I want to decrease a score whilst the screen is touched with Swift and I am unsure which way is the best to achieve this.
Placing:
score -= 1
in touches began obviously decreases it when the screen is touched, but I need it to do it the whole time the screen is touched.
I tried to create an SKAction to run the code above forever in touchesBegan and then remove the action in touchesEnded. This just caused the app to freeze.
I know it should be easy, but any help is appreciated.
Set a flag in touchesBegan to indicate that the screen has been touched:
screentouched = true
and then reset the flag in touchesEnded to show that the screen is no longer being touched:
screenTouched = false
In update, if screenTouched is true, decrease your score
if screenTouched {
score -= 1
}
Although this will result in the score being decremented up to 60 times a second, so you’ll probably want to restrict by time. To do this, have 2 properties of type TimeInterval that track how long it has been since the score was last decremented, and how often the score should be decremented:
var timeOfLastScoreDecrement: CFTimeInterval = 0.0
var timePerScoreDecrement: CFTimeInterval = 1.0
For this example, we'll decrement the score every second and set the time since the last decrement to 0, as it hasn't happened yet.
In update: call a function that checks to see if the time interval has passed. If it has, then decrement the score and reset to time since the last decrement and if it hasn’t, don’t:
override func update(_ currentTime: TimeInterval) {
if screenIsTouched {decrementScoreForTime(currentTime)}
// Rest of update code
}
func decrementScoreForTime(_ currentTime: CFTimeInterval) {
if (currentTime - timeOfLastScoreDecrement < timePerScoreDecrement) {return}
// Time per score decrement has passed...
score -= 1
timeOfLastScoreDecrement = currentTime
}
Related
I'm animating a clock hand that takes a CGFloat value from 0 to 1. While I have the animation, I would like it to be a lot smoother. The total animation takes 5 seconds, as part of an input variable. How can I make this a lot smoother?
Ideally, I'd like to get all the values from 0 to 1 in 5 seconds...
The clock hand does a complete 360 but is a little choppy
#IBAction func start(_ sender: Any) {
timer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(launchTimer), userInfo: nil, repeats: true)
launchTimer()
}
func launchTimer() {
guard seconds < 4.9 else {
timer.invalidate()
seconds = 0
return
}
seconds += 0.1
clockView.currentPressure = CGFloat(seconds / 5)
clockView.setNeedsDisplay()
}
EDIT
import UIKit
class GaugeView: UIView {
var currentPressure : CGFloat = 0.0
override func draw(_ rect: CGRect) {
StyleKitName.drawGauge(pressure: currentPressure)
}
}
Timer is not appropriate for animations on this scale. 100ms isn't a good step in any case, since it's not a multiple of the frame rate (16.67ms). Generally speaking, you shouldn't try to hand-animate unless you have a specialized problem. See UIView.animate(withDuration:...), which is generally how you should animate UI elements, allowing the system to take care of the progress for you.
For a slightly more manual animation, see CABasicAnimation, which will update a property over time. If you need very manual control, see CADisplayLink, but you almost never need this.
In any case, you must never assume that any timer is called precisely when you ask it to be. You cannot add 0.1s to a value just because you asked to be called in 0.1s. You have to look at what time it really is. Even hard-real-time systems can't promise something will be called at a precise moment. The best you can possibly get is a promise it will be within some tolerance (and iOS doesn't even give you that).
To animate this with UIView (which I recommend), it'll probably be something like:
#IBAction func start(_ sender: Any) {
self.clockView.currentPressure = 0
UIView.animate(withDuration: 5, animations: {
self.clockView.currentPressure = 1
})
}
With a CABasicAnimation (which is more complicated) it would be something like:
currentPressure = 1 // You have to set it to where it's going or it'll snap back.
let anim = CABasicAnimation(keyPath: "currentPressure")
anim.fromValue = 0
anim.toValue = 1
anim.duration = 5
clockView.addAnimation(anim)
Make the time interval smaller to make the animation smoother. That way it will seem like it's gliding around instead of jumping between values.
You can also use spritekit:
import SpriteKit
let wait = SKAction.wait(forDuration: 0.01)
let runAnim = SKAction.run {
launchTimer()
}
let n = SKNode()
n.run(SKAction.repeat(SKAction.sequence([wait, runAnim]), count: 500))
I am coding an app in sprite-kit and swift where when you touch the screen a sprite(the player) throws a projectile at another sprite moving towards it. If the player hits the other sprite then the projectile and the sprite disappear. A problem with the game is that if the player rapidly touches the screen he can easily run up his score in the game. How can I make the code only recognize that the screen is being touched every let's say .3 seconds?
In SpriteKit/GameplayKit games, most of your code is running inside a game loop where you are constantly being passed the current time. That's what this function in an SKScene is:
override public func update(_ currentTime: TimeInterval) {
}
In here it's common to keep track of time and enable/disable things. To keep it simple:
Add the following vars
var firingEnabled = true
var enableFiringAtTime: TimeInterval = 0
var currentTime: TimeInterval = 0
When they fire, add this code
if firingEnabled {
firingEnabled = false
enableFiringAtTime = self.currentTime + 0.3
// your fire code here
}
And in the update override
self.currentTime = currentTime
if currentTime > enableFiringAtTime {
firingEnabled = true
}
I am trying to build a reliable solid system to build a metronome in my app using SWIFT.
I Have built what seems to be a solid system using NSTimer so far.. The only issue I am having right now is when the timer starts the first 2 clicks are off time but then it catches into a solid timeframe.
Now after all my research I have seen people mention you should use other Audio tools not relying on NSTimer.. Or if you choose use NSTimer then it should be on its own thread. Now I see many confused by this Including myself and I would love to get down to the bottom of this Metronome business and get this solved and share it with all those who are struggling.
UPDATE
So I have implemented and cleaned up at this point after the feedback I had last recieved. At this point here is how my code is structured. Its playing back. But I am still getting 2 fast clicks in the beginning and then it settles in.
I apologize on my ignorance for this one. I hope I am on the right path.
I currently am prototyping another method as well. Where I have a very small audio file with one click and dead space at the end of it with the correct duration until for a loop point for specific tempos. I am looping this back and works very well. But the only thing Is I dont get to detect the loop points for visual updates so I have my basic NStimer just detecting the timing intervals underneath the audio being processed and it seems to matchup very well throughout and no delay. But I still would rather get it all with this NSTimer. If you can easily spot my error would be great for one more kick in the right direction and I am sure it can work soon! Thanks so much.
//VARIABLES
//AUDIO
var clickPlayer:AVAudioPlayer = AVAudioPlayer()
let soundFileClick = NSBundle.mainBundle().pathForResource("metronomeClick", ofType: ".mp3")
//TIMERS
var metroTimer = NSTimer()
var nextTimer = NSTimer()
var previousClick = CFAbsoluteTimeGetCurrent() //When Metro Starts Last Click
//Metro Features
var isOn = false
var bpm = 60.0 //Tempo Used for beeps, calculated into time value
var barNoteValue = 4 //How Many Notes Per Bar (Set To Amount Of Hits Per Pattern)
var noteInBar = 0 //What Note You Are On In Bar
//********* FUNCTIONS ***********
func startMetro()
{
MetronomeCount()
barNoteValue = 4 // How Many Notes Per Bar (Set To Amount Of Hits Per Pattern)
noteInBar = 0 // What Note You Are On In Bar
isOn = true //
}
//Main Metro Pulse Timer
func MetronomeCount()
{
previousClick = CFAbsoluteTimeGetCurrent()
metroTimer = NSTimer.scheduledTimerWithTimeInterval(60.0 / bpm, target: self, selector: Selector ("MetroClick"), userInfo: nil, repeats: true)
nextTimer = NSTimer(timeInterval: (60.0/Double(bpm)) * 0.01, target: self, selector: "tick:", userInfo: ["bpm":bpm], repeats: true)
}
func MetroClick()
{
tick(nextTimer)
}
func tick(timer:NSTimer)
{
let elapsedTime:CFAbsoluteTime = CFAbsoluteTimeGetCurrent() - previousClick
let targetTime:Double = 60/timer.userInfo!.objectForKey("bpm")!.doubleValue!
if (elapsedTime > targetTime) || (abs(elapsedTime - targetTime) < 0.003)
{
previousClick = CFAbsoluteTimeGetCurrent()
//Play the click here
if noteInBar == barNoteValue
{
clickPlayer.play() //Play Sound
noteInBar = 1
}
else//If We Are Still On Same Bar
{
clickPlayer.play() //Play Sound
noteInBar++ //Increase Note Value
}
countLabel.text = String(noteInBar) //Update UI Display To Show Note We Are At
}
}
A metronome built purely with NSTimer will not be very accurate, as Apple explains in their documentation.
Because of the various input sources a typical run loop manages, the effective resolution of the time interval for a timer is limited to on the order of 50-100 milliseconds. If a timer’s firing time occurs during a long callout or while the run loop is in a mode that is not monitoring the timer, the timer does not fire until the next time the run loop checks the timer.
I would suggest using an NSTimer that fires on the order of 50 times per desired tick (for example, if you would like a 60 ticks per minute, you would have the NSTimeInterval to be about 1/50 of a second.
You should then store a CFAbsoluteTime which stores the "last tick" time, and compare it to the current time. If the absolute value of the difference between the current time and the "last tick" time is less than some tolerance (I would make this about 4 times the number of ticks per interval, for example, if you chose 1/50 of a second per NSTimer fire, you should apply a tolerance of around 4/50 of a second), you can play the "tick."
You may need to calibrate the tolerances to get to your desired accuracy, but this general concept will make your metronome a lot more accurate.
