Pagination UIScrollView - ios

Question

Need some help with a complex issue on my paginated scrollview. Im adding multiple pages with tableviews and some more data that could be heavy for memory. But it building up memory with each scroll. I would like my code to only add a subview once and on scroll replace it and release the old on (im using ARC). But the memory is building up, i think its because its adding the subview multiple times.
- (void)scrollViewDidScroll:(UIScrollView *)sender
{
#synchronized(self) {
#autoreleasepool {
CGFloat pageWidth = mainScrollView.frame.size.width;
NSInteger page = round(mainScrollView.contentOffset.x / pageWidth);
int scrollOffset = (page * barWidth)-(mainScrollView.bounds.size.width/2);
if (scrollOffset<=0) {
scrollOffset = 0;
} else if (scrollOffset >= (pageIndicatorScrollView.contentSize.width - pageIndicatorScrollView.frame.size.width)) {
scrollOffset = (pageIndicatorScrollView.contentSize.width - pageIndicatorScrollView.frame.size.width);
}
[pageIndicatorScrollView setContentOffset:CGPointMake(scrollOffset, 0) animated:YES];
if(page < 0)
{
page = 0;
}
if(page >= [categoryScrollersArray count])
{
page = [categoryScrollersArray count] - 1;
}
//page = page +1;
//////////NSLog(#"page = %d",page);
// don't create or delete pages while rotating
if (!isRotating) {
if([categoryScrollersArray count] == 1)
{
if([categoryScrollersArray objectAtIndex:0] == [NSNull null])
{
[self loadScrollViewWithPage:0];
}
}
else if([categoryScrollersArray count] == 2)
{
if([categoryScrollersArray objectAtIndex:0] == [NSNull null])
{
[self loadScrollViewWithPage:0];
}
if([categoryScrollersArray objectAtIndex:1] == [NSNull null])
{
[self loadScrollViewWithPage:1];
}
}
else
{
if(page - 1 < 0)
{
if([categoryScrollersArray objectAtIndex:0] == [NSNull null])
{
[self loadScrollViewWithPage:0];
}
if([categoryScrollersArray objectAtIndex:1] == [NSNull null])
{
[self loadScrollViewWithPage:1];
}
}
else
{
if([categoryScrollersArray objectAtIndex:page - 1] == [NSNull null])
{
[self loadScrollViewWithPage:page - 1];
}
if([categoryScrollersArray objectAtIndex:page] == [NSNull null])
{
[self loadScrollViewWithPage:page];
}
if(page + 1 < [categoryScrollersArray count])
{
if([categoryScrollersArray objectAtIndex:page + 1] == [NSNull null])
{
[self loadScrollViewWithPage:page + 1];
}
}
}
if(page -2 >= 0 )
{
if([categoryScrollersArray objectAtIndex:page -2] != [NSNull null])
{
UIView *u = [categoryScrollersArray objectAtIndex:page-2];
//////////NSLog(#"remove page = %d",page-2);
[u removeFromSuperview];
if (page-2 < [categoryScrollersArray count]) {
if ([categoryScrollersArray objectAtIndex:page-2] == nil) {
[self showUnexpectedBehaviorAlertWithTest:#"An unknown error occured, please reopen the questionnaire. (1307)"];
}
else {
[categoryScrollersArray replaceObjectAtIndex:page-2 withObject:[NSNull null]];
}
}
else {
[self showUnexpectedBehaviorAlertWithTest:#"An unknown error occured, please reopen the questionnaire. (1314)"];
}
}
}
if(page +2 < [categoryScrollersArray count])
{
if([categoryScrollersArray objectAtIndex:page +2] != [NSNull null])
{
UIView *u = [categoryScrollersArray objectAtIndex:page+2];
// [u removeObserver:u.self forKeyPath:#"doReload"];
//////////NSLog(#"remove page = %d",page+2);
[u removeFromSuperview];
if (page+2 < [categoryScrollersArray count]) {
if ([categoryScrollersArray objectAtIndex:page+2] == nil) {
