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Repaint all components of a JFrame/JPanel

I'm working on some animation where I have a certain number of dots wandering around my JFrame and based on their distance they should be connected by lines of different strengths.
The base code for moving the dots works and actually I also had them displayed correctly in the beggining but I had some issues where the movement was stuttering (probably due to the repaint process). At that point the Window class handled the entire repaint procedure.
After reading some posts around here I adapted my code according to the github page linked in this post to use the individual Dots as JComponents and have them being repainted individually. However, now the problem is that although I still have 100 Dots as components on my JPanel, only one of them is being painted (however, the stuttering is gone at least). I also see that all components are being iterated and their repaint method is being called but they just don't display.
This is my paintComponent method in the Dot class:
#Override
protected void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g;
g2d.setPaint(new Color(0, 0, 0));
Ellipse2D.Double circle = new Ellipse2D.Double(x - 10 / 2, y - 10 / 2, 10, 10);
g2d.fill(circle);
}
And this is what my repaintTimer looks like:
final Timer repaintTimer = new Timer(20, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
for(Component component : window.getContentPane().getComponents()) {
component.repaint();
}
recalculateDots();
}
});
repaintTimer.start();
The result I get is something like this:
I tried some things of which I thought that it could solve the problem but nothing really helped and I'm really confused as to why this is happening. I'd appreciate any help very much because this issue doesn't make any sense for me.

Fading CurveVertex() trails using background opacity value not working

Using FX2D.
Hi, I'm currently drawing a line at every frame using the curveVertex() function.
Every line stays on the sketch voluntarily by not resetting the background at every step,
which leaves a trail effect.
But I would like to make these trails fade away over time. I tried resetting the background in the draw() function by giving it a small opacity value but it clears all the trails at once every time.
Right now I can only have either all trails or no trails.
//background(0, 0, 0, 10); // Reset background every time
stroke(255, 255, 255, 10); // Draw Line between all nodes
curveVertex(nodes.get(fixId(i)).position.x, nodes.get(fixId(i)).position.y);
with trails

background() does not just set the background color, it clear the entire window. It is not intended to use background within beginShape() / endShape() sequences.
What what to do can be achieved by drawing a rect() with blendMode(DIFFERENCE) on the entire window, at the begin of the frame. e.g.:
void draw() {
// "fade" the entire view
blendMode(DIFFERENCE);
fill(1, 1, 1, 255);
rect(0, 0, width, height);
blendMode(ADD);
// draw shape
// [...]
}
See also the answer to Processing - rendering shapes.

Java Graphics2D Image Moving

So in this block of code, a 40x40 square can move across a window by calling directional methods, and I'm trying to get a spaceship to appear instead of the square. No matter what I try, it just isn't working.
public void paintComponent (Graphics g) {
ImageIcon wallpaper = new ImageIcon("images/JGalagawallpaper.png");
image = wallpaper.getImage();
g.drawImage(image, 400, 400, null);
ImageIcon ship = new ImageIcon("images/galaga.png");
galaga = ship.getImage();
super.paintComponent(g);
Graphics2D graphic = (Graphics2D) g;
graphic.fill(new Rectangle.Double(x, y, 40, 40));
//graphic.drawImage(galaga, x, y, 40, 40);
}
My question is, how do I get that thing to appear? I already tried tinkering with graphic.drawImage, however that didn't really work out as well as I hoped. That's what the commented out code is.

g.drawImage(image, 400, 400, null);
First you draw the image.
super.paintComponent(g);
Then you invoke the above code which is used to pint the background color of the panel, thus overwriting the image. The above statement should be the first statement of the painting method.
ImageIcon wallpaper = new ImageIcon("images/JGalagawallpaper.png");
A painting method is for painting only. Don't do I/O in the method. The image should be read in the constructor of your class so that it is only read once, not every time the component is repainted.
You also need to look at the coordinates of where you paint the image. Maybe the panel is not that big?
Did you verify that the image was read properly by display its size?

Good practice for drawing and zooming image?

I have a JScrollPane with a JPanel where I can draw by mouse and code.
I need the possibility to zoom on details in my drawing.
But soon I get a outOfMemoryError. I think because I make my drawing to big while zooming.
This is my code:
private BufferedImage _bufferedImage;
private int _panelWidth = 2000, _panelHeight = 1500;
#Override
public void paintComponent(Graphics g){
super.paintComponent(g);
if(_bufferedImage != null){
g.drawImage(_bufferedImage, 0, 0, this);
}
}
public void draw(float zoomFactor){
try {
int width = (int)(_panelWidth * zoomFactor);
int height = (int)(_panelHeight * zoomFactor);
_bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
Graphics2D g2 = _bufferedImage.createGraphics();
g2.setBackground(Color.WHITE);
g2.setPaint(Color.BLACK);
g2.scale(zoomFactor, zoomFactor);
drawHouse(g2); ...
g2.dispose();
}
catch (Exception e) {
e.printStackTrace();
}
repaint();
}
There must be better practice then what I did.
I can just draw the area of the scrollpane, but then I can't use the scrollbars,
then I have to use buttons with arrow up, right, left, down to scroll in my drawing.
Anyone who can me give a hint?

but then I can't use the scrollbars
Scrollbars work when the preferred size of the component is greater than the size of the scrollpane. If you are zooming the image in the paintComponent() method then you would also need to override the getPreferredSize() method to return the appropriate size of the image that takes into account the zooming factor.
So in your case the preferred size would be the size of your image.

If you want to zoom in, I am assuming you are no trying to make "bigger pixels", but to draw the same figures at a higher scale. In that case, you should not be using a BufferedImage at all -- instead, you should draw to a suitably scaled JPanel or similar. You can always take a snapshot of whatever you are rendering whenever you need it; but rendering to a BufferedImage without need is wasteful (of time and memory).
See this answer for details.

