I'm creating my views programmatically. I have a UITableView in my UIViewController subclass that I want to add a scrolling subview to that is not a cell. I want to add some text-based subview to the UITableView that scrolls with the table and starts out above y=0 so the user will only see it if he pushes the table down. That is, it should reside above the first section of my table. If it helps for visualization, I intend to make something similar to those "scroll down to refresh" features and want some indication to the user that scrolling down causes a refresh. Is there any way to do this without something messy like using another UITableViewCell to represent it or abusing the UITableView delegate methods to move a view around whenever the user scrolls?
Simply using [tableView addSubview:] in my viewWillLoad only makes it appear for a split-second then disappear once the table data is loaded. This seems weird to me because UITableView is a subclass of UIScrollView, which is meant to hold other views in it. Using [tableView.backgroundView addSubview] does nothing.
P.S. Why not use a UIRefreshControl for this? I'm still undecided but leaning towards not using one because I don't like how slow that spinning wheel "feels" when the refreshes are usually very very quick. I've been looking at other options like flashing the background subtly and only showing a wheel if it's taking a longer time than usual.
I You can implement pull to refresh with only a table view
To do this using the scroll view delegate, since tableview is a subclass of scroll view.
Set view controller to be the tableview delegate and implement
(void)scrollViewDidScroll:(UIScrollView *)scrollView
When scrollview content offset y value passed a point, add a label to the viewcontroller.view not tableview. When you scroll back or release, remove the view.
You might also be able to add label to the table view and set the frame origin to negative y value, so when you pull the label will move into view (Never tested this do might not work)
Related
Is it possible to let UITableview move up/down whole cell height just like date picker (not stop between the cell top and bottom)?
The class UITableView is a subclass of UIScrollView.
This means that, if the object you specified as your table view's delegate also adopts the UIScrollViewDelegate protocol, that protocol's methods will be called on it whenever the relevant scroll events happen on the table view.
You can use that timing to "fix" the table view's scroll offset in just the right way to simulate the snap-to-row-bnoundary behaviour you're after.
Some examples:
scrollViewDidEndDragging(_:willDecelerate:): Tells the delegate when dragging ended in the scroll view.
scrollViewDidEndDecelerating(_:): Tells the delegate that the scroll view has ended decelerating the scrolling movement.
Which methods to implement, and what exactly to do in their implementations, will depend on what effect you want to achieve. Play around and see.
I've got a UITableView and a big "button" view in front of it. The "button" view, which has transparent areas, should be able to response to a tap. But enabling user interaction for this view blocks any scrolling touches from getting to the table view located under the "button" view.
The upper view is a UIView (not UIButton). Given how the two views work together, the upper view is essentially part of what's going on with the table view and reacts to the table view being scrolled. But scrolling is the main thing and I'd like the user to have the largest scrolling area possible.
How do I best resolve this conflict so that the table view is scrollable as usual?
I guess you could subclass your UIButton and UITableView common superview, and override its hitTest:withEvent: to verify which view is hit, something like if you are in a clear or an opaque part of the button?
As pbush25 is mentionning however, it goes more or less against Apple's recommendation.
I need to have iOS app with screen like this:
screen
The idea is when user start to scroll down the first UIView to move up until the second UIView reach the top where it will stick and only UICollectionView will continue to move up.
Currently I'm using this structure
UIScrollView (main scroll)
UIView (some banners)
UIView (UISegmentedControl)
UICollectionView (grid with items, scroll is disabled, main scroll is used)
I manage to do it, but I needed to set UICollectionView height constraint manually in the code (calculated based on all items in grid) in order to appear in UIScrollView (everything else is handled by AutoLayout in Storyboard). The problem with this is that UICollectionView think all cells are visible and load them, so the whole recycling & reusing thing does not work. It's even worst because I use willDisplayCell method on UICollectionView to load more data when last cell is displayed, but now it load all pages at once.
My question (actually they are 2)
How can I fix the issue above?
What is the right way to achieve this functionality? Maybe my whole approach is conceptually wrong?
Collection view is a scroll view itself. So maybe you could have same functionality only with Collection view with sections or even custom layout?
My UITableView has a bunch of reusable cells, and when I tap on one of them, it takes me to another view controller (via push segue) showing the details of that cell (let's say it's an item, so it would show details about an item - name, price, image, etc...). When I pop that view controller (by tapping on the back button), the UITableView has a strange behavior:
a) if it's scrolled all the way to the bottom, it will scroll automatically tad up (around 50 points), leaving the last cell barely visible, so I have to scroll back down again. My cell all have 60 points for height.
b) the scrollbar always shows and then disappears, indicating that something is moving that UITableView (although if not scrolled to the bottom, the content will not move automatically).
This happens in multiple UITableView's I have in my app. I am not forcing a reload of the table view in viewWillAppear, so I don't understand what is happening. My content is static after loading from the server (unless the user changes it, and then the reload is executed). But simply showing details of an item and popping that VC doesn't change anything in the table view.
