Detect iPhone Volume Button Up Press?

Question

Is there a notification that I can listen to that will tell me when an iPhone's volume is turned up ?

I know about the AVSystemController_SystemVolumeDidChangeNotification , but it is essential that the notification only be triggered when the volume has been turned up, not up or down.

Secondly, how can I hide the translucent view that appears when the volume up button is pressed, showing the system's volume? Camera+ has implemented this.

Answer 1

If you want an event you can register a listener on the "outputVolume" property:

- (void)viewWillAppear:(BOOL)animated {

    AVAudioSession* audioSession = [AVAudioSession sharedInstance];

    [audioSession setActive:YES error:nil];
    [audioSession addObserver:self
                    forKeyPath:@"outputVolume"
                       options:0
                       context:nil];
}

-(void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {

    if ([keyPath isEqual:@"outputVolume"]) {
        NSLog(@"volume changed!");
    }
}

Answer 2

There is no documented way to to this, but you can use this workaround. Register for AVSystemController_SystemVolumeDidChangeNotification notification and add an MPVolumeView which will prevent the system volume view from showing up.

MPVolumeView *volumeView = [[MPVolumeView alloc] initWithFrame:CGRectMake(-100, 0, 10, 0)];
[volumeView sizeToFit];
[self.view addSubview:volumeView];

And don't forget to start an Audio Session

AudioSessionInitialize(NULL, NULL, NULL, NULL);
AudioSessionSetActive(true);

In This case, the MPVolumeView is hidden from the user.

As for checking if volume up or down was pressed, just grab the current application's volume

float volumeLevel = [[MPMusicPlayerController applicationMusicPlayer] volume];  

and compare it with new volume after the button was pressed in notification callback

If you don't want to do it by yourself, there's a drop-in class available in github

https://github.com/blladnar/RBVolumeButtons

Answer 3

I solved this problem by adding own target/action for UISlider placed inside MPVolumeView . So it's possible to catch volume change events and determine what button was pressed. Here's github repo with implementation of this approach. It works fine with iOS 7 and above, no deprecation warnings and no rejection from Apple.

Answer 4

In order to distinguish volume action: INSTEAD OF (in observeValue guard)

temp != 0.5

USE for only volume up

temp > 0.5

and only detect volume down:

temp < 0.5 

This solution below will print if either volume up or down are pressed.

import AVFoundation
import MediaPlayer

override func viewDidLoad() {
  super.viewDidLoad()
  let volumeView = MPVolumeView(frame: CGRect.zero)
  for subview in volumeView.subviews {
    if let button = subview as? UIButton {
      button.setImage(nil, for: .normal)
      button.isEnabled = false
      button.sizeToFit()
    }
  }
  UIApplication.shared.windows.first?.addSubview(volumeView)
  UIApplication.shared.windows.first?.sendSubview(toBack: volumeView)
}

override func viewWillAppear(_ animated: Bool) {
  super.viewWillAppear(animated)
  AVAudioSession.sharedInstance().addObserver(self, forKeyPath: "outputVolume", options: NSKeyValueObservingOptions.new, context: nil)
  do { try AVAudioSession.sharedInstance().setActive(true) }
  catch { debugPrint("\(error)") }   
}

override func viewDidDisappear(_ animated: Bool) {
  super.viewDidDisappear(animated)
  AVAudioSession.sharedInstance().removeObserver(self, forKeyPath: "outputVolume")
  do { try AVAudioSession.sharedInstance().setActive(false) } 
  catch { debugPrint("\(error)") }
}

override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
  guard let key = keyPath else { return }
  switch key {
    case "outputVolume":
      guard let dict = change, let temp = dict[NSKeyValueChangeKey.newKey] as? Float, temp != 0.5 else { return }
      let systemSlider = MPVolumeView().subviews.first { (aView) -> Bool in
        return NSStringFromClass(aView.classForCoder) == "MPVolumeSlider" ? true : false
      } as? UISlider
      systemSlider?.setValue(0.5, animated: false)
      guard systemSlider != nil else { return }
      debugPrint("Either volume button tapped.")
    default:
      break
  } 
}