I'm struggling with this problem, although I'm close to the solution, but I guessing I'm missing something.
Here is the situation :
I have UITableView with 30 cells, and one section header (if it's helpful..).
The table size is exactly the size of 3 rows.
The mission : to let the user scroll 3 rows everytime, exactly 3.
I set the pagingEnabled=YES.
What happens is :
"page 1" - 3 rows - ok (rows 0-2)
swiping to "page 2" - next 3 rows - ok (row 3-5)
swiping to "page 3" - and the paging is not good, either skiping row 6 and showing row 7-9
or the page is stopped in the middle of the cell of 6 (also tried to move the scroll to complete cell visibilty with scolling end event, but it skips some of the rows on some pages)
Any ideas how to fix the situation, every page = 3 rows only ,without skipping or showing half of cell ?
I don't mind if the way will be without pagingEnabled=YES.
I arrived at the conclusion this is basic thing I will use in the future , and I think a lot of others will use the solution that other friends will give here.
Thanks.
Never thought of using this property in a Table View.
Since it is a subclass of UIScrollView, try instead to use the UIScrollViewDelegate methods and calculate where to stop.
A good place to start can be in scrollViewWillEndDragging:withVelocity:targetContentOffset:. and return the offset yourself.
P.S.
from the documentation:
This method is not called when the value of the scroll view’s
pagingEnabled property is YES. Your application can change the value
of the targetContentOffset parameter to adjust where the scrollview
finishes its scrolling animation.
Related
When creating a UITableViewController there are two situations that create an "ugly" UX
calling/open it without any data in it --> shows an empty table (i.e. empty rows,UITableViewCell, as many as fit in the window)
calling/open it with fewer rows of content that fit the window --> show the full rows followed by empty rows
I wish to receive the following result:
if there is no data show a picture or view with text - there isn't any data yet or something like that
show only the full lines and no more rows (blank or background image)
Is there a way to achieve that?
To add these effects, you will probably have to make your own UITableViewController from a regular UIViewController, and even subclass UITableView. If you have a regular UIViewController with your filler image/text as the background, you can place a UITableView on top and hook up the delegate/datasource. Now, in your code, detect when there is no data available and set the hidden property of the UITableView accordingly.
As for the following empty rows, you will either have to turn off the row separators (in IB), or subclass a UITableView (can't help you there). Good luck!
I just inherited code which hides/shows rows a UITableView by using the delegate heightForRowAtIndexPath method and returning height 0 for "hidden rows".
The code works, but it has me concerned there might be fraught with unforeseen complications. Can someone either ease my concerns or give me good reasons why this could cause problems (I couldn't find any issues with initial testing).
The table is fairly small <10 rows total and would require custom row heights even without this hidden row solution.
I do the same thing in the code I just worked on. I am not happy with different behaviour for different table view settings.
The alternative in my case is more complex (a model that adapts to what is visible or not).
For now, I put a //HACK comment on it and document a few peculiarities.
This is what I have found (iOS 5.0 tested):
Set tableView.rowHeight = 1; Zero will give a cell with zero height (as returned by tableView:tableView heightForRowAtIndexPath:) some default height.
You must have a cell separator. If none is selected, then a default height is assigned to zero height rows. The height of 1 is included with the separator.
If your code works in a different way, it would be interesting to know how it is set up.
It would be cleaner to add and remove the rows between two beginUpdates and endUpdates calls, but I don't see why this 0-height method should not work.
If there are no UI-artifacts, that is (e.g. the Delete button showing up overflowing to the next cell).
I use this method of setting hidden cell heights to 0. It works well and also means I can animate the inclusion of new cells by expanding the cell height (such as adding a DatePicker Cell like the calendar app does).
A few things I have had to watch out for in iOS 7.1 are that very squashed text does still appear even when a cell height is = 0 so I've needed to remove cell text in that case. Also, I have change the size of the cell's separatorInset as that was appearing as well.
Could you please help me with circular scrolling in tableview please.
I want that if I scroll down tableview, the rows should go in the reverse way --
it should appear that move back around (bottom rows go around and now come back down from the top) i.e, cyclic scrolling basically.
How can I do so. Any suggestions please.
Thanx in advance.
You could "fake" the cyclic scrolling repeating the same cells all over again. In the numberOfRowsInSection method, return n times the actual number of rows. Make sure n is big enough.
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return numberOfActualRows*100;
}
Then in the cellForRowAtIndexPath method (and elsewhere) use the mod operator (%) to return the proper cell.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
NSUInteger actualRow = indexPath.row % numberOfActualRows;
...
}
You may want to hide the sroll indicator.
self.tableView.showsVerticalScrollIndicator = NO;
You may also want to scoll the table view to the middle before you display the table so scrolling backwards works fine.
[self.tableView scrollToRowAtIndexPath: [NSIndexPath indexPathForRow:[self tableView:self.tableView numberOfRowsInSection:0]/2 inSection:0] atScrollPosition:UITableViewScrollPositionTop animated:NO];
Of course, the user would eventually hit the bottom or the top if he/she kept scrolling over and over.
This question has already been asked: implementing a cyclic UITableView
I'm copying that answer here to make it easier because the asker hasn't ticked my answer.
UITableView is same as UIScrollView in scrollViewDidScroll method.
So, its easy to emulate infinite scrolling.
double the array so that head and tail are joined together to emulate circular table
use my following code to make user switch between 1st part of doubled table and 2nd part of doubled table when they tend to reach the start or the end of the table.
:
/* To emulate infinite scrolling...
