使用自动布局时，iOS 8上的旋转像元高度会丢失

Question

Normally iOS 8 should be able to calculate the height of a cell itself. This is working so far, but if I rotate the device the cell gets back to its standard height of 44 points.

This is how it should look like:

This is how it does look like after rotation:

Once rotated it stays in that layout. It never calculates the real height anymore. I don't know why. I have added my complete code. For the constraints have a look into updateConstraints . The code is in C# but you should be able to read it. You can post your solution of course in Objective-C.

VC viewDidLoad :

public override void ViewDidLoad ()
{
    base.ViewDidLoad ();

    this.TableView.Source = new TestSource (this);
    this.TableView.RegisterClassForCellReuse (typeof(CustomCell), TestSource.cellIdentifier);
    //this.TableView.RowHeight = 83;
}

My data source:

public class TestSource : UITableViewSource
{
    public static readonly NSString cellIdentifier = new NSString("CustomCell");
    private TestTableVC controller;

    public TestSource (TestTableVC controller)
    {
        this.controller = controller;
    }

    public override int RowsInSection (UITableView tableview, int section)
    {
        return 10;
    }

    public override UITableViewCell GetCell (UITableView tableView, NSIndexPath indexPath)
    {
        CustomCell cell = tableView.DequeueReusableCell (cellIdentifier) as CustomCell;

        cell.UpdateCell ("Max Mustermann", "m", new DateTime (2014, 12, 10), "1234567890");

        cell.SetNeedsUpdateConstraints ();
        cell.UpdateConstraintsIfNeeded ();

        return cell;
    }
}

My CustomCell :

public class CustomCell : UITableViewCell
{
    public static readonly NSString cellIdentifier = new NSString("CustomCell");

    private UILabel fullNameLabel, genderLabel, birthdateLabel, iNumberLabel;
    private bool didSetupConstraints = false;

    public CustomCell ()
    {
        this.CreateView ();
    }

    public CustomCell (IntPtr handle) : base(handle)
    {

        this.CreateView ();
    }

    public void UpdateCell (string fullName, string gender, DateTime? birthdate, string iNumber)
    {
        fullNameLabel.Text = fullName;
        genderLabel.Text = "Gender" + ": " + gender;
        birthdateLabel.Text = "Born on" + ": " + dateOfBirth.ToString ("dd.MM.yyyy");
        iNumberLabel.Text = iNumber;
    }

    public override void LayoutSubviews()
    {
        base.LayoutSubviews();

        this.ContentView.SetNeedsLayout();
        this.ContentView.LayoutIfNeeded();
    }

    public override void UpdateConstraints()
    {
        if (!didSetupConstraints) {
            NSMutableDictionary viewsDictionary = new NSMutableDictionary ();
            viewsDictionary ["fullNameLabel"] = fullNameLabel;
            viewsDictionary ["genderLabel"] = genderLabel;
            viewsDictionary ["birthdateLabel"] = birthdateLabel;
            viewsDictionary ["iNumberLabel"] = iNumberLabel;

            fullNameLabel.TranslatesAutoresizingMaskIntoConstraints = false;
            genderLabel.TranslatesAutoresizingMaskIntoConstraints = false;
            birthdateLabel.TranslatesAutoresizingMaskIntoConstraints = false;
            iNumberLabel.TranslatesAutoresizingMaskIntoConstraints = false;


            // Sizing of content view is differently in iOS 7 (autoresizing mask) and iOS 8 (layoutSubViews).
            // Don't know why this occurs but it should only concern nibs and if you are using iOS 8 SDK and compile for iOS 7.
            // http://stackoverflow.com/questions/24750158/autoresizing-issue-of-uicollectionviewcell-contentviews-frame-in-storyboard-pro
            // http://stackoverflow.com/questions/19132908/auto-layout-constraints-issue-on-ios7-in-uitableviewcell
            // bug?
            if (!UIDevice.CurrentDevice.CheckSystemVersion (8, 0)) {
                // only one of these statements is needed
                this.ContentView.AutoresizingMask = UIViewAutoresizing.FlexibleHeight | UIViewAutoresizing.FlexibleWidth;
                this.ContentView.Bounds = new RectangleF (0, 0, 99999, 99999);
            }

            this.ContentView.AddConstraints (NSLayoutConstraint.FromVisualFormat ("H:|-[fullNameLabel]", (NSLayoutFormatOptions)0, null, viewsDictionary));
            this.ContentView.AddConstraints (NSLayoutConstraint.FromVisualFormat ("H:|-[genderLabel]|", (NSLayoutFormatOptions)0, null, viewsDictionary));
            this.ContentView.AddConstraints (NSLayoutConstraint.FromVisualFormat ("H:|-[birthdateLabel]", (NSLayoutFormatOptions)0, null, viewsDictionary));
            this.ContentView.AddConstraints (NSLayoutConstraint.FromVisualFormat ("V:|-(8)-[fullNameLabel]-(5)-[genderLabel]-(5)-[birthdateLabel]-(8)-|", (NSLayoutFormatOptions)0, null, viewsDictionary));
            this.ContentView.AddConstraint (NSLayoutConstraint.Create (iNumberLabel, NSLayoutAttribute.CenterY, NSLayoutRelation.Equal, this.ContentView, NSLayoutAttribute.CenterY, 1, 0));
            this.ContentView.AddConstraints (NSLayoutConstraint.FromVisualFormat ("H:[iNumberLabel]-|", (NSLayoutFormatOptions)0, null, viewsDictionary));

            didSetupConstraints = true;
        }

        base.UpdateConstraints ();
    }

    private void CreateView()
    {
        fullNameLabel = new UILabel () {
            Font = UIFont.BoldSystemFontOfSize(17),
            TextColor = UIColor.Black,
            BackgroundColor = UIColor.Clear,
            LineBreakMode = UILineBreakMode.TailTruncation,
            Lines = 0,
            TextAlignment = UITextAlignment.Left
        };
        genderLabel = new UILabel () {
            Font = UIFont.SystemFontOfSize(15),
            TextColor = UIColor.Black,
            BackgroundColor = UIColor.Clear,
            LineBreakMode = UILineBreakMode.TailTruncation,
            Lines = 0,
            TextAlignment = UITextAlignment.Left
        };
        birthdateLabel = new UILabel () {
            Font = UIFont.SystemFontOfSize(15),
            TextColor = UIColor.Black,
            BackgroundColor = UIColor.Clear,
            LineBreakMode = UILineBreakMode.TailTruncation,
            Lines = 0,
            TextAlignment = UITextAlignment.Left
        };
        iNumberLabel = new UILabel () {
            Font = UIFont.SystemFontOfSize(15),
            TextColor = UIColor.Black,
            BackgroundColor = UIColor.Clear,
            LineBreakMode = UILineBreakMode.TailTruncation,
            Lines = 0,
            TextAlignment = UITextAlignment.Right
        };

        ContentView.AddSubviews (fullNameLabel, genderLabel, birthdateLabel, iNumberLabel);

    }

}

Is something wrong with my constraints or is this another iOS 8 bug? BTW: I'm using Xcode 6.1 with the iOS 8.1 SDK and want to support iOS 7 as iOS 8 devices. iOS 7 is another story.

Answer 1

在viewWillTransitionToSize函数中，设置self.tableView.estimatedRowHeight = your estimated row height ，似乎可以解决此问题，也许这是苹果的一个错误，将来可以改进。