c# - 使用页面和 BitmapImage 的 WPF 应用程序中的内存泄漏

Question

我对 C# 和一般编程还是很陌生，但到目前为止我已经做了一些应用程序。只执行一项任务然后退出的普通应用程序已经足够简单，但是让一个系统例如每天拍摄 500 张用户照片给了我更大的挑战。

我的问题是关于 WPF 中的内存消耗。我有以下页面，加载时它会占用越来越多的内存。我尝试使用内存分析器工具并创建了一些快照来尝试解决此问题。但是，我很难理解何时/如何处理对象并确保 GC 负责其余的工作。我遇到特别麻烦的页面之一是:

第 2 页:

using EDSDKLib;
using PhotoBooth.Functions;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Windows.Threading;

namespace PhotoBooth.Pages
{
    /// <summary>
    /// Interaction logic for Picture.xaml
    /// </summary>
    public partial class Picture : Page
    {
        int secondsToWait = 4;
        DispatcherTimer dispatcherTimer;
        Action<BitmapImage> SetImageAction;
        ImageBrush bgbrush = new ImageBrush();

        public Picture()
        {
            InitializeComponent();

            // Define steps
            Global.CreateSteps(Global.SelectedMenuOrder, this, ((MasterPage)System.Windows.Application.Current.MainWindow).StepsWindow);
           
            // Create TempLocation
            Directory.CreateDirectory(Settings.TempLocation);
            
            // Handle the Canon EOS camera
            Global.CameraHandler.ImageSaveDirectory = Settings.TempLocation;
            SetImageAction = (BitmapImage img) => { bgbrush.ImageSource = img; };

            // Configure the camera timer
            dispatcherTimer = new DispatcherTimer();
            dispatcherTimer.Tick += DispatcherTimer_Tick;
            dispatcherTimer.Interval = new TimeSpan(0, 0, 0, 0, 800);
        }

        private void Page_Loaded(object sender, RoutedEventArgs e)
        {
            // Subscribe to camera events
            if (Global.CameraHandler != null)
            {
                Global.CameraHandler.LiveViewUpdated += CameraHandler_LiveViewUpdated;
                Global.CameraHandler.ImageSaved += CameraHandler_ImageSaved;
                Global.CameraHandler.CameraSDKError += CameraHandler_CameraSDKError;
            }

            // Start LiveView
            try
            {
                Console.WriteLine(Global.CameraHandler.IsLiveViewOn);
                if (!Global.CameraHandler.IsLiveViewOn)
                {
                    CameraLiveView.Background = bgbrush;
                    Global.CameraHandler.StartLiveView();
                }
            }
            catch (Exception)
            {
                // We cannot recover from that kind of errror. Reboot the application
                CameraCrashHandler();
            }
        }

        private void CameraTrigger_Click(object sender, RoutedEventArgs e)
        {
            // The user has clicked the trigger, change the layout
            CameraTrigger.Visibility = System.Windows.Visibility.Collapsed;
            CameraCountDown.Visibility = System.Windows.Visibility.Visible;
            CameraTrigger.IsEnabled = false;

            // Start the countdown
            secondsToWait = 4;
            dispatcherTimer.Start();
            Global.WriteToLog("INFO", "Camera shutter pressed... waiting for camera to take picture!");
        }

        private void DispatcherTimer_Tick(object sender, EventArgs e)
        {
            // Handles the countdown
            switch (secondsToWait)
            {
                case 4:
                    CameraTimer3.Foreground = new SolidColorBrush(Colors.White);
                    Global.PlaySound("pack://application:,,,/Resources/Audio/camera_beep.wav");
                    break;
                case 3:
                    CameraTimer2.Foreground = new SolidColorBrush(Colors.White);
                    Global.PlaySound("pack://application:,,,/Resources/Audio/camera_beep.wav");
                    break;
                case 2:
                    CameraTimer1.Foreground = new SolidColorBrush(Colors.White);
                    Global.PlaySound("pack://application:,,,/Resources/Audio/camera_beep.wav");
                    break;
                case 1:
                    CameraTimer0.Source = new BitmapImage(new Uri("pack://application:,,,/Resources/Images/icon_cameraWhite.png"));
                    Global.CameraFlashEffect(((MasterPage)System.Windows.Application.Current.MainWindow).CameraFlash);
                    Global.CameraHandler.TakePhoto();
                    break;
                case 0:
                    CameraTimer0.Source = new BitmapImage(new Uri("pack://application:,,,/Resources/Images/icon_cameraRed.png"));
                    CameraTimer1.Foreground = (SolidColorBrush)(new BrushConverter().ConvertFrom("#e8234a"));
                    CameraTimer2.Foreground = (SolidColorBrush)(new BrushConverter().ConvertFrom("#e8234a"));
                    CameraTimer3.Foreground = (SolidColorBrush)(new BrushConverter().ConvertFrom("#e8234a"));

