UITableView Cell Insert Row Glitch - ios

Question

I have a table view with custom cells (all configured in a subclass using auto layout).
The cells load fine, display fine, everything is fine.
The issue is when I am inserting more rows (at the bottom). The table view is representing a feed for posts, so when the user scrolls to the bottom, before reaching the last cell, I load new posts, and then insert them into the table.
When I do this, I get this weird glitchy effect where the cells randomly come down (behind the previous cells) into place, the table view scrolls up a bit, messy.
CODE AT BOTTOM
I've uploaded a clip of me scrolling. When you see the activity indicator,
I stop scrolling. The rest of the movement is from the glitchy behavior.
Is the reason for the glitch because the cells are being drawn with auto-layout?
I would hope not, but idk..I'm not sure what to do regarding a solution. If anyone has any ideas please let me know.
FYI:
I have this (of course, since the cells are all using auto layout)
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
return UITableViewAutomaticDimension;
}
I've tried setting the estimated height to an "average" of the expected cell heights, around 65. No difference.
Update
Here's some code:
HomeViewController.m --> viewDidLoad
...
self.tableView = [KATableView.alloc initWithFrame:CGRectZero style:UITableViewStylePlain];
self.tableView.delegate = self;
self.tableView.dataSource = self;
self.tableView.refreshDelegate = self;
self.tableView.estimatedRowHeight = 75;
self.tableView.rowHeight = UITableViewAutomaticDimension;
[self.view addSubview:self.tableView];
// Constrains to all 4 sides of self.view
[SSLayerEffects constrainView:self.tableView toAllSidesOfView:self.view];
my table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
if (!self.dataManager.didFinishFetchingData) return 4;
if (self.contentObjects.count == 0) return 1;
if (self.dataManager.moreToLoad) return self.contentObjects.count + 1;
return self.contentObjects.count + 1;
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
return UITableViewAutomaticDimension;
}
- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForRowAtIndexPath:(NSIndexPath *)indexPath {
return UITableViewAutomaticDimension;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
MYObject *object = self.contentObjects[indexPath.row];
SomeTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:object.documentID];
if (!cell) {
cell = [SomeTableViewCell.alloc initWithStyle:UITableViewCellStyleDefault reuseIdentifier:object.documentID];
cell.delegate = self;
} else [cell startListeningForChanges];
return cell;
}
Here is how I am loading more data and adding it to the table view..
- (void)getHomeFeedData:(nullable void(^)(BOOL finished))completed {
[self.dataManager fetchHomeFeedDataForFeedOption:self.homeNavController.feedFilterOption completion:^(NSError * _Nullable error, NSArray<__kindof KAObject *> * _Nullable feedObjects) {
if (error != nil) {
NSLog(#"something went wrong: %#", error.localizedDescription);
if (completed) completed(NO);
return;
}
NSInteger originalCount = self.contentObjects.count;
if (self.dataManager.isFirstTimeLoading) self.contentObjects = feedObjects.mutableCopy;
else {
if (self.dataManager.isGettingNew) for (MYObject *obj in feedObjects) [self.contentObjects insertObject:obj atIndex:0];
else if (feedObjects.count > 0) [self.contentObjects addObjectsFromArray:feedObjects];
}
if (feedObjects.count > 0) {
if (self.dataManager.isFirstTimeLoading) [self.tableView reloadData];
else {
[self.tableView insertCells:feedObjects forSection:0 startingIndex:self.dataManager.isGettingNew? 0 : originalCount];
}
} else if (self.dataManager.isFirstTimeLoading) [self.tableView reloadData];
if (completed) completed(YES);
}];
}
NOTE:
[self.tableView insertCells:feedObjects forSection:0 startingIndex:self.dataManager.isGettingNew? 0 : originalCount];
is simply this:
- (void)insertCells:(nullable NSArray *)cells forSection:(NSInteger)section startingIndex:(NSInteger)start {
if (!cells) return;
NSMutableArray *indexPaths = #[].mutableCopy;
for (id obj in cells) {
NSInteger index = [cells indexOfObject:obj] + start;
[indexPaths addObject:[NSIndexPath indexPathForRow:index inSection:section]];
}
[self insertRowsAtIndexPaths:indexPaths withRowAnimation:UITableViewRowAnimationFade];
}
Update 2
My UITableViewCell subclass content is hidden ATM (too much difficulty in editing all my post content for the purpose of this post). I just have the subviews of each cell set to alpha = 0.f. It's just an image view, some labels, and some buttons.
No constraint issues in console, cells render perfectly when calling [self.tableView reloadData] so maybe there is something I'm doing wrong when inserting the cells?...

Answer 1

When you dealing with UITableView glitches:
Make sure you call UIKit API's on a main thread - turn on Main Thread checker
In your case, there might be an issue that fetchHomeFeedDataForFeedOption:completion: completion block is called not on a main thread.
Your insert is definitely wrong - all delete/insert/update/move calls for UITableView should be wrapped in beginUpdates/endUpdates
Your "load more" component at the bottom might be an issue. You need to address how it's managing contentSize/contentOffset/contentInset of table view. If it does anything but manipulating contentInset - it does wrong job.
While it's hard without debugging the whole solution, I bet options 2 & 3 are the key problems out there.