Question

我在 WPF中有一个用户控件，它包含一个Image及其与ImgSource的源绑定：

    public ImageWithWatingCtl()
    {
        this.DataContext = this;
        InitializeComponent();
        story = (base.Resources["waiting"] as Storyboard);
        StartLoading();
    }
    private ImageSource imgSource;

    public ImageSource ImgSource
    {
        get { return imgSource; }
        set
        {
            if (imgSource != null)
            { 
                imgSource = null;
            }
            imgSource = value;
            this.Dispatcher.BeginInvoke(new Action(() => { StopLoading(); }));
            OnPropertyChanged("ImgSource");
        }
    }


    public string Source
    {
        get { return (string)GetValue(SourceProperty); }
        set { SetValue(SourceProperty, value); }
    }

    public static readonly DependencyProperty SourceProperty =
        DependencyProperty.Register("Source", typeof(string), typeof(ImageWithWatingCtl), new FrameworkPropertyMetadata(new PropertyChangedCallback(CallBack)));

    private static void CallBack(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        ImageWithWatingCtl imgCtl = d as ImageWithWatingCtl;
        imgCtl.path = e.NewValue != null ? e.NewValue.ToString() : "";
        imgCtl.GetImage();
    }

    private void GetImage()
    {
        if (!string.IsNullOrEmpty(path))
        {

            service.OnComplate += service_OnComplate;
            service.EnQueue(path);

        }
    }

    void service_OnComplate(string url, BitmapImage bitmap)
    {
        if (url == path)
        {

            if (bitmap != null)
            {
                if (ImgSource == null)
                    ImgSource = bitmap;

            }

        }
    }

    private void StartLoading()
    {
        this.story.Begin();
        imageLoading.Visibility = Visibility.Visible;
    }
    private void StopLoading()
    {
        this.story.Stop();
        imageLoading.Visibility = Visibility.Collapsed;
    }

此控件获取网址并将其发送到 GetImageService ：

    public delegate void ComplateDelegate(string url, BitmapImage bitmap);
    public event ComplateDelegate OnComplate;
    private List<string> LstImageInfo { get; set; }
    object lstlock = new object();

    private static GetImageService instance = null;
    private readonly static object instance_lock = new object();

    public static GetImageService GetInstance()
    {
        if (instance == null)
        {
            lock (instance_lock)
            {
                if (instance == null)
                {
                    instance = new GetImageService();
                }
            }
        }
        return instance;
    }

    private GetImageService()
    {
        LstImageInfo = new List<string>();
        Thread getTread = new Thread(new ThreadStart(GetImage));
        getTread.IsBackground = true;
        getTread.Start();
    }

    public void EnQueue(string info)
    {
        lock (lstlock)
        {
            if (!LstImageInfo.Contains(info))
                LstImageInfo.Add(info);
        }
    }

    private void GetImage()
    {
        while (true)
        {
            lock (lstlock)
            {
                if (LstImageInfo.Count > 0)
                {
                    Console.WriteLine(LstImageInfo.Count);
                    BitmapImage bitmap = null;
                    var info = LstImageInfo[0];
                    if (info.StartsWith("http:"))
                    {
                        bitmap = ShareClass.GetBitemapUrl(info);
                    }
                    else
                    {
                        bitmap = ShareClass.GetBitmapImage(info);
                    }
                    if (bitmap.CanFreeze)
                        bitmap.Freeze();
                    if (OnComplate != null)
                        OnComplate(info, bitmap);
                    LstImageInfo.RemoveAt(0);
                }
            }
            Thread.Sleep(100);
        }
    }

用于获取图片的共享类：

    public static BitmapImage GetBitmapImage(string path, int imageWidth = 0)
    {
        BitmapImage bitmap;
        if (!File.Exists(path))
        {
            path = Path.Combine(GetAssemblyPath(), path);
        }
        if (File.Exists(path))
        {
            using (MemoryStream ms = new MemoryStream(File.ReadAllBytes(path)))
            {
                bitmap = new BitmapImage();
                bitmap.BeginInit();

                bitmap.CacheOption = BitmapCacheOption.OnLoad;
                if (imageWidth > 0)
                {
                    using (System.Drawing.Image drawingImage = System.Drawing.Image.FromStream(ms))
                    {
                        int old_w = drawingImage.Width;
                        int old_h = drawingImage.Height;
                        int imageHeight = (int)(old_h * (imageWidth * 1.0 / old_w));
                        using (System.Drawing.Image thumImage = drawingImage.GetThumbnailImage(imageWidth, imageHeight, () => { return true; }, IntPtr.Zero))
                        {
                            MemoryStream ms_thum = new MemoryStream();
                            thumImage.Save(ms_thum, System.Drawing.Imaging.ImageFormat.Png);
                            bitmap.StreamSource = ms_thum;
                        }
                    }
                }
                else
                {
                    bitmap.StreamSource = ms;
                }
                bitmap.EndInit();
                bitmap.Freeze();
            }

            return bitmap;
        }
        else
            return null;
    }
     public static BitmapImage GetBitemapUrl(string url)
    {
        try
        {
            if (string.IsNullOrEmpty(url))
            {
                return null;
            }
            else
            {
                BitmapImage bitmap = new BitmapImage();
                WebClient wc = new WebClient();
                using (var ms = new MemoryStream(wc.DownloadData(url)))
                {
                    bitmap = new BitmapImage();
                    bitmap.BeginInit();
                    bitmap.CacheOption = BitmapCacheOption.OnLoad;
                    bitmap.StreamSource = ms;
                    bitmap.EndInit();
                    if (bitmap.CanFreeze)
                        bitmap.Freeze();
                }

                return bitmap;
            }
        }
        catch (Exception ex)
        {
            return null;
        }
    }

我尝试了很多方法，设置ImgSource =null，使用GC，但没有用，所以如何释放内存或者还有另一种方式来实现我的需求？

顺便说一句，实际上GetImageService中的图片都是20~30kb，但如果我设置了ImgSource = bitmap，我看到内存增加超过10mb。

Answer 1

首先应确保删除使用ImageSource的UI Control。 GC.Collect应该可以正常工作，如果GC.Collect无法释放内存，至少应该有一个对ImageSource的引用。

WPF UI就像一棵树，在你的情况下。

UserControl -> BitmapImage -> ImageSource

UserControl和BitmapImage都有Childen，VisualChildren和LogicChildren，都可以引用你的ImageSource。

Answer 2

这个主题有很多SO线程，这个问题的一些解决方案是

1. Freeze the BitmapImage

原因：[从链接中复制]

触发此泄漏是因为WPF在静态BitmapImage和Image之间保留了强大的引用。

修复/解决方法是冻结BitmapImage。

BitmapImage bitmap = ShareClass.GetBitemapUrl(info);
bitmap.Freeze(); 
OnComplate(info, bitmap);

2. Load image from stream instead of Uri.

您可以验证其中任何一个是否可以修复内存问题。

使用BitmapImage设置Image的Source后如何释放内存？

2 个答案: