C# 沙马林形式->；System.MissingMethodException:找不到[Interface]的默认构造函数

我在Xamarin.Forms上使用依赖项服务时收到此错误。我已经看到了这个错误的答案，包括iOS和链接器。然而，我在Android上运行这个，链接器关闭了

它告诉我的构造函数在PCL中找不到接口的默认构造函数

我已经搜索和调试了几个小时了。可能导致此错误的原因有哪些？我非常确定我的DependencyService实现是正确的，所以我觉得它有些不同

这是我的相关代码

Android

[assembly: Xamarin.Forms.Dependency(typeof(TextRecognition))]
namespace DiabetesAPP.Droid
{
    [Preserve(AllMembers = true)]
    [Activity(Label = "TextRecognition", Theme = "@style/Theme.AppCompat.Light.NoActionBar", MainLauncher = true)]
    public class TextRecognition : AppCompatActivity, ISurfaceHolderCallback, IProcessor, ITextRecognition
    {
        private SurfaceView cameraView;
        private TextView textView;
        private CameraSource cameraSource;
        public string Resultados;
        private const int RequestCameraPermissionID = 1001;

        protected override void OnCreate(Bundle savedInstanceState)
        {

            base.OnCreate(savedInstanceState);

            SetContentView(Resource.Layout.Main);
            cameraView = FindViewById<SurfaceView>(Resource.Id.surface_view);
            textView = FindViewById<TextView>(Resource.Id.txtview);

            TextRecognizer textRecognizer = new TextRecognizer.Builder(ApplicationContext).Build();
            if (!textRecognizer.IsOperational)
            {
                Log.Error("Main Activity", "Detector dependencies are not yet available");
            }
            else
            {
                cameraSource = new CameraSource.Builder(ApplicationContext, textRecognizer)
                    .SetFacing(CameraFacing.Back)
                    .SetRequestedFps(2.0f)
                    .SetRequestedPreviewSize(1280, 1024)
                    .SetAutoFocusEnabled(true)
                    .Build();

                cameraView.Holder.AddCallback(this);
                 textRecognizer.SetProcessor(this);
            }

            Android.Widget.Button logonButton = FindViewById<Android.Widget.Button>(Resource.Id.button_send);
            logonButton.Click += LogonButton_Click;
        }

        public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
        {
            switch (requestCode)
            {
                case RequestCameraPermissionID:
                    {
                        if (grantResults[0] == Android.Content.PM.Permission.Granted)
                        {
                           cameraSource.Start(cameraView.Holder);
                        }
                    }
                    break;
            }
        }

        public void SurfaceChanged(ISurfaceHolder holder, [GeneratedEnum] Format format, int width, int height)
        {

        }

        public void SurfaceCreated(ISurfaceHolder holder)
        {
            if (ActivityCompat.CheckSelfPermission(ApplicationContext, Manifest.Permission.Camera) != Android.Content.PM.Permission.Granted)
            {
                ActivityCompat.RequestPermissions(this, new string[]
                {
                    Android.Manifest.Permission.Camera
                }, RequestCameraPermissionID);
                return;
            }
           cameraSource.Start(cameraView.Holder);
        }

        public void SurfaceDestroyed(ISurfaceHolder holder)
        {
            cameraSource.Stop();
        }

        public void ReceiveDetections(Detections detections)
        {
            SparseArray items = detections.DetectedItems;
            if (items.Size() != 0)
            {
                textView.Post(() =>
                {
                    StringBuilder strBuilder = new StringBuilder();
                    for (int i = 0; i < items.Size(); i++)
                    {
                        strBuilder.Append(((TextBlock)items.ValueAt(i)).Value);
                        strBuilder.Append("\n");
                    }
                    textView.Text = strBuilder.ToString();
                    Resultados = strBuilder.ToString();
                });
            }
        }

        private void LogonButton_Click(object sender, EventArgs e)
        {
            //Toast.MakeText(this, "Hello from " + Resultados, ToastLength.Long).Show();
            //Intent data = new Intent(this, typeof(TextRecognition));
            //SetResult(Result.Ok, data);
            //// MessagingCenter.Send((DiabetesAPP.App)Xamarin.Forms.Application.Current, "OpenPage", "You send message:" + Resultados);
            //// MessagingCenter.Send<DiabetesAPP.App, string>(DiabetesAPP.App.Current as App, "OpenPage", "You send message:" + Resultados);
            //MessagingCenter.Send((DiabetesAPP.App)Xamarin.Forms.Application.Current, "OpenPage", "You send message:" + Resultados);
            Toast.MakeText(this, Resultados, ToastLength.Short).Show();

            MessagingCenter.Send<App, string>(App.Current as App, "OpenPage", "You send message:" + Resultados);


            Finish();
        }

        public void Release()
        {

        }

        public void LaunchActivityInAndroid()
        {
            Activity activity = Forms.Context as Activity;
            var intent = new Intent(Forms.Context, typeof(TextRecognition));
            activity.StartActivity(intent);
        }

        protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
        {
            base.OnActivityResult(requestCode, resultCode, data);


            switch (resultCode)
            {
                case Result.Ok:
                    break;
            }

