如何让AVFoundation相机画面拉伸旋转适配横向UIView

要实现相机画面横向拉伸并适配你的LiveStreamView，需要从预览层的缩放模式、视频方向适配这两个核心点入手，以下是具体修改方案：

1. 完善LiveStreamView的配置 #

给LiveStreamView添加关联捕获会话的方法，并设置预览层的缩放与方向属性：

class LiveStreamView: UIView {
    
    override class var layerClass: AnyClass {
        return AVCaptureVideoPreviewLayer.self
    }
    
    var videoPreviewLayer: AVCaptureVideoPreviewLayer {
        return layer as! AVCaptureVideoPreviewLayer
    }
    
    // 添加关联捕获会话的方法
    func setup(with session: AVCaptureSession) {
        videoPreviewLayer.session = session
        // 设置画面拉伸模式：填充整个View，保持比例但会裁剪边缘
        videoPreviewLayer.videoGravity = .resizeAspectFill
        // 自动适配设备方向
        updateVideoOrientation()
    }
    
    // 更新视频方向以匹配界面方向
    func updateVideoOrientation() {
        guard let interfaceOrientation = UIApplication.shared.windows.first?.windowScene?.interfaceOrientation else { return }
        let videoOrientation: AVCaptureVideoOrientation
        switch interfaceOrientation {
        case .portrait:
            videoOrientation = .portrait
        case .portraitUpsideDown:
            videoOrientation = .portraitUpsideDown
        case .landscapeLeft:
            videoOrientation = .landscapeRight
        case .landscapeRight:
            videoOrientation = .landscapeLeft
        default:
            videoOrientation = .portrait
        }
        videoPreviewLayer.connection?.videoOrientation = videoOrientation
    }
}

2. 调整AVFoundationHandler的初始化流程 #

设置会话预设分辨率，并确保捕获会话正常启动：

import Foundation
import AVFoundation
import UIKit

class AVFoundationHandler {
    let captureSession = AVCaptureSession()
    
    init() {
        configure()
    }
    
    func configure() {
        // 设置会话预设为高清分辨率，可根据需求调整
        captureSession.sessionPreset = .hd1920x1080
        
        guard let videoDevice = AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .back),
              let videoDeviceInput = try? AVCaptureDeviceInput(device: videoDevice),
              captureSession.canAddInput(videoDeviceInput) else { return }
        
        captureSession.addInput(videoDeviceInput)
        // 启动捕获会话
        captureSession.startRunning()
    }
}

3. 在ViewController中完成关联 #

在视图控制器里完成AVFoundationHandler与LiveStreamView的绑定，并处理屏幕旋转时的方向更新：

class ViewController: UIViewController {
    let liveStreamView = LiveStreamView()
    let avHandler = AVFoundationHandler()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        setupLiveStreamView()
    }
    
    override func viewWillLayoutSubviews() {
        super.viewWillLayoutSubviews()
        // 屏幕旋转时同步更新视频方向
        liveStreamView.updateVideoOrientation()
    }
    
    private func setupLiveStreamView() {
        liveStreamView.frame = view.bounds
        liveStreamView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        view.addSubview(liveStreamView)
        // 关联捕获会话到预览层
        liveStreamView.setup(with: avHandler.captureSession)
    }
}

关键说明 #

• videoGravity设置：
  • *.resizeAspectFill*：画面填充整个View，保持比例但会裁剪超出部分，适合全屏无黑边场景
  • *.resizeAspect*：保持画面比例，View剩余区域留黑边，适合完整显示画面的场景
• 视频方向适配：通过监听界面方向，同步更新预览层的videoOrientation，确保画面旋转后显示正常
• 会话预设：根据实际需求选择合适的分辨率，高分辨率会带来更高的性能消耗

内容的提问来源于stack exchange，提问作者NumberOne