我想显示存储在我的自定义图库中的Windows Phone 8照片文件夹中的所有图像,该图像使用ListBox
来显示图像。当我的ListBox中有图像时,为什么会出现OutOfMemoryException?
的ListBox
代码如下:
<phone:PhoneApplicationPage.Resources>
<MyApp:PreviewPictureConverter x:Key="PreviewPictureConverter" />
</phone:PhoneApplicationPage.Resources>
<ListBox Name="previewImageListbox" VirtualizingStackPanel.VirtualizationMode="Recycling">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<VirtualizingStackPanel CleanUpVirtualizedItemEvent="VirtualizingStackPanel_CleanUpVirtualizedItemEvent_1">
</VirtualizingStackPanel>
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
<ListBox.ItemTemplate>
<DataTemplate>
<Grid>
<Image Source="{Binding Converter={StaticResource PreviewPictureConverter}}" HorizontalAlignment="Center" VerticalAlignment="Center" />
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
用下面的转换器:
public class PreviewPictureConverter : System.Windows.Data.IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
PreviewImageItem c = value as PreviewImageItem;
if (c == null)
return null;
return c.ImageData;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}
图像存储在自定义类:
class PreviewImageItem
{
public Picture _picture = null;
public BitmapImage _bitmap = null;
public PreviewImageItem(Picture pic)
{
_picture = pic;
}
public BitmapImage ImageData
{
get
{
System.Diagnostics.Debug.WriteLine("Get picture " + _picture.ToString());
_bitmap = new BitmapImage();
Stream data = _picture.GetImage();
try
{
_bitmap.SetSource(data); // Out-of memory exception (see text)
}
catch (Exception ex)
{
System.Diagnostics.Debug.WriteLine("Exception : " + ex.ToString());
}
finally
{
data.Close();
data.Dispose();
data = null;
}
return _bitmap;
}
}
}
下面的代码被用于设置ListBox
数据源:
private List<PreviewImageItem> _galleryImages = new List<PreviewImageItem>();
using (MediaLibrary library = new MediaLibrary())
{
PictureCollection galleryPics = library.Pictures;
foreach (Picture pic in galleryPics)
{
_galleryImages.Add(new PreviewImageItem(pic));
}
previewImageListbox.ItemsSource = _galleryImages;
};
最后这里是“清理”代码:
private void VirtualizingStackPanel_CleanUpVirtualizedItemEvent_1(object sender, CleanUpVirtualizedItemEventArgs e)
{
PreviewImageItem item = e.Value as PreviewImageItem;
if (item != null)
{
System.Diagnostics.Debug.WriteLine("Cleanup");
item._bitmap = null;
}
}
这一切工作正常,但代码之后的几个图像与OutOfMemoryException
崩溃(滚动快尤其是当)。当滚动ListBox
时,方法VirtualizingStackPanel_CleanUpVirtualizedItemEvent_1
被称为regulary(例如,每2或3个列表框条目)。
这个示例代码有什么问题?
为什么内存不能释放(速度不够快)?
什么是'图片'和'GetImage()'方法做什么?你只能将'_bitmap'字段设置为'null',但是'_picture'字段是单独存在的,它可能是保存一些数据的对象吗?另外,公开公开领域并不是一个好习惯。在'PreviewImageItem'中实现'IDisposable'并在'VirtualizingStackPanel_CleanUpVirtualizedItemEvent_1'方法中调用'Dispose()'... – khellang
在清理过程中,您应该取消'_picture'属性。 –
图片的类型为“Microsoft.Xna。 Framework.Media.Picture“并且不需要太多内存。大部分内存由BitmapImages使用,它们是由Picture对象提供的流创建的。 – Hyndrix