使用 Swift 在 iOS 中远程控制事件

Question

试图弄清楚如何读取 Apple 耳机的音量按钮以用作相机快门的触发器（就像 Apple 相机应用程序所做的那样）。

从 Remote Control Events、 Remote Control Received With Event 和 this git repo 的文档中，我拼凑出我可能需要一个 AVAudioPlayer 对象、.beginReceivingRemoteControlEvents() 和 remoteControlReceivedWithEvent，以及制作这个查看canBecomeFirstResponder()return true。

import UIKit
import AVFoundation

class ViewController: UIViewController, AVAudioPlayerDelegate {
    var player: AVAudioPlayer!
    override func viewDidLoad() {
        super.viewDidLoad()

        var session: AVAudioSession = AVAudioSession.sharedInstance()
        session.setActive(true, error: nil)
    }

    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        println("viewDidAppear worked...")
        self.becomeFirstResponder()
        UIApplication.sharedApplication().beginReceivingRemoteControlEvents()
    }

    override func canBecomeFirstResponder() -> Bool {
        return true
    }

    override func remoteControlReceivedWithEvent(event: UIEvent) {
        let rc = event.subtype
        println("does this work? \(rc.rawValue)")
        //takePicture()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

我希望在按下耳机上的音量按钮时收到"does this work"，但我只是看到它像平常一样调节耳机音量。所以我一定是错过了什么，也许是delegate 或AVSession？

Answer 1

我在r/swift 上交叉发布了这个，有人告诉我它可能需要播放音频（直接引用自文档）。

因此，虽然这不是理想的解决方案，但它适用于我自己的私人用途。

import UIKit
import AVFoundation
import MediaPlayer

class ViewController: UIViewController, AVAudioPlayerDelegate {
    var testPlayer: AVAudioPlayer? = nil

    func loadSound(filename: NSString) -> AVAudioPlayer {
        let url = NSBundle.mainBundle().URLForResource(filename as String, withExtension: "caf")
        var error: NSError? = nil
        let player = AVAudioPlayer(contentsOfURL: url, error: &error)
        if error != nil {
            println("Error loading \(url): \(error?.localizedDescription)")
        } else {
            player.prepareToPlay()
        }
        return player
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        self.testPlayer = self.loadSound("silence")
        self.testPlayer?.numberOfLoops = -1
        self.testPlayer?.play()
    }

    override func canBecomeFirstResponder() -> Bool {
        return true
    }

    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        self.becomeFirstResponder()
        UIApplication.sharedApplication().beginReceivingRemoteControlEvents()
    }

    override func remoteControlReceivedWithEvent(event: UIEvent) {
        let rc = event.subtype
        println("rc.rawValue: \(rc.rawValue)")
        // take photo
    }
}

我注意到在 Apple 的相机应用程序中，+/- 音量按钮触发相机，麦克风按钮暂停/播放在另一个应用程序中运行的任何音频，但在此实现中，音量按钮仍然控制音量（以及任何音频应用启动时已暂停）。

rc.rawValue: 103对应单击麦克风按钮，双击返回104，三次单击返回105，然后有时一次碰到一对返回108或@ 987654327@.

Answer 2

基于 Cody 的回答，但已于 2019 年更新（Swift 5）

import UIKit
import AVFoundation
import MediaPlayer

class ViewController: UIViewController, AVAudioPlayerDelegate {
    var myPlayer: AVAudioPlayer? = nil

    func loadSound(filename: NSString) -> AVAudioPlayer? {
        let url = Bundle.main.url(forResource: filename as String, withExtension: "mp3")
        do {
            let player = try AVAudioPlayer(contentsOf: url ?? URL(fileURLWithPath: ""))
            player.prepareToPlay()
            return player
        }
        catch {
            print("Error : \(error)")
            return nil
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        guard let testPlayer = loadSound(filename: "silence") else {
            print("Not able to load the sound")
            return
        }
        testPlayer.delegate = self
        testPlayer.volume = 0.8
        testPlayer.numberOfLoops = -1
        myPlayer = testPlayer
        myPlayer?.play()
    }


    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        self.becomeFirstResponder()
        UIApplication.shared.beginReceivingRemoteControlEvents()
    }

    override func remoteControlReceived(with event: UIEvent?) {
        let rc = event?.subtype
        print("rc.rawValue: \(rc?.rawValue)")
        // Do your thing
    }
}