Question

I want to present a custom-sized modal view controller with animation from the bottom. I can achieve this animation with ModalPresentationStyle to FormSheet, but it forces me to use the default size which is 540×620 and my view doesn’t fit.

How do I make perform a similar transition to an arbitrarily sized view (controller) placed in center of the screen?

Answer 1

I didn’t find a way to do it from the modal controller itself so I created a class and an extension method:

public class ModalViewController : UIViewController
{
    public SizeF OriginalViewSize { get; private set; }

    void Initialize ()
    {
        ModalPresentationStyle = UIModalPresentationStyle.FormSheet;
    }

    public override void ViewDidLoad ()
    {
        OriginalViewSize = View.Bounds.Size;
        base.ViewDidLoad ();
    }

    public ModalViewController (IntPtr handle) : base (handle)
    {
        Initialize ();
    }

    public ModalViewController (string nibName, NSBundle bundle) : base (nibName, bundle)
    {
        Initialize ();
    }

    public ModalViewController () : base ()
    {
        Initialize ();
    }
}

public static class ModalViewControllerExtensions
{
    public static void PresentModalViewController (this UIViewController parent, ModalViewController target)
    {
        parent.PresentViewController (target, true, null);

        target.View.Superview.AutoresizingMask = UIViewAutoresizing.FlexibleMargins;
        target.View.Superview.Frame = new RectangleF (PointF.Empty, target.OriginalViewSize);
        target.View.Superview.Center = UIScreen.MainScreen.Bounds.Center ().Rotate ();
    }
}

This is roughly how I use it:

this.PresentModalViewController (
    new PublishModalViewController (Item, HandlePublishAction)
);

It is convenient that I don’t need to specify the size explicitly because it uses root View’s bounds from the interface builder. I’m not sure how this reacts to autorotate, it may need some tuning. I’m also using two extension methods here:

public static PointF Rotate (this PointF pt)
{
    return new PointF (pt.Y, pt.X);
}

public static PointF Center (this RectangleF rect)
{
    return new PointF (
        (rect.Right - rect.Left) / 2.0f,
        (rect.Bottom - rect.Top) / 2.0f
        );
}

And this is it.