Why is UILabel not updating?

Question

I have created a view that shows lost connection messages to users which pops over the current view. I want to update the view periodically based on connection status changes.

I can properly get the view and change the text of a label (verified with WriteLines), but nothing changes on the actual display. I even tried removing the view and readding it and calling SetNeedsDisplay, but nothing seems to help.

I have a global variable called OverView:

public static UIView OverView;

I create the label subview, add it to the overview and pop the overview in front of the current view:

            UILabel labelTitle = new UILabel();
            labelTitle.Text = title;

            UIView labelTitleView = (UIView) labelTitle;
            labelTitleView.Tag = 5000;
            OverView.AddSubview(labelTitleView);

            curView.InsertSubviewAbove(OverView, curView);
            curView.BringSubviewToFront(OverView);

And then at a later time, I try to modify it like this from another function:

        if ((OverView != null) && (OverView.Subviews != null))
        {
            for (int i = 0; i < OverView.Subviews.Length; i++)
            {
                WriteToConsole("Type: " + OverView.Subviews[i].GetType());

                if (OverView.Subviews[i] is UILabel) 
                {
                    WriteToConsole("Found Label with Tag: " + ((UILabel)(OverView.Subviews[i])).Tag + " Text: " + ((UILabel)(OverView.Subviews[i])).Text);

                    if (((UILabel)(OverView.Subviews[i])).Tag == 5000)
                    {
                        WriteToConsole("Setting subview Title to: " + lostConnectionTitle);

                        lock (overViewLocker)
                        {
                            appReference.InvokeOnMainThread(delegate
                            {
                                UILabel tempLabel = ((UILabel)(OverView.Subviews[i]));
                                tempLabel.Text = lostConnectionTitle;
                                OverView.Subviews[i].RemoveFromSuperview();
                                OverView.AddSubview(tempLabel);
                                OverView.BringSubviewToFront(tempLabel);
                                OverView.SetNeedsLayout();
                                OverView.SetNeedsDisplay();
                                WriteToConsole("SetNeedsDisplay");
                            });
                        }
                    }
                }
            }
        }

Nate B. · Answer 1 · 2012-08-14T14:21:27.553

0

Have you tried to use delegate methods on your label, and change their value when events occur ?

For example, if your event is clicking on a button, you should have something like that:

yourLabel.Text = "Init";
buttonExample.TouchUpInside += (sender, e) => {
    yourLabel.Text = "I touched my button";
};

When your View loads, you'll see "Init" and your button and once you click on it, the label text changed.

Xamarin has some explanation about events and delegate methods here.

I hope that helped.

edited Aug 14 '12 at 14:21

answered Aug 14 '12 at 08:30

Nate B.

942
11
31

I'm not really sure what you mean by that. Can you please post some code snippets to show how that could work with my code above? Thanks. – nbonwit Aug 14 '12 at 13:07
I edited my answer to be more complete. There are many types of delegate methods, it depends of the different object you use. – Nate B. Aug 14 '12 at 14:24
I see. I'm not really sure how that would help me...the issue is that I can change the Text (as shown by WriteLines), but the updated text never gets displayed on the screen, even though I'm updating it on the main thread. – nbonwit Aug 14 '12 at 18:04

Why is UILabel not updating?

1 Answers1