SystemVolumeDidChangeNotification 永远不会在 iOS 14 上触发

Question

另一个标题是“为什么 AVSystemController_AudioVolumeNotificationParameter 通知事件永远不会被触发？”

目标是监控音量变化事件及其值。按照的指南进行操作。

在 iOS 14.* 上，当我尝试观察音量变化事件时，该事件似乎永远不会在音量变化后触发。

import MediaPlayer

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    NotificationCenter.default.addObserver(self, selector: #selector(volumeChange(_:)), name: Notification.Name(rawValue: "AVSystemController_SystemVolumeDidChangeNotification"), object: nil)
}

@objc func volumeChange(_ notification: NSNotification) {
    let userInfo = notification.userInfo!
    let volume = userInfo["AVSystemController_AudioVolumeNotificationParameter"] as! Double

    print("volume:\(volume)")
}

Answer 1

beginReceivingRemoteControlEvents需要先调用

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    UIApplication.shared.beginReceivingRemoteControlEvents() // <- THIS LINE

    NotificationCenter.default.addObserver(self, selector: #selector(volumeChange(_:)), name: Notification.Name(rawValue: "AVSystemController_SystemVolumeDidChangeNotification"), object: nil)
}

不要忘记在视图消失后移除观察者。

SystemVolumeDidChangeNotification 永远不会在 iOS 14 上触发

SystemVolumeDidChangeNotification never get triggered on iOS 14

nsnotificationcenter

ios

swift

ios14