can you print a JPanel without actually rendering it on screen first?

[AcousticBruce]

How can I print a extended JPanel class (overridden paintComponent) without rendering it to the screen first.

Perhaps a way to copy a jpanel and its content to a buffered image?


i know about panel.print(g), but that only works for on screen graphics.
Have any ideas?

[doWhile]

i know about panel.print(g), but that only works for on screen graphics.

Just get the graphics of a BufferedImage and paint to that.

//pseudo-code
BufferedImage image = new BufferedImage(....)
Graphics g = image.getGraphics();
myJPanel.paint(g);
g.dispose();

[AcousticBruce]

Just get the graphics of a BufferedImage and paint to that.

//pseudo-code
BufferedImage image = new BufferedImage(....)
Graphics g = image.getGraphics();
myJPanel.paint(g);
g.dispose();

yes I am sure about JComponents print.(g) to an extent, I have only been successful printing this within a paintComponent method and ONLY if it is displayed first.

since I have to paint with the g2 object (in code below), how can I print a JPanal that is never rendered to screen?

The reason I want to do this is because I want to use swings FlowLayout to add more extended JPanel objects to a virtual page and then use that as a reference graphic (which will be much smaller).

//paperImage is already instantiated to specific size (not shown).

private void createPaperImage() {
		Graphics2D g2 = paperImage.createGraphics();

		g2.setPaint(Color.WHITE);
		g2.fillRect(0, 0, PAPER_X, PAPER_Y);
		g2.translate(DPI, DPI);
		g2.setPaint(Color.RED);
		g2.fillRect(0, 0, PAPER_X-DPI*2, PAPER_Y-DPI*2);


		//Main page information.
		//g2.translate(DPI, DPI);

               	[COLOR="Red"]pageInfo.print(g);[/COLOR]

	}
}

	class PageInfo extends JPanel {
		PageInfo() {
			setPreferredSize(new Dimension(250, 250));
			setBackground(Color.WHITE);
		}
		public void paintComponent(Graphics g) {
			super.paintComponent(g);

			Graphics2D g2 = (Graphics2D) g;
			g2.translate(50, 50);

			g.setColor(Color.BLACK);
			g.fillRect(0, 0, 150, 150);

		}
	}// End pageinfo class.

cannot find symbol variable g

[Tolls]

Um, that's because you called your graphics variable g2, not g...

[AcousticBruce]

yes that is why I get an error for symbol variable.... renaming to g2 would stop the error, but would call the wrong g2. I even tried instatiating a Graphics object in the class but still nothing shows. Probibly because it is not rendered ons screen.

But i am still wondering if there is a way to print a JPanel to another paintComponent or even copy a JPanel to a BufferedImage without displaying it on screen first?

[Tolls]

You've overidden paintComponent.
print() uses printComponent().

[AcousticBruce]

But i am still wondering if there is a way to print a JPanel to another paintComponent or even copy a JPanel to a BufferedImage without displaying it on screen first?

[Tolls]

But this isn't displaying it on a screen.
You are supplying the Graphics object from your Image.
It will draw onto your Image, not the screen.
That's the point.

[DarrylBurke]

You do need to set a size for the JPanel otherwise, since it is not added to any realized component hierarchy, the size will be [0, 0].

panel.setSize(panel.getPreferredSize());

db

[Tolls]

Sorry.
Just realised what's going on.

Since Swing seems to do it's layout stuff on being setVisible (which you want to avoid doing) you might have to manually set the size and location of your components. Until you do that they will all have a 0 width and height, as well as no location (I think). And note, it's setSize, not setPreferredSize in this case.

ETA: Or what Darryl said...:)

[AcousticBruce]

Thanks to darryl and tolls.

Now that I know this works and I have messed with it. I think I still need to take a different angle with my program.

Im also going to study setSize vs setPreferred and understand that more.

thanks guys

[DarrylBurke]

A similar discussion:
OTN Discussion Forums : Render JLabel without 1st displaying ...

db