I have two table views set up side by side, and I need them to scroll at exactly the same time. So, when you scroll one, the other one will scroll at the same time.
I did some searching and I couldn't find any information, but I assume it must be possible somehow.
My table views are both connected to the same class and I differentiate between them like this:
if tableView == tableView1 {
//
} else if tableView = tableView2 {
//
}
You can get set the scrollView delegate to self on both of your tableView's scrollViews. And in -scrollViewDidScroll, take the contentOffset and set the other scrollView's contentOffset to the same value.
Like Schemetrical said you should use scrollViewDidScroll.
see the first answer of this:
Scrolling two UITableViews together
- (void)scrollViewDidScroll:(UIScrollView *)scrollView;
{
UITableView *slaveTable = nil;
if (self.table1 == scrollView) {
slaveTable = self.table2;
} else if (self.table2 == scrollView) {
slaveTable = self.table1;
}
[slaveTable setContentOffset:scrollView.contentOffset];
}
If you want them to scroll in prefect lock-step then this isn't a trivial problem. UITableView is a subclass of UIScrollview, so you could probably create a custom subclass of UITableView that overrode various UIScrollView methods and when something caused the table view to scroll, it would do the same thing to the other table view.
Edit: #Schemetrical's suggestion of using the scroll view delegate is cleaner than creating subclasses. You might have to monitor quite a few of the scroll view delegate methods and use them to match the behavior in the other scroll view.
EDIT #2:
Apparently I'm wrong and scrollViewDidScroll is called for every change in the scroll view, so it's simpler than I thought to keep them synced. I'm going to leave my answer for context even though I was wrong.
Related
I have the following layout in my view controller. I want to be able to scroll vertically with the header scrolling off the view and the UISegmentedControl sticking to the top of the view, beyond that the remaining scroll should be handled by the Collection View.
However I'm a bit confused as to what is the best approach to implemented this layout.
I tried a few implementations with mixed results:
UIScrollView with UICollectionView as subviews: UIScrollView as the parent view with the header, segmented control and collection views as child controls. The problem with this approach is that the nested scrolling does not seem to work correctly. To be able to scroll the UIScrollView the tap needs to be outside the CollectionView area otherwise only the CollectionView scrolls and the header and segmented control don't move.
Header and Segmented Control in Header cell: I tried another approach by using a single CollectionView. I added the header and Segmented Control as subviews of a single Header cell of the collection view. When the segmented control value was changed, I switch the data source property of the CollectionView to achieve the 3 views required for the collection view. Visually everything works perfectly. The only problem here is the race condition when switching quickly between first,second and third tabs. I load the data from a web service, if the web service takes time and is still loading the data and I quickly switch the tabs then I run into bugs where the data returned is for a different collection view than what is currently selected, a lot of out of order sync issues.
Update constant value for Autolayout Constraint: Another approach I tried is to change the constant value of the auto layout constraint applied to "Header" view. Then I added a gesture to the view controller's view to track the scroll, as the user scrolls vertically I adjust the constant of the auto layout constraint so that the "header" cell pops out of view. Again this doesn't seem to work that smoothly, but I suppose I can tweak it, but it seems sort of a hack.
Is there a better way to implement this layout?
#2 seems like a good solution — the scrolling gestures will be most consistent with what users expect, since it's all a single scroll view. (I agree that #3 sounds like a hack.) You can make the header "sticky" with some custom layout attributes.
The only problem here is the race condition when switching quickly between first, second and third tabs.
This is a common problem with asynchronous loading when views are being switched out (especially when you are loading data into individual cells, which are being reused as you scroll). It is important that upon receiving the data you always check whether the receiver is still expecting it; i.e., you should check the segmented control value before changing the backing data source. You could also:
Use separate data source objects for the different segments, having each one manage its own data fetching so they can't get mixed up.
Cancel the outstanding requests, if you can, when quickly switching tabs, to avoid unnecessary network requests.
Cache data to avoid re-fetching every time you switch tabs.
