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Get number of columns in a JTextPane?

Posted on 2004-09-03
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Last Modified: 2012-06-27
Hi there!
I'm not all that Swing savvy, so bear with me. :)
I have a ControllablePanel containing a JScrollPane containing a JTextPane with a StyledDocument inside. Since the user can resize the window, I'd like to be able to figure out how many columns are being displayed in the JTextPane.
This is most likely pretty simple - any ideas? Or am I not giving enough information? Thanks...
epaga
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Question by:epaga
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LVL 35

Expert Comment

by:TimYates
ID: 11971017
Are you using a fixed width font?  If not, it's variable depending on what characters are in the line...
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Expert Comment

by:TimYates
ID: 11971018
X is wider than i
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Author Comment

by:epaga
ID: 11971024
nope, it's fixed width
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Expert Comment

by:Giant2
ID: 11971036
It depends on the size/style of the character setted for Panel, so you can calculate it.
Like the following:
  panelHeight/charHeight
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Expert Comment

by:expertmb
ID: 11971041
hmmmm ... textpane is not having anymethod like setColumns() getColumns() as textfield and textarea have.
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LVL 35

Expert Comment

by:TimYates
ID: 11971090
does:

   int cols = (int)( Math.floor( pane.getWidth() / pane.getGraphics().getFontMetrics( pane.getFont() ).charWidth( 'm' ) ) ) ;

give anything like the correct answer?
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Author Comment

by:epaga
ID: 11971151
It would except pane.getGraphics() gives me null - so it's a nullpointerexception.
All I have in my pane is the text, so all the text functions work fine. Am I missing a line somewhere?
But I can tell we're getting close... :)
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Expert Comment

by:objects
ID: 11971207
think you need to make the pane visible before you can get a Graphics context for it.
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Accepted Solution

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TimYates earned 1400 total points
ID: 11971449
try getGraphics() off another random visible component...

it shouldn't matter which graphics object you use, as it's the fontmetrics you want...

     int cols = (int)( Math.floor( pane.getWidth() / this.getGraphics().getFontMetrics( pane.getFont() ).charWidth( 'm' ) ) ) ;

or something..
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Author Comment

by:epaga
ID: 11971612
that worked like a charm, I just found a different component to use. Thanks Tim!
epaga
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Expert Comment

by:TimYates
ID: 11971639
:-)  Good luck!

Tim
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