[self showUnexpectedBehaviorAlertWithTest:#"An unknown error occured, please reopen the questionnaire. (1329)"];
}
else {
[categoryScrollersArray replaceObjectAtIndex:page+2 withObject:[NSNull null]];
}
}
else {
[self showUnexpectedBehaviorAlertWithTest:#"An unknown error occured, please reopen the questionnaire. (1337)"];
}
}
}
}
}
[self changeProgressBar:page];
// ////////NSLog(#"viewControllers are %#",viewControllers);
// ////////NSLog(#"questionsScroll.subviews %#",questionsScroll.subviews);
}
}
}
And the other function:
- (void)loadScrollViewWithPage:(int)page
{
if (page < 0)
return;
if (page >= [categoryScrollersArray count])
return;
//Categories * anCat;
//anCat = [catArray objectAtIndex:page];
// replace the placeholder if necessary
CategoryScrollerView *catScroll = [categoryScrollersArray objectAtIndex:page];
if ((NSNull *)catScroll == [NSNull null])
{
Step *aStep = [steps objectAtIndex:page];
NSString *coder = [[NSString alloc] init];
if ([self.visit.savedStatus integerValue] == 2 && [self.visit.state integerValue] == 1) {
coder = #"SAVED";
} else {
coder = #"OPEN";
}
NSString *questCode = [NSString stringWithFormat:#"%#",self.visit.questionnaire.version];
catScroll = [[CategoryScrollerView alloc] initWithFrame:mainScrollView.frame andStep:aStep andDelegate:self andStepname:aStep.name andVisitcode:coder andQuestionnairecode:questCode];
catScroll.autoresizesSubviews = YES;
catScroll.autoresizingMask = UIViewAutoresizingFlexibleWidth|UIViewAutoresizingFlexibleHeight|UIViewAutoresizingFlexibleLeftMargin|UIViewAutoresizingFlexibleRightMargin;
[self setNextBtnTitleForPage:page andView:catScroll];
if (page < [categoryScrollersArray count]) {
if ([categoryScrollersArray objectAtIndex:page] == nil) {
[self showUnexpectedBehaviorAlertWithTest:#"An unknown error occured, please reopen the questionnaire. (1101)"];
}
else {
[categoryScrollersArray replaceObjectAtIndex:page withObject:catScroll];
}
}
else {
[self showUnexpectedBehaviorAlertWithTest:#"An unknown error occured, please reopen the questionnaire. (1108)"];
}
}
// add the controller's view to the scroll view
if (catScroll.superview == nil)
{
CGRect frame = mainScrollView.frame;
frame.origin.x = frame.size.width * page;
frame.origin.y = 0;
catScroll.frame = frame;
[mainScrollView addSubview:catScroll];
// NSDictionary *numberItem = [self.contentList objectAtIndex:page];
// controller.numberImage.image = [UIImage imageNamed:[numberItem valueForKey:ImageKey]];
// controller.numberTitle.text = [numberItem valueForKey:NameKey];
}
}

Answer 1

Doing this inside one view controller is going to be really complex. Especially if you're trying to do all the tableview datasource stuff in there too.
You would be much better off using a UIPageViewController.
It is a container controller (a lot like UINavigationController or UITabBarController) that is used to display view controllers in a paged scroll view type of view.
There are some tutorials here about using UIPageViewController. http://www.raywenderlich.com/?s=uipageviewcontroller&cof=FORID%3A10
Essentially you pass a different table view controller in for each page. It takes a bit of settings up but once it's done it will help make it much easier and will keep memory usage down.
There are lots more tutorials out there too... http://www.appcoda.com/uipageviewcontroller-tutorial-intro/
Also, you don't have to make it full screen. You can use the Page View Controller for only the part of the screen that you want to scroll.