The table data was doubled to join the head and tail: (suppose table had 1,2,3,4)
1 2 3 4|1 2 3 4 (actual data doubled)
---------------
1 2 3 4 5 6 7 8 (visualising joined table in eight parts)
When the user scrolls backwards to 1/8th of the joined table, user is actually at the 1/4th of actual data, so we scroll instantly (we take user) to the 5/8th of the joined table where the cells are exactly the same.
Similarly, when user scrolls to 6/8th of the table, we will scroll back to 2/8th where the cells are same. (I'm using 6/8th when 7/8th sound more logical because 6/8th is good for small tables.)
In simple words, when user reaches 1/4th of the first half of table, we scroll to 1/4th of the second half, when he reaches 2/4th of the second half of table, we scroll to the 2/4 of first half. This is done simply by subtracting OR adding half the length of the new/joined table.
Written and posted by Anup Kattel. Feel free to use this code. Please keep these comments if you don't mind.
*/
-(void)scrollViewDidScroll:(UIScrollView *)scrollView_
{
CGFloat currentOffsetX = scrollView_.contentOffset.x;
CGFloat currentOffSetY = scrollView_.contentOffset.y;
CGFloat contentHeight = scrollView_.contentSize.height;
if (currentOffSetY < (contentHeight / 8.0)) {
scrollView_.contentOffset = CGPointMake(currentOffsetX,(currentOffSetY + (contentHeight/2)));
}
if (currentOffSetY > ((contentHeight * 6)/ 8.0)) {
scrollView_.contentOffset = CGPointMake(currentOffsetX,(currentOffSetY - (contentHeight/2)));
}
}
P.S. - I've used this code on one of my apps called NT Time Table (Lite). If you want the preview, you can check out the app: https://itunes.apple.com/au/app/nt-time-table-lite/id528213278?mt=8
If your table can sometimes be too short, at the beginning of the above method you can add a if logic to exit when data count is say for example less than 9.
I haven't done this myself, but you could try the approach you'd use with a UIScrollView to implement cycling scrolling of views (after all UITableView is a subclass of UIScrollView).
I would do as follows:
Create a UITableView with an arbitrary number of cells (at least 7 but will need more to prevent fast scrolling bumping at the end)
Position your UITableView so the centre cell is visible
Maintain a pointer to the index of the cell you are looking to display
In your cellForRowAtIndexPath: use your pointer to as an offset and add the row to it to get the cell that you want
When the UITableView has stopped moving (your UITableViewDelegate can serve as UIScrollViewDelegate so you can use scrollViewDidEndDecelerating). Set your offset index to the current cell, move the table view back to the centre cell without animation and reload the data.
The issue you will have is if the user keeps scrolling without stopping they will eventually hit the bumpers as the number of cells in the table is reached.
Hope this helps, and please post back if you get this working and it looks at all reasonable.
Regards
Dave
This is very much difficult to implement. However, take a look at the ScorllingMadness, which shows the demo of nested (cyclic) pages in a scroll-view.
You need to use the similar kind of trick here as UITableView is a subclass of UIScrollView.
I have a grouped UITableView, with cells in section 2 depending on cells in section 1. More precisely, each cell in section 1 is associated with multiple cells of section two and deleting a row in section 1 needs to delete the associated rows in section 2.
I have my dataSources all set up and everything works fine if all cells are visible. However, if the cells from section 2 haven't been loaded in the UITableView yet, I have a problem because the data source is updated for section 2 too.
I'm looking at this method visibleCells in UITableView. But I'm using custom UITableView cells and get an unrecognized selector exception if I try to access one of the labels in a cell.
How do I get around this?
Thanks,
Teja.
I believe what you were looking for is:
if ([tableView visibleCells] containsObject: theCellOfInterest]) {
// Do whatever you want to do.
}
Sorry if I wasn't clear the first time (or maybe even the second time too), but here's an answer to a repost of the same question.
Deleting multiple (not yet loaded) rows in UITableView
I have a UITableView with some empty sections. I'd like the user to be able to move a row into them using the standard edit mode controls. The only way I can do it so far is to have a dummy row in my "empty" sections and try to hide it by using tableView:heightForRowAtIndexPath: to give the dummy row a height of zero. This seems to leave it as a 1-pixel row. I can probably hide this by making a special type of cell that's just filled with [UIColor groupTableViewBackgroundColor], but is there a better way?
This is all in the grouped mode of UITableView.
UPDATE: Looks like moving rows into empty sections is possible without any tricks, but the "sensitivity" is bad enough that you DO need tricks in order to make it usable for general users (who won't be patient enough to slowly hover the row around the empty section until things click).
I found that in iOS 4.3, the dummy row needs to have a height of at least 1 pixel in order to give the desired effect of allowing a row to be moved into that section.
I also found that the dummy row is only needed in the first and last section; any sections in between don't have this problem.
And it looks like in iOS 5.0, no dummy rows or special tricks are needed at all.
While managing the edit, you can monitor if the table view is in Edit Mode. Use that flag inside of cellForRowAtIndexPath to decide weather or not to display the 'blank' row. While in 'regular' mode, the row will not display, but when the user taps 'edit' cellForRowAtIndexPath should get called again and this time decide to display the row. The details of how to do that depend on your data source and how you are gluing it to the display. If you aren't getting the call again, you can manually inject rows with insertRowsAtIndexPaths / deleteRowsAtIndexPaths and/or call reloadData to force a refresh.
I found that if you return -1.0 from the heightForRowAtIndexPath method it will remove the 1 pixel line.