具有附件视图的iOS 8自定义单元格

Question

Using iOS 8.3 simulator and Xcode 6.3.2.

I'm using the self sizing cells technique in iOS 8, and it works terrifically when the cell has no accessory view, but breaks when the cell has an accessory view. I set constraints on the label inside the cell:

Then I use an estimatedRowHeight and set the rowHeight to UITableViewAutomaticDimension (I'm omitting tableView:numberOfRowsInSection: here, but it just returns 3 for this example):

@implementation MyTableViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.tableView.estimatedRowHeight = 44.0f;
    self.tableView.rowHeight = UITableViewAutomaticDimension;
}

...

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    MyCell *cell = (MyCell *)[tableView dequeueReusableCellWithIdentifier:@"myCell" forIndexPath:indexPath];

    cell.titleLabel.text = @"Test comment Test comment Test comment Test comment Test comment Test comment Test comment Test comment Test comment Test comment Test comment ";

    return cell;
}

@end

And bam, everything looks great:

But when I add an accessory view in the Storyboard, without changing any of the code:

the first cell goes to hell. Xcode's view debugger tells me the label height is 1785 points, and I had to use a gif to show it here:

I do notice that the other two cells are sized fine. I also note that when I rotate the simulator, the first cell gets resized properly, including after it's rotated back to portrait.

Does anyone know why the accessory view messes this up so badly, and what I can do to fix it? A sample project is available at http://github.com/UberJason/SelfSizingNightmare .

Answer 1

This is a bug indeed. I have sent your project to Apple. There is a reply from Apple.

Answer 2

It seems to be caused by the label inside the cell having numberOfLines = 0 .

Although I'm not sure why, it looks as though adding the accessory to the cell leaves auto layout unable to calculate the height of the label when the table first loads.

I was able to fix your example by adding a preferred max width to the label - which seems to be enough to let the layout system figure out the height in time:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    MyCell *cell = (MyCell *)[tableView dequeueReusableCellWithIdentifier:@"myCell" forIndexPath:indexPath];

    // Give the layout system something to help it estimate the label height    
    cell.titleLabel.preferredMaxLayoutWidth = self.titleLabel.bounds.size.width;
    cell.titleLabel.text = @"Test comment Test comment Test comment Test comment Test comment Test comment Test comment Test comment Test comment Test comment Test comment ";

    return cell;
}

Alternatively, calling [tableView reloadData] in viewDidAppear also seems to fix it.