Question

我正在尝试使用AVFoundation创建视频录制，我将此项目用作我的标准项目。 https://github.com/ThatCSharpGuy/Forms-FullCameraPage

现在我正在尝试使用AVFoundation构建一个启动/停止录制功能，但我遇到了困难，因为我在使用AVCaptureFileOutputRecordingDelegate创建新实例时遇到了问题。项目无法运行，因为我收到错误消息：Cannot create an instance of the abstract class or interface "AVFoundation.AVCaptureFileOutputRecordingDelegate"。

我发现了一个经历同样问题的帖子https://forums.xamarin.com/discussion/33925/avcapturefileoutputrecordingdelegate-compile-error但是找不到解决方案。

下面你可以看到我的代码，我已经评论了每一步。

Boolean weAreRecording;

public override async void ViewDidLoad()
    {
        base.ViewDidLoad();
        SetupLiveCameraStream();
        SetupEventHandlers();
        weAreRecording = false; 
    }

在我的SetupLiveCameraStream内部我另外添加（我链接的项目在此函数中包含其余代码）：

Console.WriteLine("Configuring output");
output = new AVCaptureMovieFileOutput();

long totalSeconds = 10000;
Int32 preferredTimeScale = 30;
CMTime maxDuration = new CMTime(totalSeconds, preferredTimeScale);
output.MinFreeDiskSpaceLimit = 1024 * 1024;
output.MaxRecordedDuration = maxDuration;

    if (captureSession.CanAddOutput(output))
    {
        captureSession.AddOutput(output);
    }

    captureSession.SessionPreset = AVCaptureSession.PresetMedium;

......还有：

var mic = AVCaptureDevice.DefaultDeviceWithMediaType(AVMediaType.Audio);
var micInput = AVCaptureDeviceInput.FromDevice(mic);
captureSession.AddInput(micInput);

然后我设置了事件处理程序。

private void SetupEventHandlers()
    {
        takeVideoButton.TouchUpInside += startStopPushed; 
    }

这是我在下面发生编译错误的开始/停止录制功能。我在上面提到的错误消息new AVCaptureFileOutputRecordingDelegate中创建Cannot create an instance of the abstract class or interface "AVFoundation.AVCaptureFileOutputRecordingDelegate"时遇到了问题，我在代码中已经注释了您可以找到的内容：

    AVCaptureMovieFileOutput output;

    private void startStopPushed (object sender, EventArgs ea)
    {

        if (!weAreRecording)
        {
            System.Diagnostics.Debug.WriteLine("start recording");
            var documents = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
            var library = System.IO.Path.Combine(documents, "..", "Library");
            var urlpath = System.IO.Path.Combine(library, "sweetMovieFilm.mov");

            NSUrl url = new NSUrl(urlpath, false);

            NSFileManager manager = new NSFileManager();
            NSError error = new NSError();

            if (manager.FileExists(urlpath))
            {
                Console.WriteLine("Deleting File");
                manager.Remove(urlpath, out error);
                Console.WriteLine("Deleted File");
            }



            AVCaptureFileOutputRecordingDelegate avDel= new AVCaptureFileOutputRecordingDelegate (); //Error message here: Cannot create an instance of the abstract class or interface `AVFoundation.AVCaptureFileOutputRecordingDelegate`
            output.StartRecordingToOutputFile(url, avDel);
            Console.WriteLine(urlpath);
            weAreRecording = true;

        }

        //we were already recording.  Stop recording
        else {

            output.StopRecording();

            System.Diagnostics.Debug.WriteLine("stopped recording");

            weAreRecording = false;


        }
    }

所以我的问题是如何解决这个AVCaptureFileOutputRecordingDelegate问题？

Answer 1

那是因为AVCaptureFileOutputRecordingDelegat具有抽象函数FinishedRecording。你不能创建具有抽象的类的实例。您需要创建AVCaptureFileOutputRecordingDelegat的子类并在使用之前实现抽象方法。

像这样创建子类：

public class myAvCaptureFileOutPutRecordingDelegate : AVCaptureFileOutputRecordingDelegat
    {
        public override void FinishedRecording(AVCaptureFileOutput captureOutput, Foundation.NSUrl outputFileUrl, Foundation.NSObject[] connections, Foundation.NSError error)
        {
            //You can use captureOutput and outputFileUrl here.. 
            //throw new NotImplementedException();
        }


    }

现在，创建此类的实例：

 AVCaptureFileOutputRecordingDelegate avDel= new myAvCaptureFileOutPutRecordingDelegate();

尝试在带有AVFoundation的Xamarin Forms iOS中实现视频录制时AVCaptureFileOutputRecordingDelegate编译错误

1 个答案: