c# – 在Windows Phone 7上从隔离存储打开JPEG时出现问题

2023年8月14日 226次阅读

脚本

>应用程序打开
>检查隔离存储中是否存在背景图像
>如果没有,请从Web下载,并将其保存到隔离存储
>从“隔离存储”加载图像,并在Panorama控件上将其设置为“背景”

问题

图像未加载到GUI中.当我检查从隔离存储器接收的字节数组时,它包含与最初写入的字节数相同的字节数,但图像未显示.

这是我正在尝试找出问题的一些测试代码：

using (IsolatedStorageFile appStorage = IsolatedStorageFile.GetUserStoreForApplication())
            {
                if (!appStorage.FileExists(@"default.jpg"))
                {
                    BitmapImage bmp = sender as BitmapImage;
                    byte[] bytes = bmp.ConvertToBytes();
                    using (var inputfile = appStorage.CreateFile(@"default.jpg"))
                    {
                        inputfile.Write(bytes, 0, bytes.Length);
                    }
                }
                using (var isfs = appStorage.OpenFile(@"default.jpg", FileMode.OpenOrCreate, FileAccess.Read))
                {
                    BitmapImage bmp = new BitmapImage();
                    bmp.SetSource(isfs);
                    MainPanorama.Background = new ImageBrush { Opacity = 0.4, Stretch = Stretch.None, ImageSource = bmp };
                }
            }

发件人是来自其他来源的加载图片
我已经尝试在MainPanorama控件上将发件人设置为backgroundimage,这很好用.所以问题在于从隔离存储装载.

有任何想法吗？

最佳答案 编辑：这听起来像是时间或随机访问流的问题.

你可以尝试的事情：

>尝试将整个图像加载到内存数组中 – 一个MemoryStream – 然后在SetSource调用中使用它
>尝试删除未使用的代码 – .ImageOpened委托和img = new Image()调用
>如果这些事情没有帮助,那么尝试在字节级别检查两个流.

有关1的更多信息,请参阅How Do I Load an Image from Isolated Storage and Display it on the Device? – 请注意,这是Microsoft的支持官方示例,它将图像加载到内存MemoryStream中,然后在屏幕上的Image中使用它.

微软的代码：

// The image will be read from isolated storage into the following byte array
        byte [] data;

        // Read the entire image in one go into a byte array
        using (IsolatedStorageFile isf = IsolatedStorageFile.GetUserStoreForApplication())
        {
            // Open the file - error handling omitted for brevity
                                 // Note: If the image does not exist in isolated storage the following exception will be generated:
            // System.IO.IsolatedStorage.IsolatedStorageException was unhandled
            // Message=Operation not permitted on IsolatedStorageFileStream
            using (IsolatedStorageFileStream isfs = isf.OpenFile("WP7Logo.png", FileMode.Open, FileAccess.Read))
            {
                // Allocate an array large enough for the entire file
                data = new byte[isfs.Length];

                // Read the entire file and then close it
                isfs.Read(data, 0, data.Length);
                isfs.Close();
            }
        }

        // Create memory stream and bitmap
        MemoryStream ms = new MemoryStream(data);
        BitmapImage bi = new BitmapImage();

        // Set bitmap source to memory stream
        bi.SetSource(ms);

        // Create an image UI element – Note: this could be declared in the XAML instead
        Image image = new Image();

        // Set size of image to bitmap size for this demonstration
        image.Height = bi.PixelHeight;
        image.Width = bi.PixelWidth;

        // Assign the bitmap image to the image’s source
        image.Source = bi;

        // Add the image to the grid in order to display the bit map
        ContentPanel.Children.Add(image);

请报告修复它的原因.

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