iOS 8 UITableView first row has wrong height - ios

Question

I'm working on an app where I face a strange issue. I've created a UITableViewController in the storyboard and added a prototype cell. In this cell, I've added an UILabel element and this UILabel takes up the whole cell. I've set it up with Auto Layout and added left, right, top and bottom constraints. The UILabel contains some text.
Now in my code, I initialize the the rowHeight and estimatedRowHeight of the table view:
override func viewDidLoad() {
super.viewDidLoad()
self.tableView.rowHeight = UITableViewAutomaticDimension
self.tableView.estimatedRowHeight = 50
}
And I create the cell as follows:
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
var cell : UITableViewCell? = tableView.dequeueReusableCellWithIdentifier("HelpCell") as? UITableViewCell
if(cell == nil) {
cell = UITableViewCell(style: .Default, reuseIdentifier: "HelpCell")
}
return cell!
}
I return two rows in my table view. Here comes my problem: the height of the first row is way to large. It appear that the second, third row etc all have a correct height. I really don't understand why this is the case. Can someone help me with this?

Answer 1

I had a problem where the cells' height were not correct on the first load, but after scrolling up-and-down the cells' height were fixed.
I tried all of the different 'fixes' for this problem and then eventually found that calling these functions after initially calling self.tableView.reloadData.
self.tableView.reloadData()
// Bug in 8.0+ where need to call the following three methods in order to get the tableView to correctly size the tableViewCells on the initial load.
self.tableView.setNeedsLayout()
self.tableView.layoutIfNeeded()
self.tableView.reloadData()
Only do these extra layout calls after the initial load.
I found this very helpful information here: https://github.com/smileyborg/TableViewCellWithAutoLayoutiOS8/issues/10
Update:
Sometimes you might have to also completely configure your cell in heightForRowAtIndexPath and then return the calculated cell height. Check out this link for a good example of that, http://www.raywenderlich.com/73602/dynamic-table-view-cell-height-auto-layout , specifically the part on heightForRowAtIndexPath.
Update 2: I've also found it VERY beneficial to override estimatedHeightForRowAtIndexPath and supply somewhat accurate row height estimates. This is very helpful if you have a UITableView with cells that can be all kinds of different heights.
Here's a contrived sample implementation of estimatedHeightForRowAtIndexPath:
public override func tableView(tableView: UITableView, estimatedHeightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
let cell = tableView.cellForRowAtIndexPath(indexPath) as! MyCell
switch cell.type {
case .Small:
return kSmallHeight
case .Medium:
return kMediumHeight
case .Large:
return kLargeHeight
default:
break
}
return UITableViewAutomaticDimension
}
Update 3: UITableViewAutomaticDimension has been fixed for iOS 9 (woo-hoo!). So you're cells should automatically size themselves without having to calculate the cells height manually.

Answer 2

As the Apple says in the description of setNeedsLayout:
This method does not force an immediate update, but instead waits for the next update cycle, you can use it to invalidate the layout of multiple views before any of those views are updated. This behavior allows you to consolidate all of your layout updates to one update cycle, which is usually better for performance.
Because of this you should add needed lines of code (which should be executed with right layout) in dispatch_after block(which will put your method in queue of RunLoop). And your code will be executed after needs layout applies.
Example:
- (void)someMethod {
[self.tableView reloadData];
[self.tableView setNeedsLayout];
[self.tableView layoutIfNeeded];
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
//code which should be executed with the right size of table
});

Answer 3

In iOS 8, assigning the estimatedRowHeight a value turns on the new iOS 8 automatic row height calculation feature. This means that the cell's height is derived by using its internal constraints from the inside out. If there's something wrong with those constraints you'll get odd results. So there's something wrong with your cell constraints. They are probably ambiguous; that is the usual reason for inconsistency. However that's all I can tell you, since you have not actually shown / described the constraints.

Answer 4

I suggest removing the bottom constraint on the UILabel. It will resize according to the text and the cell should resize as well.
If that didn't resolve the issue, try adding the following in viewDidLoad() :
self.tableView.reloadData()

Answer 5

This worked for me
- (void)layoutSubviews
{
[super layoutSubviews];
// Your implementation
}
I got this from here >> http://askstop.com/questions/2572338/uitableview-displays-separator-at-wrong-position-in-ios8-for-some-cells