How to stop UITableView moveRowAtIndexPath from leaving blank rows upon reordering
- by coneybeare
I am having an issue where in reordering my UITableViewCells, the tableView is not scrolling with the cell. Only a blank row appears and any subsequent scrolling gets an Array out of bounds error without any of my code in the Stack Trace. Here is a quick video of the problem.
Here is the relevant code:
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath {
return indexPath.section == 1;
}
- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath {
BOOL ret = indexPath.section == 1 && indexPath.row < self.count;
DebugLog(@"canMoveRowAtIndexPath: %d:%d %@", indexPath.section, indexPath.row, (ret ? @"YES" : @"NO"));
return ret;
}
- (void)delayedUpdateCellBackgroundPositionsForTableView:(UITableView *)tableView {
[self performSelectorOnMainThread:@selector(updateCellBackgroundPositionsForTableView:) withObject:tableView waitUntilDone:NO];
}
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath {
if (fromIndexPath.row == toIndexPath.row) return;
DebugLog(@"Moved audio from %d:%d to %d:%d", fromIndexPath.section, fromIndexPath.row, toIndexPath.section, toIndexPath.row);
NSMutableArray *audio = [self.items objectAtIndex:fromIndexPath.section];
[audio exchangeObjectAtIndex:fromIndexPath.row withObjectAtIndex:toIndexPath.row];
[self performSelector:@selector(delayedUpdateCellBackgroundPositionsForTableView:) withObject:tableView afterDelay:kDefaultAnimationDuration/3];
}
And here is the generated Stack Trace of the crash:
Exception Type: EXC_BREAKPOINT (SIGTRAP)
Exception Codes: 0x0000000000000002, 0x0000000000000000
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
Application Specific Information:
iPhone Simulator 3.2 (193.3), iPhone OS 3.0 (7A341)
*** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[NSCFArray removeObjectsInRange:]: index (6) beyond bounds (6)'
Thread 0 Crashed: Dispatch queue: com.apple.main-thread
0 CoreFoundation 0x302ac924 ___TERMINATING_DUE_TO_UNCAUGHT_EXCEPTION___ + 4
1 libobjc.A.dylib 0x93cb2509 objc_exception_throw + 56
2 CoreFoundation 0x3028e5fb +[NSException raise:format:arguments:] + 155
3 CoreFoundation 0x3028e55a +[NSException raise:format:] + 58
4 Foundation 0x305684e9 _NSArrayRaiseBoundException + 121
5 Foundation 0x30553a6e -[NSCFArray removeObjectsInRange:] + 142
6 UIKit 0x30950105 -[UITableView(_UITableViewPrivate) _updateVisibleCellsNow] + 862
7 UIKit 0x30947715 -[UITableView layoutSubviews] + 250
8 QuartzCore 0x0090bd94 -[CALayer layoutSublayers] + 78
9 QuartzCore 0x0090bb55 CALayerLayoutIfNeeded + 229
10 QuartzCore 0x0090b3ae CA::Context::commit_transaction(CA::Transaction*) + 302
11 QuartzCore 0x0090b022 CA::Transaction::commit() + 292
12 QuartzCore 0x009132e0 CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 84
13 CoreFoundation 0x30245c32 __CFRunLoopDoObservers + 594
14 CoreFoundation 0x3024503f CFRunLoopRunSpecific + 2575
15 CoreFoundation 0x30244628 CFRunLoopRunInMode + 88
16 GraphicsServices 0x32044c31 GSEventRunModal + 217
17 GraphicsServices 0x32044cf6 GSEventRun + 115
18 UIKit 0x309021ee UIApplicationMain + 1157
19 XXXXXXXX 0x0000278a main + 104 (main.m:12)
20 XXXXXXXX 0x000026f6 start + 54
NOte that the array out of bounds length is not the length of my elements (I have 9), but always something smaller.
I have been trying to solve this for many hours days without avail… any ideas?
UPDATE: More code as requested
In my delegate:
- (UITableViewCellEditingStyle)tableView:(UITableView *)tableView editingStyleForRowAtIndexPath:(NSIndexPath *)indexPath {
return UITableViewCellEditingStyleNone;
}
- (NSIndexPath *)tableView:(UITableView *)tableView targetIndexPathForMoveFromRowAtIndexPath:(NSIndexPath *)sourceIndexPath toProposedIndexPath:(NSIndexPath *)proposedDestinationIndexPath {
int count = [(UAPlaylistEditDataSource *)self.dataSource count];
if (proposedDestinationIndexPath.section == 0) {
return [NSIndexPath indexPathForRow:0 inSection:sourceIndexPath.section];
}else if (proposedDestinationIndexPath.row >= count) {
return [NSIndexPath indexPathForRow:count-1 inSection:sourceIndexPath.section];
}
return proposedDestinationIndexPath;
}
…thats about it. I am using the three20 framework and I have not had any issues with reordering till now. The problem is also not in the updateCellBackgroundPositionsForTableView: method as it still crashes when this is commented out.
