Kinda confusing title but oh well.
I have a UIScrollView in my viewController, in that is 3 UIViews with some buttons in each. I download data from a server and populate it into the view and this works as soon as you start scrolling the UIScrollView, but sometimes the buttons only partially load.
Usually its the button label without my formatting added to it. The button works and as soon as you click the button the rest of view loads correctly. Basically if the UIScrollView is touched in anyway it displays correctly.
I've tried adding and removing the scrollView to the view and I've called [scrollView setNeedsDisplay] and the exact same thing happens.
Anyone come across this?
EDIT: screen shot before and after (just basic to demonstrate whats happening)
I was building the buttons in drawRect which was causing issues. Built the buttons in a separate method and it worked fine.
Related
I have a simple problem but I can't figure it out. I have a UIScrollView with three nested UIWebViews. I need to be able to "recycle" these views to actually scroll through lots of content.
My main problem is that I can't figure out how to show a view that isn't the very first, meaning that you can immediately swipe back from. Right now I have three views paging, but it starts at the first one, and you can move right two.
What can I do to make it so that I am always in the middle? With the ability to always swipe right OR left?
Thanks!
In the viewDidLoad or viewWillAppear methods for your viewController, try adding the following bit of code:
[self.myMainScrollView setContentOffset:CGPointMake(0,self.view.frame.size.width) animated:NO];
That'll scroll your larger scrollview over, so that the middle UIWebView is visible.
If that doesn't help, dig around in the UIScrollView and UIScrollViewDelegate documentation - you should find some good stuff there.
I have a UIScrollView with textviews as subviews. Now in my app there are multiple UIScrollViews like these. And depending on the selection I display the appropriate UIScrollView on top of the previous view. This works fine in all cases except when the previous view has been a UIScrollView as well. In this case the behavior I get is of two UIScrollViews stacked on top of each other and both the views capture the scrolling events. The textViews from previous scrollView is also visible (not editable though) and overlaps and causes all sorts of issues. The thing is a full screen UIScrollView placed as subview to a previous view causes problems when the previous view is a full screen UIScrollView as well.
Any pointers on how to overcome this would be great. Is there anyway to notify the parent scrollview of the child's scroll events and move it the exact same way so this mess is masked?
Thanks!
UIScrollView documentation says:
Important: You should not embed UIWebView or UITableView objects in UIScrollView objects. If you do so, unexpected behavior can result because touch events for the two objects can be mixed up and wrongly handled.
As far as I know, it is generally not recommended to embed a UIScrollView subclass instance in a UIScrollView. In one of my projects, which is an IM application, I have a UIScrollView that contains many UITableViews, it works when you try enough but it really takes a lot of effort to handle subtle bugs and make it work properly.
It is really hard to say something useful for your problem without diving in to code, but i can recommend you to not add UIScrollViews one on to another like a stack. I'd try doing it by allowing only one UIScrollView at top, and removing others. When you need to show another one, remove the top one from view hierarchy and add the new one. I wish this helps, good luck.
Found a crude solution by presenting an empty view before I present the next scrollView. Added the scrollView as subview to this empty view (with a BG image) and added the to-be presented scrollView as a subview to it and then presenting this on top of the previous scrollView.
I have a horizontal UIScrollView that contains UIButtons (though it could be any object). I would like to only download images for these buttons as the user scrolls and they are seen. I would also like an activityindicator running on each button while the images are downloading. Here's what I've tried with results:
Check content offset of uiscrollview and download images for visible buttons. Problem: issues getting activity view shown within subclassed UIButton and not desired usability since images are only downloaded once scrolling stops.
Add subviews (not buttons) to the UIScrollview hoping to use the view's ViewController to initiate a downloaded on viewDidAppear. Problem: viewDidAppear never seems to get called (because I am using addSubView?).
I've seen other apps that do this kind of loading but need some guidance on the typical set-up. Ebay's app is a great example. All items have a default image until the item comes into view, then an activityindicator runs and the items unique image is downloaded.
Thanks for assistance.
Without actually trying it out, here's my idea:
You can use the UIScrollViewDelegate method scrollViewDidScroll: to find out when your scroll view finished scrolling and then use [UIScrollView contentOffset] to determine which part of the scroll view is visible and (CGRect)convertRect:(CGRect)rect fromView:(UIView *)view to determine the button's position within the visible part of the scroll view. Have a method that checks if the button has had its image loaded yet and if not, load it and refresh the view if necessary.
Most such apps are using a UITableView, not a plain scroll view. Joe Hewitt's Three20 framework has a TTImageView class that can do lazy image loading and is pretty well suited to this kind of use.
I'm building an iPhone application and like most I am trying to implement a UIScrollView with a UIPageControl, however I am coming across a very quirky behavior, which I assume may be a bug. Hopefully one of you has seen this before because it is driving me nuts.
Basically, the page control works fine, everything is hooked up and works normally on all accounts EXCEPT, with certain placements of the UIPageControl within the UIView, the UIPageControl will cease to render.
