How to download image and save it in local storage using Xamarin-Forms.?

Create a FileService interface

in your Shared Code, create a new Interface, for instance, called IFileService.cs

 public interface IFileService
 {
      void SavePicture(string name, Stream data, string location="temp");
 }

Implementation Android

In your android project, create a new class called "Fileservice.cs".

Make sure it derives from your interface created before and decorate it with the dependency information:

[assembly: Dependency(typeof(FileService))]
namespace MyApp.Droid
{
    public class FileService : IFileService
    {
        public void SavePicture(string name, Stream data, string location = "temp")
        {
            var documentsPath = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
            documentsPath = Path.Combine(documentsPath, "Orders", location);
            Directory.CreateDirectory(documentsPath);

            string filePath = Path.Combine(documentsPath, name);

            byte[] bArray = new byte[data.Length];
            using (FileStream fs = new FileStream(filePath , FileMode.OpenOrCreate))
            {
                using (data)
                {
                    data.Read(bArray, 0, (int)data.Length);
                }
                int length = bArray.Length;
                fs.Write(bArray, 0, length);
            }
        }
    }
}

Implementation iOS The implementation for iOS is basically the same:

[assembly: Dependency(typeof(FileService))]
namespace MyApp.iOS
{
    public class FileService: IFileService
    {
        public void SavePicture(string name, Stream data, string location = "temp")
        {
            var documentsPath = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
            documentsPath = Path.Combine(documentsPath, "Orders", location);
            Directory.CreateDirectory(documentsPath);

            string filePath = Path.Combine(documentsPath, name);

            byte[] bArray = new byte[data.Length];
            using (FileStream fs = new FileStream(filePath , FileMode.OpenOrCreate))
            {
                using (data)
                {
                    data.Read(bArray, 0, (int)data.Length);
                }
                int length = bArray.Length;
                fs.Write(bArray, 0, length);
            }
        }
    }
}

In order to save your file, in your shared code, you call

DependencyService.Get<IFileService>().SavePicture("ImageName.jpg", imageData, "imagesFolder");

and should be good to go.

public void DownloadImage(string URL)
{
    var webClient = new WebClient();
    webClient.DownloadDataCompleted += (s, e) =>
    {
        byte[] bytes = new byte[e.Result.Length];
        bytes=e.Result; // get the downloaded data
        string documentsPath = Android.OS.Environment.GetExternalStoragePublicDirectory(Android.OS.Environment.DirectoryPictures).AbsolutePath;

        var partedURL = URL.Split('/');
        string localFilename = partedURL[partedURL.Length-1];
        string localPath = System.IO.Path.Combine(documentsPath, localFilename);
        File.WriteAllBytes(localPath, bytes); // writes to local storage
        Application.Current.MainPage.IsBusy = false;
        Application.Current.MainPage.DisplayAlert("Download", "Download Finished", "OK");
        MediaScannerConnection.ScanFile(Forms.Context,new string[] { localPath }, null, null);
    };
    var url = new Uri(URL);
    webClient.DownloadDataAsync(url);
}

Here you have to use dependency service from xamarin forms PCL to call this method from android project.This will store your image to public folder. Will edit this if i get time to make a demo with iOS also.