I have multiple section and each section n number of rows. i want to load more cells before end of scroll collection view . i have tried with the following in cellforrowatindexpath but it get stucks and unusual behaviour.
if indexPath.row == transactionsGroupedByDate[indexPath.section].1.count - 5 {
self.loadMore()
}
First, why do you have a .1. here :
transactionsGroupedByDate[indexPath.section].1.count
If you model is ok with this, and loadMore is called (add a breakpoint to check it)
Be sure the method loadMore load datas in background thread. If the UI is stuck, it means you have a request or long work on the main thread.
Using table views in a view controller that is being used as sub views to another controller. They are displaying fine when first created, etc. Selections are working fine, etc.
But when trying to change the display items in the table, the datasource array is being changed and a reload is done on the main thread. The Rows in Section is being called properly with the correct size of the array being returned, etc. BUT cell for row is not being called.
Here is the sub view setup...
[self addChildViewController : SQLTableNames];
[self.view addSubview : SQLTableNames.view];
[SQLTableNames didMoveToParentViewController : self];
Where SQLTableNames is a ViewController with tableview(s) in them
have tried everything, delayed reload, reload on main, etc. Delayed from the main view controller, delayed in the sub view controller, etc.
It's seems like the return from rows in section is simply being ignored.......
Have tried set need display, and Reload Rows at Index Paths. None of these will call the Cell for Row to repaint the table.
All the delegates are fine. It display's once fine and then can't change the table display.
If you called [self.tableView beginUpdates] before your inserts, ensure that you call
[self.tableView endUpdates];
after.
When I call this Code
[[self tableView]reloadRowsAtIndexPaths:[NSArray arrayWithObject:[NSIndexPath indexPathForRow:0 inSection:kSectionShoppingList]] withRowAnimation:UITableViewRowAnimationNone];
HeightForRowAtIndexPath Calls
But in CellForRowAtIndexPath for section 3 row 0 does not call.
Looking for your suggestion.
and it is specific to Device 3g iOS4.0.1.
Is anyone earlier have faced same issue.
Is the cell you are reloading visible ?
Not sure about iOS4.0.1, don't have it installed to test, but on iOS5+, the cellForRowAtIndexPath is not called if the cell is not visible, just tried it in one of my apps.
The issue i have mentioned look like a bug in iOs4.0.1. anyway I have solved it by reloading whole table using reloadData method instead of reloading particular rows.
Make sure your are reloading sections and rows that are visible and corresponding the the right indices in your tableview. Also check that your tableView delegate and datasource are correctly set.
reloadData method as the following comment :
- (void)reloadData; // reloads everything from scratch. redisplays visible rows. because we only keep info about visible rows, this is cheap. will adjust offset if table shrinks
you may also have trouble reloading single rows if your table is mutating, then you should beginUpdate / endUpdate methods
- (void)beginUpdates; // allow multiple insert/delete of rows and sections to be animated simultaneously. Nestable
- (void)endUpdates; // only call insert/delete/reload calls or change the editing state inside an update block. otherwise things like row count, etc. may be invalid.
I'm trying to insert a bunch of rows into an empty UITableView in one step using insertRowsAtIndexPaths. (I know that this doesn't sound all that useful, but it's a simplified version of what I really need to do.)
The issue I'm seeing is that after I make the insertRowsAtIndexPaths call, I get cellForRowAtIndexPath calls for every row I inserted, rather than just those that are visible.
That doesn't seem right. And it's pretty much useless to me if it does this.
The only slightly odd other artifact I see is that when I do this, it actually seems to animate the rows into place. This isn't the withRowAnimation, since that's set to none. But it seems there's some sort of higher level animation concept going on here. I had the off-idea that as it animated the rows into place it thought it needed cells for more/all the rows until they got pushed off screen. But I can't turn off this animation without just using reloadData which I'd prefer to avoid.
Generally I have a data set that changes behind the scenes. I can carefully go through and construct the changes to generate data for the insert/delete/reload calls. But I can't limit that to what's on screen since then it doesn't match the data provider.
I figure I must be missing something ... any ideas?
(I am doing this within a beginUpdates/endUpdates pair but that seems to make no difference.)
I talked to some Apple folks today. The issue is definitely related to the animation that UITableView does when you insert new rows. This is the animation that happens to create new rows for cells, separate from the animation that is used when those rows are brought in via insertRowsAtIndexPaths.
Since the table-level animation creates new rows through a sort of "grow down" kind of thing, during the insert animation small amounts of many cells are considered visible and the table will call cellForRowAtIndexPath for them.
There doesn't seem to be any alternative implementation for this that works for all cases. The recommended solution for my case is to "lie": figure out what cells will exist on page after the animation and insert those. After that animation completes, insert the remainder of cells that won't show and the table won't call cellForRowAtIndexPath.
