Consider the following scenario: A UIScrollView with content inset of top: 500. In this area there is a subview.
When "three finger swiping" to go "to the next page" of the scroll view, the UIScrollView insists that it should never scroll above it's content offset 0. Sometimes it actually scrolls there and says (Page ZERO of 3), but after a while it never jumps there. Is there any way of also including the "content inset" area in the page scrolling?
Here is some test code that replicates this behaviour. Our actual user case is more complex but this is the basic idea:
https://gist.github.com/ullstrm/45bd68032fe92ba13476b506ed70f424
The View Controller has just a single scroll view with all edges constrained to superview with constant 0.
Any ideas of how to let iOS know that it should scroll to this area as well?
You can override Voiceover's scrolling behavior using the accessibilityScroll method. You'll need to manually change UIScrollView's contentOffset, but otherwise it should work just fine.
Related
I have the following autolayout-driven setup:
Main viewController, with a scrollview inside it. Scrollview pinned to superview edges. This one scrolls up and down.
A few normal, fixed size views at the top of the scrollview
Another scrollview. This one scrolls left and right. The second scrollview contains a couple of tableviews, side by side. The idea is that the user can switch between them. They both contain a handful of cells, all the same width as the screen and 72pts tall.
The problem I'm trying to solve is that the tableview contents are not the same size. The left one has say, 6 cells, and the right one has 3.
My first approach was to dynamically change the second scrollview height to match which ever tableview was currently visible. What ended up happening was that switching between the two tableviews (by doing setContentOffset:animated:) went extremely wrong if animated was set to true - it would adjust the content offset so everything was offscreen. In fact it would set the content offset to and then as I switched, about a dozen times, then it'd reset. It was weird, I gave up.
Now I'm trying to just adjust the content inset of the main scrollview to offset the gap in the content of the current tableview, and it's also being weird. When I set the bottom content inset in viewDidLoad, it works fine. When I set it at the time the tableview becomes current, it does nothing.
What gives? What scenarios would lead to these view interactions not behaving properly?
Use different tableViewController for each table.
Embed them in pageViewController.
Add those few normal, fixed size views at the top of the pageViewControllers view.
Conform scrollViewDelegate in pageViewController.
Pass scrollViewDidScroll from tableViews to pageViewController.
Set tableViews inset to match those fixed size views at top.
Change height according to the scroll.
This is the way you can achieve the functionality you want.
I hope it helps.
I have a UITableView in the bottom of UIViewController and tableview height is 100 point now.
The tableview has 20 cells and tableview's header view is 100 point. And I've added a up UISwipeGestureRecognizer and a down UISwipeGestureRecognizer in table view header.
Now I want to change the tableview height constraint constant to 400 in up gesture action and change the tableview height constraint constant to 100 in down gesture action.
Now the problem is gesture recognizer isnt working in tableview
header when tableview scroll is enabled.
If tableview scroll is disabled then the gesture recognizer is
working. But unable to view all cells once the tableview height is
changed.
Here's a different approach. Don't use swipe gesture recognizers at all.
Instead, make the table always the full 400 points tall. Set its contentInset.top to 300. This will allow the table view to scroll so that only its top 100 points of content are visible at the bottom of the screen. Specifically, the table view will allow its contentOffset.y (which is its vertical scrolling position) to go down to -300 (instead of only down to 0). The table's content always starts at y = 0, so when the table's contentOffset.y is -300, only the top 100 points of its content are visible. As the contentOffset.y increases, more of its content becomes visible.
Then, override the table view's point(inside:withEvent:) method to return true only for points with y >= 0. This means the table will ignore (pass through) touches above its content when its content is scrolled so only the top 100 points are visible.
This is the final effect for a small table:
or for a big table:
You can find a detailed explanation (in Objective-C) and a link to the full test project (also in Objective-C) in this answer.
As it may help others, here is the simplest possible solution to this type of problem.
Extremely simple solution -
no tricks, nothing fancy -
don't have a "table view header".
Just make a new UIViewController
class TableWithRedTop: UIViewController
that has ...
[ red area .. swipe detection ]
[ main area - the table view]
Then simply put 'TableWithRedTop' inside a container view.
(Container view tutorial if you need one.)
