Question

我想在应用程序开始执行之前将jpeg文件存储在隔离的存储中。我已将这些图像设置为应用程序第一页中图像控件的源（通过数据绑定）。但每次应用程序执行时我得到一个孤立的存储异常。我已经在App.xaml.cs.s的application_launchin（）函数中插入了以下代码。我也尝试将它插入到App.xaml.cs的构造函数中但仍然有异常。我使用过第一页的数据绑定和converter.please help

中引发异常

 using (IsolatedStorageFile myIsolatedStorage = IsolatedStorageFile.GetUserStoreForApplication())
            {
                    myIsolatedStorage.CreateDirectory("DirForMyImage");
                    bi = new BitmapImage(new Uri("/images/myImage.jpg", UriKind.Relative));
                    bi.ImageOpened += new EventHandler<RoutedEventArgs>(imageTest_ImageOpened);}

这是我保存图像的事件处理程序

 void imageTest_ImageOpened(object sender, RoutedEventArgs e)
    {
        using (IsolatedStorageFile myIsolatedStorage = IsolatedStorageFile.GetUserStoreForApplication())
        {
            using (IsolatedStorageFileStream fileStream = myIsolatedStorage.CreateFile("Certificate/Birth Certificate.jpg"))
            {

                WriteableBitmap wb = new WriteableBitmap(bi);
                wb.SaveJpeg(fileStream, wb.PixelWidth, wb.PixelHeight, 0, 85);
            }}}

转换器功能如下。

public class IsoImageConverter : IValueConverter
    {
          WriteableBitmap bitmap = new WriteableBitmap(200, 200);
        //Convert Data to Image when Loading Data    
        public object Convert(object value, Type targetType, object parameter,
            System.Globalization.CultureInfo culture)
        {
            String path = (String)value;
            using (IsolatedStorageFile myIsolatedStorage = IsolatedStorageFile.GetUserStoreForApplication())
        {
            using (IsolatedStorageFileStream fileStream = myIsolatedStorage.OpenFile(path, FileMode.Open, FileAccess.Read))//=====>exception occurs here
            {
                // Decode the JPEG stream.
               bitmap = new WriteableBitmap(400,400);
               bitmap.LoadJpeg(fileStream);
                fileStream.Dispose();

            }


        }

        return bitmap; 

    }

    public object ConvertBack(object value, Type targetType, object parameter,
        System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

Answer 1

我建议将此逻辑放在应用程序Launching事件的处理程序中。当您通过Visual Studio模板创建新的WP7应用程序时，您将在App.xaml.cs文件中找到以下方法：

  // Code to execute when the application is launching (eg, from Start)
  // This code will not execute when the application is reactivated
  private void Application_Launching(object sender, LaunchingEventArgs e)
  {
  }

当Launching事件触发时调用此方法。

如何在应用程序打开之前将映像文件存储在独立存储中？

1 个答案: