I have a tableview with (say) five rows in the only section. The code to edit a custom cell all works, but the problem occurs when I need to reload the table data with new data that has fewer rows, say two. The programme crashes if I have been editing a row that has a higher index than the maximum number of rows in the reloaded table. The exception shows that it is trying to access the higher numbered element beyond the limit of the new table number of rows.
I have tried putting:
[self.tableView selectRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0] animated:YES scrollPosition:UITableViewScrollPositionTop];
in just before the
[self.tableView reloadData];
but it doesn't work.
It can only mean that you are accessing the first row here:
[self.tableView selectRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0] animated:YES scrollPosition:UITableViewScrollPositionTop];
when you do not have the first row.
When you are reloading the tableview, make sure you have atleast one row.
Try doing this:
if([self.tableview numberOfRowsInSection:0]>0)
[self.tableView selectRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0] animated:YES scrollPosition:UITableViewScrollPositionTop];
I believe you used the code below to unselect your cell
[self.tableView selectRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0] animated:YES scrollPosition:UITableViewScrollPositionTop];
If so you should use this instead
NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];
[self.tableView deselectRowAtIndexPath:indexPath animated:NO];
In the end, deselecting the old row (i.e. whilst the old data source was still current) and then selecting the first row with the new data source fixed the problem.
Related
I am trying to create a chat bot like application, I have used a UITableView with custom cells to fit my needs. Whenever a new message is added, I create and insert a new row and then scroll to the bottom of the UITableView. Everything works fine till a certain point, but when the height of the cells change (I have two different type of cells), the animation is messy, it doesn't smoothly scroll to the end and the entire UITableView flashes, which is not a good user experience. I have tried a couple of approaches:
1 - Add the data to the data source array and reload the UITableView, then scroll to the bottom.
2 - Use insertRowsAtIndexPaths then scroll to the bottom.
Both of them have the same issue with scrolling. I have used scrollToRowAtIndexPath to get to the bottom of the UITableView
I have uploaded the code of a demo app that represents simulate the same issue here so it will be easy to understand. Here is a video of the issue. Any help is really appreciated.
This issue MAY NOT occur on a simulator, kindly run the demo project on a device.
After reading all the comments and having a discussion in chat, I noticed this is happening on the iPhone 5C (10.3.3). I ran the demo on an iPhone 5S (11.3) and the issue does not occur. Not sure if this has to do something with the OS.
Reloading whole tableview results in messy scrolling instead insert row at last position.
Make following changes in your Action Methods
- (IBAction)btnLargeCellClicked:(id)sender { // To add large green colored row.
/************ This is the FIRST approach. ***********/
[arrHeight addObject:#"100"];
[arrData addObject:#"1"];
NSIndexPath* ip = [NSIndexPath indexPathForRow:[_myTable numberOfRowsInSection:0] inSection:0];
[_myTable insertRowsAtIndexPaths:#[ip] withRowAnimation:UITableViewRowAnimationFade];
[self scrollTableviewToLastRow];
/************ This is the SECOND approach. ***********/
// [arrHeight addObject:#"100"];
// [_myTable beginUpdates];
// NSIndexPath *row1 = [NSIndexPath indexPathForRow:arrData.count inSection:0];
// [arrData insertObject:#"1" atIndex:arrData.count];
// [_myTable insertRowsAtIndexPaths:[NSArray arrayWithObjects:row1, nil] withRowAnimation:UITableViewRowAnimationFade];
// [_myTable endUpdates];
// [self scrollTableviewToLastRow];
}
And
- (IBAction)btnClicked:(id)sender { // To add small red colored row.
/************ This is the FIRST approach. ***********/
[arrHeight addObject:#"50"];
[arrData addObject:#"1"];
NSIndexPath* ip = [NSIndexPath indexPathForRow:[_myTable numberOfRowsInSection:0] inSection:0];
[_myTable insertRowsAtIndexPaths:#[ip] withRowAnimation:UITableViewRowAnimationFade];
[self scrollTableviewToLastRow];
/************ This is the SECOND approach. ***********/
// [arrHeight addObject:#"50"];
// [_myTable beginUpdates];
// NSIndexPath *row1 = [NSIndexPath indexPathForRow:arrData.count inSection:0];
// [arrData insertObject:#"1" atIndex:arrData.count];
// [_myTable insertRowsAtIndexPaths:[NSArray arrayWithObjects:row1, nil] withRowAnimation:UITableViewRowAnimationFade];
// [_myTable endUpdates];
// [self scrollTableviewToLastRow];
}
Hope this helps :)
After seeing your source, can say tableView reloadData reloads cells every time, that makes animation more busy every additional cell.
