AVCaptureVideoPreviewLayer 未填满屏幕

使用AVCaptureVideoPreviewLayer可以在iOS应用中实现实时相机预览功能。但有时候，我们可能会遇到一个问题：预览层未能填满屏幕。在本文中，我将向大家介绍如何解决这个问题，并提供一些示例代码来帮助大家实现自己的相机预览。

swift
import UIKit
import AVFoundation
class ViewController: UIViewController {
    var captureSession: AVCaptureSession?
    var previewLayer: AVCaptureVideoPreviewLayer?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建捕捉会话
        captureSession = AVCaptureSession()
        
        // 设置输入设备（例如摄像头）
        guard let videoCaptureDevice = AVCaptureDevice.default(for: .video) else { return }
        guard let videoInput = try? AVCaptureDeviceInput(device: videoCaptureDevice) else { return }
        captureSession?.addInput(videoInput)
        
        // 设置预览层
        previewLayer = AVCaptureVideoPreviewLayer(session: captureSession!)
        previewLayer?.videoGravity = AVLayerVideoGravity.resizeAspectFill
        previewLayer?.frame = view.layer.bounds
        view.layer.addSublayer(previewLayer!)
        
        // 启动捕捉会话
        captureSession?.startRunning()
    }
    
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        
        // 调整预览层的frame以适应屏幕旋转或尺寸变化
        previewLayer?.frame = view.layer.bounds
    }
}