I think you want the same functionality that pinterest profile page have. To implement such functionality at easy way, you need to do following things.
Step 1 : Add UIView as tableHeaderView those who showing off while scrolling up.
self.tableHeaderView = yourView
Step 2 : Add UISegmentControl in section header view.
- (UITableViewHeaderFooterView *)headerViewForSection:(NSInteger)section{
return your_segmentcontrolView;
}
Step 3 : Add UICollectionView into first row of first section.
By implementing following way, you can got your desire functionality.
Hope this help you.
An alternative approach you could consider:
Use a UITableView to contain your UI
Create a UITableView, and set your header as the UITableView's headerView.
Use a sectionHeader to contain the segmentedControl.
Place your collectionView inside of a single UITableViewCell. Or alternatively, you may be able to use the UITableView's footerView to contain the gridView.
By using the sectionHeader, this should allow the header to scroll out of view, but then the sectionHeader will stick below the navigationBar or top of the contentView until another section comes into view (and in your case you will only have one section.)
Add Header View, Body View (Holding Segment View & Collection View) into scroll view.
Initially set userInteractionEnabled property to "NO" for collection view.
Track the insect of scroll view always.
If the y-coordinate of the scrolled insect is more than the height of header view, then set userInteractionEnabled property to "YES" so that thereafter collection view can be scrolled.
If user scroll outside the scroll view and try to bring the header view down, i.e Scroll view y-coordinate insect is less than the height of header view, then immediately change the user iteration mode of collection view and allow user to scroll the scroll view till the top.
Rather than implementing this by hand, you could use a library/cocoapod to set this up for you. This one looks like a pretty good fit: https://github.com/iosengineer/BMFloatingHeaderCollectionViewLayout
Plus, the code is open-source, so you can always modify as needed.
All I can say is that you need to subclass UIView and make it a delegate of UIGestureRecognizerDelegate and UICollectionViewDelegate, then in your UIView subclass, do the following, I can't give out anymore information on this because the code, although owned by myself, is proprietary to the point of probably enraging quite a few organizations that I've used this for, so here's the secret sauce:
CGPoint contentOffset = [scrollView contentOffset];
CGFloat newHeight = [_headerView maxHeight] - contentOffset.y;
CGRect frame = [_headerView frame];
if (newHeight > [_headerView maxHeight]) {
frame.origin.y = contentOffset.y;
frame.size.height = [_headerView maxHeight];
[_headerView setFrame:frame];
} else if (newHeight < [_headerView minHeight]) {
frame.origin.y = contentOffset.y;
frame.size.height = [_headerView minHeight];
[_headerView setFrame:frame];
} else {
frame.origin.y = contentOffset.y;
frame.size.height = newHeight;
[_headerView setFrame:frame];
}
if ([_delegate respondsToSelector:#selector(scrollViewDidScroll:)]) {
return [_delegate scrollViewDidScroll:scrollView];
}
You must subclass another UIView that is defined as the header for this custom UiCollectionView. Then, you must declare the UIView custom header view inside the custom subview of the UIView/UICollectionView delegate, and then set the header of that custom subview inside the UICollctionViewdelegate. You should then pull in this compounded subclass of UIView/UIcollectionView into your UIViewController. Oh yes, and in your layoutSubViews, make sure you do the height calculations that are passed through a double layered subclass. So, you will have the following files:
UIVew this is the delegate of UICollectionView and what I mentioned before
UIView this is a UISCrollViewDelegate and this is the header view
UIViewController that pulls in the subclassed UIView in number 1
UIView subclass of number 1 that pulls in number 2 and sets it as its header
In the number 4 part, make sure you do something like this:
- (CGFloat)maxHeight
{
if (SCREEN_WIDTH == 414)
{
return 260;
}else if (SCREEN_WIDTH == 375)
{
return 325;
}else
{
return 290;
}
}
- (CGFloat)minHeight
{
if (SCREEN_WIDTH == 414)
{
return 90;
}else if (SCREEN_WIDTH == 375)
{
return 325;
}else
{
return 290;
}
}
This will then pass through to the UIView subclass that is a compounded subclass as I already explained. The idea is to capture the maxHeight of you header in the subclass of this header UIView (number 2 above), and then pass this into the main UIView subclass that intercepts these values in the scrollViewDidScroll.
