Swift 基础之：监听音量变化

发表于 更新于 分类于 阅读次数： Disqus：
Swift 基础之：监听音量变化。

1、需要用到的库：

1
import MediaPlayer

2、重写 viewDidAppear 方法，添加监听事件：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    
    // 必须
    do{
        try AVAudioSession.sharedInstance().setActive(true)
    }catch let error as NSError{
        print("\(error)")
    }
    
    // 隐藏音量HUD(也可以不隐藏)
    let volumeView = MPVolumeView(frame: .zero)
    volumeView.clipsToBounds = true
    view.addSubview(volumeView)
    
    // 添加监听
    NotificationCenter.default.addObserver(self, selector: #selector(self.changeVolumeSlider), name: NSNotification.Name(rawValue: "AVSystemController_SystemVolumeDidChangeNotification"), object: nil)
    UIApplication.shared.beginReceivingRemoteControlEvents()
}

3、实现监听事件：

1
2
3
4
5
@objc func changeVolumeSlider(notifi: NSNotification) {
    // do something
    let volume = notifi.userInfo!["AVSystemController_AudioVolumeNotificationParameter"] as! Float
    print(volume)
}

4、重写 viewDidDisappear 方法，取消监听：

1
2
3
4
5
6
7
8
9
10
11
override func viewDidDisappear(_ animated: Bool) {
    super.viewDidDisappear(animated)
    
    do{
        try AVAudioSession.sharedInstance().setActive(false)
    }catch let error as NSError{
        print("\(error)")
    }
    NotificationCenter.default.removeObserver(self, name: NSNotification.Name(rawValue: "AVSystemController_SystemVolumeDidChangeNotification"), object:nil)
    UIApplication.shared.endReceivingRemoteControlEvents()
}