Showing downloaded image in ImageView not working in Xamarin.Android - xamarin.android

Question

I have a small png image I like to show in an imageview using Xamarin.Android.
I am downloading the file using the following code:
private void Download()
{
var url = "https://hns.d7u.de/v4/images/hvvstoerungen_facebook.png";
var directory = Environment.GetFolderPath(Environment.SpecialFolder.Personal) + "/myapp/";
var fileName = url.Substring(url.LastIndexOf("/") +1);
var path = directory + fileName;
System.Net.WebClient wC = new System.Net.WebClient();
wC.Headers.Add(System.Net.HttpRequestHeader.AcceptEncoding, "gzip");
wC.DownloadDataCompleted += WC_DownloadDataCompleted;
wC.DownloadDataAsync(new Uri(url), path);
}
private void WC_DownloadDataCompleted(object sender, System.Net.DownloadDataCompletedEventArgs e)
{
var path = e.UserState.ToString();
var bytes = e.Result;
if (File.Exists(path))
File.Delete(path);
if (!File.Exists(path))
File.WriteAllBytes(path, bytes);
}
It is stored at /data/user/0/myapp/files/hns/hvvstoerungen_facebook.png and a File.Exists(...) returns a true for that path. So I am sure, that the file is downloaded and it exists.
When I want to show it in the ImageView, I do it like this:
if (System.IO.File.Exists(imageFilePath))
{
Android.Net.Uri andrUri = Android.Net.Uri.Parse(imageFilePath);
ImageIcon.SetImageURI(andrUri);
//Also not working:
//Bitmap bitmap = BitmapFactory.DecodeFile(imageFilePath);
//ImageIcon.SetImageBitmap(bitmap);
//And also not working:
//Android.Net.Uri andrUri = Android.Net.Uri.Parse(imageFilePath);
//Bitmap bmp = BitmapFactory.DecodeStream(Android.App.Application.Context.ContentResolver.OpenInputStream(andrUri));
//ImageIcon.SetImageBitmap(bmp);
}
The Output windows shows the following when the image should be shown:
02-01 23:41:24.770 E/Drawable(19815): Unable to decode stream:
android.graphics.ImageDecoder$DecodeException: Failed to create image
decoder with message 'unimplemented'Input contained an error. 02-01
23:41:24.770 W/ImageView(19815): resolveUri failed on bad bitmap uri:
/data/user/0/myapp/files/hns/hvvstoerungen_facebook.png
But I cannot figured out what exactly this means.
One additional thing is: If I run the app in a brand new Android Emulator instance, this image and all other of its kind are not shown.
If I run the app in an old Android Emulator instance, where the app was already running before but on Android.Forms basis, the old images that were known by the old project are shown while the newly downloaded images are not. All images are in the same folder and I cannot see any differences between them.
Does anyone has an Idea?
Edit:
My working version has the following Download() Method instead:
private void Download()
{
var noCompression = new string[] { ".png", ".jpg", ".jpeg", ".gif", ".zip", ".7z", ".mp3", ".mp4" };
var url = "https://hns.d7u.de/v4/images/hvvstoerungen_facebook.png";
var directory = Environment.GetFolderPath(Environment.SpecialFolder.Personal) + "/myapp/";
var fileName = url.Substring(url.LastIndexOf("/") +1);
var path = directory + fileName;
System.Net.WebClient wC = new System.Net.WebClient();
if (!noCompression.Contains(url.Substring(url.LastIndexOf('.'))))
wC.Headers.Add(System.Net.HttpRequestHeader.AcceptEncoding, "gzip");
wC.DownloadDataCompleted += WC_DownloadDataCompleted;
wC.DownloadDataAsync(new Uri(url), path);
}

Answer 1

You could try the code below.
Download the image from Url:
public Bitmap GetImageBitmapFromUrl(string url)
{
Bitmap imageBitmap = null;
using (var webClient = new WebClient())
{
var imageBytes = webClient.DownloadData(url);
if (imageBytes != null && imageBytes.Length > 0)
{
imageBitmap = BitmapFactory.DecodeByteArray(imageBytes, 0, imageBytes.Length);
}
}
return imageBitmap;
}
Usage:
bitmap = GetImageBitmapFromUrl("https://hns.d7u.de/v4/images/hvvstoerungen_facebook.png");
And save the image as png:
void ExportBitmapAsPNG(Bitmap bitmap)
{
var folderPath = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal);
filePath = System.IO.Path.Combine(folderPath, "test.png");
var stream = new FileStream(filePath, FileMode.Create);
bitmap.Compress(Bitmap.CompressFormat.Png, 100, stream);
stream.Close();
}
Usage:
ExportBitmapAsPNG(bitmap);
Check the file exists or not and set into the imageview:
if (File.Exists(filePath))
{
Bitmap myBitmap = BitmapFactory.DecodeFile(filePath);
imageview.SetImageBitmap(myBitmap);
}