检测音量按钮按下

未调用音量按钮通知功能.

码:

func listenVolumeButton(){
    // Option #1
    NSNotificationCenter.defaultCenter().addObserver(self, selector: "volumeChanged:", name: "AVSystemController_SystemVolumeDidChangeNotification", object: nil)
    // Option #2
    var audioSession = AVAudioSession()
    audioSession.setActive(true, error: nil)
    audioSession.addObserver(self, forKeyPath: "volumeChanged", options: NSKeyValueObservingOptions.New, context: nil)
}

override func observeValueForKeyPath(keyPath: String, ofObject object: AnyObject, change: [NSObject : AnyObject], context: UnsafeMutablePointer) {
    if keyPath == "volumeChanged"{
        print("got in here")
    }
}

func volumeChanged(notification: NSNotification){
   print("got in here")
}

listenVolumeButton() 正在viewWillAppear中调用

"got in here"在任何一种情况下,代码都没有进入print语句.

我正在尝试两种不同的方法来实现它,两种方式都不起作用.

我跟着这个:检测iPhone音量按钮向上按？

使用第二种方法,键路径的值应该是"outputVolume".这是我们正在观察的财产.所以将代码更改为,

func listenVolumeButton(){

    let audioSession = AVAudioSession.sharedInstance()
    audioSession.setActive(true, error: nil)
    audioSession.addObserver(self, forKeyPath: "outputVolume",
        options: NSKeyValueObservingOptions.New, context: nil)
}

override func observeValueForKeyPath(keyPath: String, ofObject object: AnyObject,
    change: [NSObject : AnyObject], context: UnsafeMutablePointer) {
    if keyPath == "outputVolume"{
        print("got in here")
    }
}

上面的代码在Swift 3中不起作用,在这种情况下,试试这个:

func listenVolumeButton() {
   do {
    try audioSession.setActive(true)
   } catch {
    print("some error")
   }
   audioSession.addObserver(self, forKeyPath: "outputVolume", options: NSKeyValueObservingOptions.new, context: nil)
}

override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
  if keyPath == "outputVolume" {
    print("got in here")
  }
}