Android Question Canvas Draw Text Center Is Not Centering

Mahares

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Below is my full project. I would like to use ‘CENTER’ for ‘World Cup 2018’ in cvs.DrawText line, but the only way I can do it is to manipulate the position x and use LEFT. How can I use ‘CENTER’ and achieve a horizontally centered text. I only want to make use of the core lib. I do not wish to use XUI lib.
Thank you
B4X:
Sub Activity_Resume
    CreateBitmap
End Sub

Sub Activity_Pause (UserClosed As Boolean)
    If UserClosed Then Activity.Finish
End Sub

Sub Activity_Create(FirstTime As Boolean)  
End Sub

Sub CreateBitmap As Canvas
   Dim bmp As Bitmap
   bmp.InitializeMutable(200dip, 200dip)
   Dim cvs As Canvas
   cvs.Initialize2(bmp)
   Dim r As Rect
   r.Initialize(0, 0, bmp.Width, bmp.Height)
   cvs.DrawRect(r, Colors.Transparent, False, 5dip)
   DrawBitmap(cvs, LoadBitmap(File.DirAssets, "worldcuprussia2018.png"))
    cvs.DrawText("World Cup 2018",0,cvs.Bitmap.Height/2,Typeface.DEFAULT_BOLD,12,Colors.blue,"CENTER")
'   cvs.DrawText("World Cup 2018",0,cvs.Bitmap.Height/2,Typeface.DEFAULT_BOLD,12,Colors.blue,"LEFT")
   Activity.SetBackgroundImage(cvs.Bitmap)
   Return cvs
End Sub

Sub DrawBitmap (cvs As Canvas, bmp As Bitmap)
   Dim r As Rect
   r.Initialize(0, 0, cvs.Bitmap.Width, cvs.Bitmap.Height)
   cvs.DrawBitmap(bmp, Null, r)
End Sub
 

Attachments

  • WorldCupRussia2018.png
    WorldCupRussia2018.png
    57.1 KB · Views: 291
  • CenterProblem.png
    CenterProblem.png
    35.2 KB · Views: 231

Mahares

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This post might be helpful in answering your question
The link is quite old from 2010 and does not address the 'CENTER' position. I am attaching the full project. Perhaps someone can figure it out.
 

Attachments

  • CanvasTextNotCentered062218.zip
    65.5 KB · Views: 179
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stevel05

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As Jeffrey said, the alignment in relation to drawing on a canvas defines how the text is positioned relative to the specified x point.

You would need to change

B4X:
cvs.DrawText("World Cup 2018",0,cvs.Bitmap.Height/2,Typeface.DEFAULT_BOLD,12,Colors.blue,"CENTER")

to

B4X:
cvs.DrawText("World Cup 2018",cvs.Bitmap.Width/2,cvs.Bitmap.Height/2,Typeface.DEFAULT_BOLD,12,Colors.blue,"CENTER")

The text will then be drawn centered on the x position (cvs.Bitmap.Width/2), which is at the center of the bitmap,

To test it, change the Alignment from "CENTER" to "LEFT" or "RIGHT" to see the difference.
 
Last edited:
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Jeffrey Cameron

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The link is quite old from 2010 and does not address the 'CENTER' position.
Correct, but it did nicely illustrate the origin point of the drawtext method which is what I was attempting to emphasize.

It should also be noted that the text is drawn starting from the origin point, UP and left/right from the origin point. So, if you wish to correctly center the text on the Y axis you should add 1/2 of the text height to your Y value (see Canvas.MeasureStringHeight).
 
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