I am using [self.messageList scrollToRowAtIndexPath:indexPath atScrollPosition:UITableViewScrollPositionTop animated:NO]; in cellForRowAtIndexPath and it is working fine, when a row is added in table array then it auto scroll upside but the problem is that when I try to see the top rows then it automatically come again last rows. And I am not able to see my all rows. Please let me know where I use this or any other approach to do this.
cellForRowAtIndexPath method is not called for all cell that you have. It is only called for visible cell in your TableView. When You Scroll UITableView then it ask to UITableView that you want to use reusable cell or add to new one. generally we use reusable cell so, it is use 1st no of cell and add at end of cell . it is not create another new cell at the end. so, when you scroll your UITableView it not scroll to end of cell it indexPath is similar to indexPath of first no of cell. so you can not scroll your UITableView at to Down.
use following code may be helpful for you.... :)
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *CellIdentifier = [NSString stringWithFormat:#"S%1dR%1d",indexPath.section,indexPath.row];
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:CellIdentifier];
[self.tblView scrollToRowAtIndexPath:indexPath atScrollPosition: UITableViewScrollPositionTop animated: YES];
// your code
}
// your code
return cell;
}
If you write this code in your cell for row at index path, then it will get called every time you try to scroll manually coz this message is called to draw your cell and you will b directed to the row you specified. Try checking your indexpath in a IF--Else block and scroll only when a certain action happens.
cellForRowAtIndexPath is a method for creating a cell to view .When you scroll this method is called when a cell is viewed.So each time the method called the [self.messageList scrollToRowAtIndexPath:indexPath method(which is called inside cellForRow) is also called and the table scrolls down to that row!!!
Related
In my tableview have custom cells that I initialize from a UITableViewCell class. I have sections for first letters of records and have an indexPath that is being created dynamically.
I wanted to add a search display controller to my tableview. So I did, created all methods to filter data. I am sure that my functions are working well because I am printing array count to screen for search results.
My problem is that the first time view loads, the data is on the screen. But when I hit the search input and type a letter, than I get 'UITableView dataSource must return a cell from tableView:cellForRowAtIndexPath:' error. After I used a breakpoint I saw that my custom cell is nil after searching. Data is exist, but cell is not being initialized.
Here is the code I use for custom cell initializing:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"ObjectCell";
SpeakerCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
NSDictionary *myObject = [[sections valueForKey:[[[sections allKeys] sortedArrayUsingSelector:#selector(localizedCaseInsensitiveCompare:)] objectAtIndex:indexPath.section]] objectAtIndex:indexPath.row];
cell.label1.text = [myObject objectForKey:#"myValue"];
return cell;
}
I believe I made a mistake when putting controls in IB. So I added screenshots of objects:
Connections inspector for my table view
Connections inspector for my search display controller
EDIT: Problem is actually solved, I have used a UISearchBar instead of Search Display Controller but I guess this issue remains unsolved. So I'm willing to try any ways to make it work.
As of here search display controller question,
you need to access the self.tableView instead of tableView:
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:#"CellId"];
// do your thing
return cell;
}
For those using iOS 5 and StoryBoards, you would want to use the following method instead of initWithIdentifier:
initWithStyle:(UITableViewCellStyle)stylereuseIdentifier:(NSString *)reuseIdentifier
Example:
NSString *cellIdentifier = #"ListItemCell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];
}
I'm not sure about how this should work in storeboarding.
But normally you would check if the [tableView dequeueReusableCellWithIdentifier:CellIdentifier] returns a cell.
Because if the cell in not loaded before or there aren't any cells to reuse you will have to create a new cell:
SpeakerCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[SpeakerCell alloc] initWithIdentifier: CellIdentifier];
}
Also when in declaring local variables in Objective-C we tent not to capitalize the first letter.
I had the same issue, with custom cells (built in Storyboard) not being drawn as soon as the first letter was put in the search field. The search was successful however.
Finally I found a good tutorial from Brenna Blackwell suggesting to configure manually the cell drawing in the corresponding subclass of UITableViewCell, adding UILabels and other items.
I am about to go out of my mind here, in my Core Data databse I have a lot of users, i have hooked the database up to a tableviewcontroller via NSFetchedResultController, and when the view loads, I see all my users, and i can perform a push to a detail viewcontroller via storyboard segue... so far so god, my tableview contains a custom cell with an image view and 2 uitextlabels that all has their tag values assigned..
Now, when I perform the search I create a new NSFetchedResultController with a predicate, and performs the performFetch.. I then get the fetchedObjects property and it contains the users that match, so the search request is also working like a charm.. in all my tableviews datasources I check if self.tableView == self.searchdispl.view to see which controller I should query data from.. In all the controllers delegates I check to see which controller is active so i know which view to reload. If i nslog a lot of data it is all fine behind the scenes, the delegate and datasource methods all use the correct view and fetchcontroller..
In my cellForRowAtIndexPath i can log out my user.name, and that is always correct, also when searching.
The issue is that the UISearchDisplayController view that is on top only has empty cells, unless i set my UITableViewControllers dynamic prototype cell to basic, then both tableviews contain that label with the users name ! The segue from the cell still doesn't work, but there is data in the cell.
