android media picker from Xamarin forms - xamarin

Question

I am writting an application with xamarin forms for iOS and Android.
I want to pick a photo from image gallery.
I have created an android specific static helper:
var i = new Intent();
i.SetType("*/*");
Forms.Context.StartActivity(Intent.CreateChooser(i, ""));
But i have no way to get the selected picture bytes.
I have seen on android tutorials i should implement onActivityResult, but i am not on an activity, this is a specific static call...
Thanks

Answer 1

Via a Form's dependency service:
Create your dependency interface (IMediaPicker)
Create a Activity subclass (MediaChooserActivityProxy) that will act as your Intent.ActionPick proxy
In your Xamarin.Android implementation of the IMediaPicker, use a AutoResetEvent to convert the Android StartActivityForResult / OnActivityResult callback to an await-able synchronous flow.
Dependency Service Interace:
public interface IMediaPicker
{
Task<string> ChooseAFileAsync();
}
Android Dependency Implementation:
public class MediaPicker : IMediaPicker
{
public static string filePickedPath;
public static AutoResetEvent waitHandle;
public async Task<string> ChooseAFileAsync()
{
waitHandle = new AutoResetEvent(false);
filePickedPath = "";
Forms.Context.StartActivity(typeof(MediaChooserActivityProxy));
await Task.Run(() => waitHandle.WaitOne());
return filePickedPath;
}
}
The Proxy/Pseudo Activity to capture OnActivityResult:
public class MediaChooserActivityProxy : Activity
{
const string mimeType = "image/*";
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
var intent = new Intent(Intent.ActionPick);
intent.SetType(mimeType);
if (Build.VERSION.SdkInt >= BuildVersionCodes.Kitkat)
{
intent.PutExtra(Intent.ExtraMimeTypes, mimeType);
}
StartActivityForResult(Intent.CreateChooser(intent, "StackOverflow"), 73);
}
protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
if (requestCode == 73)
if (resultCode == Result.Ok)
{
string[] filePathColumn = { MediaStore.Images.ImageColumns.Data };
var cursor = ContentResolver.Query(data.Data, filePathColumn, null, null, null);
cursor.MoveToFirst();
var colummIndex = cursor.GetColumnIndex(filePathColumn[0]);
MediaPicker.filePickedPath = cursor.GetString(colummIndex);
}
MediaPicker.waitHandle.Set();
Finish();
}
}
Note: This can be implemented on the MainActivity/FormsAppCompatActivity to avoid this additional Activity if desired...
Usage:
var filePath = await DependencyService.Get<IMediaPicker>().ChooseAFileAsync();
System.Diagnostics.Debug.WriteLine(filePath);