Swift:如何录制音频，然后反向播放？

Swift是一种流行的编程语言，常用于iOS和macOS应用程序的开发。在Swift中，可以使用AVFoundation框架来录制音频并进行反向播放。

录制音频的步骤如下：

导入AVFoundation框架：在Swift文件的顶部添加import AVFoundation语句。
创建音频会话：使用AVAudioSession类创建一个音频会话，设置会话的类别和模式。

let audioSession = AVAudioSession.sharedInstance()
do {
    try audioSession.setCategory(.playAndRecord, mode: .default)
    try audioSession.setActive(true)
} catch {
    print("Error setting up audio session: \(error.localizedDescription)")
}

创建音频录制器：使用AVAudioRecorder类创建一个音频录制器，指定录制的文件路径、格式和设置。

var audioRecorder: AVAudioRecorder?

func setupAudioRecorder() {
    let audioFilename = getDocumentsDirectory().appendingPathComponent("recording.wav")
    let settings = [
        AVFormatIDKey: kAudioFormatLinearPCM,
        AVSampleRateKey: 44100.0,
        AVNumberOfChannelsKey: 2,
        AVEncoderAudioQualityKey: AVAudioQuality.high.rawValue
    ]
    
    do {
        audioRecorder = try AVAudioRecorder(url: audioFilename, settings: settings)
        audioRecorder?.prepareToRecord()
    } catch {
        print("Error setting up audio recorder: \(error.localizedDescription)")
    }
}

func getDocumentsDirectory() -> URL {
    let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
    return paths[0]
}

开始录制音频：调用音频录制器的record()方法开始录制音频。

func startRecording() {
    audioRecorder?.record()
}

停止录制音频：调用音频录制器的stop()方法停止录制音频。

func stopRecording() {
    audioRecorder?.stop()
}

反向播放音频的步骤如下：

创建音频播放器：使用AVAudioPlayer类创建一个音频播放器，指定要播放的音频文件路径。

var audioPlayer: AVAudioPlayer?

func setupAudioPlayer() {
    let audioFilename = getDocumentsDirectory().appendingPathComponent("recording.wav")
    
    do {
        audioPlayer = try AVAudioPlayer(contentsOf: audioFilename)
        audioPlayer?.prepareToPlay()
    } catch {
        print("Error setting up audio player: \(error.localizedDescription)")
    }
}

反向播放音频：调用音频播放器的play()方法开始播放音频，设置音频播放器的rate属性为负值即可实现反向播放。

func playReversedAudio() {
    audioPlayer?.rate = -1.0
    audioPlayer?.play()
}

完整的示例代码如下：

import AVFoundation

class AudioRecorder {
    var audioRecorder: AVAudioRecorder?
    var audioPlayer: AVAudioPlayer?
    
    func setupAudioRecorder() {
        let audioSession = AVAudioSession.sharedInstance()
        do {
            try audioSession.setCategory(.playAndRecord, mode: .default)
            try audioSession.setActive(true)
        } catch {
            print("Error setting up audio session: \(error.localizedDescription)")
        }
        
        let audioFilename = getDocumentsDirectory().appendingPathComponent("recording.wav")
        let settings = [
            AVFormatIDKey: kAudioFormatLinearPCM,
            AVSampleRateKey: 44100.0,
            AVNumberOfChannelsKey: 2,
            AVEncoderAudioQualityKey: AVAudioQuality.high.rawValue
        ]
        
        do {
            audioRecorder = try AVAudioRecorder(url: audioFilename, settings: settings)
            audioRecorder?.prepareToRecord()
        } catch {
            print("Error setting up audio recorder: \(error.localizedDescription)")
        }
    }
    
    func startRecording() {
        audioRecorder?.record()
    }
    
    func stopRecording() {
        audioRecorder?.stop()
    }
    
    func setupAudioPlayer() {
        let audioFilename = getDocumentsDirectory().appendingPathComponent("recording.wav")
        
        do {
            audioPlayer = try AVAudioPlayer(contentsOf: audioFilename)
            audioPlayer?.prepareToPlay()
        } catch {
            print("Error setting up audio player: \(error.localizedDescription)")
        }
    }
    
    func playReversedAudio() {
        audioPlayer?.rate = -1.0
        audioPlayer?.play()
    }
    
    func getDocumentsDirectory() -> URL {
        let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
        return paths[0]
    }
}

使用示例代码：

let audioRecorder = AudioRecorder()
audioRecorder.setupAudioRecorder()
audioRecorder.startRecording()
// 等待一段时间后停止录制
audioRecorder.stopRecording()

audioRecorder.setupAudioPlayer()
audioRecorder.playReversedAudio()

这样就可以使用Swift录制音频并进行反向播放了。请注意，示例代码中的录制文件路径为应用程序的文档目录，可以根据实际需求进行修改。