IOS image viewer in swift, programmatically - ios

Question

i am trying to make an imageViewer using this toturial
this toturial
i want to use the "PagedScrollViewController" example and make it using swift,
i am able to display images on screen, but i have issues with the scroll.
the scroll is not stoping between pages/photos, it scrolling freely, so that way loadVisiblePages is always called each pixel that i scroll.
probably i am missing something, can you help me with this please?
here is what i am doing :
thank you
import UIKit
class PagedScrollViewController:UIViewController,UIScrollViewDelegate {
var pageImages:[UIImage] = [UIImage]()
var pageViews:[UIView?] = [UIView]()
var scrollView:UIScrollView = UIScrollView()
var pageControl:UIPageControl = UIPageControl()
func loadVisiblePages() {
// First, determine which page is currently visible
var pageWidth:CGFloat = self.scrollView.frame.size.width;
var page = Int(floor((self.scrollView.contentOffset.x * 2.0 + pageWidth) / (pageWidth * 2.0)));
// Update the page control
self.pageControl.currentPage = page;
// Work out which pages we want to load
var firstPage = page - 1;
var lastPage = page + 1;
// Purge anything before the first page
for (var i=0; i<firstPage; i++) {
println("1) purge index \(i)")
self.purgePage(i)
}
for (var i=firstPage; i<=lastPage; i++) {
println("2) load index \(i)")
self.loadPage(i)
}
for (var i = lastPage+1 ; i < self.pageImages.count ; i++) {
println("3) purge index \(i)")
self.purgePage(i)
}
}
//
func loadPage(page:Int) {
if page < 0 || page >= self.pageImages.count {
// If it's outside the range of what we have to display, then do nothing
return;
}
// Load an individual page, first seeing if we've already loaded it
var pageView:UIView? = self.pageViews[page];
if pageView == nil {
var frame:CGRect = self.scrollView.bounds;
//frame.origin.x = frame.size.width * CGFloat(page)
frame.origin.x = 320.0 * CGFloat(page)
frame.origin.y = 0.0
var newPageView:UIImageView = UIImageView(image: self.pageImages[page])
newPageView.contentMode = UIViewContentMode.ScaleAspectFit;
newPageView.frame = frame;
self.scrollView.addSubview(newPageView)
self.pageViews[page] = newPageView
}
}
func purgePage(page:Int) {
if page < 0 || page >= self.pageImages.count {
// If it's outside the range of what we have to display, then do nothing
return;
}
// Remove a page from the scroll view and reset the container array
var pageView:UIView? = self.pageViews[page];
if pageView != nil {
pageView?.removeFromSuperview()
self.pageViews[page] = UIView()//nil
}
}
override func viewDidLoad() {
super.viewDidLoad()
self.title = "Paged";
self.view.backgroundColor = UIColor.blueColor()
// Set up the image we want to scroll & zoom and add it to the scroll view
self.pageImages.append(UIImage(named: "first.png"))
self.pageImages.append(UIImage(named: "second.png"))
self.pageImages.append(UIImage(named: "first.png"))
self.pageImages.append(UIImage(named: "second.png"))
self.pageImages.append(UIImage(named: "first.png"))
var pageCount = self.pageImages.count
self.scrollView.delegate = self
//self.tableView.showsHorizontalScrollIndicator = false
//self.tableView.showsVerticalScrollIndicator = false
// Set up the page control
self.pageControl.currentPage = 0;
self.pageControl.numberOfPages = pageCount;
self.pageControl.setTranslatesAutoresizingMaskIntoConstraints(false)
self.scrollView.setTranslatesAutoresizingMaskIntoConstraints(false)
self.view.addSubview(self.pageControl)
self.view.addSubview(self.scrollView)
//Set layout
var viewsDict = Dictionary <String, UIView>()
viewsDict["control"] = self.pageControl;
viewsDict["scrollView"] = self.scrollView;
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|-0-[scrollView]-0-|", options: NSLayoutFormatOptions(0), metrics: nil, views: viewsDict))
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|-0-[control]-0-|", options: NSLayoutFormatOptions(0), metrics: nil, views: viewsDict))
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|-0-[scrollView(400)]-[control]-0-|", options: NSLayoutFormatOptions(0), metrics: nil, views: viewsDict))
// Set up the array to hold the views for each page
for (var i = 0; i < pageCount; ++i) {
self.pageViews.append(nil)
}
}
override func viewDidAppear(animated:Bool) {
super.viewDidAppear(animated)
// Set up the content size of the scroll view
var pagesScrollViewSize:CGSize = self.scrollView.frame.size;
self.scrollView.contentSize = CGSizeMake(pagesScrollViewSize.width * CGFloat(self.pageImages.count), pagesScrollViewSize.height);
// Load the initial set of pages that are on screen
self.loadVisiblePages()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// self.scrollView = nil
// self.pageControl = nil
// self.pageImages = nil
// self.pageViews = nil
}
func scrollViewDidScroll(scrollView:UIScrollView ) {
// Load the pages which are now on screen
self.loadVisiblePages()
println("scrollViewDidScroll")
}
}