                    dispatcherTimer.Stop();
                    break;
                default:
                    break;
            }

            secondsToWait--;
        }

        private void Page_Unloaded(object sender, RoutedEventArgs e)
        {
            // Stop LiveView
            if (Global.CameraHandler.IsLiveViewOn)
            {
                CameraLiveView.Background = null;
                Global.CameraHandler.StopLiveView();
            }

            // Unsubscribe from events
            Global.CameraHandler.LiveViewUpdated -= CameraHandler_LiveViewUpdated;
            Global.CameraHandler.ImageSaved -= CameraHandler_ImageSaved;
            Global.CameraHandler.CameraSDKError -= CameraHandler_CameraSDKError;
        }

        #region CameraHandler

        void CameraHandler_CameraSDKError(string error)
        {
            // Handle known errors
            Global.WriteToLog("ERROR", "CameraSDKError: " + error);
            switch (error)
            {
                case "0x00008D01":
                    // Reset cameraTrigger for taking another photo
                    this.Dispatcher.Invoke((Action)(() =>
                    {
                        CameraTrigger.Visibility = System.Windows.Visibility.Visible;
                        CameraCountDown.Visibility = System.Windows.Visibility.Collapsed;
                        CameraTrigger.IsEnabled = true;
                    }));
                    break;
                default:
                    CameraCrashHandler();
                    break;
            }
        }

        void CameraHandler_ImageSaved(string img)
        {
            // Assign image to user
            Global.PersonObject.Image = img;

            // We have a image, let's navigate to the next page
            this.Dispatcher.Invoke((Action)(() =>
            {
                NavigationService.Navigate(Global.FindPageByString(Global.NavigateManager(this, Functions.Enums.Navigation.Forward)));
            }));
        }

        void CameraHandler_LiveViewUpdated(Stream img)
        {
            try
            {
                if (Global.CameraHandler.IsLiveViewOn)
                {
                    using (WrappingStream s = new WrappingStream(img))
                    {
                        img.Position = 0;
                        BitmapImage EvfImage = new BitmapImage();
                        EvfImage.BeginInit();
                        EvfImage.StreamSource = s;
                        EvfImage.CacheOption = BitmapCacheOption.OnLoad;
                        EvfImage.EndInit();
                        EvfImage.Freeze();
                        Application.Current.Dispatcher.Invoke(SetImageAction, EvfImage);
                    }
                }
            }
            catch (Exception ex)
            {
                Global.WriteToLog("ERROR", "LiveViewUpdated failed: " + ex.Message);
            }
        }

        static void CameraCrashHandler()
        {
            // Camera cannot start
            Global.WriteToLog("ERROR", "Unkown CameraSDKError. Automatic reboot needed");
            MessageWindow mw = new MessageWindow("CameraErrorTitle", "CameraErrorMessage");
            mw.ShowDialog();

            // We cannot recover from that kind of errror. Reboot the application
            System.Windows.Forms.Application.Restart();
            System.Windows.Application.Current.Shutdown();
        }
  
        #endregion
    }
}

第 3 页:

using PhotoBooth.Functions;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace PhotoBooth.Pages
{
    /// <summary>
    /// Interaction logic for PreviewID.xaml
    /// </summary>
    public partial class PreviewID : Page
    {
        public PreviewID()
        {
            InitializeComponent();

            // Define steps
            Global.CreateSteps(Global.SelectedMenuOrder, this, ((MasterPage)System.Windows.Application.Current.MainWindow).StepsWindow);

