swift 3：如何添加 UISlider？

Question

我有ViewController 和AVAudioPlayer。现在我有了这个代码

import UIKit
import AVFoundation

var audioPlayer = AVAudioPlayer()

class ViewController: UIViewController {

@IBOutlet weak var slider: UISlider!
@IBOutlet weak var playButton: UIButton!
var index = 0
var timer: Timer?

override func viewDidLoad() {
    super.viewDidLoad()

    if index == 0{

       let url = Bundle.main.url(forResource: "1", withExtension: "mp3")!

        do {
            audioPlayer = try AVAudioPlayer(contentsOf: url)
            audioPlayer.prepareToPlay()
            //audioPlayer.play()
            //play(sender:AnyObject.self as AnyObject)

        } catch let error {
            print(error.localizedDescription)
        }
    }
}

@IBAction func slide(_ slider: UISlider) {
    audioPlayer.currentTime = TimeInterval(slider.value)
}

@IBAction func play(sender: AnyObject) {
    if !audioPlayer.isPlaying{
        audioPlayer.play()
        // **** The line below is the new line ****
        timer = Timer(timeInterval: 1.0, target: self, selector: #selector(self.updateSlider), userInfo: nil, repeats: true)
        RunLoop.main.add(timer!, forMode: .commonModes)
    } else {
        audioPlayer.pause()
        playButton.setImage(UIImage(named: "pause.png"), for: UIControlState.normal)
        timer?.invalidate()
    }
}

func updateSlider(_ timer: Timer) {
    slider.value = Float(audioPlayer.currentTime)
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
}
}

我想添加 UISlider 以更改通过音频文件的擦洗。怎么做？

Answer 1

首先，您必须从滑块添加一个新的 IBAction，以确保您的类在滑块值更改时得到通知（在此处查找“响应用户交互”：https://developer.apple.com/reference/uikit/uislider#2557863）

在此事件处理程序中，您必须设置音频当前时间

@IBAction func slide(_ slider: UISlider) {
    audioPlayer.currentTime = TimeInterval(slider.value)
}

为确保滑块根据当前时间更新其值，您必须在启动播放器时添加一个计时器，该计时器调用自定义方法来更新滑块值。

@IBAction func play(sender: AnyObject) {
    if !audioPlayer.isPlaying{
        audioPlayer.play()
        // **** The line below is the new line ****
        timer = Timer(timeInterval: 1.0, target: self, selector: #selector(self.updateSlider), userInfo: nil, repeats: true)
        RunLoop.main.add(timer, forMode: .commonModes)
    } else {
        audioPlayer.pause()
        playButton.setImage(UIImage(named: "pause.png"), for: UIControlState.normal)
        timer.invalidate()
    }
}

之后你必须创建更新滑块值的方法

func updateSlider(_ timer: Timer) {
    slider.value = Float(audioPlayer.currentTime)
}

然后你必须设置滑块的最大值

override func viewDidLoad() {
    super.viewDidLoad()

    if index == 0{

       let url = Bundle.main.url(forResource: "1", withExtension: "mp3")!

        do {
            audioPlayer = try AVAudioPlayer(contentsOf: url)
            audioPlayer.prepareToPlay()
            // **** These two lines below are new ****
            slider.maximumValue = Float(audioPlayer.duration)
            slider.value = 0.0
        } catch let error {
            print(error.localizedDescription)
        }
    }
}

最后你必须在你的 IBOutlets 下创建一个属性来保存计时器

var timer: Timer?