feature: refresh list & save to gallery

Pixiview.iOS/Info.plist

@@ -44,5 +44,7 @@
 	<false/>
 	<key>UIStatusBarStyle</key>
 	<string>UIStatusBarStyleDefault</string>
+	<key>NSPhotoLibraryUsageDescription</key>
+	<string>需要访问您的图片库</string>
 </dict>
 </plist>

Pixiview.iOS/Pixiview.iOS.csproj

@@ -76,6 +76,7 @@
     <Compile Include="Renderers\RoundImageRenderer.cs" />
     <Compile Include="GlobalSuppressions.cs" />
     <Compile Include="Renderers\AdaptedNavigationPageRenderer.cs" />
+    <Compile Include="Services\FileStore.cs" />
   </ItemGroup>
   <ItemGroup>
     <InterfaceDefinition Include="Resources\LaunchScreen.storyboard" />

Pixiview.iOS/Services/FileStore.cs

@@ -0,0 +1,45 @@
+using System.Threading.Tasks;
+using Pixiview.iOS.Services;
+using Pixiview.Utils;
+using Xamarin.Forms;
+using Xamarin.Forms.Platform.iOS;
+
+[assembly: Dependency(typeof(FileStore))]
+namespace Pixiview.iOS.Services
+{
+    public class FileStore : IFileStore
+    {
+
+        public Task<string> SaveImageToGalleryAsync(ImageSource image)
+        {
+            IImageSourceHandler renderer;
+            if (image is UriImageSource)
+            {
+                renderer = new ImageLoaderSourceHandler();
+            }
+            else if (image is FileImageSource)
+            {
+                renderer = new FileImageSourceHandler();
+            }
+            else
+            {
+                renderer = new StreamImagesourceHandler();
+            }
+            var photo = renderer.LoadImageAsync(image).Result;
+
+            var task = new TaskCompletionSource<string>();
+            if (photo == null)
+            {
+                task.SetResult(null);
+            }
+            else
+            {
+                photo.SaveToPhotosAlbum((img, error) =>
+                {
+                    task.SetResult(error?.ToString());
+                });
+            }
+            return task.Task;
+        }
+    }
+}