tableView:cellForRowAtIndexPath called with nil indexPath after deleting item - ios

I have a rather vanilla UITableView managed by an NSFetchedResultsController to display all instances of a given Core Data entity.
When the user deletes an entry in the table view by swiping over it, tableView:cellForRowAtIndexPath: eventually gets called on my UITableViewController with a nil indexPath. Since I had not expected it to be called with a nil indexPath, the app crashes.
I can work around the crash by checking for that nil value and then returning an empty cell. This seems to work, but I still worry that I may have handled something wrong. Any ideas? Has anybody ever seen tableView:cellForRowAtIndexPath: called with a nil indexPath?
Note that this only happens when the user deletes from the table view by swiping over the cell. When deleting an item using the table view editing mode, it doesn't happen. What would be different between the two ways to delete a cell?
So is it really an OK situation to get a nil indexPath in a table view delegate method?
My view controller code is really standard. Here is the deletion:
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
if (editingStyle == UITableViewCellEditingStyleDelete) {
// Delete the row from the data source
NSManagedObject *managedObject = [self.fetchedResultsController objectAtIndexPath:indexPath];
[self.moc deleteObject:managedObject];
NSError *error = NULL;
Boolean success = [self.moc save:&error];
if (!success) { <snip> }
// actual row deletion from table view will be handle from Fetched Result Controller delegate
// [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
} else { <snip> }
}
This will lead to the NSFetchedResultsController delegate method being called:
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
newIndexPath:(NSIndexPath *)newIndexPath
{
UITableView *tableView = self.tableView;
switch(type) {
case NSFetchedResultsChangeDelete:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeInsert: <snip> break;
case NSFetchedResultsChangeUpdate: <snip> break;
case NSFetchedResultsChangeMove: <snip> break;
}
}
And of course, the data source methods are handled by the NSFetchedResultsController, e.g.:
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
id <NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section];
return [sectionInfo numberOfObjects];
}
Many thanks.

It seems like you are deleting the indexPath from table but table data source is not updating.
Did you verify the data source udation process by NSFetchedResultsController is correctly updationg the table data source.?

I would do like this, since you are populating the table directly from your managed context, why not on delete first delete the object from the managed context and then imediately update the table from the context using reloadData. But using your approach i think you need to add beginUpdates and endUpdates:
#pragma mark -
#pragma mark Fetched results controller delegate
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
[self.tableView beginUpdates];
}
- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {
switch(type) {
case NSFetchedResultsChangeInsert:
[self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
newIndexPath:(NSIndexPath *)newIndexPath {
UITableView *tableViews = self.tableView;
switch(type) {
case NSFetchedResultsChangeInsert:
[tableViews insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[tableViews deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeUpdate:
[_delegate configureCell:[tableViews cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
break;
case NSFetchedResultsChangeMove:
[tableViews deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
[tableViews insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
[self.tableView endUpdates];
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection:0];
[self.tableView scrollToRowAtIndexPath:indexPath
atScrollPosition:UITableViewScrollPositionMiddle
animated:NO];
}

I use CoreData in table views and allow the users to delete records and update them all the time, I have them in 4 apps without encountering the problem you mentioned.
I have these FetchedResultsController Delegate Method in my code
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
// The fetch controller is about to start sending change notifications, so prepare the table view for updates.
[self.myTableView beginUpdates];
}
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
// The fetch controller has sent all current change notifications, so tell the table view to process all updates.
[self.myTableView endUpdates];
}

