iOS 无法使用 Xamarin 和 MvvmCross 拍照

Question

我正在开发一个 iOS 应用程序，它需要能够拍照（用来做一些事情）。

我将 Xamarin 与 MvvmCross 6.2.0 一起使用，并导入了 MvxPictureChooser 插件。

我已将 NSPhotoLibraryAddUsageDescription 添加到我的 Info.plist

...
<key>NSPhotoLibraryAddUsageDescription</key>
<string>This app needs to be able to save your expense attachments as images.</string>
<key>UIRequiresFullScreen</key>
<true/>
...

现在，当我尝试使用 ChoosePictureFromLibrary 时，一切顺利。

另一方面，如果我尝试使用 TakePicture(int, int, Action, Action)，我会得到一个包含错误的异常：NSInvalidArgumentException 原因：源类型 1 不可用

我的代码如下所示：

private void DoTakePictureCommand()
    {
        var picChooser = Mvx.IoCProvider.Resolve<IMvxPictureChooserTask>();
        try
        {
            picChooser.TakePicture(_envProvider.Environment.JpegSize, _envProvider.Environment.JpegQuality, (stream) =>
            {
                using (var ms = new MemoryStream())
                {
                    stream.CopyToAsync(ms);
                    ReceiptJpegData = ms.ToArray();

                    _log.Trace("Picture bytes: {0}", ReceiptJpegData.Length);

                    InvokeOnMainThread(ImageComplete);
                }
            }, () =>
            {

            });
        }
        catch (Exception e)
        {
            Debug.Write(e);
        }
    }

完整的错误在这里：

[0:] Foundation.MonoTouchException: Objective-C exception thrown. Name: NSInvalidArgumentException Reason: Source type 1 not available Native stack trace:

0 CoreFoundation 0x000000011c41429b __exceptionPreprocess + 331 1 libobjc.A.dylib 0x000000011d2e8735 objc_exception_throw + 48 2 UIKitCore 0x0000000126d03553 -[UIImagePickerController sourceType] + 0 3 xxxiOS 0x000000010ed801b9 xamarin_dyn_objc_msgSend + 217 4 ??? 0x0000000141e58257 0x0 + 5400527447

at ObjCRuntime.Runtime.ThrowNSException (System.IntPtr ns_exception) [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/ObjCRuntime/Runtime.cs:398

at ObjCRuntime.Runtime.throw_ns_exception (System.IntPtr exc) [0x00000] in /Users/builder/jenkins/workspace/xamarin-macios/xamarin-macios/runtime/Delegates.generated.cs:126

at (wrapper native-to-managed) ObjCRuntime.Runtime.throw_ns_exception(intptr) --- End of stack trace from previous location where exception was thrown --- at (wrapper managed-to-native) ObjCRuntime.Messaging.void_objc_msgSend_Int64(intptr,intptr,long) at UIKit.UIImagePickerController.set_SourceType (UIKit.UIImagePickerControllerSourceType value) [0x00015] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/UIKit/UIImagePickerController.g.cs:587 at MvvmCross.Plugin.PictureChooser.Platforms.Ios.MvxImagePickerTask.TakePicture (System.Int32 maxPixelDimension, System.Int32 percentQuality, System.Action`1[T] pictureAvailable, System.Action assumeCancelled) [0x00014] in <8539a731432e4b45b49dd5ca22de5afd>:0 at xxx.DoTakePictureCommand () [0x0000d] in C:\Users\xxxx\Documents\IdeaProjects\xxxx\xxxx\XXX.Core\ViewModels\AddExpenseViewModel.cs:447 0 CoreFoundation 0x000000011c41429b __exceptionPreprocess + 331 1 libobjc.A.dylib 0x000000011d2e8735 objc_exception_throw + 48 2 UIKitCore
0x0000000126d03553 -[UIImagePickerController sourceType] + 0 3
xxxiOS 0x000000010ed801b9 xamarin_dyn_objc_msgSend + 217 4 ???
0x0000000141e58257 0x0 + 5400527447 2018-09-27 23:15:03.294036+0200 xxxiOS[46563:4418172] 2018-09-27 11:15:03 [TRACE] (MvvmCross.Logging.MvxLog) iOSNavigation 2018-09-27 23:15:03.294886+0200 xxxiOS[46563:4418172] 2018-09-27 11:15:03 [TRACE] (MvvmCross.Logging.MvxLog) PresentationAttribute not found for AddExpenseView. Assuming animated Child presentation CalabashServer | XTC_SKIP_LPSERVER_TOKEN is not in the app environment CalabashServer | Will start LPServer with identifier: c36c12ce937d044d55d0c208f9d4502868233513

更新

我现在已经尝试将代码部署到我的 iPhone 7，它已更新为 iOS 12，但应用程序在尝试启动相机时立即崩溃。

我也尝试过对 int 值进行硬编码：

private void DoTakePictureCommand()
{
    var picChooser = Mvx.IoCProvider.Resolve<IMvxPictureChooserTask>();
    try
    {
        picChooser.TakePicture(640, 50, (stream) =>
        {
            using (var ms = new MemoryStream())
            {
                stream.CopyToAsync(ms);
                ReceiptJpegData = ms.ToArray();

                _log.Trace("Picture bytes: {0}", ReceiptJpegData.Length);

                InvokeOnMainThread(ImageComplete);
            }
        }, () =>
        {

        });
    }
    catch (Exception e)
    {
        Debug.Write(e);
    }
}

但是结果是一样的

更新

我创建了一个小示例项目来复制该问题。该应用程序同时使用选择图片和拍照 - 仅选择图片作品。我已将其发布到 Github 上的 public 回购：PictureApp

Answer 1

您的问题与您传递的变量有关，请检查它是否不为空且其类型为int。

_envProvider.Environment.JpegSize, 
_envProvider.Environment.JpegQuality,

来自docs：

 void TakePicture(int maxPixelDimension, int percentQuality, Action<Stream> pictureAvailable,
                     Action assumeCancelled);

Answer 2

好的，搞定了！

我会在这里为其他运行关注此问题的应用程序开发新手留下一个解决方案。

问题的解决实际上很简单：我所要做的就是添加

<key>NSCameraUsageDescription</key>
<string></string>

至Info.plist。

直到我决定放弃 MvvmCross.Plugin.PictureChooser 并改用 Xam.Plugin.Media，我才收到一条可以理解的错误消息 - 基本上是这样的："you need to add NSCameraUsageDescription to Info.plist since iOS 10"

iOS 无法使用 Xamarin 和 MvvmCross 拍照

Unable to take picture with Xamarin and MvvmCross on iOS

visual-studio

ios

mvvmcross

xamarin