For your goals you should use another system:
[self.tableView beginUpdates];
[self.tableView reloadRowsAtIndexPaths:#[indexPathOfYourCell] withRowAnimation:UITableViewRowAnimationAutomatic];
[self.tableView endUpdates];
And than, maybe you will need scrollToRowAtIndexPath at the end too
You would need this, change second approach like below
[arrHeight addObject:#"50"];
// [_myTable beginUpdates];
NSIndexPath *row1 = [NSIndexPath indexPathForRow:arrData.count inSection:0];
[arrData insertObject:#"1" atIndex:arrData.count];
[_myTable insertRowsAtIndexPaths:[NSArray arrayWithObjects:row1, nil] withRowAnimation:UITableViewRowAnimationNone];
[_myTable reloadRowsAtIndexPaths:#[row1] withRowAnimation:UITableViewRowAnimationNone];
// [_myTable endUpdates];
[self scrollTableviewToLastRow];
So it's easy to select a row that is currently in the UITableView. For example, to select the first row:
[self.tableView selectRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0]
animated:YES
scrollPosition:UITableViewScrollPositionNone];
Say that I have an array that is the data source for the table and the array count is greater than the number of cells displayed in the tableview. How can I get the UITableView to scroll to an index from the array that is beyond what is currently being displayed in the tableview?
All I am trying to do is to replicate programmatically what a user would do with their index finger as they scroll down the table.
My specific table displays 9 rows. My array has 20+ items. As the UIViewController loads, it retrieves the row number that should be selected (from an integer stored in NSUserDefaults). But I find that it will only scroll to the correct array position if that integer value is between 0 and 8. If it is 9 or greater, nothing happens, and I can't figure out how to make it respond to this. I've looked at all the UITableViewDelegate methods and none seems to address this.
What I've been doing to scroll and select a specific row is this (example arbitrarily selecting row 11):
[self.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:11 inSection:0]
atScrollPosition:UITableViewScrollPositionTop
animated:YES];
[self.tableView selectRowAtIndexPath:[NSIndexPath indexPathForRow:11 inSection:0]
animated:YES
scrollPosition:UITableViewScrollPositionTop];
Can anyone help me? I assume it isn't difficult, but I'm stuck.
Thanks!
Your cells that are off the screen ain't selecting because you are using reusable cells. The cells from the visible screen will be used later, it isn't that all 100 cells are cached and each cell is responsible for each row. What it means is that they could or couldn't have something in it already. For example, lets say you have cell for row 1. When it comes off the screen, in the next few cells it will be reused as cell 15 or something, and if it had selected properties, it will still have it. It is like a new job and you get a desk from the developer before you - you could have desk with his trash, but it could also be clean.
I wouldn't select them as you select them by method, but in if statement in your cellForRowAtIndexPath. Something along the lines (added comments):
- (UITableViewCell *) tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *cellIdentifier = #"Cell";
// When using method with forIndexPath you don't have to check for nil because you will always get cell
MyTableCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier forIndexPath:indexPath];
MyObj *obj = [self.myArray objectAtIndex:indexPath.row];
cell.location.text = obj.location.location_description;
// other formatting, text display, image loading, etc.
if ([self.selectedObjects containsObject:obj]) {
// do some selecting stuff
} else {
// but don't forget to unselect because you can get already selected cell
}
return cell;
}
Edit: To select invisible cell, first scroll to it, then select:
[self.tableView scrollToRowAtIndexPath:indexPath atScrollPosition:UITableViewScrollPositionTop animated:YES];
[self.tableView selectRowAtIndexPath:indexPath animated:YES scrollPosition:UITableViewScrollPositionTop];
Try using UITableViewScrollPositionBottom instead of UITableViewScrollPositionNone
That is use this code
[self.tableView selectRowAtIndexPath:[NSIndexPath indexPathForRow:10 inSection:0]
animated:YES
scrollPosition:UITableViewScrollPositionBottom];
I figured this out. My code was running in viewDidLoad which is too early. I needed to move it to viewDidAppear. At least I know that I am not losing my mind.