Related

Edit TableView containing NSFetchedResults

When deleting an object from my Core Data that is fetched using NSFetchedResultsController and displayed in a TableView, it does not update the table. It deletes the object just fine however the row remains there until I swap views and return. I have noticed that this issue has only started happening since iOS8 but could be wrong. Below is my code:
#pragma mark - Fetched Results Controller Delegate
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath {
return YES;
}
// Override to support editing the table view.
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
if (editingStyle == UITableViewCellEditingStyleDelete) {
NSManagedObjectContext * context = [self managedObjectContext];
entity * rowToDelete = [self.fetchedResultsController objectAtIndexPath:indexPath];
[context deleteObject:rowToDelete];
//check that the row has deleted data
NSLog(#"Shhiiiiiiiiii...... You done did delete a row...");
NSError * error = nil;
if (![context save:&error]){
NSLog(#"Error: %#", error);
}
//causes a crash
//[self.tableView deleteRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationRight];
//DOES NOT UPDATE THE TABLE
[self.tableView reloadData];
}
}
I use all the normall delegates like so:
- (void) controllerWillChangeContent:(NSFetchedResultsController *)controller{
[self.tableView beginUpdates];
}
- (void) controllerDidChangeContent:(NSFetchedResultsController *)controller{
[self.tableView endUpdates];
}
- (void) controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath{
switch (type) {
case NSFetchedResultsChangeInsert:
[self.tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationRight];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationRight];
break;
case NSFetchedResultsChangeUpdate:{
entity * details = [self.fetchedResultsController objectAtIndexPath:indexPath];
UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:indexPath];
cell.textLabel.text = details.detailString;
}
break;
case NSFetchedResultsChangeMove:
[self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
[self.tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
-(void) controller:(NSFetchedResultsController *)controller didChangeSection:(id<NSFetchedResultsSectionInfo>)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type{
switch (type) {
case NSFetchedResultsChangeInsert:
[self.tableView insertSections:[NSIndexSet indexSetWithIndex: sectionIndex] withRowAnimation:UITableViewRowAnimationRight];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationRight];
break;
case NSFetchedResultsChangeMove:
NSLog(#"A table item was moved");
break;
case NSFetchedResultsChangeUpdate:
NSLog(#"A table item was updated");
break;
}
}
I have searched on Stack and find the generic response "You need to use [self.tableView deleteRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationRight];". This does not work.
Thanks in advance for any help. If I do not respond immediately it's because I am taking a breather or asleep ;-)
NSFetchedResultsController should be able to communicate all the changes for you.
Check that the update functions are being called (i.e. narrow down where the failure might be)
Check that the NSFetchedResultsController instance has the delegate set
Check that you are working the the same, or connected, context (i.e. check that there is even a chance of the notification propagating)
I'm not sure if you can ignore re-ordering (might depend on your approach) but imagine that [object A, row 1] is swapped with [object B, row 2], then object B is deleted, how does the system know which table row to delete (unless you do something extra with the information)
Manually deleting a row from the table will cause a crash as the data source will be out of line with the table -- thus, causing all manner of confusion. The delegate methods for the results are there to enable the synchronisation of the actual results with those shown in the table.
I cut the following out of a working demo (although modified a bunch of stuff on the way). It works and receives changes, and updates the table. There are a few blog posts only a google away that will help too.
- (void)viewDidLoad {
[super viewDidLoad];
_fetchedResultsController = /* my fetched results controller... */;
_fetchedResultsController.delegate = self;
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
NSInteger count = [[_fetchedResultsController sections] count];
return count;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
id sectionInfo = [[_fetchedResultsController sections] objectAtIndex:section];
NSInteger count = [sectionInfo numberOfObjects];
return count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
return [self configureCell:nil atIndexPath:indexPath];
}
- (UITableViewCell *)configureCell:(UITableViewCell*)cell atIndexPath:(NSIndexPath*)indexPath {
id obj = [self.fetchedResultsController objectAtIndexPath:indexPath];
if(!cell) {
cell = [self.tableView dequeueReusableCellWithIdentifier:#"MyTableViewCell" forIndexPath:indexPath];
}
cell.textLabel.text = obj.someProperty;
return cell;
}
#pragma mark NSFetechResults delegate
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
[self.tableView beginUpdates];
}
- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id )sectionInfo
atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {
switch(type) {
case NSFetchedResultsChangeInsert:
[self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex]
withRowAnimation:UITableViewRowAnimationAutomatic];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex]
withRowAnimation:UITableViewRowAnimationAutomatic];
break;
default:
break;
}
}
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
newIndexPath:(NSIndexPath *)newIndexPath {
UITableView *tableView = self.tableView;
switch(type) {
case NSFetchedResultsChangeInsert:
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]
withRowAnimation:UITableViewRowAnimationAutomatic];
break;
case NSFetchedResultsChangeDelete:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]
withRowAnimation:UITableViewRowAnimationAutomatic];
break;
case NSFetchedResultsChangeUpdate:
[self configureCell:[tableView cellForRowAtIndexPath:indexPath]
atIndexPath:indexPath];
break;
case NSFetchedResultsChangeMove:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]
withRowAnimation:UITableViewRowAnimationAutomatic];
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]
withRowAnimation:UITableViewRowAnimationAutomatic];
break;
}
}
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
[self.tableView endUpdates];
}
I stupidly placed
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
[self.tableView endUpdates];
}
At the beginning before the actions could update. Rookie mistake. Hope it helps anyone else who falls for the same thing.