            // Load image and data
            PreviewIDText = GetIDText(Global.PersonObject, PreviewIDText);
            PreviewIDCard.Source = GetIDPhoto(Global.PersonObject);
            PreviewIDPhoto.Background = new ImageBrush(new BitmapImage(new Uri(Global.PersonObject.Image)));
        }

        private void PreviewIDRetry_Click(object sender, RoutedEventArgs e)
        {
            Global.WriteToLog("INFO", "User did not approve the image, retry!");
            NavigationService.Navigate(Global.FindPageByString(Global.NavigateManager(this, Functions.Enums.Navigation.Backward)));
        }

        private void PreviewIDAccept_Click(object sender, RoutedEventArgs e)
        {
            Global.WriteToLog("INFO", "User approved the image");
            NavigationService.Navigate(Global.FindPageByString(Global.NavigateManager(this, Functions.Enums.Navigation.Forward)));
        }

        public TextBlock GetIDText(Functions.Enums.Person p, TextBlock tb)
        {
            tb.Text = "";
            tb.FontSize = 24;

            if (p.Affiliation == Functions.Enums.Affiliation.Employee)
            {
                // Ansatt
                tb.Inlines.Add(new Run(p.FirstName + " " + p.LastName + Environment.NewLine) { FontWeight = FontWeights.Bold, FontSize = 30 });
                tb.Inlines.Add(p.Title + Environment.NewLine);
                tb.Inlines.Add(p.Department + Environment.NewLine);
                tb.Inlines.Add("Ansatt nr: " + p.EmployeeNumber + Environment.NewLine);
            }
            else
            {
                // Student
                tb.Inlines.Add("Last name:  ");
                tb.Inlines.Add(new Run(p.LastName + Environment.NewLine) { FontWeight = FontWeights.Bold });
                tb.Inlines.Add("First name:  ");
                tb.Inlines.Add(new Run(p.FirstName + Environment.NewLine) { FontWeight = FontWeights.Bold });
                tb.Inlines.Add("Date of birth:  ");
                tb.Inlines.Add(new Run("dd.mm.yyyy" + Environment.NewLine) { FontWeight = FontWeights.Bold });
                tb.Inlines.Add("Studentnr:  ");
                tb.Inlines.Add(new Run("xxxxxx" + Environment.NewLine) { FontWeight = FontWeights.Bold });
            }

            return tb;
        }

        public BitmapImage GetIDPhoto(Functions.Enums.Person p)
        {
            BitmapImage result;
            switch (p.Affiliation)
            {
                case PhotoBooth.Functions.Enums.Affiliation.Student:
                    result = new BitmapImage(new Uri("pack://application:,,,/Resources/Images/idcard_student.png"));
                    break;
                case PhotoBooth.Functions.Enums.Affiliation.Employee:
                    result = new BitmapImage(new Uri("pack://application:,,,/Resources/Images/idcard_employee.png"));
                    break;
                default:
                    result = new BitmapImage(new Uri("pack://application:,,,/Resources/Images/idcard_student.png"));
                    break;
            }

            return result;
        }

        private void Page_Unloaded(object sender, RoutedEventArgs e)
        {
            PreviewIDPhoto.Background = null;
        }
    }
}

虽然大部分是全局的。所有其他页面上都使用了函数，它们似乎很好，因为据我所知，正是这个页面造成了我的大部分麻烦。

这是我的内存性能测试的屏幕截图。

1. 用户从第 1 页导航到第 2 页(或其他页面)，据我所知没有问题。内存使用似乎很稳定。

2. 用户使用 LiveView 触发佳能相机(第 2 页)。内存消耗上下波动，但稳定。

3. 用户拍摄图像并进行预览(第 3 页)、重试(返回到第 2 页)、拍摄另一张、重试等等...

   每次加载后面的代码时:

是位图图像导致了这个问题吗？如果该代码中没有明显的内容，我应该如何继续测试内存泄漏？

Answer 1

我认为是因为 DispatcherTimer。卸载页面时可能仅停止计时器是不够的，因为 WPF 仍会存储对您的类的引用。卸载页面时尝试注销该事件。