I have set the row insertion with the following code. I am only using UITableViewRowAnimationNone when inserting and deleting the rows, but sometimes ,as you can see in the gif below, the row animates in from the top or bottom. For the most part it doesn't animate, as I want it, but sometimes it animates on insertion and deletion. I am not talking about the table view expanding to show the inserted cell, I mean the cell appears to be sliding in from the bottom or top.
Here is the method that controls the insertion animation:
- (void)contentHeaderFooterView:(NFContentHeaderFooterView *)headerFooterView sectionOpened:(NSInteger)section{
NSIndexPath *pathToAdd = [NSIndexPath indexPathForRow:0 inSection:section];
[self.tableView beginUpdates];
[self.tableView insertRowsAtIndexPaths:#[pathToAdd] withRowAnimation:UITableViewRowAnimationNone];
[self.tableView endUpdates];
}
And here is the method that controls the deletion animation.
- (void)contentHeaderFooterView:(NFContentHeaderFooterView *)headerFooterView sectionClosed:(NSInteger)section{
NSIndexPath *pathToDelete = [NSIndexPath indexPathForRow:0 inSection:section];
[self.tableView beginUpdates];
[self.tableView deleteRowsAtIndexPaths:#[pathToDelete] withRowAnimation:UITableViewRowAnimationNone];
[self.tableView endUpdates];
}
I've had similar issues with table updates not performing the animation I gave it directly. I can't say for sure why, but one thing I can suggest is, instead of doing a specific row deletion between begin/endUpdates, you can just to a hard reloadData.
Answered here: https://stackoverflow.com/a/37352789/577237
Reposted since it's brief:
[UIView performWithoutAnimation:^{
[self.tableView beginUpdates];
[self.tableView deleteRowsAtIndexPaths:rowsToRemove withRowAnimation:UITableViewRowAnimationNone];
[self.tableView endUpdates];
}];
Note that this is iOS 7.0+
When I Use
[self.chatContentTable scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:bottomFlag+2 inSection:0] atScrollPosition:UITableViewScrollPositionTop animated:YES];
when the animated set YES,my tableView will scroll,but when the animated set NO,it donest work
I also found it.
My code is:
[self.tableView reloadData];
[self.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:index inSection:0]atScrollPosition:UITableViewScrollPositionMiddle animated:animation];
It work after remove reloadData.
I guess the reason why it does not take effect is that it's executed immediately after reload
I'm an amateur at best, and stuck on this error! surely something simple...
- (void)addTapped:(id)sender {
TechToolboxDoc *newDoc = [[TechToolboxDoc alloc] initWithTitle:#"New Item" thumbImage:nil fullImage:nil];
[_itemArray addObject:newDoc];
//[self.tableView beginUpdates];
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:_itemArray.count-1 inSection:0];
NSArray *indexPaths = [NSArray arrayWithObject:indexPath];
NSLog(#"%#",indexPath);
[self.tableView insertRowsAtIndexPaths:indexPaths withRowAnimation:YES];
[self.tableView selectRowAtIndexPath:indexPath animated:YES scrollPosition:UITableViewScrollPositionMiddle];
[self performSegueWithIdentifier:#"MySegue" sender:self];
//[self.tableView endUpdates];
it is breaking on the line the says
[self.tableView insertRowsAtIndexPaths:indexPaths withRowAnimation:YES];
You need to add [UITableView beginUpdates] and [UITableView endUpdates] around:
[self.tableView insertRowsAtIndexPaths:indexPaths withRowAnimation:YES];
From the class reference:
Note the behavior of this method when it is called in an animation
block defined by the beginUpdates and endUpdates methods. UITableView
defers any insertions of rows or sections until after it has handled
the deletions of rows or sections. This happens regardless of ordering
of the insertion and deletion method calls. This is unlike inserting
or removing an item in a mutable array, where the operation can affect
the array index used for the successive insertion or removal
operation. For more on this subject, see Batch Insertion, Deletion,
and Reloading of Rows and Sections in Table View Programming Guide for
iOS.
I think you are inserting the row in your tableView but not updating the number of rows at section that's why you are getting error in this line. So along with inserting the row You should also increase the array count or whatever you are using to show the number of rows in table view.
In my case, I was using Parse and I deleted a few users (one of which was my iPhone simulator). I got this error whenever refreshing the tableView.
I just deleted the app from the Simulator and made a new account and it works flawlessly.
#droppy's answer helped give me the lightbulb moment of what was wrong!
Hope that helps someone.