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Re: How do I paint on an existing Panel?

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On 1/18/2012 8:55 AM, A B wrote:
> I expect this is a really obvious question; I must get round to getting
> a bigger Java book! Part of my program starts by displaying a JPanel,
> with an image put on it using paintComponent(). How do I then draw some
> shapes over the top of that image when a particular button is clicked? I
> can't just put them in paintComponent(), because they haven't to appear
> at first. Would it be easier in an applet, rather than an application?
>
> I'm sure this comes up in the example programs in the JDK package, but
> for some mysterious reason they won't work. Wrong version of IE,
> probably; have to look into that.
>


You just need to disconnect the button action from the drawing.

Make a second image.  Then copy the base image to this second image. 
Redo paintComponent method to display the second image.

When the button is clicked, update the 2nd image with the new shape. 
Then, in the button action method, ask for a repaint of the panel (call 
repaint() on it).  Now your panel will be updated with the new shape.

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How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-01-18 16:55 +0000
  Re: How do I paint on an existing Panel? Knute Johnson <nospam@knutejohnson.com> - 2012-01-18 09:29 -0800
    Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-01-18 18:12 +0000
      Re: How do I paint on an existing Panel? Knute Johnson <nospam@knutejohnson.com> - 2012-01-18 15:00 -0800
  Re: How do I paint on an existing Panel? markspace <-@.> - 2012-01-18 10:55 -0800
  Re: How do I paint on an existing Panel? Roedy Green <see_website@mindprod.com.invalid> - 2012-01-20 19:54 -0800
  Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-01-30 17:59 +0000
  Re: How do I paint on an existing Panel? Neil Morris <neil.morris4@googlemail.com> - 2012-02-04 20:58 +0000
    Re: How do I paint on an existing Panel? Lew <lewbloch@gmail.com> - 2012-02-05 01:01 -0800
    Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-02-10 12:10 +0000
    Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-02-16 20:55 +0000
      Re: How do I paint on an existing Panel? Lew <lewbloch@gmail.com> - 2012-02-16 13:04 -0800
        Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-02-16 21:33 +0000
  Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-02-16 21:05 +0000
    Re: How do I paint on an existing Panel? Lew <lewbloch@gmail.com> - 2012-02-16 13:28 -0800
      Re: How do I paint on an existing Panel? "John B. Matthews" <nospam@nospam.invalid> - 2012-02-16 21:18 -0500
      Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-02-17 18:20 +0000
        Re: How do I paint on an existing Panel? Lew <lewbloch@gmail.com> - 2012-02-17 10:45 -0800
        Re: How do I paint on an existing Panel? Lew <lewbloch@gmail.com> - 2012-02-17 10:49 -0800
          Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-02-19 19:31 +0000
            Re: How do I paint on an existing Panel? Lew <noone@lewscanon.com> - 2012-02-19 14:41 -0800
              Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-03-04 16:51 +0000
                Re: How do I paint on an existing Panel? Jeff Higgins <jeff@invalid.invalid> - 2012-03-04 12:36 -0500
                Re: How do I paint on an existing Panel? Lew <noone@lewscanon.com> - 2012-03-04 10:47 -0800
                Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-03-14 17:39 +0000
                Re: How do I paint on an existing Panel? Lew <lewbloch@gmail.com> - 2012-03-14 11:07 -0700
                Re: How do I paint on an existing Panel? "John B. Matthews" <nospam@nospam.invalid> - 2012-03-14 23:01 -0400
                Re: How do I paint on an existing Panel? markspace <-@.> - 2012-03-15 09:30 -0700
        Re: How do I paint on an existing Panel? Knute Johnson <nospam@knutejohnson.com> - 2012-02-17 17:01 -0800
    Re: How do I paint on an existing Panel? Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2012-02-16 13:59 -0800
      Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-02-17 18:07 +0000
        Re: How do I paint on an existing Panel? Knute Johnson <nospam@knutejohnson.com> - 2012-02-17 17:04 -0800
        Re: How do I paint on an existing Panel? Knute Johnson <nospam@knutejohnson.com> - 2012-02-17 17:08 -0800

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