Last tidbit of information, make sure you set up your layoutSubviews in all methods to intercept scroll events. For example in number 1 above, the layoutsubviews method is this:
- (void)layoutSubviews
{
CGRect frame = [_headerView frame];
frame.size.width = [self frame].size.width;
[_headerView setFrame:frame];
[super layoutSubviews];
}
This is all I can give you, I wish I could post more, but this should give you an idea of how it's done in production environments for the big time apps you see out in the wild.
One more thing to note. When you start going down the road of intense implementations like this, don't be surprised to learn that, for example, a single view controller in an app that works with methods like I've explained will have anywhere from 30-40 custom subclasses that are either subclasses in their own right or compounded subclasses or subclasses of my own subclasses or my own subclasses. I'm telling you this so you get an idea of how much code is required to get this right, not to scare you, but to let you know that it might take a while to get right, and to not kick yourself in the butt if it takes awhile to make work. Good luck!!
I'm trying to synchronize scrolling in all collection views within a table view (see image link below) :
Example Image :
http://postimg.org/image/dduhr89e5/
The sample that I have been able to find explains how you can sync two separate scroll views by identifying each. However I am unsure how to identify each collection view when they are in a table view. There could be 1 or hundreds that all need synchronized.
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
if ([scrollView isEqual: theFirstScrollView])
{
theSecondScrollView.contentOffset =
CGPointMake(theFirstScrollView.contentOffset.x, 0);
}
else
{
theFirstScrollView.contentOffset =
CGPointMake(theSecondScrollView.contentOffset.x, 0);
}
}
Assuming each collection view has its own cell and the collection views are similar widths (or at least you have that part figured out), here is the approach I would use:
1) Make your VC the delegate for all of the collection views.
2) When any of them scrolls, go through the TableViews visibleCells and set the content offset for the cells collectionView. Also, store the content offset in the viewController.
3) Whenever a new cell is dequeued, set the content offset to that last stored value in the VC.
I'm racking my head over this one, I know this has to be possible but after going over every bit of documentation I still can't come up with something that works well.
Basically, I have a UICollectionView in the LAST cell of a UITableView. What I want to happen is, only when the UITableView is totally scrolled to the bottom, can the UICollectionView in it's last cell start scrolling. And, if the TableView offset reaches the bottom of the CollectionView's tableviewcell during a drag / pan, any additional dragging of the current table view drag / pan should effect the collection view instead of the table view.
Also, when the collection view is scrolling, if a user starts scrolling on the collection view, if the collection view reaches the top of it's scroll (Content Y offset of 0 or less), and additional scrolling of the current pan/drag gesture in affect should cause the containing table view to scroll up.
The reason I want to achieve this effect, is because the table view cell above the last cell containing the collection view, contains a UISegmentControl that toggles the contents of the UICollectionView, and I want the user to be able to toggle this segment at any time while scrolling in the CollectionView. Meaning the collection view has to scroll but the parent table view needs to not scroll..
I've tried playing with the gesture recognizers, and doing something with
– gestureRecognizer:shouldRecognizeSimultaneouslyWithGestureRecognizer:
This gets me halfway there, I can use a flag to return yes/no to this method if the collection view is to scroll into a negative offset (Past it's top offset) or if the table view has reached the end of it's total scroll.. I get sort of close to what I want to achieve, but if I scroll up slowly on the collection view, it doesn't fire the simultaneous recognizer, same happens if I scroll down on the table view too slowly.
Another issue is, I do NOT want the collection view to bounce. However setting bounces to NO totally prevents the simultaneous recognizer to fire at all. I even tried setting content offset to CGPointZero on the collection view in it's viewDidScroll if it's y offset were to dip below zero. This also doesn't work and prevents the simultaneous method from firing...
