SystemVolumeDidChangeNotification永远不会在iOS 14上触发 [英] SystemVolumeDidChangeNotification never get triggered on iOS 14

问题描述

目标是监视音量更改事件及其值.遵循检测音量变化迅速的指南.

The goal is to monitor the volume change event and its value. Followed the guide at detect up volume change swift.

在iOS 14. *上，当我尝试观察音量变化事件时，似乎在音量变化后从未触发该事件.

On iOS 14.* when I try to observe volume change event, the event seems to never get triggered after volume change.

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)")
}

推荐答案

beginReceivingRemoteControlEvents首先需要调用.

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)
}

在视图消失后，不要忘记删除观察者.

Do not forget to remove the observer after the view disappeared.

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