c# - WPF UserControl 属性更改不更新

Question

我有一个添加到我的主应用程序中的 UserControl。该 UserControl 包含一个 UIElement 按钮

UserControl 包含一个 DispatchTimer，每 2 秒根据一些 int 值确定按钮图像将是什么。

在 UserControl 中调用的方法之一应该设置它的图像，但该控件从不显示它更改后的图像。

public void SetNormal()
    {
        btnFlashAlert.Content = new BitmapImage(new Uri("Images/FlashButton.png", UriKind.RelativeOrAbsolute));
    }

在主应用程序上查看控件更新时，我是否遗漏了什么？

当我查看 .Content 包含的内容时，它是正确的。 UI 未反射(reflect)更改。

XAML

<UserControl x:Class="SC.FlashSystem.MainButton"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         mc:Ignorable="d" Height="53" Width="164">
<Button x:Name="btnFlashAlert" Background="{x:Null}" BorderBrush="{x:Null}" Cursor="Hand" Click="btnFlashAlert_Click">
    <Button.Template>
        <ControlTemplate>
            <Image Source="Images/FlashButton.png"/>
        </ControlTemplate>
    </Button.Template>
</Button>

代码隐藏已更新

        public partial class MainButton : UserControl
{
    private SupportConsoleWeb.MessageData messageCounts { get; set; }
    private readonly DispatcherTimer flashButtonChangeTimer = new DispatcherTimer();
    private BitmapImage NormalImage { get; set; }
    private BitmapImage CriticalImage { get; set; }
    private BitmapImage AlertImage { get; set; }
    private BitmapImage InfoImage { get; set; }

    public MainButton()
    {
        InitializeComponent();

        messageCounts = new SupportConsoleWeb.MessageData();
        messageCounts.CriticalCount = 0;
        messageCounts.AlertCount = 0;
        messageCounts.InfoCount = 0;

        NormalImage = new BitmapImage(new Uri("Images/FlashButton.png", UriKind.RelativeOrAbsolute));
        CriticalImage = new BitmapImage(new Uri("Images/FlashButtonRed.png", UriKind.RelativeOrAbsolute));
        AlertImage = new BitmapImage(new Uri("Images/FlashButtonOrange.png", UriKind.RelativeOrAbsolute));
        InfoImage = new BitmapImage(new Uri("Images/FlashButtonGreen.png", UriKind.RelativeOrAbsolute));

        flashButtonChangeTimer.Interval = TimeSpan.FromSeconds(2);
        flashButtonChangeTimer.Tick += flashButtonChangeTimer_Tick;
        flashButtonChangeTimer.Start();
    }

    void flashButtonChangeTimer_Tick(object sender, EventArgs e)
    {
        btnFlashAlert.Dispatcher.BeginInvoke(new Action(() =>
        {
            if (btnFlashAlert.Content == null)
            {
                SetNormal();
            }
            else if (messageCounts.CriticalCount > 0 && btnFlashAlert.Content.Equals(CriticalImage))
            {
                SetNormal();
            }
            else if (messageCounts.AlertCount > 0 && btnFlashAlert.Content.Equals(AlertImage))
            {
                SetNormal();
            }
            else if (messageCounts.InfoCount > 0 && btnFlashAlert.Content.Equals(InfoImage))
            {
                SetNormal();
            }
            else if (messageCounts.CriticalCount > 0)
            {
                SetCritical();
            }
            else if (messageCounts.AlertCount > 0)
            {
                SetAlert();
            }
            else if (messageCounts.InfoCount > 0)
            {
                SetInfo();
            }
        }));
    }

    public void UpdateMessageCounts(SupportConsoleWeb.MessageData messageCounts)
    {
        this.messageCounts = messageCounts;
    }

    private void btnFlashAlert_Click(object sender, RoutedEventArgs e)
    {
        MainWindow window = new MainWindow();
        window.WindowStartupLocation = WindowStartupLocation.CenterScreen;
        window.ShowDialog();
    }

    public void SetMessageCount(int criticalCount, int alertCount, int infoCount)
    {
        messageCounts.CriticalCount = criticalCount;
        messageCounts.AlertCount = alertCount;
        messageCounts.InfoCount = infoCount;
    }

    private void SetNormal()
    {
        btnFlashAlert.Content = NormalImage;
    }

    private void SetCritical()
    {
        btnFlashAlert.Content = CriticalImage;
    }

    private void SetAlert()
    {
        btnFlashAlert.Content = AlertImage;
    }

    private void SetInfo()
    {
        btnFlashAlert.Content = InfoImage;
    }
}

Answer 1

将您的 XAML 更改为此

 <Image Source="{Binding TheImage}"/>

添加通知属性改变

 public partial class MainButton : UserControl, INotifyPropertyChanged

创建 OnPropertyChanged 事件

    void OnPropertyChanged(String prop)
    {
        PropertyChangedEventHandler handler = PropertyChanged;

        if (handler != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(prop));
        }
    }
    public event PropertyChangedEventHandler PropertyChanged;

创建一个 Bitmap Prop 并通知 Prop 更改事件

    private BitmapImage _TheImage;

    public BitmapImage TheImage
    {
        get { return _TheImage; }
        set { _TheImage = value; OnPropertyChanged("TheImage"); }
    }

在你的初始化程序中

  public MainButton()
    {
        this.DataContext = this;
        InitializeComponent();
        TheImage = new BitmapImage();

现在在你的设置方法中调用

TheImage = //Your Bitmap Goes here

我知道这看起来有些过分，但从长远来看，您会发现这是一个更简洁的实现。