我的 WPF 页面中的按钮不会更新，除非我重新打开页面

Question

我的 WPF 应用程序中有一个页面。我需要一个可以激活和停用的按钮。它实际上可以工作，但是当它激活时，我在屏幕上看不到它。如果我打开另一个页面，然后再次打开我的页面，它就会变为活动状态。

用户控制代码：

<UserControl x:Class="MediaAuthentication.UserControls.LandingFooterUserControl"
             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" 
             xmlns:local="clr-namespace:MediaAuthentication.UserControls"
             xmlns:vm="clr-namespace:MediaAuthentication.ViewModels"
             mc:Ignorable="d" 
             d:DataContext="{d:DesignInstance Type=vm:LandingFooterViewModel}"
             d:DesignHeight="450" d:DesignWidth="800">
    <Grid>
        <Button Content="Apply" 
                HorizontalAlignment="Center" 
                VerticalAlignment="Center" 
                Width="200" Height="50"
                IsEnabled="{Binding IsButtonEnabled}" 
                Command="{Binding ButtonCommand}" />
    </Grid>
</UserControl>

ViewModel代码：

using MediaAuthentication.Models;
using GalaSoft.MvvmLight.Command;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;
using MediaAuthentication.Business.Services.Logging;
using MediaAuthentication.Business.Services.Metadata;

namespace MediaAuthentication.ViewModels
{
    public class LandingFooterViewModel
    {
        private ILoggerService _loggerService;
        private IVideoMetadataService _videoMetadataService;

        private MetaDataFooterViewModel _metaFooterViewModel;

        public int markBeginning = -1;
        public int markEnd = -1;

        private bool _isButtonEnabled;
        public bool IsButtonEnabled
        {
            get => _isButtonEnabled;
            set
            {
                if (_isButtonEnabled != value)
                {
                    _isButtonEnabled = value;
                    OnPropertyChanged(nameof(IsButtonEnabled));
                    (ButtonCommand as RelayCommand)?.RaiseCanExecuteChanged();
                }
            }
        }

        // ICommand Property
        public ICommand ButtonCommand { get; }

        public LandingFooterViewModel(ILoggerService loggerService, IVideoMetadataService videoMetadataService, MetaDataFooterViewModel metaFooterViewModel)
        {
            _loggerService = loggerService;
            _videoMetadataService = videoMetadataService;

            _metaFooterViewModel = metaFooterViewModel;

            IsButtonEnabled = false;

            ButtonCommand = new RelayCommand(OnButtonClicked, () => IsButtonEnabled);
        }

        private void OnButtonClicked()
        {
            Storage.firstFrameIndex = markBeginning;
            Storage.lastFrameIndex = markEnd;

            if (Storage.media == null || string.IsNullOrEmpty(Storage.path))
            {
                _loggerService.LogWarning("No media file loaded. Please upload a file first.");
                return;
            }
            //IsLoading = true;
            try
            {
                if (Storage.media.StreamList != null)
                {
                    foreach (var stream in Storage.media.StreamList)
                    {
                        stream.FrameList.Clear();
                    }
                    Storage.media.StreamList.Clear();
                }

                _videoMetadataService.ExtractMetadata(Storage.media);

                _metaFooterViewModel.UpdateMetadata(Storage.media);

                _loggerService.LogInfo("Metadata extraction completed successfully.");

                _metaFooterViewModel.UpdateMetadata(Storage.media);

                /*
                List<string> frameTypes = new List<string>();
                foreach (Frame frame in media.StreamList[0].FrameList)
                {
                    frameTypes.Add(frame.Metadata[FrameMetadataKey.FrameType]);
                } */
            }
            catch (Exception ex)
            {
                _loggerService.LogError($"Error extracting metadata: {ex.Message}");
            }
            finally
            {
             //   IsLoading = false;
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
        protected virtual void OnPropertyChanged(string propertyName)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

我在 IsButtonEnabled 行中插入了一个断点，但是它工作正常。每当我想更改按钮的活动时，断点就会起作用并且该布尔变量的值是正确的。

Answer 1

WPF 绑定依赖于 INotifyPropertyChanged 来检测底层数据的更改。当您在属性设置器中引发 PropertyChanged 事件时，WPF 的绑定系统会侦听该事件并相应地更新 UI。

您实现了接口，但没有用它标记类：

public class LandingFooterViewModel : INotifyPropertyChanged