Here is some more information on another SO post. It also includes some code that uses the theory I discussed. I hope this helps!
Update
The way you are calculating your tolerances is incorrect. In your calculations, notice that the tolerance is inversely proportional to the square of the bpm. The problem with this is that the tolerance will eventually be less than the number of times the timer fires per second. Take a look at this graph to see what I mean. This will generate problems at high BPMs. The other potential source of error is your top bounding condition. You really don't need to check an upper limit on your tolerance, because theoretically, the timer should have already fired by then. Therefore, if the elapsed time is greater than the theoretical time, you can fire it regardless. (For example if the elapsed time is 0.1s and and the actual time with the true BPM should be 0.05s, you should go ahead and fire the timer anyways, no matter what your tolerance is).
Here is my timer "tick" function, which seems to work fine. You need to tweak it to fit your needs (with the downbeats, etc.) but it works in concept.
func tick(timer:NSTimer) {
let elapsedTime:CFAbsoluteTime = CFAbsoluteTimeGetCurrent() - lastTick
let targetTime:Double = 60/timer.userInfo!.objectForKey("bpm")!.doubleValue!
if (elapsedTime > targetTime) || (abs(elapsedTime - targetTime) < 0.003) {
lastTick = CFAbsoluteTimeGetCurrent()
# Play the click here
}
}
My timer is initialized like so: nextTimer = NSTimer(timeInterval: (60.0/Double(bpm)) * 0.01, target: self, selector: "tick:", userInfo: ["bpm":bpm], repeats: true)
Ok! You can't get things right basing on time, because somehow we need to deal with DA converters and their frequency - samplerate. We need to tell them the exact sample to start play the sound. Add a single view iOS app with two buttons start and stop and insert this code into ViewController.swift. I keep things simple and it's just an Idea of how we can do this. Sorry for forcing try... This one is made with swift 3. Also check out my project on GitHub https://github.com/AlexShubin/MetronomeIdea
Swift 3
import UIKit
import AVFoundation
class Metronome {
var audioPlayerNode:AVAudioPlayerNode
var audioFile:AVAudioFile
var audioEngine:AVAudioEngine
init (fileURL: URL) {
audioFile = try! AVAudioFile(forReading: fileURL)
audioPlayerNode = AVAudioPlayerNode()
audioEngine = AVAudioEngine()
audioEngine.attach(self.audioPlayerNode)
audioEngine.connect(audioPlayerNode, to: audioEngine.mainMixerNode, format: audioFile.processingFormat)
try! audioEngine.start()
}
func generateBuffer(forBpm bpm: Int) -> AVAudioPCMBuffer {
audioFile.framePosition = 0
let periodLength = AVAudioFrameCount(audioFile.processingFormat.sampleRate * 60 / Double(bpm))
let buffer = AVAudioPCMBuffer(pcmFormat: audioFile.processingFormat, frameCapacity: periodLength)
try! audioFile.read(into: buffer)
buffer.frameLength = periodLength
return buffer
}
func play(bpm: Int) {
let buffer = generateBuffer(forBpm: bpm)
self.audioPlayerNode.play()
self.audioPlayerNode.scheduleBuffer(buffer, at: nil, options: .loops, completionHandler: nil)
}
func stop() {
audioPlayerNode.stop()
}
}
class ViewController: UIViewController {
var metronome:Metronome
required init?(coder aDecoder: NSCoder) {
let fileUrl = Bundle.main.url(forResource: "Click", withExtension: "wav")
metronome = Metronome(fileURL: fileUrl!)
super.init(coder: aDecoder)
}
#IBAction func StartPlayback(_ sender: Any) {
metronome.play(bpm: 120)
}
#IBAction func StopPlayback(_ sender: Any) {
metronome.stop()
}
}
Thanks to the great work already done on this question by vigneshv & CakeGamesStudios, I was able to put together the following, which is an expanded version of the metronome timer discussed here.
Some highlights:
It's updated for Swift v5
It uses a Grand Central Dispatch timer to run on a separate queue, rather than just a regular NSTimer (see here for more details)
It uses more calculated properties for clarity
It uses delegation, to allow for any arbitrary 'tick' action to be handled by the delegate class (be that playing a sound from AVFoundation, updating the display, or whatever else - just remember to set the delegate property after creating the timer). This delegate would also be the one to distinguish beat 1 vs. others, but that'd be easy enough to add within this class itself if desired.
It has a % to Next Tick property, which could be used to update a UI progress bar, etc.
Any feedback on how this can be improved further is welcome!
protocol BPMTimerDelegate: class {
func bpmTimerTicked()
}
class BPMTimer {
// MARK: - Properties
weak var delegate: BPMTimerDelegate? // The class's delegate, to handle the results of ticks
var bpm: Double { // The speed of the metronome ticks in BPM (Beats Per Minute)
didSet {
changeBPM() // Respond to any changes in BPM, so that the timer intervals change accordingly
}
}
var tickDuration: Double { // The amount of time that will elapse between ticks
return 60/bpm
}
var timeToNextTick: Double { // The amount of time until the next tick takes place
if paused {
return tickDuration
} else {
return abs(elapsedTime - tickDuration)
}
}
var percentageToNextTick: Double { // Percentage progress from the previous tick to the next
if paused {
return 0
} else {
return min(100, (timeToNextTick / tickDuration) * 100) // Return a percentage, and never more than 100%
}
}
// MARK: - Private Properties
private var timer: DispatchSourceTimer!
private lazy var timerQueue = DispatchQueue.global(qos: .utility) // The Grand Central Dispatch queue to be used for running the timer. Leverages a global queue with the Quality of Service 'Utility', which is for long-running tasks, typically with user-visible progress. See here for more info: https://www.raywenderlich.com/5370-grand-central-dispatch-tutorial-for-swift-4-part-1-2
private var paused: Bool
private var lastTickTimestamp: CFAbsoluteTime
private var tickCheckInterval: Double {
return tickDuration / 50 // Run checks many times within each tick duration, to ensure accuracy
}
private var timerTolerance: DispatchTimeInterval {
return DispatchTimeInterval.milliseconds(Int(tickCheckInterval / 10 * 1000)) // For a repeating timer, Apple recommends a tolerance of at least 10% of the interval. It must be multiplied by 1,000, so it can be expressed in milliseconds, as required by DispatchTimeInterval.
}
private var elapsedTime: Double {
return CFAbsoluteTimeGetCurrent() - lastTickTimestamp // Determine how long has passed since the last tick
}
// MARK: - Initialization
init(bpm: Double) {
self.bpm = bpm
self.paused = true
self.lastTickTimestamp = CFAbsoluteTimeGetCurrent()
self.timer = createNewTimer()
}
// MARK: - Methods
func start() {
if paused {
paused = false
lastTickTimestamp = CFAbsoluteTimeGetCurrent()
timer.resume() // A crash will occur if calling resume on an already resumed timer. The paused property is used to guard against this. See here for more info: https://medium.com/over-engineering/a-background-repeating-timer-in-swift-412cecfd2ef9
} else {
// Already running, so do nothing
}
}
func stop() {
if !paused {
paused = true
timer.suspend()
} else {
// Already paused, so do nothing
}
}
// MARK: - Private Methods
// Implements timer functionality using the DispatchSourceTimer in Grand Central Dispatch. See here for more info: http://danielemargutti.com/2018/02/22/the-secret-world-of-nstimer/
private func createNewTimer() -> DispatchSourceTimer {
let timer = DispatchSource.makeTimerSource(queue: timerQueue) // Create the timer on the correct queue
let deadline: DispatchTime = DispatchTime.now() + tickCheckInterval // Establish the next time to trigger
timer.schedule(deadline: deadline, repeating: tickCheckInterval, leeway: timerTolerance) // Set it on a repeating schedule, with the established tolerance
timer.setEventHandler { [weak self] in // Set the code to be executed when the timer fires, using a weak reference to 'self' to avoid retain cycles (memory leaks). See here for more info: https://learnappmaking.com/escaping-closures-swift/
self?.tickCheck()
}
timer.activate() // Dispatch Sources are returned initially in the inactive state, to begin processing, use the activate() method
// Determine whether to pause the timer
if paused {
timer.suspend()
}
return timer
}
private func cancelTimer() {
timer.setEventHandler(handler: nil)
timer.cancel()
if paused {
timer.resume() // If the timer is suspended, calling cancel without resuming triggers a crash. See here for more info: https://forums.developer.apple.com/thread/15902
}
}
private func replaceTimer() {
cancelTimer()
timer = createNewTimer()
}
private func changeBPM() {
replaceTimer() // Create a new timer, which will be configured for the new BPM
}
#objc private func tickCheck() {
if (elapsedTime > tickDuration) || (timeToNextTick < 0.003) { // If past or extremely close to correct duration, tick
tick()
}
}
private func tick() {
lastTickTimestamp = CFAbsoluteTimeGetCurrent()
DispatchQueue.main.sync { // Calls the delegate from the application's main thread, because it keeps the separate threading within this class, and otherwise, it can cause errors (e.g. 'Main Thread Checker: UI API called on a background thread', if the delegate tries to update the UI). See here for more info: https://stackoverflow.com/questions/45081731/uiapplication-delegate-must-be-called-from-main-thread-only
delegate?.bpmTimerTicked() // Have the delegate respond accordingly
}
}
// MARK: - Deinitialization
deinit {
cancelTimer() // Ensure that the timer's cancelled if this object is deallocated
}
}
I am trying to build a reliable solid system to build a metronome in my app using SWIFT.
I Have built what seems to be a solid system using NSTimer so far.. The only issue I am having right now is when the timer starts the first 2 clicks are off time but then it catches into a solid timeframe.
Now after all my research I have seen people mention you should use other Audio tools not relying on NSTimer.. Or if you choose use NSTimer then it should be on its own thread. Now I see many confused by this Including myself and I would love to get down to the bottom of this Metronome business and get this solved and share it with all those who are struggling.
UPDATE
So I have implemented and cleaned up at this point after the feedback I had last recieved. At this point here is how my code is structured. Its playing back. But I am still getting 2 fast clicks in the beginning and then it settles in.
I apologize on my ignorance for this one. I hope I am on the right path.
I currently am prototyping another method as well. Where I have a very small audio file with one click and dead space at the end of it with the correct duration until for a loop point for specific tempos. I am looping this back and works very well. But the only thing Is I dont get to detect the loop points for visual updates so I have my basic NStimer just detecting the timing intervals underneath the audio being processed and it seems to matchup very well throughout and no delay. But I still would rather get it all with this NSTimer. If you can easily spot my error would be great for one more kick in the right direction and I am sure it can work soon! Thanks so much.
//VARIABLES
//AUDIO
var clickPlayer:AVAudioPlayer = AVAudioPlayer()
let soundFileClick = NSBundle.mainBundle().pathForResource("metronomeClick", ofType: ".mp3")
//TIMERS
var metroTimer = NSTimer()
var nextTimer = NSTimer()
var previousClick = CFAbsoluteTimeGetCurrent() //When Metro Starts Last Click
//Metro Features
var isOn = false
var bpm = 60.0 //Tempo Used for beeps, calculated into time value
var barNoteValue = 4 //How Many Notes Per Bar (Set To Amount Of Hits Per Pattern)
var noteInBar = 0 //What Note You Are On In Bar
//********* FUNCTIONS ***********
func startMetro()
{
MetronomeCount()
barNoteValue = 4 // How Many Notes Per Bar (Set To Amount Of Hits Per Pattern)
noteInBar = 0 // What Note You Are On In Bar
isOn = true //
}
//Main Metro Pulse Timer
func MetronomeCount()
{
previousClick = CFAbsoluteTimeGetCurrent()
metroTimer = NSTimer.scheduledTimerWithTimeInterval(60.0 / bpm, target: self, selector: Selector ("MetroClick"), userInfo: nil, repeats: true)
nextTimer = NSTimer(timeInterval: (60.0/Double(bpm)) * 0.01, target: self, selector: "tick:", userInfo: ["bpm":bpm], repeats: true)
}
func MetroClick()
{
tick(nextTimer)
}
func tick(timer:NSTimer)
{
let elapsedTime:CFAbsoluteTime = CFAbsoluteTimeGetCurrent() - previousClick
let targetTime:Double = 60/timer.userInfo!.objectForKey("bpm")!.doubleValue!
if (elapsedTime > targetTime) || (abs(elapsedTime - targetTime) < 0.003)
{
previousClick = CFAbsoluteTimeGetCurrent()
//Play the click here
if noteInBar == barNoteValue
{
clickPlayer.play() //Play Sound
noteInBar = 1
}
else//If We Are Still On Same Bar
{
clickPlayer.play() //Play Sound
noteInBar++ //Increase Note Value
}
countLabel.text = String(noteInBar) //Update UI Display To Show Note We Are At
}
}
A metronome built purely with NSTimer will not be very accurate, as Apple explains in their documentation.
Because of the various input sources a typical run loop manages, the effective resolution of the time interval for a timer is limited to on the order of 50-100 milliseconds. If a timer’s firing time occurs during a long callout or while the run loop is in a mode that is not monitoring the timer, the timer does not fire until the next time the run loop checks the timer.
I would suggest using an NSTimer that fires on the order of 50 times per desired tick (for example, if you would like a 60 ticks per minute, you would have the NSTimeInterval to be about 1/50 of a second.
You should then store a CFAbsoluteTime which stores the "last tick" time, and compare it to the current time. If the absolute value of the difference between the current time and the "last tick" time is less than some tolerance (I would make this about 4 times the number of ticks per interval, for example, if you chose 1/50 of a second per NSTimer fire, you should apply a tolerance of around 4/50 of a second), you can play the "tick."
You may need to calibrate the tolerances to get to your desired accuracy, but this general concept will make your metronome a lot more accurate.
Here is some more information on another SO post. It also includes some code that uses the theory I discussed. I hope this helps!
Update
The way you are calculating your tolerances is incorrect. In your calculations, notice that the tolerance is inversely proportional to the square of the bpm. The problem with this is that the tolerance will eventually be less than the number of times the timer fires per second. Take a look at this graph to see what I mean. This will generate problems at high BPMs. The other potential source of error is your top bounding condition. You really don't need to check an upper limit on your tolerance, because theoretically, the timer should have already fired by then. Therefore, if the elapsed time is greater than the theoretical time, you can fire it regardless. (For example if the elapsed time is 0.1s and and the actual time with the true BPM should be 0.05s, you should go ahead and fire the timer anyways, no matter what your tolerance is).
Here is my timer "tick" function, which seems to work fine. You need to tweak it to fit your needs (with the downbeats, etc.) but it works in concept.
func tick(timer:NSTimer) {
let elapsedTime:CFAbsoluteTime = CFAbsoluteTimeGetCurrent() - lastTick
let targetTime:Double = 60/timer.userInfo!.objectForKey("bpm")!.doubleValue!
if (elapsedTime > targetTime) || (abs(elapsedTime - targetTime) < 0.003) {
lastTick = CFAbsoluteTimeGetCurrent()
# Play the click here
}
}
My timer is initialized like so: nextTimer = NSTimer(timeInterval: (60.0/Double(bpm)) * 0.01, target: self, selector: "tick:", userInfo: ["bpm":bpm], repeats: true)
Ok! You can't get things right basing on time, because somehow we need to deal with DA converters and their frequency - samplerate. We need to tell them the exact sample to start play the sound. Add a single view iOS app with two buttons start and stop and insert this code into ViewController.swift. I keep things simple and it's just an Idea of how we can do this. Sorry for forcing try... This one is made with swift 3. Also check out my project on GitHub https://github.com/AlexShubin/MetronomeIdea
Swift 3
import UIKit
import AVFoundation
class Metronome {
var audioPlayerNode:AVAudioPlayerNode
var audioFile:AVAudioFile
var audioEngine:AVAudioEngine
init (fileURL: URL) {
audioFile = try! AVAudioFile(forReading: fileURL)
audioPlayerNode = AVAudioPlayerNode()
audioEngine = AVAudioEngine()
audioEngine.attach(self.audioPlayerNode)
audioEngine.connect(audioPlayerNode, to: audioEngine.mainMixerNode, format: audioFile.processingFormat)
try! audioEngine.start()
}
func generateBuffer(forBpm bpm: Int) -> AVAudioPCMBuffer {
audioFile.framePosition = 0
let periodLength = AVAudioFrameCount(audioFile.processingFormat.sampleRate * 60 / Double(bpm))
let buffer = AVAudioPCMBuffer(pcmFormat: audioFile.processingFormat, frameCapacity: periodLength)
try! audioFile.read(into: buffer)
buffer.frameLength = periodLength
return buffer
}
func play(bpm: Int) {
let buffer = generateBuffer(forBpm: bpm)
self.audioPlayerNode.play()
self.audioPlayerNode.scheduleBuffer(buffer, at: nil, options: .loops, completionHandler: nil)
}
func stop() {
audioPlayerNode.stop()
}
}
class ViewController: UIViewController {
var metronome:Metronome
required init?(coder aDecoder: NSCoder) {
let fileUrl = Bundle.main.url(forResource: "Click", withExtension: "wav")
metronome = Metronome(fileURL: fileUrl!)
super.init(coder: aDecoder)
}
#IBAction func StartPlayback(_ sender: Any) {
metronome.play(bpm: 120)
}
#IBAction func StopPlayback(_ sender: Any) {
metronome.stop()
}
}
Thanks to the great work already done on this question by vigneshv & CakeGamesStudios, I was able to put together the following, which is an expanded version of the metronome timer discussed here.
Some highlights:
It's updated for Swift v5
It uses a Grand Central Dispatch timer to run on a separate queue, rather than just a regular NSTimer (see here for more details)
It uses more calculated properties for clarity
It uses delegation, to allow for any arbitrary 'tick' action to be handled by the delegate class (be that playing a sound from AVFoundation, updating the display, or whatever else - just remember to set the delegate property after creating the timer). This delegate would also be the one to distinguish beat 1 vs. others, but that'd be easy enough to add within this class itself if desired.
It has a % to Next Tick property, which could be used to update a UI progress bar, etc.
Any feedback on how this can be improved further is welcome!
protocol BPMTimerDelegate: class {
func bpmTimerTicked()
}
class BPMTimer {
// MARK: - Properties
weak var delegate: BPMTimerDelegate? // The class's delegate, to handle the results of ticks
var bpm: Double { // The speed of the metronome ticks in BPM (Beats Per Minute)
didSet {
changeBPM() // Respond to any changes in BPM, so that the timer intervals change accordingly
}
}
var tickDuration: Double { // The amount of time that will elapse between ticks
return 60/bpm
}
var timeToNextTick: Double { // The amount of time until the next tick takes place
if paused {
return tickDuration
} else {
return abs(elapsedTime - tickDuration)
}
}
var percentageToNextTick: Double { // Percentage progress from the previous tick to the next
if paused {
return 0
} else {
return min(100, (timeToNextTick / tickDuration) * 100) // Return a percentage, and never more than 100%
}
}
// MARK: - Private Properties
private var timer: DispatchSourceTimer!
