Swipe back and forth across an array of Swift images

Question

I have an array of images that I want to scroll forward (left) to the next image or backward (right) to the previous image. When imageList falls in -1 / out of range, the application crashes. I am having trouble figuring out the logic of how to keep it in range.

Here is my code:

var imageList:[String] = ["image1.jpg", "image2.jpg", "image3.jpg"] let maxImages = 2 var imageIndex: NSInteger = 1 

Napkin gestures are in my viewDidLoad () method, not sure if this is the right place ...:

  override func viewDidLoad() { super.viewDidLoad() // Do any additional setup after loading the view, typically from a nib. var swipeRight = UISwipeGestureRecognizer(target: self, action: "swiped:") // put : at the end of method name swipeRight.direction = UISwipeGestureRecognizerDirection.Right self.view.addGestureRecognizer(swipeRight) var swipeLeft = UISwipeGestureRecognizer(target: self, action: "swiped:") // put : at the end of method name swipeLeft.direction = UISwipeGestureRecognizerDirection.Left self.view.addGestureRecognizer(swipeLeft) image.image = UIImage(named:"image1.jpg") } func swiped(gesture: UIGestureRecognizer) { if let swipeGesture = gesture as? UISwipeGestureRecognizer { switch swipeGesture.direction { case UISwipeGestureRecognizerDirection.Right : println("User swiped right") /*No clue how to make it go back to the previous image and when it hits the last image in the array, it goes back to the first image.. */ case UISwipeGestureRecognizerDirection.Left: println("User swiped Left") if imageIndex > maxImages { imageIndex = 0 } image.image = UIImage(named: imageList[imageIndex]) imageIndex++ default: break //stops the code/codes nothing. } } } 

Many thanks!

Answer 1

First of all, your image index should be zero, since the elements of the array start from zero, but this is not the source of your problem.

 var imageIndex: NSInteger = 0 

then your scroll function should look like this

 func swiped(gesture: UIGestureRecognizer) { if let swipeGesture = gesture as? UISwipeGestureRecognizer { switch swipeGesture.direction { case UISwipeGestureRecognizerDirection.Right : println("User swiped right") // decrease index first imageIndex-- // check if index is in range if imageIndex < 0 { imageIndex = maxImages } image.image = UIImage(named: imageList[imageIndex]) case UISwipeGestureRecognizerDirection.Left: println("User swiped Left") // increase index first imageIndex++ // check if index is in range if imageIndex > maxImages { imageIndex = 0 } image.image = UIImage(named: imageList[imageIndex]) default: break //stops the code/codes nothing. } } } 

Answer 2

You can do something like this.

First you need to set up a position counter that tells you where you are right now. Important: you need to set the start to 0 if you want to start from the first element, because arrays start counting from 0:

 var swipePosition = 0 

Then, if you swipe forward, you need to check if the current swipePosition is greater than the number of images. For this you can use the count method of your array. But you have to subtract 1, because the position starts at 0. Therefore, if it is already at the highest or lowest position in your array, you do not need to do anything. Otherwise, you add or subtract one position:

 //swipe forward if swipePosition > imageList.count-1{ //do nothing because it is already at the highest position }else{ swipePosition += 1 } image.image = UIImage(named: imageList[swipePosition]) //swipe backward if swipePosition == 0 { //Do nothing because it is already at start. }else{ swipePosition -= 1 } image.image = UIImage(named: imageList[swipePosition]) 

Answer 3

`

 @IBOutlet weak var img: UIImageView! var currentnImageIndex:NSInteger = 0 let arrayOfImages = ["Home Filled-50","Bullish-50","Line Chart Filled-50","Stack of Photos Filled-50","News-50","Download From Ftp Filled-50","Administrator Male Filled-50","Trophy Filled-50","Page Overview Filled-50"] override func viewDidLoad() { super.viewDidLoad() img.userInteractionEnabled = true//do not forget to right this line otherwise ...imageView image will not move let swipeRight = UISwipeGestureRecognizer(target: self, action: "swipedRight:") swipeRight.direction = UISwipeGestureRecognizerDirection.Right img.addGestureRecognizer(swipeRight) let swipeLeft = UISwipeGestureRecognizer(target: self, action: "swipedRight:") swipeLeft.direction = UISwipeGestureRecognizerDirection.Left img.addGestureRecognizer(swipeLeft) img.image = UIImage(named: arrayOfImages[currentnImageIndex]) // Do any additional setup after loading the view. } func swipedRight(gesture : UIGestureRecognizer){ if let swipeGesture = gesture as? UISwipeGestureRecognizer{ switch swipeGesture.direction{ case UISwipeGestureRecognizerDirection.Right: print("User swiped right") if currentnImageIndex < arrayOfImages.count - 1 { ++currentnImageIndex } if currentnImageIndex < arrayOfImages.count { img.image = UIImage(named: arrayOfImages[currentnImageIndex]) } case UISwipeGestureRecognizerDirection.Left: print("User swiped left") // --currentnImageIndex if currentnImageIndex > 0{ --currentnImageIndex } if currentnImageIndex >= 0{ img.image = UIImage(named: arrayOfImages[currentnImageIndex]) } // if curretnImageIndex default: break } ` 

Answer 4

 @IBOutlet weak var imageView: UIImageView! var imageIndex:NSInteger = 0 var maximages = 3 var imageList: [String] = ["burger", "burger2", "burger3", "burger4"] override func viewDidLoad() { super.viewDidLoad() let swipeRight = UISwipeGestureRecognizer(target: self, action: #selector(swiped)) // put : at the end of method name swipeRight.direction = UISwipeGestureRecognizerDirection.right self.view.addGestureRecognizer(swipeRight) let swipeLeft = UISwipeGestureRecognizer(target: self, action: #selector(swiped)) // put : at the end of method name swipeLeft.direction = UISwipeGestureRecognizerDirection.left self.view.addGestureRecognizer(swipeLeft) imageView.image = UIImage(named:"burger") } func swiped(gesture: UIGestureRecognizer) { if let swipeGesture = gesture as? UISwipeGestureRecognizer { switch swipeGesture.direction { case UISwipeGestureRecognizerDirection.right : print("User swiped right") // decrease index first imageIndex -= 1 // check if index is in range if imageIndex < 0 { imageIndex = maximages } imageView.image = UIImage(named: imageList[imageIndex]) case UISwipeGestureRecognizerDirection.left: print("User swiped Left") // increase index first imageIndex += 1 // check if index is in range if imageIndex > maximages { imageIndex = 0 } imageView.image = UIImage(named: imageList[imageIndex]) default: break //stops the code/codes nothing. } } } }