VolumeButtonEvents.swift

VolumeButtons.swift

//
//  VolumeButtons.swift
//  multitouch
//
//  Created by Mo Kari on 04.08.21.
//

import Foundation
import SwiftUI
import UIKit
import MediaPlayer
import AVFoundation


@objcMembers
class VolumeButtonsUIViewController: UIViewController  {
    
    var delegate: VolumeButtonsDelegate?
    
    var volumeSlider: UISlider = (MPVolumeView(frame: CGRect(x: 0, y: 0, width: 0, height: 0)).subviews.filter{NSStringFromClass($0.classForCoder) == "MPVolumeSlider"}.first) as! UISlider
    
    var audioSession = AVAudioSession()
    
    init(delegate: VolumeButtonsDelegate) {
        super.init(nibName: nil, bundle: nil)
        self.delegate = delegate
        volumeSlider.frame = .zero
        volumeSlider.clipsToBounds = true
        view.addSubview(self.volumeSlider)
        self.setup()
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func becomeFirstResponder() -> Bool {
        return true
    }
    
    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        
        guard let change = change else {
            return
        }
        
        guard let valAny = change[.newKey] else {
            return
        }
        
        let val = Double("\(valAny)")!
        
        guard let delegate = self.delegate else {
            return
        }
        
        // print(val)
        
        if val == 0.5 {
            return
        }
        
        if val < 0.5 {
            self.reset()
            delegate.volumeDownPressed()
        } else if val > 0.5 {
            self.reset()
            delegate.volumeUpPressed()
        }
    }
    
    
    func setup() {
        try! audioSession.setActive(true)
        audioSession.addObserver(self, forKeyPath: "outputVolume", options: NSKeyValueObservingOptions.new, context: nil)
        self.reset()
    }
    
    func reset() {
        // There seems to be a bug in the API. Took hours to get it. We need to use both the setter and the assignment.
        // However, pressing first up, then down turn by turn randomly still doesn't work. Probably, we would need to track the exact values and infer which value sequences would have caused which updates, but let's keep it simple and wrong for now.
        
        // TODO: Resetting costs times (100 to 200 ms I'd guess), thus reducing event frequency.
        // To increase frequency, we could not reset after every event but only e. g. < 0.1 or > 0.9.
        // Then however, we don't know direction from < or > 0.5 but rather must memorize the last value and see if it got smaller.
        volumeSlider.setValue(0.5, animated: false)
        volumeSlider.value = 0.5
    }
    
}

protocol VolumeButtonsDelegate {
    func volumeUpPressed()
    func volumeDownPressed()
}

struct VolumeButtonsView: UIViewControllerRepresentable {
    typealias UIViewControllerType = VolumeButtonsUIViewController
    
    var delegate: VolumeButtonsDelegate
    
    func makeUIViewController(context: Context) -> VolumeButtonsUIViewController {
        let volumeButtonsUIViewController = VolumeButtonsUIViewController(delegate: delegate)
        
        volumeButtonsUIViewController.delegate = delegate
        
        return volumeButtonsUIViewController
    }
    
    func updateUIViewController(_ uiViewController: VolumeButtonsUIViewController, context: Context) {
    }
}




class VolumeButtonsHandler: VolumeButtonsDelegate {
    func volumeUpPressed() {
        print("volume up pressed")
    }
    
    func volumeDownPressed() {
        print("volume down pressed")
    }
    
    
}

struct ContentView: View {
    
    var body: some View {
        // Make sure the VolumeButtonsView is not deallocated (e.g. by putting it in a switch here) 
        // If so, the UISlider would be deallocated resulting ina EXC_BAD_ACCESS exception when accesses again
        // If you wanna do this, rewrite the code to create the UISlider as a singleton in the ContentView directly and passing it into the VolumeButtonsView as a reference        
        VolumeButtonsView(delegate: VolumeButtonsHandler()).frame(width: 0, height: 0, alignment: .center)
    }
       
}