It seems as the UISearchDisplayControllers view is a generic view, at least when it comes to segues and cell layout...
I have checked all the connections from the UISearchDisplayController to my UITableViewController, and all looks fine...
Why will the SearchDisplayControllers view not accept my cell layout and segue ?
Thank you :)
Update : has just figured out what is going wrong, but not found the solution yet.
In my cellForRowAtIndexPath the cell is always configured as the Default Cell when thr searchdisplayview is in this method.. Do i really need to create my cell in code for the uisearchdisplay to work ? Why can it not use the configured cell from the storyboard ?
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath: (NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"PersonCell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
NSLog(#"Default Cell");
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
NSFetchedResultsController *controller = tableView == self.tableView ? self.fetchedResultsController : self.fetchedResultsControllerForSearch;
Person *p;
p = [controller objectAtIndexPath:indexPath];
[(UILabel*) [cell viewWithTag:1] setText:p.name];
[(UILabel*) [cell viewWithTag:2] setText:#"Status"];
if(p.avatarImage){
UIImage *avatar = [[UIImage alloc] initWithData:p.avatarImage];
[(UIImageView *) [cell viewWithTag:3] setImage:avatar];
}
return cell;
}
The issue was that when i got the cell in cellforrowatindexpath, it didn't get it from the original viewcontrollers tableview, so i changed the line from
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
to
UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:CellIdentifier];
and now all is good, the cell has the layout from storyboard and segues works like a charm..
I have a UITableView with one section. If I click on a cell, the didSelectRowAtIndexPath is triggered as expected. but if the tableview has more rows than that can be shown in a single screen, and if I vertically scroll the tableview and click on a row, the didSelectRowAtIndexPath is not called. It is only triggered if i click on the same row one more time. Is this how the tableviews are supposed to function when you scroll? If not, is there something that I'm missing?
thanks for any help.
Thanks Tim for your input. Adding the if condition did not help though. scrolling was disabled in nib file, enabling it fixed the issue. Thanks again!!
The problem is that your cellForRowAtIndexPath is using dequeue wrong.
(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *SingleCellIdentifier = #"selectioncell";
UITableViewCell *selectionCell = [tableView dequeueReusableCellWithIdentifier:SingleCellIdentifier];
if(selectionCell == nil)
selectionCell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:SingleCellIdentifier] autorelease];
[selectionCell setSelectionStyle:UITableViewCellSelectionStyleBlue];
[selectionCell setAccessoryType:UITableViewCellAccessoryDisclosureIndicator];
}
[[selectionCell textLabel] setText:[[possibleAnswers objectAtIndex:indexPath.row] answerText]];
}
The idea is that dequeueReusableCellWithIdentifier:
gives you a usable cell, but if none is available, it returns nil; if it's nil, you should allocate it yourself. Your code was fetching the dequeued cell, but then ignoring it and simply allocing regardless of dequeue status. Try this and see if it solves your issue.
In my app if user press on any cell in UITableView then accessoryType of cell will be set to check mark like following
-(void)Check:(UITableView *)tableView Mark:(NSIndexPath *)indexPath
{
[self.tableView cellForRowAtIndexPath:indexPath].accessoryType = UITableViewCellAccessoryCheckmark;
buttonCount++;
[selectedCellArray addObject:indexPath];
}
and if user press the same cell then uncheck will happen as follows
-(void)UnCheck:(UITableView *)tableView Mark:(NSIndexPath *)indexPath
{
[self.tableView cellForRowAtIndexPath:indexPath].accessoryType = UITableViewCellAccessoryNone;
buttonCount--;
if (buttonCount == 0) {
[selectedCellArray removeAllObjects];
}
}
and i am calling this
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
if([tableView cellForRowAtIndexPath:indexPath].accessoryType == UITableViewCellAccessoryCheckmark)
{
[self UnCheck:tableView Mark:indexPath];
}
else
{
[self Check:tableView Mark:indexPath];
}
Problem is when i am pressing on 1st cell it call Check method and mark the cell to but when i am scroll down i find 2-3 more cheked cell ...even i did not select those cell...i dont know why and how it checked automatically ...
i hope some one know where is the problem
thank you very much
Because cells will be reused by the tableview. Also set the checkmark/accessory type in your tableView:cellForRowAtIndexPath: method.
ya.. I see this happen a lot.
the correct pattern to manage the UITableViewCell state is NOT to directly manipulate the TableViewCell to update the UI, and always set, draw and create the correct state from cellForRowAtIndexPath (or tableView:willDisplayCell:forRowAtIndexPath:)
Meaning, if the user clicks on the cell and you need to update the UI of that cell, store the new state of that cell in an array or dictionary (I find that an NSMutableDictionary with the NSIndexPath as the key works very well).
then call the reloadRowsAtIndexPaths:withRowAnimation: or just [tableView reloadData] so that the cellForRowAtIndexPath reads that array or Dictionary and correctly draws the cell.
otherwise, the cellForRowAtIndexPath will constantly overwrite your changes and use recycled cells that hold incorrect state.
one exception to this rule would be if you would like a nice animation between the two states... if that is the case, save off your new state, perform your animation right there on the cell, then when the animation completes, call the same reloadRowsAtIndexPaths:withRowAnimation or reloadData so that the cell is redrawn in its new state.