private lazy var timerQueue = DispatchQueue.global(qos: .utility) // The Grand Central Dispatch queue to be used for running the timer. Leverages a global queue with the Quality of Service 'Utility', which is for long-running tasks, typically with user-visible progress. See here for more info: https://www.raywenderlich.com/5370-grand-central-dispatch-tutorial-for-swift-4-part-1-2
private var paused: Bool
private var lastTickTimestamp: CFAbsoluteTime
private var tickCheckInterval: Double {
return tickDuration / 50 // Run checks many times within each tick duration, to ensure accuracy
}
private var timerTolerance: DispatchTimeInterval {
return DispatchTimeInterval.milliseconds(Int(tickCheckInterval / 10 * 1000)) // For a repeating timer, Apple recommends a tolerance of at least 10% of the interval. It must be multiplied by 1,000, so it can be expressed in milliseconds, as required by DispatchTimeInterval.
}
private var elapsedTime: Double {
return CFAbsoluteTimeGetCurrent() - lastTickTimestamp // Determine how long has passed since the last tick
}
// MARK: - Initialization
init(bpm: Double) {
self.bpm = bpm
self.paused = true
self.lastTickTimestamp = CFAbsoluteTimeGetCurrent()
self.timer = createNewTimer()
}
// MARK: - Methods
func start() {
if paused {
paused = false
lastTickTimestamp = CFAbsoluteTimeGetCurrent()
timer.resume() // A crash will occur if calling resume on an already resumed timer. The paused property is used to guard against this. See here for more info: https://medium.com/over-engineering/a-background-repeating-timer-in-swift-412cecfd2ef9
} else {
// Already running, so do nothing
}
}
func stop() {
if !paused {
paused = true
timer.suspend()
} else {
// Already paused, so do nothing
}
}
// MARK: - Private Methods
// Implements timer functionality using the DispatchSourceTimer in Grand Central Dispatch. See here for more info: http://danielemargutti.com/2018/02/22/the-secret-world-of-nstimer/
private func createNewTimer() -> DispatchSourceTimer {
let timer = DispatchSource.makeTimerSource(queue: timerQueue) // Create the timer on the correct queue
let deadline: DispatchTime = DispatchTime.now() + tickCheckInterval // Establish the next time to trigger
timer.schedule(deadline: deadline, repeating: tickCheckInterval, leeway: timerTolerance) // Set it on a repeating schedule, with the established tolerance
timer.setEventHandler { [weak self] in // Set the code to be executed when the timer fires, using a weak reference to 'self' to avoid retain cycles (memory leaks). See here for more info: https://learnappmaking.com/escaping-closures-swift/
self?.tickCheck()
}
timer.activate() // Dispatch Sources are returned initially in the inactive state, to begin processing, use the activate() method
// Determine whether to pause the timer
if paused {
timer.suspend()
}
return timer
}
private func cancelTimer() {
timer.setEventHandler(handler: nil)
timer.cancel()
if paused {
timer.resume() // If the timer is suspended, calling cancel without resuming triggers a crash. See here for more info: https://forums.developer.apple.com/thread/15902
}
}
private func replaceTimer() {
cancelTimer()
timer = createNewTimer()
}
private func changeBPM() {
replaceTimer() // Create a new timer, which will be configured for the new BPM
}
#objc private func tickCheck() {
if (elapsedTime > tickDuration) || (timeToNextTick < 0.003) { // If past or extremely close to correct duration, tick
tick()
}
}
private func tick() {
lastTickTimestamp = CFAbsoluteTimeGetCurrent()
DispatchQueue.main.sync { // Calls the delegate from the application's main thread, because it keeps the separate threading within this class, and otherwise, it can cause errors (e.g. 'Main Thread Checker: UI API called on a background thread', if the delegate tries to update the UI). See here for more info: https://stackoverflow.com/questions/45081731/uiapplication-delegate-must-be-called-from-main-thread-only
delegate?.bpmTimerTicked() // Have the delegate respond accordingly
}
}
// MARK: - Deinitialization
deinit {
cancelTimer() // Ensure that the timer's cancelled if this object is deallocated
}
}
I have searched many times on the internet but could not find the answer to this question. I know how to pause and resume NSTimers by using the invalidate functions - timer.invalidate. and I know how to resume them. But I have a SpriteKit game. When I pause my game, I stop everything and the timers. I know that I can stop them using .invalidate but when I invalidate them:
For example lets say I have a 5 second timer that runs continously that spawns one block.
