When I try to observe the progress of a NSBundleResourceRequest, observeValue(forKeyPath: object: change: context:) is not called for the .new observing option. Therefore, the NSProgressIndicator isn't updated. Here is the setup and code:
Setup:
Xcode 8.3.1
Deployment Target iOS 10.3
Device: iPad 4
Resource tags (368 KB) are located located in Download Only On Demand and consist of thumbnails displayed in a UICollectionView. Thumbnail images are located in MyCollection.xcassets. All IBOutlets are connected.
Images are correctly displayed in the collection view, but progress bar remains at zero.
Code:
final class MyCollectionVC: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate {
var myCollectionVCResourceRequest: NSBundleResourceRequest!
var myCollectionVCResourceRequestLoaded = false
static var myCollectionProgressObservingContext = UUID().uuidString
private let designThumbnailTags: Set<String> = ["Resource1", "Resource2", "Resource3"]
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
loadOnDemandResources()
}
func loadOnDemandResources() {
myCollectionVCResourceRequest = NSBundleResourceRequest(tags: designThumbnailTags)
myCollectionVCResourceRequest.progress.addObserver(self, forKeyPath: "fractionCompleted", options: [.new, .initial], context: &MyCollectionVC.myCollectionProgressObservingContext)
myCollectionVCResourceRequest.beginAccessingResources(completionHandler: { (error) in
print("Complete: \(self.myCollectionVCResourceRequest.progress.fractionCompleted)") // Prints Complete: 0.0
self.myCollectionVCResourceRequest.progress.removeObserver(self, forKeyPath: "fractionCompleted", context: &MyCollectionVC.myCollectionProgressObservingContext)
OperationQueue.main.addOperation({
guard error == nil else { self.handleOnDemandResourceError(error! as NSError); return }
self.myCollectionVCResourceRequestLoaded = true
self.updateViewsForOnDemandResourceAvailability()
self.fetchDesignThumbnailsWithOnDemandResourceTags(self.myCollectionVCResourceRequest) // Correctly creates Core Data Instances
})
})
}
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
if context == &MyCollectionVC.myCollectionProgressObservingContext {
OperationQueue.main.addOperation({
let progressObject = object as! Progress
self.progressView.progress = Float(progressObject.fractionCompleted)
print(Float(progressObject.fractionCompleted)) // Prints 0.0 as a result of including the .initial option
self.progressDetailLabel.text = progressObject.localizedDescription
})
}
else {
super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
}
}
}
Related
I‘ve read a lot solution provided by stackOverFlow and gitHub, and all of them doesn's work for me.I've tried the following tow way:
using audioSession
override func viewWillAppear(_ animated: Bool) {
let audioSession = AVAudioSession.sharedInstance()
do {
try audioSession.setActive(true, options: [])
} catch {
print("error")
}
// this print shows, got the current volume.
//but what I need is the notification of the change of volume
print("view will appear ,this volume is \(audioSession.outputVolume)")
audioSession.addObserver(self,
forKeyPath: "outputVolume",
options: [.new],
context: nil)
}
override class func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
if keyPath == "outputVolume"{
let audioSession = AVAudioSession.sharedInstance()
let volume = audioSession.outputVolume
//this print doesn't shows up
print("observed volume is \(volume)")
}
}
using notification
override func viewWillAppear(_ animated: Bool) {
NotificationCenter.default.addObserver(self, selector: #selector(observed(_:)), name: Notification.Name(rawValue: "AVSystemController_SystemVolumeDidChangeNotification"), object: nil)
}
#objc func observed(_ notification: Notification){
print("observed")
}
by the way, I'm using simulator(iPhone11, iOS13.1),Xcode version is 11.1
Try to use following:
import UIKit
import MediaPlayer
import AVFoundation
class ViewController: UIViewController {
private var audioLevel: Float = 0.0
deinit {
audioSession.removeObserver(self, forKeyPath: "outputVolume")
}
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
listenVolumeButton()
}
func listenVolumeButton() {
let audioSession = AVAudioSession.sharedInstance()
do {
try audioSession.setActive(true, options: [])
audioSession.addObserver(self, forKeyPath: "outputVolume",
options: NSKeyValueObservingOptions.new, context: nil)
audioLevel = audioSession.outputVolume
} catch {
print("Error")
}
}
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey: Any]?, context: UnsafeMutableRawPointer?) {
if keyPath == "outputVolume" {
let audioSession = AVAudioSession.sharedInstance()
if audioSession.outputVolume > audioLevel {
print("Hello")
audioLevel = audioSession.outputVolume
}
if audioSession.outputVolume < audioLevel {
print("Goodbye")
audioLevel = audioSession.outputVolume
}
if audioSession.outputVolume > 0.999 {
(MPVolumeView().subviews.filter { NSStringFromClass($0.classForCoder) == "MPVolumeSlider" }.first as? UISlider)?.setValue(0.9375, animated: false)
audioLevel = 0.9375
}
if audioSession.outputVolume < 0.001 {
(MPVolumeView().subviews.filter { NSStringFromClass($0.classForCoder) == "MPVolumeSlider"}.first as? UISlider)?.setValue(0.0625, animated: false)
audioLevel = 0.0625
}
}
}
}
Hope this will help you!