I'll just take screenshots of the XIB window to help illustrate... here's a placement that works perfectly fine:
http://www.jasconi.us/prob1.png
The UIPageControl is placed physically above the UIScrollView. Works great, everything is visible and working.
The next two DO NOT work:
http://www.jasconi.us/prob2.png
http://www.jasconi.us/prob3.png
The first one is simply placed below the scroll view. Doesn't render at all.
The second one is placed above the scroll view without technically being inside of it. Also doesn't render.
What the hell is up with this? I've tried using
[[self view] bringSubviewToFront:pageControl];
...to no avail.
Any ideas?
OK I found the answer to this, it's a little six degrees of Kevin Bacon.
This isn't actually a software bug, but a XIB quirk, for some reason the lower placement of the page control in combination with the default settings for autosize and anchor seem to jettison the control into outer space.
If you turn off all auto-scaling and auto-sizing and auto-anchoring and all that other crap, the controls appear exactly as you expected. The fact that it appears reliably when placed above the ScrollView is an oddity.
shrug.
Hope this helps future iPhone initiates.
Did you check to make sure that numberOfPages is not 0?
If you set a breakpoint can you see that pageControl is not nil?
I was still encountering this exact same problem, even after trying everyone's posted answers. My issue ended up being a little more "DOH":
I was using UIPageControl at the bottom of a modal FormSheet, however, I forgot to set the size of the view as Form Sheet in the xib. This caused my page control to be off the screen and never visible.
Moral: set view size (Full, Form, Page, etc) in your xib on the base view.
This will sound like a real no brainer, but I got caught out by it.
By default, UIPageControl expects to be on a dark background. IE: The dots are light gray, and white for the current page.
I used UIPageControl on it's own with no scrollview to change the time range of a graph I was rendering with drawRect:
Long story short, the graph background was white, so the page controller worked, I just couldn't see it. The solution was putting the graph itself in a subview, and making the parent that contained the page control have a dark background.
I'm having a fundamental problem with getting scrolling to work normally on my iPhone app. I have two views, each created in IB (although I've tried this programmatically and it makes no difference) which scroll very sloppily. Instead of the scrolling that we're used to (which is smooth and continues to scroll and eventually dampen and rubber band at the top/bottom), my scrolling only scrolls as long as my finger is in contact with the view. Swiping down quickly on a view has no more effect than swiping slowly. And when you scroll beyond the top or bottom, the view just stays there scrolled with empty area above/below.
One of my views is a UITableView and the other is a UIScrollView. Both have exactly the same problem and are in different XIBs, coupled to different classes, so this is why I think I'm missing a key concept in general.
My UITableView is a child to a UIView (since there is also a nav bar at the top) with my UIViewController's view connected to the UIView. The referencing outlets datasource and delegate are both hooked to the UITableView. Nothing is subclassed here aside from the ViewController of course which has overrides to populate the table.
In the second instance, I again have a non-subclassed UIView which my UIViewController's view is connected to. I have a subclassed UIScrollView as a child to the UIView and then a have a subclassed UIView (with larger size than the scroll view) as a child to the subclassed UIScrollView. This in itself seems ridiculously complicated to me, but I was not able to get scrolling working at all with fewer than 3 views (again there is a nav bar at the top of the non-subclassed UI-View). I am overriding drawRect: in my UIScrollView, which is putting the content up fine except for this scrolling issue.
Is there something I'm doing wrong organizationally? I've come across many suggestions on stackoverflow and other sites for UIScrollView and none make a difference. And I don't see anyone having scrolling issues with UITableView. I'm not pasting in any code because I would have to post full classes at this point (making the post ridiculously long) and I believe the problems to really lie with the way I'm using IB.
Thanks!!
OK, it turns out that this has nothing to do with UIKit. This code is part of a game I'm developing using cocos2d and that framework is what is causing the problem. For those who are developing on cocos2d, you cannot use FastDirector and expect scrolling to work in UIViews. Just remove any code like [[Director sharedDirector] useFastDirector] and everything will be fine.
Some code might help narrow down your problem.
In the mean time, try creating a new project in Xcode using the 'Navigation-based Application' template and take a look at how the navigation controller is being created in MainWindow.xib. Take a look at how the UITableViewController subclass called 'RootViewController' is defined and how the corresponding xib is setup too. You'll notice there is no UIScrollView explicitly defined anywhere but you get scrolling functionality from the tableview controller 'for free'.
This should give you a pretty good starting point down the right path. I question the need for overriding drawRect: without seeing some code or fully understanding your goal.
Take a look at:
http://developer.apple.com/iphone/library/documentation/UIKit/Reference/UIScrollView_Class/Reference/UIScrollView.html
http://developer.apple.com/iPhone/library/featuredarticles/ViewControllerPGforiPhoneOS/UsingNavigationControllers/UsingNavigationControllers.html