Does anyone have any idea what to do? Or something to point me in the right direction?
UPDATE -
Still trying at this, I've made little progress towards the behavior I'm trying to achieve. I've messed with toggling userInteractionEnabled in the viewDidScroll method, as have I tried in willBeginDragging. The same with scrollEnabled property.. No luck :( I get a behavior similar to what I want with this, however the parent view will not scroll up until the user lets off the screen and attempts to scroll again..
UPDATE -
Is there anyway to transition the panGestureRecognizer currently handling scroll events DURING scrolling? If I could transition the scroll handler from the child to the parent while still scrolling this would solve my issue. I've looked through apple's gesture related and uiscrollview related documentation and can't find anything close to doing that.
UPDATE -
Just got done trying something like this..
- (CGPoint)maxParentContentOffset
{
return CGPointMake(0, self.parentScrollView.contentSize.height - self.frame.size.height - 44);
}
- (void)parentScrollViewDidScroll:(UIScrollView *)parentScrollView
{
if (self.contentOffset.y > 0) {
self.parentScrollView.contentOffset = [self maxParentContentOffset];
}
}
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
if (scrollView.contentOffset.y < 0) {
scrollView.contentOffset = CGPointZero;
}
}
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
CGPoint translation = [scrollView.panGestureRecognizer velocityInView:scrollView.superview];
if (translation.y < 0) {
[UIView animateWithDuration:0.5f animations:^(void) {
self.parentScrollView.contentOffset = [self maxParentContentOffset];
}];
}
}
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
return YES;
}
However there is a problem... for some reason I keep getting a bad access error on the following method
- (void)parentScrollViewDidScroll:(UIScrollView *)parentScrollView
{
if (self.contentOffset.y > 0) {
self.parentScrollView.contentOffset = [self maxParentContentOffset];
}
}
Specifically setting the content offset. Which is really strange, because with breakpoints I'm seeing parentScrollView and self as being set. I'm wondering if it's not a bad access but it's getting trapped in an infinite loop for some reason? Any ideas?
Even though you may manage to make it work now, embedding a collection view inside a table view (both UIScrollView subclasses) is not a good idea and it will bug as soon as apple modifies their implementation.
Try to migrate to a single UICollectionView layout. After all there's nothing you can't achieve with a collection view that a table view can.
Separate your "table view" and "collection view" in two (or more) collection view sections, then implement layoutAttributesForItemAtIndexPath: differently according to the indexPath.section.
To make it table view-like you'll want to return frames whose width are the same as the collection view.
If your layout is simpler then you could use a UICollectionViewFlowLayout (maybe your already are) and implement collectionView:layout:sizeForItemAtIndexPath: as described above.
Figured this out after a good 8 hours.. I had a confliction due to infinite setting of the parent scroll view offset, since I had multiple objects that were of the same class that received a call whenever their parent view scrolled, both trying to set the same parent view offset to zero, which caused the other class to see scroll changing, and calling their method to change offset, and the process happening infinitely causing a crash.
This code however, solved everything and functions exactly as I was desiring. Hopefully this helps anyone else in the future looking to get congruent scrolling between a parent and child scroll view.
- (CGPoint)maxParentContentOffset
{
return CGPointMake(0, self.parentScrollView.contentSize.height - self.frame.size.height - 44);
}
- (void)parentScrollViewDidScroll:(UIScrollView *)parentScrollView
{
if (self.contentOffset.y > 0 && self.isDragging) {
self.parentScrollView.contentOffset = [self maxParentContentOffset];
}
}
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
if (scrollView.contentOffset.y < 0) {
scrollView.contentOffset = CGPointZero;
}
}
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
CGPoint translation = [scrollView.panGestureRecognizer velocityInView:scrollView.superview];
if (translation.y < 0) {
[UIView animateWithDuration:0.5f animations:^(void) {
self.parentScrollView.contentOffset = [self maxParentContentOffset];
}];
}
}
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
return YES;
}
In an application that I've worked, we needed something close to that, we wanted to have a uitableview inside the first cell of another uitableview, which should be scrollable (you can check the app here)
Our approach was quite different, and we thought about doing it your way, but that way was a bit overkill for the time we had, and needed too much custom control instead of using what apple already gives us.