You need to ensure your app's audio session is active for this to work:
let audioSession = AVAudioSession.sharedInstance()
do {
try audioSession.setActive(true)
startObservingVolumeChanges()
} catch {
print(“Failed to activate audio session")
}
So if all you need is to query the current system volume:
let volume = audioSession.outputVolume
Or we can be notified of changes like so:
private struct Observation {
static let VolumeKey = "outputVolume"
static var Context = 0
}
func startObservingVolumeChanges() {
audioSession.addObserver(self, forKeyPath: Observation.VolumeKey, options:
[.Initial, .New], context: &Observation.Context)
}
override func observeValueForKeyPath(keyPath: String?, ofObject object:
AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>)
{
if context == &Observation.Context {
if keyPath == Observation.VolumeKey, let volume = (change?
[NSKeyValueChangeNewKey] as? NSNumber)?.floatValue {
// `volume` contains the new system output volume...
print("Volume: \(volume)")
}
} else {
super.observeValueForKeyPath(keyPath, ofObject: object, change: change,
context: context)
}
}
Don't forget to stop observing before being deallocated:
func stopObservingVolumeChanges() {
audioSession.removeObserver(self, forKeyPath: Observation.VolumeKey,
context: &Observation.Context)
}
I needed to write an iOS App which counts down by pressing the Up Volume Key on an iPhone or iPad. Therefore I used some advice from here to use AVAudioSession and observe the "outputVolume" key.
Here you can find the code of my ViewController:
import UIKit
import MediaPlayer
class ViewController: UIViewController, UIPopoverPresentationControllerDelegate {
#IBOutlet weak var chickenLabel: UILabel!
let audioSession = AVAudioSession.sharedInstance()
var maxHendl:Int = 100
var istHendl:Int = 100
var isVolumeChanged = false
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewWillAppear(_ animated: Bool) {
listenVolumeButton()
removeVolumeView()
}
func listenVolumeButton() {
do {
try audioSession.setActive(true)
}
catch {
print(error.localizedDescription)
}
audioSession.addObserver(self, forKeyPath: "outputVolume", options: .new, context: nil)
}
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
if keyPath == "outputVolume" {
if isVolumeChanged == false {
// Set Volume to 50%
MPVolumeView().subviews.filter{NSStringFromClass($0.classForCoder) == "MPVolumeSlider"}.first as? UISlider)?.setValue(0.5, animated: false)
//do some Counting
}
}
}
func removeVolumeView() {
let volumeView: MPVolumeView = MPVolumeView(frame: CGRect.zero)
view.addSubview(volumeView)
}
}
Everything works as it should after starting the App for the first time. When I now press the Home Button and return back to the App the Events of pressing the volume buttons are not captured and the MPVolumeWindow is displayed again.
Can somebody help me to solve this issue?
Regards
Armin
When you come back from being in the background, your audio session is no longer active. You need to activate it again.