Answer 1

the problem was i didn't set the 'self.scrollView.pagingEnabled' to true. still i am now to UIKit.
any way i made some performance improvement, and the layout is call only when needed now,
hope someone will find this usfull :)
thanks to http://www.raywenderlich.com
import UIKit
class PagedScrollViewController:UIViewController,UIScrollViewDelegate {
var pageImages:[UIImage] = [UIImage]()
var pageViews:[UIView?] = [UIView]()
var scrollView:UIScrollView = UIScrollView()
var pageControl:UIPageControl = UIPageControl()
var viewingPage = -1
func loadVisiblePages() {
// First, determine which page is currently visible
var pageWidth:CGFloat = self.scrollView.frame.size.width;
var page = Int(floor((self.scrollView.contentOffset.x * 2.0 + pageWidth) / (pageWidth * 2.0)));
/*
Check that page have changed,
in case that user drag left in first page, or drag right in last page
a 'scrollViewDidEndDecelerating' is fired
*/
if viewingPage != page {
// Update the page control
self.pageControl.currentPage = page;
// Work out which pages we want to load
var firstPage = page - 1;
var lastPage = page + 1;
// Purge anything before the first page
for (var i=0; i<firstPage; i++) {
self.purgePage(i)
}
for (var i=firstPage; i<=lastPage; i++) {
self.loadPage(i)
}
for (var i = lastPage+1 ; i < self.pageImages.count ; i++) {
self.purgePage(i)
}
viewingPage = page
}
}
func loadPage(page:Int) {
if page < 0 || page >= self.pageImages.count {
// If it's outside the range of what we have to display, then do nothing
return;
}
// Load an individual page, first seeing if we've already loaded it
var pageView:UIView? = self.pageViews[page];
if pageView == nil {
var frame:CGRect = self.scrollView.bounds;
//frame.origin.x = frame.size.width * CGFloat(page)
frame.origin.x = 320.0 * CGFloat(page)
frame.origin.y = 0.0
var newPageView:UIImageView = UIImageView(image: self.pageImages[page])
newPageView.contentMode = UIViewContentMode.ScaleAspectFit;
newPageView.frame = frame;
self.scrollView.addSubview(newPageView)
self.pageViews[page] = newPageView
}
}
func purgePage(page:Int) {
if page < 0 || page >= self.pageImages.count {
// If it's outside the range of what we have to display, then do nothing
return;
}
// Remove a page from the scroll view and reset the container array
var pageView:UIView? = self.pageViews[page];
if pageView != nil {
pageView?.removeFromSuperview()
self.pageViews[page] = nil
}
}
override func viewDidLoad() {
super.viewDidLoad()
self.title = "Image viewer";
self.view.backgroundColor = UIColor.blueColor()
// Set up the image we want to scroll & zoom and add it to the scroll view
self.pageImages.append(UIImage(named: "message_full.png"))
self.pageImages.append(UIImage(named: "heart_full"))
self.pageImages.append(UIImage(named: "star_full.png"))
self.pageImages.append(UIImage(named: "second.png"))
self.pageImages.append(UIImage(named: "first.png"))
var pageCount = self.pageImages.count
self.scrollView.pagingEnabled = true
self.scrollView.delegate = self
self.scrollView.showsHorizontalScrollIndicator = false
self.scrollView.showsVerticalScrollIndicator = false
// Set up the page control
self.pageControl.currentPage = 0;
self.pageControl.numberOfPages = pageCount;
self.pageControl.setTranslatesAutoresizingMaskIntoConstraints(false)
self.scrollView.setTranslatesAutoresizingMaskIntoConstraints(false)
self.view.addSubview(self.pageControl)
self.view.addSubview(self.scrollView)
//Set layout
var viewsDict = Dictionary <String, UIView>()
viewsDict["control"] = self.pageControl;
viewsDict["scrollView"] = self.scrollView;
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|-0-[scrollView]-0-|", options: NSLayoutFormatOptions(0), metrics: nil, views: viewsDict))
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|-0-[control]-0-|", options: NSLayoutFormatOptions(0), metrics: nil, views: viewsDict))
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|-0-[scrollView(400)]-[control]-0-|", options: NSLayoutFormatOptions(0), metrics: nil, views: viewsDict))
// Set up the array to hold the views for each page
for (var i = 0; i < pageCount; ++i) {
self.pageViews.append(nil)
}
}
override func viewDidAppear(animated:Bool) {
super.viewDidAppear(animated)
// Set up the content size of the scroll view
var pagesScrollViewSize:CGSize = self.scrollView.frame.size;
self.scrollView.contentSize = CGSizeMake(pagesScrollViewSize.width * CGFloat(self.pageImages.count), pagesScrollViewSize.height);
// Load the initial set of pages that are on screen
self.loadVisiblePages()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
//TODO make cleaning
// self.scrollView = nil
// self.pageControl = nil
// self.pageImages = nil
// self.pageViews = nil
}
func scrollViewDidEndDecelerating(scrollView: UIScrollView!) {
self.loadVisiblePages()
}
}