I'll share our method just for you to have another way to solve your problem, since I can't figure out what is wrong in that method call.
On the outer tableview's datasource lifecycle, we were able to know how our inner table view would be, allowing us to feed our inner table view with all the data, which would then gave us the total content size of the inner table view.
With this info, and since we knew (and in your case, you know) the actual cell where the inner table view would be placed, we make that cell's height equal to the height of the inner tableview content size. With this, the inner table view is 'totally visible'(in your case, the collection view) inside the outer table view cell, but since the cell is so big, it looks like we are scrolling the inner table view when we are simply scrolling a really big, special, cell.
And it won't bounce, if you don't want it too.
In our case, this worked, and the implementation was pretty straight forward.
In your case, and since you have a UISegmentedController, you should do a beginUpdates endUpdates and a 'reloadData', upon press in the UISegmenedController, in your outer table view in order to be able to recalculate the collection view's content size and resize the last cell, but that is pretty straight forward.
I know I'm not answering your question, but this method allowed us to achieve something so similar in such a fast and straight forward way that I thought it was worth sharing.
Hope it helps.
I need to get an array of all the subviews in a UIScrollView. Right now I'm using
NSArray *subviews = [myScrollView subviews];
but this seems to only be returning the subviews that are visible at the time the code is run. I need all the subviews in the whole extent of the UIScrollView, even those that are currently hidden (as in off screen). How would I get that?
Essentially, I'm looking for something like the contentSize property of a UIScrollView, except instead of returning just the size of the UIScrollView if it were big enough to display all of it's content, I want it to return the content itself.
EDIT: I think I've figured it out: the scroll view this isn't working for is actually a UITableView - and I think it's deque-ing the cells that are off screen on me, and that's why they aren't showing up. I'm going to do some testing to confirm.
Try with following code its working for me.
for(UIView * subView in myScrollView.subviews ) // here write Name of you ScrollView.
{
// Here You can Get all subViews of your myScrollView.
// But For Check subview is specific UIClass such like label, button, textFiled etc.. write following code (here checking for example UILabel class).
if([subView isKindOfClass:[UILabel class]]) // Check is SubView Class Is UILabel class?
{
// You can write code here for your UILabel;
}
}
tl;dr
It turns out that
NSArray *subviews = [myScrollView subviews];
will indeed return all the subviews in a UIScrollView *myScrollView, even if they are off-screen.
The Details
The problem I was actually having was that the scroll view I was trying to use this on was actually a UITableView, and when a UITableViewCell in a UITableView goes off-screen, it actually gets removed from the UITableView - so by the time I was calling subviews, the cells I was looking for were no longer in the scroll view.
My workaround was to build all of my UITableViewCells in a separate method called by my viewDidLoad, then put all of those cells into an array. Then, instead of using subviews, I just used that array. Of course, doing it this way hurts the performance a little (in cellForRowAtIndexPath you just return the cell from the array, which is slower than the dequeueReusableCellWithIdentifier method that is typically used), but it was the only way I could find to get the behavior I needed.
I am making a custom header view on my tableview. The custom view has a gradient on it.
I only want that gradient to show if it is the only header visible.
So if a user is scrolling and happens to see two sections of the tableview, the second section on the tableview should not have a gradient.
What is the best approach to do this?
Here are some thoughts:
Perhaps in your table's delegate, you can cache the header views, and every time one is requested, check it's peers to see if they are on screen (determined by UIView's .window property being non-nil).
- (UIView *)tableView:tableView viewForHeaderInSection:section {
if([_headerViews objectAtIndex:section-1].window || [_headerViews objectAtIndex:section+1].window) {
// there are peers on screen
} else {
// this is the only one onscreen
}
}
This is just sample code, and does not ensure that the views are properly initialized, etc. just an idea.