SystemVolumeDidChangeNotification永远不会在iOS 14上触发

编程问答 2022-06-05

问题描述

目标是监视音量更改事件及其值。遵循了detect up volume change swift上的指南。

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。

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)")
}

解决方法

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)
}

视图消失后，不要忘记删除观察者。

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