Error when Try to Implement ImagePicker On Xamarin Forms

Question

Hi I tried to implement ImagePicker on my xamarin forms but i have issues on my MainActivty OnActivityResult, whenever i choose the image it will got this error message

android.runtime.JavaProxyThrowable: System.NullReferenceException: Object reference not set to an instance of an object
  at Microsoft.Identity.Client.WebUI.SetAuthorizationResult (Microsoft.Identity.Client.Internal.AuthorizationResult authorizationResultInput) [0x00006] in <df3bbcf06538443e9963d82dd707b6fa>:0 
  at Microsoft.Identity.Client.AuthenticationAgentContinuationHelper.SetAuthenticationAgentContinuationEventArgs (System.Int32 requestCode, Android.App.Result resultCode, Android.Content.Intent data) [0x00032] in <df3bbcf06538443e9963d82dd707b6fa>:0 
  at KGVC.Droid.MainActivity.OnActivityResult (System.Int32 requestCode, Android.App.Result resultCode, Android.Content.Intent data) [0x0000b] in <e83f90a066ab4f6c95402217456751e2>:0 
  at Android.Support.V4.App.FragmentActivity.n_OnActivityResult_IILandroid_content_Intent_ (System.IntPtr jnienv, System.IntPtr native__this, System.Int32 requestCode, System.Int32 native_resultCode, System.IntPtr native_data) [0x00014] in <7a2a36256f1648ecbd0c15a75bc5a349>:0 
  at (wrapper dynamic-method) System.Object:409b2b82-0807-4c59-b475-d61eb538da78 (intptr,intptr,int,int,intptr)
    at md5926298ec23f3b6e841a6fb18f139a084.MainActivity.n_onActivityResult(Native Method)
    at md5926298ec23f3b6e841a6fb18f139a084.MainActivity.onActivityResult(MainActivity.java:39)
    at android.app.Activity.dispatchActivityResult(Activity.java:6533)
    at android.app.ActivityThread.deliverResults(ActivityThread.java:3919)
    at android.app.ActivityThread.handleSendResult(ActivityThread.java:3966)
    at android.app.ActivityThread.access$1500(ActivityThread.java:180)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1545)
    at android.os.Handler.dispatchMessage(Handler.java:111)
    at android.os.Looper.loop(Looper.java:207)
    at android.app.ActivityThread.main(ActivityThread.java:5795)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:907)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:768)

my first though about this problem is because resultcode for my AzureB2c got replaced by resultcode from my PicturePickerImplementation, its because when i try to remove this code AuthenticationAgentContinuationHelper.SetAuthenticationAgentContinuationEventArgs(requestCode, resultCode, data); from my OnActivityResult it will works as charm, my question is how to fix this conflict ? here is my full code

public static readonly int PickImageId = 1000;

public TaskCompletionSource<Stream> PickImageTaskCompletionSource { set; get; }
protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
    {
        base.OnActivityResult(requestCode, resultCode, data);
        AuthenticationAgentContinuationHelper.SetAuthenticationAgentContinuationEventArgs(requestCode, resultCode, data);

        if (requestCode == PickImageId)
        {
            if ((resultCode == Result.Ok) && (data != null))
            {
                Android.Net.Uri uri = data.Data;
                Stream stream = ContentResolver.OpenInputStream(uri);

                // Set the Stream as the completion of the Task
                PickImageTaskCompletionSource.SetResult(stream);
            }
            else
            {
                PickImageTaskCompletionSource.SetResult(null);
            }
        }
    }

here is my DependencyService

using System;
using System.IO;
using System.Threading.Tasks;

using Android.Content;

using Xamarin.Forms;

using KGVC.Droid;
using KGVC.Interfaces;

[assembly: Dependency(typeof(PicturePickerImplementation))]
namespace KGVC.Droid
{
    public class PicturePickerImplementation : IPicturePicker
    {
        public Task<Stream> GetImageStreamAsync()
        {
            // Define the Intent for getting images
            Intent data = new Intent();
            data.SetType("image/*");
            data.SetAction(Intent.ActionGetContent);

            // Get the MainActivity instance
            MainActivity activity = Forms.Context as MainActivity;

            // Start the picture-picker activity (resumes in MainActivity.cs)
            activity.StartActivityForResult(
                Intent.CreateChooser(data, "Select Picture"),
                MainActivity.PickImageId);

            // Save the TaskCompletionSource object as a MainActivity property
            activity.PickImageTaskCompletionSource = new TaskCompletionSource<Stream>();

            // Return Task object
            return activity.PickImageTaskCompletionSource.Task;
        }
    }
}

any suggestion to fix my problem ? thanks EDIT: after a little observation, i notice some strange behavior that trigger this error. My error will only apears after i succesfull login and then i'm close the application and kill it from background, and to make my picker image work what should i do is 1.Make My App run on background 2.Relogin Again and i can use image picker again. Anyone has experience this issue ?

Check to see if any of the parameters passed to AuthenticationAgentContinuationHelper.SetAuthenticationAgentContinuationEventArgs() are null — sme
– sme, Commented Feb 7, 2018 at 6:33
@sme requestcode = 1000, resultcode = Android.App.Result.Canceled, data = null — Theodorus Agum Gumilang
– Theodorus Agum Gumilang, Commented Feb 7, 2018 at 7:14
It may be because data is null; Perhaps it requires the value to be non-null. Do a null check on data, and only call it if it is non-null (though I'll admin I'm not sure exactly what the function is doing) — sme
– sme, Commented Feb 7, 2018 at 7:17
@sme hmm as i expected , i tried to see the parameter after i login and the parameter totaly different with when i click the pick image , so when use this dependency service the parameter will be replaced from my dependency service parameter, hmm can you suggest me the code i should change so i dont have to change the paremeter? this code i got from developer.Xamarin, — Theodorus Agum Gumilang
– Theodorus Agum Gumilang, Commented Feb 7, 2018 at 7:27
my paremter when im not using the dependency service (this paremter i got from microsoft.identity.client / azure b2c) requestcode = 0 , resultcoded= Android.App.Result.Ok , data = {intent{act=return(has extras)}} — Theodorus Agum Gumilang
– Theodorus Agum Gumilang, Commented Feb 7, 2018 at 7:29

Elvis Xia - MSFT · Accepted Answer · 2018-02-08 02:02:28Z

my first though about this problem is because resultcode for my AzureB2c got replaced by resultcode from my PicturePickerImplementation, its because when i try to remove this code AuthenticationAgentContinuationHelper.SetAuthenticationAgentContinuationEventArgs(requestCode, resultCode, data); from my OnActivityResult it will works as charm, my question is how to fix this conflict ?

OnActivityResult will be triggered when you call PublicClientApplication.AcquireTokenAsync and when you call StartActivityForResult. So the two parts logics should be separated according to the requestCode:

if (requestCode == PickImageId)
    {
        if ((resultCode == Result.Ok) && (data != null))
        {
            Android.Net.Uri uri = data.Data;
            Stream stream = ContentResolver.OpenInputStream(uri);

            // Set the Stream as the completion of the Task
            PickImageTaskCompletionSource.SetResult(stream);
        }
        else
        {
            PickImageTaskCompletionSource.SetResult(null);
        }
    }else
    {
      AuthenticationAgentContinuationHelper.SetAuthenticationAgentContinuationEventArgs(requestCode, resultCode, data);
    }

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