WP7 可以在XAML中使用的 缓存图片控件(适合静态)

首先感谢 kiminozo 分享的代码

可以先看下他的这篇博客：　

WP7应用开发笔记 继承BitmapSource并使用独立存储来缓存远程的图片

我修改了下使它可以再XAML中使用

像这样

 <Image Margin="5"     Width="{Binding imgWidth}"  DoubleTap="PleasureListImage_DoubleTap"  Stretch="Uniform"    MaxWidth="400"  >
   <Image.Source>
         <StorageCached:StorageCachedImage   UriSource="{Binding imgUrl}"  /> 
   </Image.Source>  
</Image>

改造后的代码如下:

    /// <summary>
    /// 独立存储缓存的图片源
    /// </summary>
    public sealed class StorageCachedImage : BitmapSource
    {
        private Uri uriSource;
        private string filePath;
        //缓存目录
        private const string CacheDirectory = StringResources.TEMP_IMAGE_URL;


        public  DependencyProperty UriSourceProperty ;

        void UriSourcePropertyChangedCallback(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
            
            string s = e.NewValue as string;
            if (s != null)
            {
                uriSource = new Uri(s, UriKind.Absolute);
                Debug.WriteLine(uriSource);
                //文件路径
                filePath = Path.Combine(CacheDirectory, uriSource.AbsolutePath.TrimStart('/').Replace('/', '_'));
                this.OpenCatchSource();
            }
        }

 

        public string UriSource
        {
            get { return (string)GetValue(UriSourceProperty); }
            set { SetValue(UriSourceProperty, value); }
        }

        static StorageCachedImage()
        {

            //创建缓存目录
            using (var isolatedStorageFile = IsolatedStorageFile.GetUserStoreForApplication())
            {
                if (!isolatedStorageFile.DirectoryExists(CacheDirectory))
                {
                    isolatedStorageFile.CreateDirectory(CacheDirectory);
                }
            }
        }

        /// <summary>
        /// 创建一个独立存储缓存的图片源
        /// </summary>
        /// <param name="uriSource"></param>
        public StorageCachedImage(Uri uriSource)
        {           
            uriSource = uriSource;

            //文件路径
            filePath = Path.Combine(CacheDirectory, uriSource.AbsolutePath.TrimStart('/').Replace('/', '_'));
            OpenCatchSource();
        }

        /// <summary>
        /// 放在xaml 需要这个构造方法
        /// </summary>
        public StorageCachedImage()
        {
            UriSourceProperty =
            DependencyProperty.Register(
            "UriSource",
            typeof(string),
            typeof(StorageCachedImage),
            new PropertyMetadata(new PropertyChangedCallback(UriSourcePropertyChangedCallback)));

        }


        /// <summary>
        /// 打开缓存源
        /// </summary>
        public void OpenCatchSource()
        {
            bool exist;
            using (var isolatedStorageFile = IsolatedStorageFile.GetUserStoreForApplication())
            {
                exist = isolatedStorageFile.FileExists(filePath);
            }
            if (exist)
            {
                SetCacheStreamSource();
            }
            else
            {
                SetWebStreamSource();
            }
        }

        /// <summary>
        /// 设置缓存流到图片
        /// </summary>
        private  void SetCacheStreamSource()
        {
            using (var isolatedStorageFile = IsolatedStorageFile.GetUserStoreForApplication())
            using (var stream = isolatedStorageFile.OpenFile(filePath, FileMode.Open, FileAccess.Read))
            {
                 SetSource(stream);
            }
        }

        /// <summary>
        /// 下载Uri中的图片
        /// </summary>
        private  void SetWebStreamSource()
        {
            var httpWebRequest = (HttpWebRequest)WebRequest.Create(uriSource);
            httpWebRequest.AllowReadStreamBuffering = true;
            httpWebRequest.BeginGetResponse(ResponseCallBack, httpWebRequest);
        }

        /// <summary>
        /// 下载回调
        /// </summary>
        /// <param name="asyncResult"></param>
        private  void ResponseCallBack(IAsyncResult asyncResult)
        {

            var httpWebRequest = asyncResult.AsyncState as HttpWebRequest;
            if (httpWebRequest == null) return;
            try
            {
                var response = httpWebRequest.EndGetResponse(asyncResult);
                using (var stream = response.GetResponseStream())
                using (var isolatedStorageFile = IsolatedStorageFile.GetUserStoreForApplication())
                using (var fileStream = isolatedStorageFile.OpenFile(filePath, FileMode.OpenOrCreate, FileAccess.Write))
                {
                    stream.CopyTo(fileStream);
                }
                Dispatcher.BeginInvoke(SetCacheStreamSource);
            }
            catch (Exception err)
            {
                Debug.WriteLine(err.Message);
            }
        }
    }

在XAML中引用

 xmlns:StorageCached="clr-namespace:类所在的命名空间"

 参考 : .Net3.0里的DependencyProperty（1）

建议:适合场景广告或者背景等静态的位置

 备注: 这个方法还是有些要注意的地方,这个方法只适合于是用在静态的地方,不会连续要加载图片的地方,如果写在xaml的<list>中不会释放图片,会造成内存泄露,当然 BitmapImage这么用也是一样 , 如果是在代码中new 出的就不会有这些问题 

 我修改了下 在我的<List> 是这么用的 

<List>
....
　　<Image Source="{Binding img}"  />

.....
</List>

 

vo.img = new StorageCachedImage(uri)