The following code is crashing at
currentCellRect = tableView.rectForRowAtIndexPath(indexPaths[0])
But only sometimes.
public func showCellScrollCount(animated:Bool) {
self.tableView.addObserver(self, forKeyPath: "contentOffset", options: NSKeyValueObservingOptions.New, context: nil)
self.tableView.addObserver(self, forKeyPath: "dragging", options: NSKeyValueObservingOptions.New, context: nil)
}
override public func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
switch (keyPath, object) {
case (.Some("contentOffset"), _):
self.updateScrollPosition()
default:
super.observeValueForKeyPath(keyPath, ofObject: object, change: change, context: context)
}
}
func updateScrollPosition() {
let indexPaths = tableView.indexPathsForVisibleRows
var currentCellRect:CGRect?
if let indexPaths = indexPaths {
if indexPaths.count > 0 {
currentCellRect = tableView.rectForRowAtIndexPath(indexPaths[0])
scrollCountView.currentScrollCountNum = indexPaths[0].row
}
}
}
It crashes with "BAD_ACCESS". Does anyone have any idea why?
...
EDIT: Is it possible it's happening because I'm calling tableView.reloadData() right before I add observers, and the call isn't finished yet?
Updated
Your code works fine since I added it to my tableView controller and called showCellScrollCount func once. Where you call showCellScrollCount, do you call it multiple times? It can be problem if so.
Update 3
here is the problem:
public var totalScrollCountNum = 0 {
didSet {
scrollCountView.totalScrollCountNum = totalScrollCountNum
showCellScrollCount(false)
}
}
move showCellScrollCount(false) to initializers
I want to remove an observer after it run or when the view dissapeared. Here is the code but sometimes the observer was already removed when i want to remove it again. How to check if it is still registered?
override func observeValueForKeyPath(keyPath: String, ofObject object: AnyObject, change: [NSObject : AnyObject], context: UnsafeMutablePointer<Void>) {
if(!didOnce){
if(keyPath == "myLocation"){
location = mapView.myLocation.coordinate;
self.mapView.animateToLocation(self.location!);
self.mapView.animateToZoom(15);
didOnce = true;
self.mapView.removeObserver(self, forKeyPath: "myLocation");
}
}
}
override func viewDidAppear(animated: Bool) {
didOnce = false;
}
override func viewWillDisappear(animated: Bool) {
if(!didOnce){
self.mapView.removeObserver(self, forKeyPath: "myLocation");
didOnce = true;
}
}
You're on the right track. Add an isObserving property to your class. Set it to true when you start observing, and set it to false when you stop observing. In all cases check the flag before starting/stopping observing to make sure you are not already in that state.
You can also add a willSet method to the property and have that code start/stop observing when the property changes states.
Main reason: addObserver() is called 1 time (at viewDidLoad or init), but removeObserver() can be called 2 times or more (base on the times viewWillDisappear() was called).
To resolve: move addObserver() to viewWillAppear():
private var didOnce = false
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
self.mapView.addObserver(self, forKeyPath: "myLocation", options: .new, context: nil)
}
override func observeValueForKeyPath(keyPath: String, ofObject object: AnyObject, change: [NSObject : AnyObject], context: UnsafeMutablePointer<Void>) {
if(!didOnce){
if(keyPath == "myLocation"){
location = mapView.myLocation.coordinate;
self.mapView.animateToLocation(self.location!);
self.mapView.animateToZoom(15);
didOnce = true;
self.mapView.removeObserver(self, forKeyPath: "myLocation");
}
}
}
override func viewWillDisappear(animated: Bool) {
if(!didOnce){
self.mapView.removeObserver(self, forKeyPath: "myLocation");
didOnce = true;
}
}
Volume button notification function is not being called.
Code:
func listenVolumeButton(){
// Option #1
NSNotificationCenter.defaultCenter().addObserver(self, selector: "volumeChanged:", name: "AVSystemController_SystemVolumeDidChangeNotification", object: nil)
// Option #2
var audioSession = AVAudioSession()
audioSession.setActive(true, error: nil)
audioSession.addObserver(self, forKeyPath: "volumeChanged", options: NSKeyValueObservingOptions.New, context: nil)
}
override func observeValueForKeyPath(keyPath: String, ofObject object: AnyObject, change: [NSObject : AnyObject], context: UnsafeMutablePointer<Void>) {
if keyPath == "volumeChanged"{
print("got in here")
}
}
func volumeChanged(notification: NSNotification){
print("got in here")
}
listenVolumeButton() is being called in viewWillAppear
The code is not getting to the print statement "got in here", in either case.