In your MainView just have a call
func toggleTableHeight
When 'TableWithRedTop' gets a swipe, have one line of code to call toggleTableHeight in MainView
Note that in toggleTableHeight you can easily animate the height change, tilt it on an angle, duplicate it or do anything you want, as you're using a container view in MainView.
I'm going to make another suggestion that may solve the issue for you.
It could be what you want is an:
"self-expanding" table...
First implement the following with no animations, for simplicity.
You have two heights for the table, small and large.
Start the table on height small.
Remarkably, you only have to implement these two rules: just two simple lines of code:
Any time the user is scrolling upwards - in fact, change to "height large".
Any time the user is scrolling downwards, and, you are at the top position of the table (i.e. you can see cell #1) in fact change to "height small".
It's one of those things that is "so simple, it's hard to believe it works!"
It's sometimes referred to as a "pull-up table" I think.
(Note. If you're not familiar with detecting when the user is scrolling, fortunately it is trivial - code shown here for example.)
Set both swipe gesture’s cancelsTouchesInView to true and make sure that the gestures are added directly to the header and not the tableView.
That should do the trick, but so should adding a view with the gesture recognizes to the container view and setting it’s constraints to match the tableView’s top, left, and right constraints and setting its height to 100.
I have a scroll view which works fine. Almost. I'm building in Any/Any. The problem is that the scroll view won't scroll past the view controller. I have a switch that is mostly in the view controller window, but the rest is off the box (not really sure how to describe it; it's in the view in the scroll view, but the view is longer than the view controller so part of it is hidden).
The scroll view will scroll down until it hits the part where the view controller would end if you were looking at it in Xcode. There is some more stuff under the switch (labels and another switch). To view these you have to forcefully scroll down. Xcode shows no constraint errors (little red circle with white arrow).
Hopefully this makes sense
A ScrollView needs to know the height and width of the content it is holding in order to know how much to scroll and which direction. Here is a quick read on how ScrollViews work in iOS: https://www.objc.io/issues/3-views/scroll-view/
You can set this programmatically using the contentSize property, but this requires you to know and or calculate the contentSize, which is pretty tedious in most cases.
The correct way of defining the contentSize in iOS is to define AutoLayout constraints in your View. Here is an excellent tutorial on doing just that:
https://www.natashatherobot.com/ios-autolayout-scrollview/
I have a UIScrollView designed with IB.
UIView
UIScrollView
UIView
UITextField
UIButton
...
If I tap on the text field the view scrolls away towards the upper left corner of the screen before the keyboard is appearing. The space above the keyboards remains empty. I can scroll back the view if I drag in this empty space.
I have googled around, but found only postings where users want to scroll UIScrollView. I want the view to stay where it is.
Thanks in advance for any suggestions.
Here's what happened.
You designed the whole thing in Interface Builder.
The scroll view was not scrolling, so you set its contentSize in code to the size of the scroll view's primary subview (what I like to call the content view).
The scroll view was still not scrolling, so you munged the content insets - and this caused the problem that brought you here.
Your mistake was (3). Instead, you should have thought more about (2), i.e., why isn't my scroll view scrolling even though I have given it a nice big content size?
The answer is that, in a storyboard or xib that has auto layout turned on, that's not what you do. What you do is use constraints from the content view to its superview (the scroll view), on all four sides. Set the constant for all four constraints to zero. This causes the content size to match the size of the content view, automatically.
UIScroll view lets me declared a scrollable area when I have too much content for one page. Strangely, the scroll view in question behaves as desired in the X-axis, with no scrolling whatsoever allowed. Unfortunately, the Y axis -- where scrolling is necessary -- doesn't 'clip' the allowed scroll area to the content size. The user can scroll outside of the content size, and only after they let go does scroll view 'bounce' back to the allowed zone.
I want to prevent the user from scrolling further up than there is content to view (down doesn't bother me) because it looks 'wrong' to have the header at the top of the scroll view pull down, leaving the regular background behind it.
If you are making your UIScrollView in interface this is as simple as deselecting the
"Bounces, Bounces Horizontally, and Bounces Vertically"
check boxes in your scrollView's attributes. If you are designing the UIScrollView in code you can add this.
self.textView.alwaysBounceHorizontal = NO;
self.textView.alwaysBounceVertical = NO;
self.textView.bounces = NO;