订阅 RxSwift 可观察对象<VideoCaptureOutput>未触发 onNext()

Question

我想使用RxSwift来处理从iPhone相机捕获的视频帧。我正在使用一个社区维护的项目，https://github.com/RxSwiftCommunity/RxAVFoundation，它桥接了AVFoundation(用于捕捉相机输出(和RxSwift。

每当新的视频帧被写入输出缓冲区时，我试图只打印一个伪日志语句。以下是我的ViewController。我配置AVCaptureSession，设置Rx链，然后启动会话。但是，.next情况下的print语句从未被触发。我联系了项目负责人。以下代码正确吗？以下是社区维护项目中AVCaptureSession类的Reactive扩展：https://github.com/RxSwiftCommunity/RxAVFoundation/blob/master/RxAVFoundation/AVCaptureSession%2BRx.swift

//  ViewController.swift
import UIKit
import AVFoundation
import RxSwift
class ViewController: UIViewController {
// capture session
private let session = AVCaptureSession()
private var videoDevice: AVCaptureDevice!

override func viewDidLoad() {
super.viewDidLoad()

self.videoDevice = AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .back)

session
.rx
.configure(captureDevice: videoDevice)

let disposeBag = DisposeBag()

let videoSettings = [(kCVPixelBufferPixelFormatTypeKey as NSString) : NSNumber(value: kCVPixelFormatType_32BGRA)] as [String : Any]
session
.rx
.videoCaptureOutput(settings: videoSettings)
.observeOn(MainScheduler.instance)
.subscribe { [unowned self] (event) in
switch event {
case .next(let captureOutput):
print("got a frame")
case .error(let error):
print("error: %@", "(error)")
case .completed:
break // never happens
}
}
.disposed(by: disposeBag)
session
.rx
.startRunning()
}
}

Answer 1

因为您已经在viewDidLoad内部本地定义了DisposeBag，一旦viewDidLoad完成，添加到包中的所有订阅都将被处理。

将您的DisposeBag声明为要修复的ViewController的实例变量：

...
// capture session
private let session = AVCaptureSession()
private var videoDevice: AVCaptureDevice!
private let disposeBag = DisposeBag()
override func viewDidLoad() {
super.viewDidLoad()
...

使用.debug()是捕捉这种事情的好方法，因为它将打印包括处置在内的所有事件，例如：

session
.rx
.videoCaptureOutput(settings: videoSettings)
.observeOn(MainScheduler.instance)
.debug("Video Capture Output Observable:")
.subscribe { [unowned self] (event) in
switch event {
case .next(let captureOutput):
print("got a frame")
case .error(let error):
print("error: %@", "(error)")
case .completed:
break // never happens
}
}
.disposed(by: disposeBag)