Calculating Label Size in Codebehind

Question

Calculating Label Size in Codebehind

Nathan Sokalski 4,111

I need to determine the size of multiple Label(s) in codebehind. My reason for doing this is to determine which one is widest/tallest. Waiting until they are rendered & visible would be very inefficient because that would mean displaying & resizing all the Label(s) multiple times. What I would like to do is use an "imaginary" Label (one that is declared in codebehind but never actually added to the UI). However, this does not seem to work because the measuring does not happen if the Label is not displayed (which could also cause a problem if they are scrolled out of view in the initial layout). Is there a way to determine the size that a Label will require before it is actually rendered (sort of a virtual rendering)? Thanks.

Anonymous

2020-12-04T06:39:37.367+00:00

Do you get characters' number before display it to screen in the Label? If you get it, then you can get one character's size(Height and WidthRequest), calculating label size in Codebehind, you can use (characters' number * character's height= label's Width). If you have many lines, you should calculate one row the contains how many characters. Use total characters' number/ one row the contains characters=lines. (Label's Height=Lines*One characters height )
Nathan Sokalski 4,111 Reputation points

2020-12-04T17:41:18.027+00:00

Some of them do not get displayed to the screen at all (at least not until after actions from the user, such as scrolling). But I still need to know their size so that I can use it in other areas to properly layout & align my UI.
Anonymous

2020-12-08T01:10:28.133+00:00

If some of them do not displayed to the screen, it is hard to cacluted it, based on your description, you should want to create an custom control, you can create an contentview that contains ScrollView, then put the Labels to the Scrollview.No matter you Label's content, you can scroll it.
https://learn.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/layouts/contentview

2 answers

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Anonymous

2020-12-04T06:39:37.367+00:00

Do you get characters' number before display it to screen in the Label? If you get it, then you can get one character's size(Height and WidthRequest), calculating label size in Codebehind, you can use (characters' number * character's height= label's Width). If you have many lines, you should calculate one row the contains how many characters. Use total characters' number/ one row the contains characters=lines. (Label's Height=Lines*One characters height )
Nathan Sokalski 4,111 Reputation points

2020-12-04T17:41:18.027+00:00

Some of them do not get displayed to the screen at all (at least not until after actions from the user, such as scrolling). But I still need to know their size so that I can use it in other areas to properly layout & align my UI.
Anonymous

2020-12-08T01:10:28.133+00:00

If some of them do not displayed to the screen, it is hard to cacluted it, based on your description, you should want to create an custom control, you can create an contentview that contains ScrollView, then put the Labels to the Scrollview.No matter you Label's content, you can scroll it.
https://learn.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/layouts/contentview

Answer 1

Nathan Sokalski 4,111

Will that work for Label(s) that are never displayed? I know it sounds strange to need the size of something that will never be displayed, but I need to know it so that everything is aligned if the user does scroll to those elements. If I wait until they are rendered, layout passes, resizing, and scrolling will repeating exponentially. The Label(s) are in the ItemTemplate(s) of CollectionView(s), so resetting the ItemsSource would be a major performance hit. When the rendering engine does the layout, how does that get the size? Having access to that code would be great (although it's probably not available to us). Is there a way to simulate the measuring without causing a performance hit?

Anonymous

2020-12-09T09:34:24.67+00:00

If you cacluate the size of until they are rendered, it will be a major performance hit. So I suggest you just show label in line with fixed, if the text is too long, you can use Label's LineBreakMode=TailTruncation.. This will display a text with “…” at the end (ellipsis) when the text doesn’t fit, If user want to know more information, you can push an details page or popup page.
Nathan Sokalski 4,111 Reputation points

2020-12-09T18:32:34.727+00:00

That would be an inappropriate design for my page, because the Label(s) I am measuring are for Header(s) & data in a table (displayed using CollectionView(s)). Having a Header displayed as, for example, "Player Na..." or a total score displayed as "97586312..." would obviously not be appropriate. The Label(s) will never have "more information" because none of them are anything more than either a name or a number. My app is a scorekeeping app, so being able to see as much as possible at a time is very important (there is no point in looking at 1/2 a number).
Anonymous

2020-12-11T07:51:40.117+00:00

Based on your description, I make a test with CollectionView's header, I put an long text to make an test.
I put two Labels in the Header and long text in Label

Answer 2

Alessandro Caliaro 4,206

I think you can use

    Label label = new Label();
    label.SizeChanged += Label_SizeChanged;

SizeChanged fires when the size change so you can get height and width

Nathan Sokalski 4,111 Reputation points

2020-12-04T18:15:44.997+00:00

Will SizeChanged be triggered even if the Label is never actually added to the UI? What I am basically trying to do is the measuring that happens behind the scenes when a Label is rendered, I just don't want the Label to be actually displayed. Also, using the SizeChanged event would be very inefficient because it would require me to manually keep track of the sizes and changing the size of one Label would result in setting the size of all the others, therefore triggering SizeChanged many more times.

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Calculating Label Size in Codebehind

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