I have a UILabel in a custom UITableViewCell that gets resized when the device is rotated. The text in this label needs to be recalculated after the rotation because I am cutting it down to size and appending some text at the end.
E.g. the datamodel has: "This is a run-on sentence that needs to stop."
In portrait mode it becomes "This is a run-on sent... more"
In landscape mode it becomes "This is a run-on sentence that... more"
From (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation
I am able to access the visible UITableViewCells and update the descriptions.
The problem seems to be that there are UITableViewCells that are cached but I can't get to. When I scroll the UITableView after a rotation, one or two cells that are below the visible area after the rotation don't have the correct text in the label. So they haven't been rendered via (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath - but they weren't returned by [tableView visibleCells] (or via looping through all views returned via [tableView subViews]).
I've tried to access the "extra" cells via this method:
for (int index=max + 1; index < max + 3 && index < [cellTypes count]; index++) {
NSIndexPath *updatedPath = [NSIndexPath indexPathForRow:index inSection:0];
UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:updatedPath];
if (cell == nil) { continue; }
[self updateCellForRotate:cell forRow:index];
}
(where max is the biggest row returned from visibleCells) but cell is always nil.
Is there anyway to flush the cache of UITableViewCells so that they don't get re-used? Or to access them so I can update them?
Thanks!
Two things.
First. In your didRotateFromInterfaceOrientation method you can simply reload the visible rows like so:
- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation) fromInterfaceOrientation
{
[super didRotateFromInterfaceOrientation:fromInterfaceOrientation];
NSLog(#"didRotateFromInterfaceOrientation:%d",fromInterfaceOrientation);
[tableView reloadRowsAtIndexPaths:[tableView indexPathsForVisibleRows] withRowAnimation:UITableViewRowAnimationNone];
}
Then I would recommend you add either the interfaceOrientation number or simply the table width to the dequeue cell name that way the tableView knows that cells in one rotation are different from those in another. Like so:
- (UITableViewCell *)tableView:(UITableView *)tv cellForRowAtIndexPath:(NSIndexPath *)indexPath withType:(NSString *)s_type
{
UITableViewCell *cell = nil;
// add width of table to the name so that rotations will change the cell dequeue names
s_cell = [s_cell stringByAppendingString:[NSString stringWithFormat:#"%#%d",#"Width",(int)tv.bounds.size.width]];
NSLog(#"%#",s_cell);
cell = [tv dequeueReusableCellWithIdentifier:s_cell];
if( cell == nil ) {
cell = [[[UITableViewCell alloc];
initWithFrame:CGRectZero reuseIdentifier:s_cell] autorelease];
}
}
Firstly, to reload all of your table cells use [self.tableView reloadData]
Secondly, add the line of code that is responsible for the shrinking inside the (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath method.
Example:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
//Some identifier and recycling stuff
if (UIInterfaceOrientationIsPortrait(self.interfaceOrientation)) {
//Make labels smaller
}
else {
//Make them bigger
}
}
Or you can just call your updateCellForRotate:forRow: method when making them. But I'm not sure how that function works, so I can't be too specific.
When you create the cell in cellForRowAtIndexPath:, add it to an array. Then, loop through the array, updating the text as necessary.
Hope this helps,
jrtc27
EDIT:
You say they are custom cells - could you not update your text in your UITableViewCell subclass?
So, I was having (what I think was) a very similar problem recently, and none of the posted answers helped me, I'm sorry to say.
My issue was that I deliberately resized and repositioned the UITableView upon rotation, and I did that programatically. The table cells in portrait took up the width of the view, and in Landscape were made somewhat higher but less wide. I then repositioned the elements of the cell depending on the orientation we'd come to.
Upon application start, the first viewing of the table was fine. Then I rotated and found that I appeared to have two instances of some elements, and these appeared to be where the cells had been visible in the first table. Rotating back then corrupted the initial orientation table with elements from the previous table.
I tried all of the applicable answers above, until I looked closer at the cellForRowAtIndexPath code:
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}
I understand cell re-use is a great idea and all, but I really didn't need to retain (as in preserve) any cells and wanted them all bright, spangly and new after each rotation.
EDIT: In my own app I'll have maybe 20-30 rows maximum, as I personally don't like hugely long tables. If there were going to be lots of rows returned for a particular query I'd have some filters available to the user to help them sort out which rows they wanted. If you're going to have loads of rows displayed, then dequeuing them may cause you a performance impact that you don't want.
All I did was comment out the if and the following bracket, and my table cells renewed exactly as I wanted them to:
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
//if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
//}
Apologies for the waffle, and the late answer to an old question.
Ben.
Waffles and cream, or syrup.
You can use this simple line on the shouldAutorotateToInterfaceOrientation method :
self.view.autoresizesSubviews = YES;
For me it works always successfully