/// <summary>
/// Caches the given object to the Application's ImageCache
/// and returns the uri of the cached file.
/// </summary>
/// <param name="objectToCache">Object to cache</param>
/// <param name="cacheFileName">Name of the cache file</param>
/// <param name="progressHandler">Delegate for handling progress</param>
/// <returns>Uri</returns>
public async Task <Uri> GetCachedUriAsync(object objectToCache, string cacheFileName,
CacheProgressHandler progressHandler = null)
{
// Check if the objectToCache is a valid Uri
var uri = objectToCache as Uri;
if (uri == null)
{
// Is the objectToCache a string representing a Uri?
var uriString = objectToCache as string;
if (uriString != null)
{
// Try creating the Uri from the uriString
if (!(Uri.TryCreate(uriString, UriKind.RelativeOrAbsolute, out uri)))
{
return(null);
}
}
}
// Calculate the expiry date
var expirationDate = DateTime.Now.Subtract(ImageCache.CacheDuration);
// Get the cache folder location
var cacheFolder = await ImageCache.GetCacheFolderAsync();
if (cacheFolder == null)
{
return(null);
}
// Report Progress
progressHandler?.Invoke(0);
// Get the cache file corresponding to the cacheFileName
var cacheFile = await cacheFolder.TryGetItemAsync(cacheFileName) as StorageFile;
// Has the cache file expired or does it not exist?
if (await cacheFile.IsNullOrExpired(expirationDate))
{
try
{
// Create/Recreate the cache file
cacheFile = await cacheFolder.CreateFileAsync(cacheFileName, CreationCollisionOption.ReplaceExisting);
using (var httpClient = new HttpClient())
{
// Use HttpCompletionOption.ResponseHeadersRead for the GetAsync call so that it returns as
// soon as response headers are received and not when the whole response is received
using (var response = await httpClient.GetAsync(uri, HttpCompletionOption.ResponseHeadersRead))
{
// If respose status is not success then raise exception
response.EnsureSuccessStatusCode();
// Open the cache file for writing
using (var cacheStream = await cacheFile.OpenAsync(FileAccessMode.ReadWrite))
{
// Start reading the content as a stream
using (var inputStream = await response.Content.ReadAsInputStreamAsync())
{
ulong totalBytesRead = 0;
var prevProgress = -1;
var totalContentLength = response.Content.Headers.ContentLength ?? 0UL;
while (true)
{
// Read from the stream
IBuffer buffer = new Windows.Storage.Streams.Buffer(2048);
buffer = await inputStream.ReadAsync(buffer, buffer.Capacity,
InputStreamOptions.None);
if (buffer.Length == 0)
{
// There is nothing else to read
break;
}
// The following code can be used to report progress
totalBytesRead += buffer.Length;
if (totalContentLength > 0UL)
{
// We will report a progress percent between 0%-80% because caching represents 80%
// of the task of displaying the image. The other 20% requires successful loading
// of the cached image.
var progress =
(int)Math.Round((totalBytesRead * 80) / (double)totalContentLength);
if (progress != prevProgress)
{
// Report Progress
progressHandler?.Invoke(progress);
prevProgress = progress;
}
}
else
{
prevProgress = Math.Min(prevProgress + 1, 80);
// Report Progress
progressHandler?.Invoke(prevProgress);
}
// Write to cache file
await cacheStream.WriteAsync(buffer);
}
}
}
}
}
}
catch (Exception)
{
// In case any exception occurs during the downloading or caching
// delete the cacheFile and return a 'null' Uri
cacheFile = await cacheFolder.TryGetItemAsync(cacheFileName) as StorageFile;
if (cacheFile != null)
{
await cacheFile.DeleteAsync();
}
// Report Progress
progressHandler?.Invoke(-1);
return(null);
}
}
// Report Progress
// Caching indicates only half of the task completed i.e. 50% progress,
// Progress will be 100% only when the image is loaded successfully on the ImageFrame
progressHandler?.Invoke(80);
// Now that we have a valid cached file for the Uri, return the Uri of the cached inputFile
return(new Uri($"ms-appdata:///temp/{ImageCache.CacheFolderName}/{cacheFileName}"));
}
/// <summary>
/// Caches the given object to the Application's ImageCache
/// and returns the uri of the cached file.
/// </summary>
/// <param name="objectToCache">Object to cache</param>
/// <param name="cacheFileName">Name of the cache file</param>
/// <param name="progressHandler">Delegate for handling progress</param>
/// <returns>Uri</returns>
public async Task <Uri> GetCachedUriAsync(object objectToCache, string cacheFileName,
CacheProgressHandler progressHandler = null)
{
// Check if the objectToCache is a valid IRandomAccessStream
var stream = objectToCache as IRandomAccessStream;
if ((stream == null) || !stream.CanRead)
{
return(null);
}
// Calculate the expiry date
var expirationDate = DateTime.Now.Subtract(ImageCache.CacheDuration);
// Get the cache folder location
var cacheFolder = await ImageCache.GetCacheFolderAsync();
if (cacheFolder == null)
{
return(null);
}
// Report Progress
progressHandler?.Invoke(0);
// Get the cache file corresponding to the cacheFileName
var cacheFile = await cacheFolder.TryGetItemAsync(cacheFileName) as StorageFile;
// Has the cache file expired or does it not exist?