            Finish();
        }



        public interface ITextRecognition
        {

        }

//Update code - 16/09/2020
        public TextRecognition()
        {

        }


    }
}

[assembly:Xamarin.Forms.Dependency（typeof（TextRecognition））]
名称空间DiabetesAPP.Droid
{
[保留（所有成员=真）]
[活动（Label=“TextRecognition”，Theme=“@style/Theme.AppCompat.Light.NoActionBar”，MainLauncher=true）]
公共类文本识别：AppCompativeActivity、ISurfaceHolderCallback、IProcessor、ITextRecognition
{
私人水面观景摄像师；
私有文本视图文本视图；
私人摄像源摄像源；
公共字符串Resultados；
private const int RequestCameraPermissionID=1001；
创建时受保护的覆盖无效（Bundle savedInstanceState）
{
base.OnCreate（savedInstanceState）；
SetContentView（Resource.Layout.Main）；
cameraView=findviewbyd（Resource.Id.surface\u视图）；
textView=FindViewById（Resource.Id.txtview）；
TextRecognizer TextRecognizer=新的TextRecognizer.Builder（ApplicationContext.Build（）；
如果（！textRecognitor.IsOperational）
{
Log.Error（“主要活动”，“探测器依赖项尚不可用”）；
}
其他的
{
cameraSource=新建cameraSource.Builder（ApplicationContext，TextRecognitor）
.SetFacing（摄像机定位。背面）
.SetRequestedFps（2.0f）
.SetRequestedPreviewSize（12801024）
.SetAutoFocusEnabled（真）
.Build（）；
cameraView.Holder.AddCallback（this）；
textRecognizer.SetProcessor（此）；
}
Android.Widget.Button logonButton=findviewbyd（Resource.Id.Button\u send）；
logonButton.Click+=logonButton\u Click；
}
public override void OnRequestPermissionsResult（int-requestCode，string[]permissions，[GeneratedEnum]Android.Content.PM.Permission[]grantResults）
{
开关（请求代码）
{
案例请求CameraPermissionID:
{
if（grantResults[0]==Android.Content.PM.Permission.grated）
{
cameraSource.Start（cameraView.Holder）；
}
}
打破
}
}
public void surfacechange（ISurfaceHolder持有人，[GeneratedEnum]格式，整数宽度，整数高度）
{
}
已处理的公共空隙表面（ISurfaceHolder）
{
if（ActivityCompat.CheckSelfPermission（ApplicationContext，Manifest.Permission.Camera）！=Android.Content.PM.Permission.grated）
{
ActivityCompat.RequestPermissions（此，新字符串[]）
{
Android.Manifest.Permission.Camera
}，RequestCameraPermissionID）；
返回；
}
cameraSource.Start（cameraView.Holder）；
}
公共空隙表面置换（ISurfaceHolder）
{
cameraSource.Stop（）；
}
公共无效接收检测（检测）
{
SparseArray项目=检测。检测项目；
如果（items.Size（）！=0）
{
textView.Post（（）=>
{
StringBuilder strBuilder=新StringBuilder（）；
对于（int i=0；i[assembly: Xamarin.Forms.Dependency(typeof(ITextRecognition))]
namespace DiabetesAPP.Views.FoodMenu
{

    [XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class FoodMenu : ContentPage
    {
        public FoodMenu()
        {
            InitializeComponent();
        }

        async void Food_ManualEntry(object sender, EventArgs e)
        {
            await Navigation.PushAsync(new SearchFood());
        }

        public void Food_CameraEntry(object sender, EventArgs e)
        {
            Xamarin.Forms.DependencyService.Register<ITextRecognition>();
            DependencyService.Get<ITextRecognition>().LaunchActivityInAndroid();

        }

        public interface ITextRecognition
        {
            void LaunchActivityInAndroid();
        }

    }
}

namespace App384
{
    [XamlCompilation(XamlCompilationOptions.Compile)]
    public partial class FoodMenu : ContentPage
    {
        public FoodMenu()
        {
            InitializeComponent();
        }

        public void Food_CameraEntry(object sender, EventArgs e)
        {
            Xamarin.Forms.DependencyService.Register<ITextRecognition>();
            DependencyService.Get<ITextRecognition>().LaunchActivityInAndroid();

        }
    }

    public interface ITextRecognition
    {
        void LaunchActivityInAndroid();
    }
}

[assembly: Xamarin.Forms.Dependency(typeof(TextRecognition))]
namespace App384.Droid
{
    [Preserve(AllMembers = true)]
    [Activity(Label = "TextRecognition", Theme = "@style/Theme.AppCompat.Light.NoActionBar", MainLauncher = true)]
    public class TextRecognition : AppCompatActivity, ITextRecognition
    {
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
        }

        public void LaunchActivityInAndroid()
        {
            Console.WriteLine("LaunchActivityInAndroid");
        }

    }
}