Iphone上的滑块崩溃程序，但在模拟器上工作

Posted 2023-02-24

【中文标题】Iphone上的滑块崩溃程序，但在模拟器上工作

【英文标题】：Slider Crashes program on Iphone, but worked on simulator

【发布时间】：2017-08-03 22:58:26

【问题描述】：

我正在使用此代码来跟踪和更新滑块值，然后转换为字符串并显示在标签上。问题是，此代码在模拟器上工作，但在实际手机上崩溃。出现错误“在展开可选值时意外发现 nil”。我不知道是什么原因造成的，任何帮助将不胜感激。

func updateSlider()

    sliderBar.value = Float(CMTimeGetSeconds(self.audioPlayer.currentItem!.currentTime()))
    let currentTime = Int((CMTimeGetSeconds(self.audioPlayer.currentItem!.currentTime())))
    let duration = Int((CMTimeGetSeconds(self.audioPlayer.currentItem!.asset.duration)))
    //let total = currentTime - duration

    let minutes = currentTime/60
    let seconds = currentTime - minutes * 60

    let minutes2 = duration/60
    let seconds2 = duration - minutes2 * 60

    self.lblPastTime.text = NSString(format: " %02d:%02d / %02d:%02d  ",minutes2,seconds2, minutes,seconds) as String

【问题讨论】：

看起来该代码中唯一可能的 Optional 是 self.lblPastTime。我建议它可能为零。

@Michael 如果是这样，它不会在模拟器上也崩溃吗？

【参考方案1】：

避免强制展开变量是避免此类错误的好方法：

func updateSlider () 

    guard let currentItem = self.audioPlayer.currentItem else  return 
    sliderBar.value = Float(CMTimeGetSeconds(currentItem.currentTime()))
    let currentTime = Int((CMTimeGetSeconds(currentItem.currentTime())))
    let duration = Int((CMTimeGetSeconds(currentItem.asset.duration)))
    //let total = currentTime - duration

    let minutes = currentTime/60
    let seconds = currentTime - minutes * 60

    let minutes2 = duration/60
    let seconds2 = duration - minutes2 * 60

    self.lblPastTime.text = NSString(format: " %02d:%02d / %02d:%02d  ",minutes2,seconds2, minutes,seconds) as? String

使用guard let 我可以安全地解包变量，所以如果它是nil，函数就会返回。

【参考方案2】：

回答

必须使用 audioPlayer.currentTime()

而不是 audioPlayer.currentItem!.currentTime()

func updateSlider()

    sliderBar.value = Float(CMTimeGetSeconds(audioPlayer.currentTime()))

//sliderBar.value = Float(CMTimeGetSeconds(self.audioPlayer.currentItem!.currentTime()))

    let currentTime = Int((CMTimeGetSeconds(self.audioPlayer.currentItem!.currentTime())))
    let duration = Int((CMTimeGetSeconds(self.audioPlayer.currentItem!.asset.duration)))
    //let total = currentTime - duration

    let minutes = currentTime/60
    let seconds = currentTime - minutes * 60

    let minutes2 = duration/60
    let seconds2 = duration - minutes2 * 60

    self.lblPastTime.text = NSString(format: " %02d:%02d / %02d:%02d ",minutes2,seconds2, minutes,seconds) as String