
     static public string mainBody; 

     AlertMsg alertMsg = new AlertMsg(); 

     public void PubNubSubscribe() 
     { 
      // config 
      PNConfiguration config = new PNConfiguration() 
      { 
       AuthKey = authKey, 
       Secure = false, 
       SubscribeKey = subscribeKey, 
       LogVerbosity = PNLogVerbosity.BODY 
      }; 
      try 
      { 

       pubnub = new Pubnub(config); 

       // add listener 
       pubnub.AddListener(new SubscribeCallbackExt(
       (pubnubObj, message) => { 
     // grab data from json and parse 
     System.Diagnostics.Debug.WriteLine(pubnub.JsonPluggableLibrary.SerializeToJsonString(message)); 
        string jsonMessage = pubnub.JsonPluggableLibrary.SerializeToJsonString(message); 
        dynamic data = JObject.Parse(jsonMessage); 
     // update alertmsg properties with json from pubnub 
     alertMsg.MainMessage = data.Message.mainmessage; 
        alertMsg.PopUpBackGroundColor = data.Message.popupbackgroundcolor; 


       }, 
       (pubnubObj, presence) => { 
        System.Diagnostics.Debug.WriteLine(pubnub.JsonPluggableLibrary.SerializeToJsonString(presence)); 
       }, 
       (pubnubObj, status) => { 
        System.Diagnostics.Debug.WriteLine("{0} {1} {2} ", status.Operation, status.Category, status.StatusCode); 
       } 
       )); 

       System.Diagnostics.Debug.WriteLine("Running subscribe()"); 

       // subscribe 
       pubnub.Subscribe<object>() 
       .WithPresence() 
       .Channels(channel.Split(',')) 
       .ChannelGroups(channelGroup.Split(',')) 
       .Execute(); 
      } 
      catch (Exception e) 
      { 
       System.Diagnostics.Debug.WriteLine("FAILED TO SUBSCRIBE: " + e.Message); 
      } 

     } 

    } 
} 

MainWindow Image

Answer 1

你有AlertMsg两个不同的实例。

在“MainWindow.xaml”你实例化一个实例为您在这里窗口的数据上下文：

<Window.DataContext> 
    <Models:AlertMsg /> 
</Window.DataContext> 

而在“PubNubAlerts.cs”你是在第19行实例化一个实例：

AlertMsg alertMsg = new AlertMsg(); 

您需要将窗口的DataContext传递给PubNubAlerts，或者需要公开PubNubAlerts使用的实例并将窗口的DataContext绑定到该实例。