Canvas vs. JPanel
Hi everyone,
I am new to Swing and Graphics. recently I am trying to design a mutiple window GUI. I use JDesktopPane and JInternalFrame. I try to draw contours onto a Canvas or JPanel whis is itself added to the IInternalFrame.
Since Canvas is AWT so when write pure Swing I should use JPanel, that is my understanding. To my dismay, when I use Canvas and draw the contours by overwritting paint() method my contours can be drawn rather fast, However, when I use JPanel and paintComponent method the drawing is much slower. Worse, when I resize or move the internalFrame the JPanel is really slow, almost frozen.
What is the problem? Any suggestion is greatly appreciated!!
Thanks in advance
Taogo
[736 byte] By [
taogoa] at [2007-11-26 20:01:42]
# 1
> when I use JPanel and paintComponent method the drawing is much slower
Yes, painting in Swing is slower than painting in AWT. Its usually not a problem.
Since we don't know what you are doing in your custom painting we can't make any suggestions on how to improve the painting performance.
# 2
Thanks camickr,
The code for paint() when drawing on Canvas and paintComponent when on JPanel are rather simple:
public void paint(Graphics g){//draw onto Canvas
public void paintComponent(Graphics g){//draw onto a JPanel
super.paintComponent(g);//draw onto JPanel
SetMeasurements();
DrawGrid(g, 50);//draw grid using step of 50 pixels.
workSpace = new boolean[workLength]; // workLength = 512 x 1024 x 32
ContourPlot(g, workSpace); // draw contour using a 512x1024 matrix floats
}
void SetMeasurements() {
d = getSize();
d.width -= 2*PLOT_MARGIN;
d.height -= 2*PLOT_MARGIN;
deltaX = d.width / (xSteps - 1.0); //grid interval
deltaY = d.height / (ySteps - 1.0);
}
Other part of codes are identical for either drawing on Canvas or JPanel.
I suspect my paintComponent method has some problem. I am considering first create Image and then use bufferedImage to draw, do you think that will speed up the display of
contours?
Thanks for all the help and
Cheers!!
# 3
> I am considering first create Image and then use bufferedImage to
> draw, do you think that will speed up the display of contours?
I don't know what a contour is, but using a buffered image is a good idea whenever possible.
If you need further help then you need to create a [url http://homepage1.nifty.com/algafield/sscce.html]Short, Self Contained, Compilable and Executable, Example Program[/url] (SSCCE) that demonstrates the incorrect behaviour, because I can't guess exactly what you are doing based on the information provided.
And don't forget to use the [url http://forum.java.sun.com/help.jspa?sec=formatting]Code Formatting Tags[/url] so the code retains its original formatting.
# 4
Thanks again.
With imageBuffering most of the problems associated with JPanel are gone. However, it
still draw slowly when the figure is rendered for the first time. I mean slower than drawing using Canvas. Otherwise I am pretty happy with it. I almost must use JPanel since I need layeres of other components on the the contour (JPanel) and Canvas likely will block other components.
BTW:
What I try to draw is the visualization of peaks using contour as the peaks shown on maps of mountains for hikers.