This requires implementing an object between the table view and the "real" data source that can "lie" to the table view about the number of rows in the table for the duration of the animation. Painful, but that's apparently what has been done in similar cases.
I had the same problem, what I did was to declare an attribute called bMassiveLoad initialized to false.
Before I do the 'massive load' I set it to true and the first thing I do in the cellForRowAtIndexPath was to check for that attribute.
At the end of the 'maseive load' I set it to false again and call reloadData...
I know that it is not a beautiful answer, but it helps me.
I was able to solve this by combining a few answers from here:
set the massive load boolean as needed as suggested by pocjoc
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {
UITableView *tableView = self.tableView;
switch(type) {
case NSFetchedResultsChangeInsert:
massiveLoad = YES;
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
...
}
}
and reload the visible rows when it ends
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
[self.tableView endUpdates];
if (massiveLoad) {
massiveLoad = NO;
[self.tableView reloadRowsAtIndexPaths:[self.tableView indexPathsForVisibleRows] withRowAnimation:UITableViewRowAnimationFade];
}
}
UITableView calls the relevant delegate and data source methods immediately after a call to insertRowsAtIndexPaths to get the cells and other content for visible cells. This is regardless of whether or not animated is set to YES or NO.
See the discussion here
If you only want the tableView to update the visible cells, then just update your dataSource and call [tableView reloadData].
I don't know whether the behavior you describe is correct, but UITableView has got two methods: beginUpdates and endUpdates (here) that are meant to optimize redrawing (so that animating is done only at the end, otherwise they are done one by one and this could possibly produce the call to cellForRowAtIndexPath).
Now, I am not sure if this could help you, but perhaps you can give this a try...
I feel like there may be a different way to go about this, but what I have found is that if you have existing cells in the visible range (for example, if you have 10 cells visible at all times and you initialize the tableView with 10 blank cells), when you add new rows, the extra rows are not called in cellForRowAtIndexPath.
So, what to do about it. This is how I went about fixing this. When I created the tableView, I added cells to the visible region. They were blank. Then, when I inserted new rows, I only added index paths for the extra rows (i.e. if I have 10 visible rows and want to add 50 rows, including the visible rows, I only added 40 since the first 10 already exist). This of course leaves you with 10 blank cells. At this point, you can use:
NSArray *indexPaths = [myTableView indexPathsForVisibleCells];
[myTableView reloadRowsAtIndexPaths:indexPaths withRowAnimation:UITableViewRowAnimationNone];
This selects your 10 visible blank cells and reloads them with the new information you have passed in (I assume you load data into an array for this part). You will need to add a little logic to your cellForRowAtIndexPath method such as:
if (![myDataArray count]) {
// create a blank cell;
} else {
// add context to your cells as you want;
}
This should do the trick for you and only load the cells you have showing on the screen
For swift you can try this
self.mainTableView.beginUpdates()
self.mainTableView.insertRowsAtIndexPaths(indexPaths, withRowAnimation: UITableViewRowAnimation.Fade)
self.mainTableView.reloadRowsAtIndexPaths(self.mainTableView.indexPathsForVisibleRows!, withRowAnimation: UITableViewRowAnimation.Fade)
self.mainTableView.endUpdates()
The UITableView will request the visible cells by cellForRowAtIndexPath: method, and it can reduce the processing time when there are many cells, ex 1k cells, and reduce spent memory by reusable cell mechanism. If you need to process all cells, then you should implement a custom method to re-process your source data, and then call [tableView reloadData] to update the UI.
i am getting images with messages from .net webserver by giving xml input.
that's working fine.
i am sending request for every 3 sec and if any new messages and images are there i just add those messages and images to the array and reload the table view.
That is also fine,But what i need is when i reload table view when ever there is new messages that will be displayed on table view by smooth scrolling the existing row.
same as twitter.
can any one please help me.
Thank u in advance.
if you know the indexPath of newly added row , you could use the below function of UITableView to scroll upto new row with animation (smooth effect).
- (void)scrollToRowAtIndexPath:(NSIndexPath *)indexPath atScrollPosition:(UITableViewScrollPosition)scrollPosition animated:(BOOL)animated
Instead Of completely reloading the table, you should call insertRowsAtIndexPaths:withRowAnimation:
The second option will let you specify how you want it animated
(this will also be much more efficient than reloading all the data every time)
You can do something like the following:
(this makes the assumptions that recievedImageFrom server will be called after the data has already been loaded into the data source object. Also, myDataSourceArray is the array where the data is being stored for the table and myTableView is the UITableView.
-(void)recievedImageFromServer
{
NSUInteger row = [myDataSourceArray count]-1; // This can also be set to 0 if you want
// to insert at the top of the table
NSIndexPath* newIndex = [NSIndexPath indexPathWithIndex:row];
[myTableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndex]
withRowAnimation:UITableViewRowAnimationTop];
}
It will then request the cell from its data source.