Bug 34206 - Can't dinamically Add layouts to content of a scrollView
Summary: Can't dinamically Add layouts to content of a scrollView
Alias: None
Product: Forms
Classification: Xamarin
Component: Forms ()
Version: 1.4.4
Hardware: PC Windows
: --- normal
Target Milestone: ---
Assignee: Bugzilla
Depends on:
Reported: 2015-09-23 10:23 UTC by Estef
Modified: 2016-01-20 13:57 UTC (History)
5 users (show)

Is this bug a regression?: ---
Last known good build:

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Description Estef 2015-09-23 10:23:06 UTC
When trying to dinamically add layouts to the content of a scrollView, it doesn't render until the second layout added.
For example: This code add a layout each time the user click the button, for some reason it doesn't render the first layout added.

public class PageExperiment
    ScrollView _page;

    public PageExperiment()
        _page = new ScrollView { Orientation = ScrollOrientation.Vertical,
                                 Content = new RelativeLayout { BackgroundColor = Color.White} };

        var button = new Button { Text="Add Button"};
        button.Clicked += OnButtonClicked;

    public ScrollView getPage()
        return _page;
    void OnButtonClicked(object sender, EventArgs e)
        var relative = AddLayout();
        var content = (RelativeLayout)_page.Content;
        var v = content.Children[content.Children.Count - 1];
        Constraint xConstraint = Constraint.Constant(0);
        Constraint yConstraint = Constraint.RelativeToView(v, (parent, sibling) => {
            return sibling.Y + sibling.Height;

        ((RelativeLayout)_page.Content).Children.Add((View)relative, xConstraint, yConstraint);        


    public VisualElement AddLayout()
        var root = new RelativeLayout();

        root.BackgroundColor = Color.Red;
        var a = new Label { Text = "Button Added!!!!", BackgroundColor = Color.Purple};
        a.FontSize = 30;
        root.Children.Add(a, xConstraint:null);

        return root;

Here is the main:

public class App : Application
    public App()
        var root = new PageExperiment();
        MainPage = new ContentPage
            Content = root.getPage()

Comment 1 David Strickland 2015-09-26 11:59:03 UTC
Chased this for a bit today. It does appear to be occurring for me as well.

I did simplify the code above a bit. From what I can tell It's not just layouts, it appears that no visual elements will add on the first trip through the event handler.

using System;
using Xamarin.Forms; 
namespace ScrollViewPageExperiment
 public class PageExperiment
  ContentView view;
  public ContentView getPage()
   return view;

  public PageExperiment()
   view = new ContentView {Content = new RelativeLayout()};
   var button = new Button { Text="Add"};
   button.Clicked += OnButtonClicked;
  void OnButtonClicked(object sender, EventArgs e)
   var testLabel = new Label { Text="test"};
   int controlCount = ((RelativeLayout)view.Content).Children.Count;
Comment 2 Stephane Delcroix 2016-01-20 13:57:57 UTC
Using the code from comment #2, I was unable to reproduce the reported behavior on either iOS or Android.

If you still can trigger it using latest Xamarin.Forms release, please reopen this issue, with some extra information about the platform (type, version, device) you use for producing this failure.

Warm regards,

the xf team