问题
I have plain UITableView with many sections and rows. Sections work fine. But sometimes after reload data of table, section change position. For example it was happened when i change tabs. What could be the problem?
Image before changed tabs:
Image after changed tabs:
Update: Add code below:
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
self.dishesListTableView.reloadData()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
func customizeCollectionView() {
self.collectionView.delegate = self
self.collectionView.dataSource = self
self.collectionView.dataProviderDelegate = self.dishesListDataProvider
self.collectionView.showsHorizontalScrollIndicator = false
self.collectionView.decelerationRate = UIScrollViewDecelerationRateFast
self.collectionView.registerClass(HPCollectionViewCell.self, forCellWithReuseIdentifier: HPCollectionViewCellConstants.reuseIdentifier)
}
//MARK: - UITableViewDelegate
func customziseDishesListTableView(){
self.dishesListTableView.delegate = self
self.dishesListTableView.dataSource = self
self.dishesListTableView.registerNib(UINib(nibName: DishesListSingleTableViewCell.nibName, bundle: nil), forCellReuseIdentifier: DishesListSingleTableViewCell.nibName)
self.dishesListTableView.registerNib(UINib(nibName: DishesListSinglePizzaTableViewCell.nibName, bundle: nil), forCellReuseIdentifier: DishesListSinglePizzaTableViewCell.nibName)
self.dishesListTableView.estimatedRowHeight = 123
self.dishesListTableView.rowHeight = UITableViewAutomaticDimension
if self.dishesListDataProvider.isPizza() {
self.dishesListTableView.separatorColor = UIColor.clearColor()
}else{
self.dishesListTableView.separatorColor = UIColor.expSilverColor()
}
}
func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.dishesListDataProvider.countOfDishes(section)
}
func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return self.dishesListDataProvider.countOfKitchenTypes()
}
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
if self.dishesListDataProvider.getDishItemByIndex(indexPath.section, indexDish: indexPath.row).isPizza() {
let cell = tableView.dequeueReusableCellWithIdentifier(DishesListSinglePizzaTableViewCell.nibName, forIndexPath: indexPath) as! DishesListSinglePizzaTableViewCell
cell.customizeView(self.dishesListDataProvider.getDishItemByIndex(indexPath.section, indexDish: indexPath.row), dishesListSingleTableViewCellProtocol: self, indexPath: indexPath)
return cell
}else{
let cell = tableView.dequeueReusableCellWithIdentifier(DishesListSingleTableViewCell.nibName, forIndexPath: indexPath) as! DishesListSingleTableViewCell
cell.customizeView(self.dishesListDataProvider.getDishItemByIndex(indexPath.section, indexDish: indexPath.row), dishesListSingleTableViewCellProtocol: self, indexPath: indexPath)
return cell
}
}
func tableView(tableView: UITableView, willDisplayFooterView view: UIView, forSection section: Int) {
self.collectionView.scrollToIndex(section, animated: true)
self.collectionView.changeSelectionForCellAtIndexPath(NSIndexPath(forItem: section, inSection: 0))
}
func tableView(tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
let sectionView = NSBundle.mainBundle().loadNibNamed(DishesListSectionView.nibName, owner: self, options: nil)[0] as! DishesListSectionView
sectionView.customizeView(self.dishesListDataProvider.getKitchenItemByIndex(section).kitchenTypeTitle)
return sectionView
}
//MARK: - UIScrollViewDelegate
func scrollViewDidScroll(scrollView: UIScrollView) {
if currentSectionIndex != self.dishesListTableView.indexPathsForVisibleRows![0].section {
currentSectionIndex = self.dishesListTableView.indexPathsForVisibleRows![0].section
self.collectionView.scrollToIndex(currentSectionIndex, animated: true)
self.collectionView.changeSelectionForCellAtIndexPath(NSIndexPath(forItem: currentSectionIndex, inSection: 0))
}
}
回答1:
I know it's an old thread but uncheck the Adjust Scroll View Insets doesn't help. I had this problem and solved it by reload table twice.
回答2:
tableView.reloadData()
tableView.layoutIfNeeded()
tableView.beginUpdates()
tableView.endUpdates()
This help me out.
Double reloadData will cause flickering while this solution won't.
回答3:
Calling reloadData() twice also works for me, but I would suggest calling tableView.layoutSubviews() after reloadData(), which also works for me.
回答4:
It looks like the issue in estimated height for your table view cells. Due to internal optimisations system calculates the height of absent cells based on estimated height value, that's why it can position your headers on wrong calculated height (like real cells bigger or smaller than their estimated size). It usually happens when you call reloadData() in the middle of the list. As a proper solution you should avoid calling reloadData() when you want to update the content of the list with second page for example. So you should use tableView.beginUpdates() and
tableView.endUpdates() and update items collection for table view. There is also new closure based API performBatchUpdates (just like it was for UICollectionView), but it's available from iOS 11.
Hope it may help to find proper solution for you
回答5:
This is because of UI viewcontroller property. Please first select UIViewController From Storyboard , Attribute Inspector
回答6:
In my project ,this error happened when i pull up tableView to request more data then reload the data after requesting. I need create many sections after requesting the data and it may effect the performance if i reloadData twice. More than, i found that if i scroll up or down the tableView, the position of section's headerView get right. So i fix this bug(my condition) i requesting the data by this:
[_tableView reloadData];
CGPoint offSetOrigin = _tableView.contentOffset;
CGPoint offSetSecond = CGPointMake(0, offSet.y-1);
_tableView.contentOffset = offSetSecond;
_tableView.contentOffset = offSet;
回答7:
The solutions here didn't fix my problem, so I'm leaving one more possible solution that helped me.
Set the estimatedSectionHeaderHeight, it seems that my tableView wasn't being able to calculate the initial position of my first section without it.
来源：https://stackoverflow.com/questions/37206807/swift-ios-9-section-header-change-position-after-reload-data