When the timer reaches second 3 of the cycle and when I paused the game, and invalidate the timers. When I resume, Now the timers second goes back to 0 and I must wait another 5 seconds. I want it to continue from where it left off, 3 , and wait 2 seconds for the block to spawn.
blockGenerator.generationTimer?.invalidate()
self.isGamePaused = true
self.addChild(self.pauseText)
self.runAction(SKAction.runBlock(self.pauseGame))
e`
and when I resume it:
blockGenerator.generationTimer = ...
I have to wait another 5 seconds, I want the timer to continue from where it left off
If you can help me, I appreciate it thank you.
There is a way to pause/resume Timer instances, because using repeating timers we know the next fire date.
This is a simple class SRTimer and a protocol SRTimerDelegate
Protocol SRTimerDelegate
protocol SRTimerDelegate : AnyObject {
func timerWillStart(_ timer : SRTimer)
func timerDidFire(_ timer : SRTimer)
func timerDidPause(_ timer : SRTimer)
func timerWillResume(_ timer : SRTimer)
func timerDidStop(_ timer : SRTimer)
}
Class SRTimer
class SRTimer : NSObject {
var timer : Timer?
var interval : TimeInterval
var difference : TimeInterval = 0.0
var delegate : SRTimerDelegate?
init(interval: TimeInterval, delegate: SRTimerDelegate?)
{
self.interval = interval
self.delegate = delegate
}
#objc func start(_ aTimer : Timer?)
{
if aTimer != nil { fire(self) }
if timer == nil {
delegate?.timerWillStart(self)
timer = Timer.scheduledTimer(timeInterval: interval, target: self, selector: #selector(fire), userInfo: nil, repeats: true)
}
}
func pause()
{
if timer != nil {
difference = timer!.fireDate.timeIntervalSince(Date())
timer!.invalidate()
timer = nil
delegate?.timerDidPause(self)
}
}
func resume()
{
if timer == nil {
delegate?.timerWillResume(self)
if difference == 0.0 {
start(nil)
} else {
Timer.scheduledTimer(timeInterval: difference, target: self, selector: #selector(start), userInfo: nil, repeats: false)
difference = 0.0
}
}
}
func stop()
{
if timer != nil {
difference = 0.0
timer!.invalidate()
timer = nil
delegate?.timerDidStop(self)
}
}
#objc func fire(_ sender : SRTimer)
{
delegate?.timerDidFire(self)
}
}
Make your class conform to the protocol SRTimerDelegate and initialize a SRTimer instance with
var timer : SRTimer!
timer = SRTimer(interval: 5.0, delegate: self)
Methods
start() calls the delegate method timerWillStart and starts the timer.
pause() saves the difference between the current date and the next fire date, invalidates the timer and calls the delegate method timerDidPause.
resume() calls the delegate method timerWillResume, creates a temporary one shot timer with the saved difference time interval. When this timer fires the main timer will be restarted.
stop() calls the delegate method timerDidStop and invalidates the timer.
When the timer fires, the delegate method timerDidFire is called.
First, let me say this - it is not possible to do with just NSTimer, there is no inbuilt function to do that (you can build logic around that as the answer from Vadian suggests). BUT.
Why NSTimer is not good idea
Lets stop and think for a little. For game objects and precise spawning, you should never use NSTimer in the first place. The problem is implementation of NSTimer (quoting the docs):
Because of the various input sources a typical run loop manages, the
effective resolution of the time interval for a timer is limited to on
the order of 50-100 milliseconds. If a timer’s firing time occurs
during a long callout or while the run loop is in a mode that is not
monitoring the timer, the timer does not fire until the next time the
run loop checks the timer. Therefore, the actual time at which the
timer fires potentially can be a significant period of time after the
scheduled firing time.
There are other problems with NSTimer but that is out of scope of that question.
Solution
What you can do instead, you should listen to delta time change in each update call
let delta = currentPreciseTime - previousPreciseTime
Now, when you have that delta, you can have your counter : Double, and on each update, you increase counter by delta.
let counter : Double
counter += delta
Now that your "timer" is running properly, you can check with simple condition if your period of time already passed, or do whatever you want with it:
let SPAWN_OBJECT_AFTER : Double = 5.0
if counter > SPAWN_OBJECT_AFTER {
// Do something on fire event
self.spawn()
// This line effectively restarts timer
counter -= SPAWN_OBJECT_AFTER
}
You can easily build your own, very easy timer class to do it. Also! This way you have control over what happens in your update call, which is where the update logic belongs. Timer breaks that model by allowing method execution outside that - it might be intended, but usually is not).
I built a games running in production every day and this is I'd say most common solution for periodic events, as it saves the most resources when used appropriately. Obviously not fitting for everything but definitely fits your need.
Hope it helps!
I don't believe there is a way to pause/resume a NSTimer in the way you are talking about. You must use timer.invalidate() and timer.fire(). However, perhaps you can use an int (that starts at 5 and goes down every second) to keep track of how many seconds the initial timer has before fires again and once the times fires again, make sure the new int value is passed to start the initial timer from the correct point in time.