Question

您好我尝试在我的xamarin表单上实现ImagePicker但是我的MainActivty OnActivityResult有问题，每当我选择图像时它都会收到此错误消息

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)

我的第一个问题是因为我的AzureB2c的结果代码被我的PicturePickerImplementation的结果代码替换了，因为当我尝试从我的OnActivityResult中删除此代码AuthenticationAgentContinuationHelper.SetAuthenticationAgentContinuationEventArgs(requestCode, resultCode, data);时，它将作为魅力，我的问题是如何解决这个冲突？这是我的完整代码

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);
            }
        }
    }

这是我的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;
        }
    }
}

任何修复我的问题的建议？谢谢修改经过一番观察，我注意到一些奇怪的行为会触发这个错误。我的错误只会在我成功登录之后出现，然后我关闭应用程序并从后台杀死它，并使我的选择器图像工作我应该做的是1.Make My App在后台运行2.Relogin再次，我可以再次使用图像选择器。有人遇到过这个问题吗？

Answer 1

我的第一个虽然关于这个问题是因为我的AzureB2c的结果代码被我的PicturePickerImplementation的结果代码取代，因为当我尝试删除此代码时，AuthenticationAgentContinuationHelper.SetAuthenticationAgentContinuationEventArgs（requestCode，resultCode，data）;从我的OnActivityResult它将作为魅力，我的问题是如何解决这个冲突？

当您致电OnActivityResult并致电PublicClientApplication.AcquireTokenAsync时，系统会触发

StartActivityForResult。因此，应根据requestCode：

分离两部分逻辑

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);
    }

尝试在Xamarin表单上实现ImagePicker时出错

1 个答案: