Xamarin Forms 在拍照时抛出 Plugin.Media.Abstractions.MediaPermissionException

Question

我正在尝试从 Xamarin Forms 应用程序的图库中捕获图像/拾取图像。我已经安装了 nuget 管理器 > Birdie.MediaPlugin。在单击注册页面中的按钮期间，会引发以下错误；

Plugin.Media.Abstractions.MediaPermissionException: <Timeout exceeded getting exception details 有人可以告诉我们应该在 Xamarin.Forms 应用程序的哪里添加权限吗？

// Register.xaml:

<Image x:Name="imageDisplay" />
<Button x:Name="uploadButton" 
                    Text="Upload Image" Clicked="UploadButton_Clicked"/>

// PlayerDetails.cs

public ImageSource Source { get; internal set; }

//Register.xaml.cs

PlayerDetails myDetails;

 public Register(PlayerDetails playD)
        {
            InitializeComponent();            
            BindingContext = myDetails;

        }

    private async void UploadButton_Clicked(object sender, EventArgs e)
    {
        //myDetails.Image = new Image();

        if (!CrossMedia.Current.IsCameraAvailable || !CrossMedia.Current.IsTakePhotoSupported)
        {
            await DisplayAlert("No Camera", ":( No camera avaialble.", "OK");
            return;
        }

        var status = await GetPermissions();

        if(status == true)
        {

            var file = await CrossMedia.Current.TakePhotoAsync(new StoreCameraMediaOptions
            {
                Directory = "Sample",
                Name = "flower1.jpg"
            });

            if (file == null)
                return;

            await DisplayAlert("File Location", file.Path, "OK");

            myDetails.Source = ImageSource.FromStream(() =>
            {
                var stream = file.GetStream();
                file.Dispose();
                return stream;
            });
        }
        else
        {
            await DisplayAlert("Permissions Denied", "Unable to take photos.", "OK");

            //On iOS you may want to send your user to the settings screen.
            if (Device.RuntimePlatform == Device.iOS)
                CrossPermissions.Current.OpenAppSettings();
        }

    }

//我已经将权限功能拆分如下；

public static async Task<bool> GetPermissions()
    {
        bool permissionsGranted = true;

        var permissionsStartList = new List<Permission>()
    {
        Permission.Location,
        Permission.LocationAlways,
        Permission.LocationWhenInUse,
        Permission.Storage,
        Permission.Camera
    };

        var permissionsNeededList = new List<Permission>();
        try
        {
            foreach (var permission in permissionsStartList)
            {
                var status = await CrossPermissions.Current.CheckPermissionStatusAsync(permission);
                if (status != PermissionStatus.Granted)
                {
                    permissionsNeededList.Add(permission);
                }
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine("Nice, exception! " + ex);
        }

        var results = await CrossPermissions.Current.RequestPermissionsAsync(permissionsNeededList.ToArray());

        try
        {
            foreach (var permission in permissionsNeededList)
            {
                var status = PermissionStatus.Unknown;
                //Best practice to always check that the key exists
                if (results.ContainsKey(permission))
                    status = results[permission];
                if (status == PermissionStatus.Granted || status == PermissionStatus.Unknown)
                {
                    permissionsGranted = true;
                }
                else
                {
                    permissionsGranted = false;
                    break;
                }
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine("Last, exception! " + ex);
        }
        return permissionsGranted;
    }

Answer 1

您也可以更新您的OnClick 事件代码以添加权限逻辑：

var cameraStatus = await CrossPermissions.Current.CheckPermissionStatusAsync<CameraPermission>();
var storageStatus = await CrossPermissions.Current.CheckPermissionStatusAsync<StoragePermission>();

if (cameraStatus != PermissionStatus.Granted || storageStatus != PermissionStatus.Granted)
{
    cameraStatus = await CrossPermissions.Current.RequestPermissionAsync<CameraPermission>();
    storageStatus = await CrossPermissions.Current.RequestPermissionAsync<StoragePermission>();
}

if (!CrossMedia.Current.IsCameraAvailable || !CrossMedia.Current.IsTakePhotoSupported)
{
    await DisplayAlert("No Camera", ":( No camera avaialble.", "OK");
    return;
}

if (cameraStatus == PermissionStatus.Granted && storageStatus == PermissionStatus.Granted)
{
     var file = await CrossMedia.Current.TakePhotoAsync(new StoreCameraMediaOptions
    {
        Directory = "Sample",
        Name = "flower1.jpg"
    });

    if (file == null)
    return;

    await DisplayAlert("File Location", file.Path, "OK");

    myDetails.Source = ImageSource.FromStream(() =>
    {
        var stream = file.GetStream();
        file.Dispose();
        return stream;
    });
}
else
{
    await DisplayAlert("Permissions Denied", "Unable to take photos.", "OK");

    //On iOS you may want to send your user to the settings screen.
    if (Device.RuntimePlatform == Device.iOS)
        CrossPermissions.Current.OpenAppSettings();
}

注意：它会变成一个很长的函数，所以我建议把它分解成不同的函数。