How can I repaint efficiently when using big custom component in Swing?

I have made a custom component (derived from JComponent) which represents
a draggable Bezier-curve.
(looks like a hanging cable, someone might know it
from Bender or Cubase)
My problem is: The curve may become really long,
let's say from top left to bottom right corners of the desktop.
This makes Swing's repaint functionality inefficient:
The area of the curve is perhaps few hundred pixels, but the area of
the component (being mostly 'transparent') is millions of pixels big.
My subjection impression is:
The longer the curve, the more flicker I get when dragging it.
I hope I made myself clear about the problem.
Perhaps it would help when I somehow could choose by myself, which regions
of the component needs repainting at all.
EDIT:
Such a mess! I'm profiling the application using Netbeans, which helps to
find inefficient code normally, but this Swing framework is making hundreds
of nested calls! I just can't figure out, what is slow and why.
By the way, disabling super.paint(...) or super.paintComponent(...) doesn't help.

Check out Filthy Rich Clients by Chet Haase and Romain Guy. They address these very optimizations among others along the way to producing responsive and graphically impressive UI.

Doing all of your bezier mathematics on the paint thread everytime the component is refreshed is (as you've gathered) a bad idea. Does your curve change often? If not then why not paint it to a BufferedImage as and when it changes, and change your paint() code to simply draw the buffered image to the component instead.
class CurveComponent extends JComponent {
private BufferedImage image;
#Override
public void paintComponent( Graphics g ) {
if ( image == null ) {
return;
}
g.drawImage( image, 0, 0, this );
}
private void updateCurve() {
image = new BufferedImage( getWidth(), getHeight(), BufferedImage.ARGB );
Graphics g = image.getGraphics();
// draw the curve onto image using g.
g.dispose();
}
}
Only call updateCurve() when you need to and all that expensive mathematics won't be needlessly repeated. Painting should be pretty responsive, even for a fullscreen window. drawImage() will be doing a straightforward memory copy and should be lightning fast.

Try writing a tiny test app, which consists of nothing except what you need to reproduce this problem. This will make profiling easier. Then post that app here, so we can take a look at possible solutions.
I found your question interesting so I wrote a test app myself. This draws a Bezier curve which is continually resized as you drag. I created a gradient background to ensure this works well with a nasty background. I get good performance and low flicker, although I use top-notch machine.
It pays to read "Filthy Rich Clients" to learn all the tricks of writing custom Swing components that perform really well.
import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.CubicCurve2D;
import java.awt.geom.Point2D;
public class CustomComponent extends JComponent {
private Point2D start = new Point2D.Double(0, 0);
private Point2D end = new Point2D.Double(300, 200);
private CustomComponent() {
this.setOpaque(true);
final MouseAdapter mouseAdapter = new MouseAdapter() {
#Override
public void mouseDragged(MouseEvent e) {
setEnd(e.getPoint());
}
};
this.addMouseListener(mouseAdapter);
this.addMouseMotionListener(mouseAdapter);
}
public void setStart(Point2D start) {
this.start = start;
repaint();
}
public void setEnd(Point2D end) {
this.end = end;
repaint();
}
#Override
protected void paintComponent(Graphics g) {
final Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// draw gradient background
final int width = getWidth();
final int height = getHeight();
g2.setPaint(new GradientPaint(0, 0, Color.WHITE, width, height, Color.YELLOW));
g2.fillRect(0, 0, width, height);
// draw Bezier curve
final Shape shape = new CubicCurve2D.Double(start.getX(), start.getY(), start.getX(), end.getY(), end.getX(), start.getY(), end.getX(), end.getY());
g2.setColor(Color.BLACK);
g2.draw(shape);
g2.drawString("Click and drag to test for flickering", 100, 20);
}
public static void main(String[] args) {
final CustomComponent component = new CustomComponent();
final Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
final Dimension size = new Dimension(screenSize.width - 20, screenSize.height - 100);
component.setPreferredSize(size);
final JFrame frame = new JFrame();
frame.add(component);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}
Some things to note:
only overwrite paintComponent(Graphics g), not the other paintXXX() methods
set custom component to opaque if possible
only use repaint() to request repainting. Never directly order a repaint directly in your code. This lets Swing handle it well.

There is no efficient way to create lots of small clip rectangles for a diagonal structure which leaves you with two strategies to avoid flickering:
Double buffering. This needs an enormous amount of memory but the memory copy is very fast (it usually happens in the time the "electron beam" goes back from lower right to upper left ... if there was still a beam in your LCD).
Don't call super.paint() (which draws or "erases" the background) and draw the curve a second time with the background color to erase it.
For more details, see this document.
[EDIT] If fillRect() wasn't abstract, you could set a break point :) Set a break point in paint(), check who calls it and whether the background got cleared at that time. It should be since rendering would be completely wrong. Then set break points further up in the call chain.

You can redraw a smaller portion of the screen using repaint(Rectangle r)
http://java.sun.com/j2se/1.4.2/docs/api/javax/swing/JComponent.html#repaint(java.awt.Rectangle)
Then you mention flicker. Since you are using swing, which uses double buffering your flickering must be coming from something else. Are you clearing the screen in paintComponent(...)? I.e. call to fillRect(...)? Don't do that, it's not needed (IIRC).

Which method do yo use to paint your curve? paint or paintComponent?

My solution was a partial re-design:
Now I don't represent each "cable"-element by a component.
Now, cables are just dummy objects (with no involved JComponent).
The repaint takes place "globally", on the content pane of the parent JFrame.
Now it's efficient, and flickers less.

just use getVisibleRect(); inside paintComponent(Graphics g) to get the area you actually need to redraw