if (await cacheFile.IsNullOrExpired(expirationDate))
{
try
{
// Create/Recreate the cache file
cacheFile = await cacheFolder.CreateFileAsync(cacheFileName, CreationCollisionOption.ReplaceExisting);
// Open the cache file for writing
using (var cacheStream = await cacheFile.OpenAsync(FileAccessMode.ReadWrite))
{
// Start reading the content as a stream
using (var inputStream = stream.GetInputStreamAt(0))
{
ulong totalBytesRead = 0;
var prevProgress = -1;
var totalContentLength = stream.Size;
if (totalContentLength <= 0UL)
{
prevProgress = 0;
}
while (true)
{
// Read from the stream
IBuffer buffer = new Windows.Storage.Streams.Buffer(2048);
buffer = await inputStream.ReadAsync(buffer, buffer.Capacity,
InputStreamOptions.None);
if (buffer.Length == 0)
{
// There is nothing else to read
break;
}
// The following code can be used to report progress
totalBytesRead += buffer.Length;
if (totalContentLength > 0UL)
{
// We will report a progress percent between 0%-80% because caching represents 80%
// of the task of displaying the image. The other 20% requires successful loading
// of the cached image.
var progress =
(int)Math.Round((totalBytesRead * 80) / (double)totalContentLength);
if (progress != prevProgress)
{
// Report Progress
progressHandler?.Invoke(progress);
prevProgress = progress;
}
}
else
{
prevProgress = Math.Min(prevProgress + 1, 80);
// Report Progress
progressHandler?.Invoke(prevProgress);
}
// Write to cache file
await cacheStream.WriteAsync(buffer);
}
}
}
}
catch (Exception)
{
// In case any exception occurs during the copying of the StorageFile
// delete the cacheFile and return a 'null' Uri
cacheFile = await cacheFolder.TryGetItemAsync(cacheFileName) as StorageFile;
if (cacheFile != null)
{
await cacheFile.DeleteAsync();
}
// Report Progress
progressHandler?.Invoke(-1);
return(null);
}
}
// Report Progress
// Caching indicates only half of the task completed i.e. 50% progress,
// Progress will be 100% only when the image is loaded successfully on the ImageFrame
progressHandler?.Invoke(80);
// Now that we have a valid cached file for the Uri, return the Uri of the cached inputFile
return(new Uri($"ms-appdata:///temp/{ImageCache.CacheFolderName}/{cacheFileName}"));
}
/// <summary>
/// Caches the given object to the Application's ImageCache
/// and returns the uri of the cached file.
/// </summary>
/// <param name="objectToCache">Object to cache</param>
/// <param name="cacheFileName">Name of the cache file</param>
/// <param name="progressHandler">Delegate for handling progress</param>
/// <returns>Uri</returns>
public async Task <Uri> GetCachedUriAsync(object objectToCache, string cacheFileName,
CacheProgressHandler progressHandler = null)
{
// Check if the objectToCache is a valid StorageFile
var inputFile = objectToCache as StorageFile;
if (inputFile == null)
{
return(null);
}
// Calculate the expiry date
var expirationDate = DateTime.Now.Subtract(ImageCache.CacheDuration);
// Get the cache folder location
var cacheFolder = await ImageCache.GetCacheFolderAsync();
if (cacheFolder == null)
{
return(null);
}
// Report Progress
progressHandler?.Invoke(0);
// Get the cache file corresponding to the cacheFileName
var cacheFile = await cacheFolder.TryGetItemAsync(cacheFileName) as StorageFile;
// Has the cache file expired or does it not exist?
if (await cacheFile.IsNullOrExpired(expirationDate))
{
try
{
// Report Progress
progressHandler?.Invoke(10);
// Copy the storage file to the cacheFolder. If the file already exists, overwrite it
await inputFile.CopyAsync(cacheFolder, cacheFileName, NameCollisionOption.ReplaceExisting);
// Report Progress
// Caching indicates only 80% of the task completed i.e. 80% progress,
// Progress will be 100% only when the image is loaded successfully on the ImageFrame
progressHandler?.Invoke(80);
}
catch (Exception)
{
// In case any exception occurs during the copying of the StorageFile
// delete the cacheFile and return a 'null' Uri
cacheFile = await cacheFolder.TryGetItemAsync(cacheFileName) as StorageFile;
if (cacheFile != null)
{
await cacheFile.DeleteAsync();
}
// Report Progress
progressHandler?.Invoke(-1);
return(null);
}
}
// Report Progress
progressHandler?.Invoke(80);
// Now that we have a valid cached file for the Uri, return the Uri of the cached inputFile
return(new Uri($"ms-appdata:///temp/{ImageCache.CacheFolderName}/{cacheFileName}"));
}