Edit: Okay, I've figured what the problem is: I'm hiding a UIToolbar when pushing that segue. If I keep it always visible (which I don't want), it still shows the scrollbars animating when popping in my table view but doesn't scroll the table view if on the last few rows.
Add the following to viewDidLoad.
self.automaticallyAdjustsScrollViewInsets = NO;
This solved my problem of table view moving down after navigating back to view controller.
I managed to fix the first issue. It seems like the tableview is not taking into account the 44 points of the UIToolbar.
Save the tableview offset in prepareForSegue: (save it in a CGPoint property)
self.tableViewScrollOffset = self.tableView.contentOffset;
Then, in viewWillAppear:, check if it has been modified. If so, restore it.
if(self.tableView.contentOffset.y != self.tableViewScrollOffset.y) {
[self.tableView setContentOffset:self.tableViewScrollOffset];
self.tableViewScrollOffset = CGPointZero;
}
This behavior is indeed a bug in iOS 8.x.
All answers given so far can not really solve the issue. The issue is, that iOS forgets (or doesn't) consider the previously calculated cell sizes, when a table is being redrawn for instance when the view is being pushed.
One approach to solve this can be found here: UITableView layout messing up on push segue and return. (iOS 8, Xcode beta 5, Swift) (so this question is even a duplicate to this one).
However, the solution provided there is overkill and there are certain situations why this caching will fail (for instance a UIContentSizeCategoryDidChangeNotification is not regarded)
But there is a quite simpler solution even though it is odd:
If you are using a manual performSequeWithIdentifier in didSelectRowAtIndexPath, just add a [self.tableView reloadData] just before.
If you are using a IB seque from the cell, just add [self.tableView reloadData] in your prepareForSeque code.
The reason, why this solves the issue is, that this will force iOS to re-estimate the visible cells and so it no longer scrolls the content to another location. Fortunately, tableView reloadData doesn't cost too much overhead here as only the visible cells will be re-estimated.
Just a hunch, have you got a rogue scrollToRowAtIndexPath:atScrollPosition:animated hanging around?
I was also facing this issue. I managed to find it out. The reason in my case is tableview header height was calculating based text and text height was negative due to which tableview was shifting down even though the contentinset and scrollinset are zero.
This was only occurring for first time. Next time it is calculating correct. One weired thing i found is that when Class A (having tableview) have pushed another Class B from init. When keyboard from Class B is opened viewDidLoad of Class A is called. and before Class B is unloaded from navigation controller. Tableview is reloaded for Class A.
Setting the automaticallyAdjustsScrollViewInsets as suggested above did not work neither did caching and setting the tableViewScrollOffset work.
Hence came up with an workaround which worked like a charm for me.
The workaround was to add an Dummy UIView which has height of 1px and width of 320px and place it between the "Top Layout Guide" and the UITableView. This view's background could be set to clear so that it is invisible.
Now using Autolayouts, fix the Dummy View's top to the Top. Now set the tableview's top constraint with respect to Dummy View. Found that this resolved the issue of the tableview's misplacement.
Screenshot of the Dummy View along with the autolayout constraints have been provided for easy reference. The Dummy View has been set to a larger height and red background colour for illustration purpose only.
I have added a subview to my tableview and when ever the user scrolls the tableview, the subview scrolls with it. How do I prevent this? I know it's probably along the lines of not adding the view to the tableview's subviews, but I have no knowledge of any other ways to do this. Thanks.
If you want to make a view a subview of the table view, then you can make it floating (non-scrolling) by changing its origin.y value in the scrollViewDidScroll method.
-(void)scrollViewDidScroll:(UIScrollView *)scrollView {
self.iv.frame = CGRectMake(self.ivOrigin.x, self.ivOrigin.y + self.tableView.bounds.origin.y, self.iv.frame.size.width, self.iv.frame.size.height);
}
In this example, "iv" is a property for an image view, and "ivOrigin" is a property for the initial origin of the image view (defined when I created the image view and its frame in viewDidLoad).
The UITableView is built and intended to be a view of things that scroll.
So, you can either fight that, which as you're discovering is quite hard since everything about the component is built and focused around scrolling and fast display of a subset of the full list data... Or, you can not fight it and put your static item on top of the table as a fixed-position item.
If there's a reason you can't add the table view and your animate-out item in your main view, you can always add a custom UIView class that contains both the table view and your animated view. Have your custom view class expose the contained table view as a .table property, and the container you're putting things in can be tweaked to use "mycontainerObject.tableview" instead of just "tableview" where needed.
Yes, it's a little more work to write the custom UIView subclass and give it a couple properties to hold the UITableView and whatever UIView you're animating out.. but it's likely a lot safer in the long run than trying to "hack" into the UITableView's methods and view hierarchy to try to give it a "fixed in place" behavior.