UITableView row delete crashes app

I have a Core Data based table view that has a simple delete method. It is straightforward code that can be found in countless tutorials, however, it crashes the app with the following message:
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid update: invalid number of rows in section 0. The number of rows contained in an existing section after the update (2) must be equal to the number of rows contained in that section before the update (2), plus or minus the number of rows inserted or deleted from that section (0 inserted, 1 deleted) and plus or minus the number of rows moved into or out of that section (0 moved in, 0 moved out).'
The delete method is as follows:
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
if (editingStyle == UITableViewCellEditingStyleDelete) {
// get garden to delete, delete it through Core Data
Garden *gardenToDelete = [self.fetchedResultsController objectAtIndexPath:indexPath];
NSLog(#"Garden name: %#", gardenToDelete.gardenName);
[self.managedObjectContext deleteObject:gardenToDelete];
[self.managedObjectContext save:nil];
[self.tableView beginUpdates];
[self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationRight];
[self.tableView endUpdates];
}
}
I have spent hours rearranging the code, removing the beginUpdate and endUpdate calls, checking other solutions. Help is greatly appreciated.
You just need to delete the object from your NSFetchedResultsController, the fetched results controller will then update the table view assuming you've implemented the delegate methods as described in the docs. You shouldn't touch the table view rows, the NSFetchedResultsControllerDelegate does all of that.
-(void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath{
if (editingStyle == UITableViewCellEditingStyleDelete) {
// deleting cell from fetched results contoller
Garden *gardenToDelete = [self.fetchedResultsController objectAtIndexPath:indexPath];
NSLog(#"Garden name: %#", gardenToDelete.gardenName);
[self.managedObjectContext deleteObject:gardenToDelete];
[self.managedObjectContext save:nil];
}
}
Do you implement - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section with a return value with NSFetchedResultsController? After you do save, self.fetchedResultsController will refresh, but make sure all of the dataSource of tableView return value is depended on self.fetchedResultsController.
Do you implement these methods:
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
// The fetch controller is about to start sending change notifications, so prepare the table view for updates.
[self.tableView beginUpdates];
}
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {
UITableView *tableView = self.tableView;
// my comment: mapIndexPathFromFetchResultsController function, I just use to get indexPath. You can remove it
indexPath = [self mapIndexPathFromFetchResultsController:indexPath];
newIndexPath = [self mapIndexPathFromFetchResultsController:newIndexPath];
switch(type) {
case NSFetchedResultsChangeInsert:
{
[tableView insertRowsAtIndexPaths:#[newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
}
case NSFetchedResultsChangeDelete:
{
[tableView deleteRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
}
case NSFetchedResultsChangeUpdate:
{
UITableViewCell *cell;
cell = [tableView cellForRowAtIndexPath:indexPath];
if (cell != nil)
{
// my comment: just use the same with cellForRowAtIndexPath
// - (void)syncViewConfigureCell:(UITableViewCell *)cell {
// cell.textLabel.text = #""; etc. }
[self syncViewConfigureCell:cell];
}
break;
}
case NSFetchedResultsChangeMove:
{
[tableView deleteRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationFade];
[tableView insertRowsAtIndexPaths:#[newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
}
- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {
switch(type) {
case NSFetchedResultsChangeInsert:
[self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
// The fetch controller has sent all current change notifications, so tell the table view to process all updates.
[self.tableView endUpdates];
}

UITableView isn't updating when didChangeObject is called NSFetchedResultsController

