change picture in Canvas

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Dimitris \(GIS\) - 20 Jun 2005 14:24 GMT

I have a frame with
a awt.List and a awt.Canvas
I want by selecting diferent elements from the list to change my canvas
picture.
How can I do it?

I try this but it gives me NullPointerException:
if(simList.getSelectedIndex()==0){
ImageCanvas ic=new ImageCanvas("image.jpg");
simPicture.update(ic);
}

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Andrew Thompson - 20 Jun 2005 14:53 GMT

On Mon, 20 Jun 2005 13:24:01 GMT, Dimitris (GIS) wrote:

> I have a frame with a awt.List and a awt.Canvas

I have rarely found uses for the Canvas class.
Even image rendering is generally simpler to do on a Component.

> I want by selecting diferent elements from the list to change my canvas
> picture.
> How can I do it?

- Use a number of Canvas's in a CardLayout, and flip
between them.

- Alternately, you might try refreshing the current Canvas
by either it's own methods (I am not that familiar with
them - check the API docs) or by instantiating a fresh
Canvas and refreshing the GUI.

> I try this but it gives me NullPointerException:
> if(simList.getSelectedIndex()==0){
> ImageCanvas ic=new ImageCanvas("image.jpg");
> simPicture.update(ic);
> }

It sounds as though you are trying the second method
mentioned above, but (shrug) I cannot do much with
code snippets[1] and vague descriptions of errors[2].

[1] <http://www.physci.org/codes/sscce.jsp>
[2] <http://www.physci.org/codes/javafaq.jsp#exact>

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Dimitris \(GIS\) - 21 Jun 2005 20:55 GMT

Thank you Andrew

> On Mon, 20 Jun 2005 13:24:01 GMT, Dimitris (GIS) wrote:
>
[quoted text clipped - 27 lines]
> [1] <http://www.physci.org/codes/sscce.jsp>
> [2] <http://www.physci.org/codes/javafaq.jsp#exact>

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Andrew Thompson - 22 Jun 2005 05:42 GMT

On Tue, 21 Jun 2005 19:55:43 GMT, Dimitris (GIS) wrote:

> Thank you Andrew

You're welcome.. By the way - did you solve the problem?

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change picture in Canvas

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