How to hide a UIView and remove the "empty" space? -iOS/Monotouch - ios

Question

I need to be able to hide controls on a page that uses constraints and remove the empty space that Hidden=true leaves. It needs to be similar to how the web handles visibility. If it's invisible, it doesn't take up space.
Does anyone know of a clean way to accomplish this?
Please let me know if you need more details.
Thx
Example:
UIButton | UIButton | UIButton
"empty space for hidden UIButton"
UIButton
That should really be rendered like this:
UIButton | UIButton | UIButton
UIButton
Edit: I'm using Xamarin Studio and VS2012 for development.

Answer 1

Since original question is related to Xamarin, I provide complete C# solution.
First, create height constraint for your view and give it an identifier in Xcode Interface Builder:
Then in controller override ViewDidAppear() method and wrap view with HidingViewHolder:
public override void ViewDidAppear(bool animated)
{
base.ViewDidAppear(animated);
applePaymentViewHolder = new HidingViewHolder(ApplePaymentFormView, "ApplePaymentFormViewHeightConstraint");
}
It is important to create HidingViewHolder when view was laid out, so it has real height assigned.
To hide or show view you can use corresponding methods:
applePaymentViewHolder.HideView();
applePaymentViewHolder.ShowView();
HidingViewHolder source:
using System;
using System.Linq;
using UIKit;
/// <summary>
/// Helps to hide UIView and remove blank space occupied by invisible view
/// </summary>
public class HidingViewHolder
{
private readonly UIView view;
private readonly NSLayoutConstraint heightConstraint;
private nfloat viewHeight;
public HidingViewHolder(UIView view, string heightConstraintId)
{
this.view = view;
this.heightConstraint = view
.GetConstraintsAffectingLayout(UILayoutConstraintAxis.Vertical)
.SingleOrDefault(x => heightConstraintId == x.GetIdentifier());
this.viewHeight = heightConstraint != null ? heightConstraint.Constant : 0;
}
public void ShowView()
{
if (!view.Hidden)
{
return;
}
if (heightConstraint != null)
{
heightConstraint.Active = true;
heightConstraint.Constant = viewHeight;
}
view.Hidden = false;
}
public void HideView()
{
if (view.Hidden)
{
return;
}
if (heightConstraint != null)
{
viewHeight = heightConstraint.Constant;
heightConstraint.Active = true;
heightConstraint.Constant = 0;
}
view.Hidden = true;
}
}

Answer 2

In storyboard wire your constrains first. Then try this
self.viewToHideHeight.constant = 0;
self.lowerButtonHeightFromTop.constant = self.viewToHideHeightFromTop.constant + self.viewToHideHeight.constant;
[UIView animateWithDuration:0.5f animations:^{
self.viewToHide.alpha = 0.0f;
[self.view layoutIfNeeded];
}];