I'm using an NSFetchedResultsController with my UITableView. I successfully receive delegate calls to - (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
newIndexPath:(NSIndexPath *)newIndexPath but none of the changes I make to insert/update/delete rows in the UITableView actually show up. I even just try to set the background color on the UITableView to see if any changes will show up, but they don't show up unless I push a new view controller and then pop back. Then I'll see the background color and the table updates.
My implementation of the didChangeObject: method is really just the boilerplate template:
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
[self.tableView beginUpdates];
}
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
[self.tableView endUpdates];
}
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
newIndexPath:(NSIndexPath *)newIndexPath
{
UITableView *tableView = self.tableView;
switch(type) {
case NSFetchedResultsChangeInsert:
[tableView insertRowsAtIndexPaths:#[newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
tableView.backgroundColor = [UIColor redColor];
break;
case NSFetchedResultsChangeDelete:
[tableView deleteRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeUpdate:
[tableView reloadRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationFade];
tableView.backgroundColor = [UIColor blueColor];
break;
case NSFetchedResultsChangeMove:
[tableView deleteRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationFade];
[tableView insertRowsAtIndexPaths:#[newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
I added a button in the navbar with an IBAction which just calls [self.tableView reloadData]; and whenever I tap that, then all of the insertions and updates show up in the table. However, they don't show up as the changes happen.
What is wrong?
It looks like the delegate calls to didChangeObject (and the other methods) are not happening on the Main thread which means they can't update the UI, but those changes were just silently being dropped.
I updated the three methods I included above so that the bodies of those methods were all dispatched on the main thread and everything works as expected. Here is an example below:
dispatch_sync(dispatch_get_main_queue(), ^{
[self.tableView beginUpdates];
});

Can't drag UITableViewCell from its current position when reorder

I'm trying to make my Core data backed UITableView have reorder ability, After implement all those delegate and some technique for core data mentioned here I found strange behavior. After tap edit button, reorder icon show just fine and I can tap on it, the shadow show up, but when I try to move it to other row, I suddenly lose the focus and the cell move back to its place. Have anyone know the cause of this problem ?
Here is video showing the problem
http://www.youtube.com/watch?v=ugxuLNL7BnU&feature=youtu.be
Here is my code
- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath
{
return YES;
}
in -tableView:moveRowAtIndexPath:toIndexPath I tried the code below and just an empty implementation, but the problem still exist, so I don't think this is not a problem.
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath
{
_changeIsUserDriven = YES;
NSUInteger fromIndex = sourceIndexPath.row;
NSUInteger toIndex = destinationIndexPath.row;
NSMutableArray *newsArray = [[self.fetchedResultsController fetchedObjects] mutableCopy];
News *news = [self.fetchedResultsController.fetchedObjects objectAtIndex:fromIndex];
[newsArray removeObject:news];
[newsArray insertObject:news atIndex:toIndex];
int i = 1;
for (News *n in newsArray) {
n.displayOrder = [NSNumber numberWithInt:i++];
}
[self saveContext];
_changeIsUserDriven = NO;
}
FetchedResultController delegate
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller
{
if (_changeIsUserDriven) {
return;
}
[self.tableView beginUpdates];
}
- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type
{
if (_changeIsUserDriven) {
return;
}
switch(type) {
case NSFetchedResultsChangeInsert:
[self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
newIndexPath:(NSIndexPath *)newIndexPath
{
if (_changeIsUserDriven) {
return;
}
UITableView *tableView = self.tableView;
switch(type) {
case NSFetchedResultsChangeInsert:
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeUpdate:
[self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
break;
case NSFetchedResultsChangeMove:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
if (_changeIsUserDriven) {
return;
}
[self.tableView endUpdates];
}
Finally I found the problem its because external library that I use, IIViewDeckController, After remove that the problem go away.
This is indeed due to the ViewDeckController. I'm using a port in MonoTouch and still encounter the issue. It is due (more specifically) to the UIPanGestureRecognizer. The gesture recognizer is picking up the pan/drag movement and believing that it is meant for itself, so it cancels the touch being sent to the UITableView.
Unfortunately, there is no UIPanGestureRecognizer.direction (horizonal/vertical) property, but there is a post here: UIPanGestureRecognizer - Only vertical or horizontal regarding how to limit the pan gesture to only a certain direction. You will need to modify the ViewDeckController code where it adds the UIPanGestureRecognizer to use the subclassed version from the question above.
I haven't yet tested this (as its 2am and im done for today!) but will update my answer once I have had time to implement this.
As a quick and dirty fix, you can set
panner.cancelsTouchesInView = NO;
This will allow you to move your items, however it will also have its intended result of not cancelling touches in the view, so, depending on your center view's content, it may result in your users pressing a button when they meant to just swipe the view deck to the side.
Another possibility would be to set this property to NO when you set your table into edit mode, and change it back to YES once you are done.

Best way to select a row after inserting it?

