Plugin.Media在Prism Xamarin表单上不起作用（TakePhotoAsync）

Question

我知道这个问题并不新鲜，但是我确实坚持了好几天，我需要您的支持。 我的问题是： 我无法使用Android的插件媒体在我的棱镜xamarin表单项目中拍照（尽管它可以从图库中选择图片）。 我得到的错误是：

无法获取XAM插件媒体站点的文件位置

我希望收到您的来信，并在此先感谢您的支持。

这是我的代码：

Android清单

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionCode="1" android:versionName="1.0" package="com.niternational.Hope" android:installLocation="auto">
    <uses-sdk android:minSdkVersion="21" android:targetSdkVersion="27" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.CAMERA" />
    <application android:label="Hope.Android" android:icon="@mipmap/ic_launcher">
        <provider android:name="android.support.v4.content.FileProvider" android:authorities="com.niternational.Hope.fileprovider" android:exported="false" android:grantUriPermissions="true">
            <meta-data android:name="android.support.FILE_PROVIDER_PATHS" android:resource="@xml/file_paths"></meta-data>
        </provider>
    </application>
</manifest>

资源xml文件夹上的file_paths文件

<?xml version="1.0" encoding="utf-8" ?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
  <external-path name="my_images" path="Pictures" />
  <external-files-path name="my_movies" path="Movies" />
</paths>

主要活动

[Activity(Label = "Hope", Icon = "@mipmap/ic_launcher", Theme = "@style/MainTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)]
    public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
    {
        protected override void OnCreate(Bundle bundle)
        {
            TabLayoutResource = Resource.Layout.Tabbar;
            ToolbarResource = Resource.Layout.Toolbar;

            base.OnCreate(bundle);

            global::Xamarin.Forms.Forms.Init(this, bundle);
            CrossCurrentActivity.Current.Init(this, bundle);
            LoadApplication(new App(new AndroidInitializer()));
        }
        public override void OnRequestPermissionsResult(int requestCode, string[] permissions, Android.Content.PM.Permission[] grantResults)
        {
            Plugin.Permissions.PermissionsImplementation.Current.OnRequestPermissionsResult(requestCode, permissions, grantResults);
        }
    }

    public class AndroidInitializer : IPlatformInitializer
    {
        public void RegisterTypes(IContainerRegistry container)
        {
            // Register any platform specific implementations
        }
    }

AssemblyInfo文件 我添加了：

[assembly: UsesFeature("android.hardware.camera", Required = false)]
[assembly: UsesFeature("android.hardware.camera.autofocus", Required = false)]

隐藏代码

 private async void TakeImage()
        {
            var actions = await Application.Current.MainPage.DisplayActionSheet("ActionSheet: Image?", "Cancel", null, "Take Picture", "From Gallery");
            switch (actions)
            {
                case "Take Picture":

                    await CrossMedia.Current.Initialize();
                    if (!CrossMedia.Current.IsCameraAvailable || !CrossMedia.Current.IsPickPhotoSupported)
                    {
                        var message = "No Camera available";
                        //DependencyService.Get<IMessage>().ShortAlert(message);
                        return;
                    }

                    var mediaOptions = new StoreCameraMediaOptions
                    {
                        Directory = "UploaDoc",
                        Name = $"{DateTime.UtcNow}.jpg",
                        SaveToAlbum = true,
                        CompressionQuality = 75,
                        CustomPhotoSize = 50,
                        PhotoSize = PhotoSize.MaxWidthHeight,
                        MaxWidthHeight = 2000,
                        DefaultCamera = CameraDevice.Front
                    };

                    // Take a photo of the business receipt.
                    var file = await CrossMedia.Current.TakePhotoAsync(mediaOptions);

                    if (file == null)
                        return;

                    image.Source = ImageSource.FromStream(() =>
                    {
                        var stream = file.GetStream();

                        return stream;
                    });
                    var memoryStream = new MemoryStream();
                    file.GetStream().CopyTo(memoryStream);
                    file.Dispose();
                    imgAsBytes = memoryStream.ToArray();
                    memoryStream.Dispose();

                    break;
                case "From Gallery":
                    if (!CrossMedia.Current.IsPickPhotoSupported)
                    {
                        var message = "Picking image is not supported";
                        //DependencyService.Get<IMessage>().ShortAlert(message);
                        return;
                    }
                    var files = await CrossMedia.Current.PickPhotoAsync();
                    if (files == null)
                        return;

                    image.Source = ImageSource.FromStream(() =>
                    {
                        var stream = files.GetStream();

                        return stream;
                    });
                    var ms = new MemoryStream();
                    files.GetStream().CopyTo(ms);
                    files.Dispose();
                    imgAsBytes = ms.ToArray();
                    ms.Dispose();
                    break;
            }