I am trying two different ways to do it, neither way is working.
I have followed this: Detect iPhone Volume Button Up Press?
Using the second method, the value of the key path should be "outputVolume". That is the property we are observing.
So change the code to,
var outputVolumeObserve: NSKeyValueObservation?
let audioSession = AVAudioSession.sharedInstance()
func listenVolumeButton() {
do {
try audioSession.setActive(true)
} catch {}
outputVolumeObserve = audioSession.observe(\.outputVolume) { (audioSession, changes) in
/// TODOs
}
}
The code above won't work in Swift 3, in that case, try this:
func listenVolumeButton() {
do {
try audioSession.setActive(true)
} catch {
print("some error")
}
audioSession.addObserver(self, forKeyPath: "outputVolume", options: NSKeyValueObservingOptions.new, context: nil)
}
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
if keyPath == "outputVolume" {
print("got in here")
}
}
With this code you can listen whenever the user taps the volume hardware button.
class VolumeListener {
static let kVolumeKey = "volume"
static let shared = VolumeListener()
private let kAudioVolumeChangeReasonNotificationParameter = "AVSystemController_AudioVolumeChangeReasonNotificationParameter"
private let kAudioVolumeNotificationParameter = "AVSystemController_AudioVolumeNotificationParameter"
private let kExplicitVolumeChange = "ExplicitVolumeChange"
private let kSystemVolumeDidChangeNotificationName = NSNotification.Name(rawValue: "AVSystemController_SystemVolumeDidChangeNotification")
private var hasSetup = false
func start() {
guard !self.hasSetup else {
return
}
self.setup()
self.hasSetup = true
}
private func setup() {
guard let rootViewController = UIApplication.shared.windows.first?.rootViewController else {
return
}
let volumeView = MPVolumeView(frame: CGRect.zero)
volumeView.clipsToBounds = true
rootViewController.view.addSubview(volumeView)
NotificationCenter.default.addObserver(
self,
selector: #selector(self.volumeChanged),
name: kSystemVolumeDidChangeNotificationName,
object: nil
)
volumeView.removeFromSuperview()
}
#objc func volumeChanged(_ notification: NSNotification) {
guard let userInfo = notification.userInfo,
let volume = userInfo[kAudioVolumeNotificationParameter] as? Float,
let changeReason = userInfo[kAudioVolumeChangeReasonNotificationParameter] as? String,
changeReason == kExplicitVolumeChange
else {
return
}
NotificationCenter.default.post(name: "volumeListenerUserDidInteractWithVolume", object: nil,
userInfo: [VolumeListener.kVolumeKey: volume])
}
}
And to listen you just need to add the observer:
NotificationCenter.default.addObserver(self, selector: #selector(self.userInteractedWithVolume),
name: "volumeListenerUserDidInteractWithVolume", object: nil)
You can access the volume value by checking the userInfo:
#objc private func userInteractedWithVolume(_ notification: Notification) {
guard let volume = notification.userInfo?[VolumeListener.kVolumeKey] as? Float else {
return
}
print("volume: \(volume)")
}
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
}
}
When observing a new value, I set the system volume back to 0.5. This will probably anger users using music simultaneously, therefore I do not recommend my own answer in production.
If interested here is a RxSwift version.
func volumeRx() -> Observable<Void> {
Observable<Void>.create {
subscriber in
let audioSession = AVAudioSession.sharedInstance()
do {
try audioSession.setActive(true)
} catch let e {
subscriber.onError(e)
}
let outputVolumeObserve = audioSession.observe(\.outputVolume) {
(audioSession, changes) in
subscriber.onNext(Void())
}
return Disposables.create {
outputVolumeObserve.invalidate()
}
}
}
Usage
volumeRx()
.subscribe(onNext: {
print("Volume changed")
}).disposed(by: disposeBag)