I'm working on an iOS app using the Navigation based, CoreData template.
I would like to select and "scroll to visible" a row after it was inserted into the table view. Ideally i'd like to select it, deselect it and select it again, in order to get a kind of flashing effect.
As i am using the method, that the template provaides, namely:
#pragma mark - Fetched results controller delegate
- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller
{
[self.tableView beginUpdates];
}
- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type
{
switch(type)
{
case NSFetchedResultsChangeInsert:
[self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeDelete:
[self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
newIndexPath:(NSIndexPath *)newIndexPath
{
UITableView *tableView = self.tableView;
switch(type)
{
case NSFetchedResultsChangeInsert:
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationTop];
[self.tableView selectRowAtIndexPath:newIndexPath animated:YES scrollPosition:UITableViewScrollPositionMiddle];
break;
case NSFetchedResultsChangeDelete:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
break;
case NSFetchedResultsChangeUpdate:
[self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
break;
case NSFetchedResultsChangeMove:
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]withRowAnimation:UITableViewRowAnimationFade];
break;
}
}
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
[self.tableView endUpdates];
}
i am a bit confused and don't know, where to put that selection code.
If i put a
[tableView selectRowAtIndexPath:<#(NSIndexPath *)#> animated:<#(BOOL)#> scrollPosition:<#(UITableViewScrollPosition)#>]
into
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller,
it selects the row, but deselects it immediately and the scrolling doesn't behave as it should either.
in method controller:didChangeObject:atIndexPath:forChangeType:newIndexPath:
change this section:
case NSFetchedResultsChangeInsert:
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
[tableView scrollToRowAtIndexPath:newIndexPath atScrollPosition:UITableViewScrollPositionMiddle animated:YES];
insertedIndexPath = newIndexPath; //remember for selection
break;
and add method from UIScrollViewDelegate:
- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView {
[self.tableView selectRowAtIndexPath:insertedIndexPath animated:YES scrollPosition:UITableViewScrollPositionNone];
}
remember to add insertedIndexPath variable.
I solved similar problem. I inserted item to beginning of Table and I wanted to select it just right after.
Step 1. - Create a switch to keep state if it shall select first row
#implementation MyTableViewController {
BOOL _selectFirstRow;
}
Step 2. - Switch it to YES while inserting
- (void) controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath
{
UITableView *tableView = self.tableView;
switch (type) {
case NSFetchedResultsChangeInsert:
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]
withRowAnimation:UITableViewRowAnimationFade];
_selectFirstRow = YES;
break;
Step 3. - Create a method to select first row
- (void) selectFirstTableRow
{
[self.tableView selectRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0]
animated:YES
scrollPosition:UITableViewScrollPositionTop];
}
Step 4. - Call the method to select row right after table is updated
- (void) controllerDidChangeContent:(NSFetchedResultsController *)controller
{
[self.tableView endUpdates];
if (_selectFirstRow) {
[self selectFirstTableRow];
_selectFirstRow = NO;
}
}
That's all folks .. if you want select different row, store newIndexPath in class parameter too. That's all. I hope it will help you. Cia!
Mostly same answer as above but with corrected placement of when to call scrollToRowAtIndexPath
in method controller:didChangeObject:atIndexPath:forChangeType:newIndexPath:
change this section:
case NSFetchedResultsChangeInsert:
[tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
//save new index path into your own ivar
self.newlyInsertIndex = newIndexPath
break;
if using boiler plate FRC code, cannot scroll to newly inserted index until table updates finished
Do this in method - (void)controllerDidChangeContent:
if (!self.changeIsUserDriven){
[self.tableView endUpdates];
if (self.newlyInsertedIndex){
//ScrollPositionNone == use least amount of effort to show cell
[self.tableView scrollToRowAtIndexPath:self.newlyInsertedIndex
atScrollPosition:UITableViewScrollPositionNone animated:YES];
//cleanup
self.newlyInsertedIndex = Nil;
}
}
and add method from UIScrollViewDelegate:
- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView {
[self.tableView selectRowAtIndexPath:insertedIndexPath animated:YES scrollPosition:UITableViewScrollPositionNone];
}
remember to add newlyInsertedIndex ivar
This all did not work for me. What I did was:
when I create a new object, I remember it in an instance variable _newInstance
when the object is saved or the creation cancelled, I clear it: _newInstance = nil;
in controllerDidChangeObject I select the row:
- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller
{
[self.tableView endUpdates];
if (_newObject) {
NSIndexPath *ip = [self.fetchedResultsController indexPathForObject:_newObject];
[self.tableView selectRowAtIndexPath:ip animated:YES
scrollPosition:UITableViewScrollPositionMiddle];
}
}

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