iOS 8 Auto height cell not correct height at first

问题:

I have an iOS 8 application where I have a search results page that each cell is autosized based on the height of a certain label. However, after the view first loads the cells that are displayed don't autosize. After you scroll down the cells that follow are sized correctly. I am wiring up the auto layout constraints in my storyboard. I have the following code in viewDidLoad.

- (void)viewDidLoad {
    [super viewDidLoad];

    //configure tableView so that we use autolayout enabled row heights
    self.tableView.estimatedRowHeight = 68;
    self.tableView.rowHeight = UITableViewAutomaticDimension;
}

Has anyone else experienced this?

回答1:

Yes, I've seen this same problem when making the views and constraints in the storyboard (but not with code added views). Iv'e fixed this by adding this code in the custom cell class,

-(void)didMoveToSuperview { 
    [self layoutIfNeeded];
}

This could probably go other places, but this method seems to be called only once, so I thought it was a good place to do it.

回答2:

The answer from rdelmar did not work for me.

What I have done is added this code:

[tableView setNeedsLayout];
[tableView layoutIfNeeded];
[tableView reloadData];

after data is fetched and first [tableView reloadData] is called, which in my case is located in viewDidLoad method of my View Controller.

So result code would be:

NSArray *fetchedData = ...

[tableView reloadData]; //Fist table reload
[tableView setNeedsLayout];
[tableView layoutIfNeeded];
[tableView reloadData]; //Second table reload

This answer is taken from here: http://useyourloaf.com/blog/self-sizing-table-view-cells.html#comment-1783719287

回答3:

I think instead of forcing a tableView.reloadData() and tableView.layoutIfNeeded() in viewDidLoad, you can just set your tableView's auto height in viewWillLayoutSubviews():

Swift:

override func viewWillLayoutSubviews() {
    super.viewWillLayoutSubviews()
    tableView.estimatedRowHeight = 300
    tableView.rowHeight = UITableViewAutomaticDimension
}

回答4:

I had the same problem and fixed it by moving assignments to the cell's UILabels' text properties (being the only components that could influence the height calculation in my particular cell) to:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath

instead of:

-(void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath

Before doing this I noticed that the cell height would be correctly calculated if a cell was scrolled momentarily off-screen and then back into view. Most likely because, at that point, the cell had the necessary information regarding the UILabel content determining the final height.

回答5:

I was able to go around this one by not using nibs/storyboards but rather have the layout done programmatically.