/// <summary>
/// Requests loading the image of <paramref name="size"/> located on <paramref name="uri"/>.
/// </summary>
/// <param name="uri">
/// An uri of the image to load.
/// </param>
/// <param name="size">
/// The desired size of the image.
/// </param>
/// <returns>
/// Returns an observable sequence which contains an image(s) of <paramref name="size"/> loaded using <paramref name="uri"/>.
/// </returns>
/// <remarks>
/// Override this method to provide concrete logic of loading the image per each <see cref="BaseImageLoader"/>.
/// </remarks>
protected override IObservable<ImageInfo> WhenLoadedInternal(Uri uri, Size size)
{
var result = Observable.Create<ImageInfo>(observer =>
{
var imageLoadContext = new ImageLoadContext(uri, size, observer);
this.downloadManager.EnqeueReqeust(imageLoadContext);
return () => this.downloadManager.DequeueRequest(imageLoadContext);
});
return result;
}
/// <summary>
/// Requests loading the image of <paramref name="size"/> located on <paramref name="uri"/>.
/// </summary>
/// <param name="uri">
/// An uri of the image to load.
/// </param>
/// <param name="size">
/// The desired size of the image.
/// </param>
/// <returns>
/// Returns an observable sequence which contains an image(s) of <paramref name="size"/> loaded using <paramref name="uri"/>.
/// </returns>
/// <remarks>
/// The observable sequence may generate several instances of same image but with different size. For example,
/// there cam be a smaller sample of the requested image in the local cache, so this image will be returned immediatly while the image of requested
/// size is loading. Once the image of the desired size is loaded, it will be pushed into the same observable sequence.
/// </remarks>
/// <exception cref="ArgumentNullException">
/// <paramref name="uri"/> is <c>null</c>.
/// </exception>
/// <exception cref="ArgumentException">
/// <paramref name="size"/> has non positive width or height.
/// </exception>
public IObservable<ImageInfo> WhenLoaded(Uri uri, Size size)
{
if (uri == null)
{
throw new ArgumentNullException("uri");
}
if (size == default(Size) || size.Width <= 0 || size.Height <= 0)
{
throw new ArgumentException("The size should have positive width and height", "size");
}
return this.WhenLoaded(uri, size, new Size(0, 0));
}
protected override IObservable<ImageInfo> WhenLoadedInternal(Uri uri, Size size)
{
return Observable.Create<ImageInfo>(observer =>
{
if (imageData != null)
{
var imageInfo = new ImageInfo(uri, size, imageData) { ForceFallback = true };
observer.OnNext(imageInfo);
}
observer.OnCompleted();
return () => { };
});
}
public ImageLoadContext(Uri uri, Size size, IObserver<ImageInfo> observer)
{
this.Uri = uri;
this.Size = size;
this.Observer = observer;
}
public ImageInfo(Uri uri, Size size, byte[] data)
{
this.Uri = uri;
this.Size = size;
this.Data = data;
}
internal ImageInfo WithSize(Size size)
{
this.Size = size;
return this;
}
internal bool IsFittedIn(Size size)
{
return this.Size.Width >= size.Width || this.Size.Height >= size.Height;
}
/// <summary> /// Requests loading the image of <paramref name="size"/> located on <paramref name="uri"/>. /// </summary> /// <param name="uri"> /// An uri of the image to load. /// </param> /// <param name="size"> /// The desired size of the image. /// </param> /// <returns> /// Returns an observable sequence which contains an image(s) of <paramref name="size"/> loaded using <paramref name="uri"/>. /// </returns> /// <remarks> /// Override this method to provide concrete logic of loading the image per each <see cref="BaseImageLoader"/>. /// </remarks> protected abstract IObservable<ImageInfo> WhenLoadedInternal(Uri uri, Size size);
/// <summary>
/// Requests loading the image of <paramref name="size"/> located on <paramref name="uri"/>.
/// </summary>
/// <param name="uri">
/// An uri of the image to load.
/// </param>
/// <param name="size">
/// The desired size of the image.
/// </param>
/// <param name="minSize">
/// Thi mimimum accetable size.
/// </param>
/// <returns>
/// Returns an observable sequence which contains an image(s) of <paramref name="size"/> loaded using <paramref name="uri"/>.
/// </returns>
/// <remarks>
/// If the image cannot be loaded or loaded image has smaller size than requested, then it tries to load the image using fallback
/// <see cref="BaseImageLoader"/>. All intermediate images (the images of smaller size than requested), are pushed into observable sequence.
/// </remarks>
protected IObservable<ImageInfo> WhenLoaded(Uri uri, Size size, Size minSize)
{
var result = Observable.Create<ImageInfo>(observer =>
{
ImageInfo image = null;
var compositeDisposable = new CompositeDisposable();
compositeDisposable.Add(this.WhenLoadedInternal(uri, size).Subscribe(
img =>
{
observer.OnNext(img);
image = img;
},
err =>
{
if (fallbackLoader != null)
{
compositeDisposable.Add(this.fallbackLoader.WhenLoaded(uri, size, minSize)
.Do(this.OnFallbackImageLoaded)
.Subscribe(observer));
}
else
{
observer.OnError(err);
}
},
() =>
{
if ((image == null || image.IsFittedIn(size) == false || image.ForceFallback) && fallbackLoader != null)
{
compositeDisposable.Add(this.fallbackLoader.WhenLoaded(uri, size, image == null ? minSize : image.Size)
.Do(this.OnFallbackImageLoaded)
.Subscribe(observer));
}
else
{
observer.OnCompleted();
}
}));
return () => { compositeDisposable.Dispose(); };
});
return result;
}
