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Paint hidden Java swing component

I've tried to paint component to PDF. I've got itextpdf 4.2 and everything works perfectly.
But this works only if I make visible the frame that I've tried to render.
The similar question that I've found is How to paint an invisible JFrame elsewhere? that has the same issue, but the solution wasn't provided in answer.
A little of code.
I've created a JFrame and insert main view that I want to render.
JFrame jframe = new ShowingFrame();
jframe.setPreferredSize(new Dimension(PDFHelper.getOriginalWidth().intValue(), PDFHelper.getOriginalHeight().intValue()));
jframe.setMinimumSize(new Dimension(PDFHelper.getOriginalWidth().intValue(), PDFHelper.getOriginalHeight().intValue()));
jframe.add(view);
jframe.setUndecorated(true);
jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jframe.setState(Frame.ICONIFIED);
jframe.setState(Frame.NORMAL);
//jframe.setVisible(true);
If I uncomment jframe.setVisible(true) than everything works.
But user will see this frame that I want to avoid.
So the question is: How to paint hidden control?
Inside Swing Component.java class all paint methods first check if the component is visible:
public void paint(Graphics g) {
if (isShowing()) {
// rest of the code...
}
}
I've tried to create inherit class ShowingFrame extends JFrame, that override isShowing and always return true. But this not helps to.

Swing (and the Java Graphics API) is optimized to stop rendering as soon as possible.
So the solution is to create a BufferedImage, get the Graphics instance from it and then call component.paint(g); with it.
Now you have a tab component. Try to get the content of the tab instead of rendering the tab itself. If that doesn't work, you can try to clone the tree of children, create a new JPanel, attach the children and render the result. But cloning can become tedious if the models don't behave well.
See this question for some code: Swing: Obtain Image of JFrame

Why do you want to paint something that is not visible? Your computer does not want to waste CPU cycles rendering graphics that can't be seen. In fact, there is a lot of computations done to see what parts of each window are visible and only paint the visible parts (the so called clip window).
If you want to paint something so you can use it later or save it you can always create a BufferedImage of the size you want and paint to that.

If I uncomment jframe.setVisible(true) than everything works. But user will see this frame that I want to avoid.
You can set the frame location so that it is not visible on the screen. Maybe something like:
frame.pack();
Dimension d = frame.getSize();
frame.setLocation(-d.witdh, 0);

Using an image instead of JDialog/frame to hold swing components?

I currently have a JDialog (class that implements JDialog and is constructed like a jframe), and has 3 swing buttons placed on it. Currently I have it set, undecorated = true, to hide the outer frame. Is there any way to use my image to replace the default square frame?
This is what I aim for :
The blue square with shadow is the pre made image.
Regards

The blue square with shadow is the pre made image.
Well, the best way would be to set the background of the panel and then add a ShadowBorder to the panel. This will provide you with far more flexibility in the future as you can create many panels with different colors and reuse the same ShadowBorder instead of having to create an Image every time. I don't have an example of a ShadowBorder, but you might find one if you search the web.
Is there any way to use my image to replace the default square frame?
But if you really want to use your premade Image, then you can just:
create a JLabel and add your Image to the label as an Icon
add the label to the dialog
set the layout manager of the label
add your components to the label.

java code for TextBox in MS Paint

I am trying to create a code that simulates a MS Paint in java using Jframe. I want to create a textbox like field like MS Paint has,wherein you drag a box and according to your preference you set a size for it. What I do is I draw a rectangle first and then get the dimensions by mouse event listener and pass these values to a function that creates a JtextArea of given size and width. However, I need to extend the Jframe class which creates a new frame on top of the one that already exists. I try to pass my original frame as a parameter to draw upon for the JtextArea which does not work. Is there any way of implementing JtextArea without extending the frame class? And If possible any relevant example to draw a textbox which is similar to MS Paint. Please note that I don't want to use the Graphics.drawstring method. Thanx.

Since you don't want to use drawString() directly, java.awt.font.TextLayout is probably the best option for rendering text.

Create a temp JTextArea and add to your drawing panel with null layout to be placed over the rectangle.
When edit is done (text entered) remove the temp textarea, get the user entered text and draw it in the original rectangle.

How can I change colors of components when the mouse is pressed in a JFrame in Java?

I am coding a piano in java using rectangles from the java.awt.graphics library. I am using a mouselistener to play the sound of each individual key when the mouse clicks a certain area on the JFrame.
How would I add a shape to the panel upon clicking, repaint, then repaint the keyboard back over top when the user releases the mouse?

Consider adding JLabels to a JPanel that uses GridLayout. Give each JLabel a MouseListener and either swap ImageIcons on mousePress/mouseRelease or change the JLabel's background with press and release. If you go the latter route, you'll want to make sure that the JLabels opaque property is set to true so that the background colors show.
Then for the black keys, you can add the above JPanel to a JLayeredPane and on top of this, add another JPanel that holds the black keys that function in the same way.
Also, you'll want to take care to "play" any notes in a background thread, such as can be obtained with a SwingWorker so as not to tie up the Swing event thread and completely freeze your program.

Consider solution: source
It might not be exactly what you're after, but it might give you an idea of how to approach your problem. It took me a long time to figure out how to use JLayeredPane without setting a null layout, but in the end this was the best I could come up with. Also, assumed some naming conventions for your sound files. :p

Painting a JComponent without adding it to a container

I've implemented a custom JPanel, whose paint method I've extended to do a lot of manual rendering in full screen mode. Now I would like to integrate another JComponent to this (in my case a JPanel that contains a JScrollpane with a JTextPane as its viewport) that should appear on top of my first panel, but because my custom rendering pipeline is complex, adding the JComponent to my panel and having it painted the traditional way through the AWT system is not an option (I tried and it's quirky at best, not functional at worst), so my question is: is it possible to manually order the JComponent to be painted at one point in my program by calling its regular paint method without tying it to a JContainer and if yes, how do I do this?
Thanks in advance for your answers.

See the LabelRenderTest.java source on this thread. The label is eventually drawn to screen, but it is painted to BufferedImage before ever being displayed.
The important line of the source is..
textLabel.setSize(textLabel.getPreferredSize());

You can take a look at CellRendererPane and see how for example BasicTableUI paints component images with it.

Yes, just call the normal paint method on the object and pass the Graphics you want it to paint on. However, this is just going to paint it and it sounds like you want it to possibly scroll which means you will need to add it to your custom JPanel. In that case just add the panel and you a layout manager that will place the component where you need it.

You should set size for the component. Then to position it use your Graphics' translate(x,y) to position the component in desired Point.

if there is any container higher level in the hierarchy you can use
validate(); repaint();
pair to do that.
if not you can change it's size or bounds ( like +1 , -1 ) at the end to make it repaint itself.