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Drawing a circle and line onto a JFrame using JPanels without GridLayout

Currently I am trying to draw a line and a circle (which will become animated, like a wheel) onto my canvas.
I have a constructor called WheelAnimation().
Within this constructor, I have these two implementation classes, the first one is the circle:
class CircleComponent extends JComponent
{
private static final long serialVersionUID = 1L;
public void paintComponent(Graphics g)
{
Graphics2D g2 = (Graphics2D) g;
for(int i = 0; i < 200; i++)
{
// repaint();
g2.fillOval(i, 50, 50, 50);
}
}
}
final CircleComponent component2 = new CircleComponent();
panel.add(component2);
And this draws the line under the circle:
class LineComponent extends JComponent
{
public void paintComponent(Graphics g)
{
Graphics2D g2 = (Graphics2D) g;
g2.drawLine(120, 120, 380, 120);
}
}
final LineComponent component = new LineComponent();
panel.add(component);
If I use a setLayout method such as: panel.setLayout(new GridLayout(1, 1));
I can make the two items show up (though their formatting is not good).
http://puu.sh/8fm9B/4f1dc1d0e5.png
But if I remove the setLayout method, nothing shows up onto my frame, despite the coordinates staying the same.
Could someone tell me why this is happening and give me a recommendation on how to set those layouts and make them show up?

I can make the two items show up (though their formatting is not good).
When you use a layout manager it is responsible for setting the size and location of the component added to the panel.
If you don't use a layout manager then your application code is responsible for setting the size and location of each component.

Drawing a Component to BufferedImage causes display corruption

I am using the JScrollNavigator component described here, in order to provide a navigation window onto a large "canvas-like" CAD component I have embedded within a JScrollPane.
I have tried to adapt the JScrollNavigator to draw a thumbnail image of the canvas to provide some additional context to the user. However, the action of doing this causes the rendering of my application's main frame to become corrupted. Specifically, it is the action of calling paint(Graphics) on the viewport component (i.e. my main canvas), passing in the Graphics object created by the BufferedImage that causes subsequent display corruption; if I comment this line out everything works fine.
Below is the JScrollNavigator's overridden paintComponent method:
#Override
protected void paintComponent(Graphics g) {
Component view = jScrollPane.getViewport().getView();
BufferedImage img = new BufferedImage(view.getWidth(), view.getHeight(), BufferedImage.TYPE_INT_ARGB);
Graphics2D g2d = img.createGraphics();
// Paint JScrollPane view to off-screen image and then scale.
// It is this action that causes the display corruption!
view.paint(g2d);
g2d.drawImage(img, 0, 0, null);
Image scaled = img.getScaledInstance(getWidth(), getHeight(), 0);
super.paintComponent(g);
g.drawImage(scaled, 0, 0, null);
}
Does anyone have any suggestions as to the cause of the corruption? I would have thought that painting to an offscreen image should have no effect on existing paint operations.
EDIT
To provide some additional detail: The JScrollNavigator forms a sub-panel on the left-hand side of a JSplitPane. The JScrollPane associated with the navigator is on the right-hand side. The "corruption" causes the splitter to no longer be rendered and the scrollbars to not be visible (they appear white). If I resize the JFrame, the JMenu section also becomes white. If I attempt to use the navigator or interact with the scrollbars, they become visible, but the splitter remains white. It's as if the opaque settings of the various components has been affected by the rendering of the viewport view to an offscreen image.
Also, if I make the JScrollNavigator appear in a completely separate JDialog, everything works correctly.
EDIT 2
I can reproduce the problem consistently by doing the following:
Add a JMenuBar to the mFrame:
JMenuBar bar = new JMenuBar();
bar.add(new JMenu("File"));
mFrame.setJMenuBar(bar);
In the main() method of JScrollNavigator replace:
jsp.setViewportView(textArea);
... with:
jsp.setViewportView(new JPanel() {
{
setBackground(Color.GREEN);
setBorder(BorderFactory.createLineBorder(Color.BLACK, 5));
}
});
Ensure that the JScrollNavigator is embedded as a panel within mFrame, rather than appearing as a separate JDialog:
mFrame.add(jsp, BorderLayout.CENTER);
mFrame.add(nav, BorderLayout.NORTH);
Now when the application runs the JMenuBar is no longer visible; the act of painting the view (i.e. a green JPanel with thick black border) to the Graphics2D returned by BufferedImage.createGraphics() actually appears to be rendering it onscreen, possibly from the top-left corner of the JFrame, thus obscuring other components. This only seems to happen if a JPanel is used as the viewport view, and not another component such as JTextArea, JTable, etc.
EDIT 3
Looks like this person was having the same problem (no solution posted though): http://www.javaworld.com/community/node/2894/
EDIT 4
Here's the main and paintComponent methods that result in the reproducible error described in Edit 2:
public static void main(String[] args) {
JScrollPane jsp = new JScrollPane();
jsp.setViewportView(new JPanel() {
{
setBackground(Color.GREEN);
setBorder(BorderFactory.createLineBorder(Color.BLACK, 5));
}
});
JScrollNavigator nav = new JScrollNavigator();
nav.setJScrollPane(jsp);
JFrame mFrame = new JFrame();
JMenuBar bar = new JMenuBar();
bar.add(new JMenu("File"));
mFrame.setJMenuBar(bar);
mFrame.setTitle("JScrollNavigator Test");
mFrame.setSize(800, 600);
mFrame.setLayout(new GridLayout(1, 2));
mFrame.add(jsp);
mFrame.add(nav);
Dimension screenDim = Toolkit.getDefaultToolkit().getScreenSize();
mFrame.setLocation((screenDim.width - mFrame.getSize().width) / 2, (screenDim.height - mFrame.getSize().height) / 2);
mFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
mFrame.setVisible(true);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Component view = jScrollPane.getViewport().getView();
if (img == null) {
GraphicsConfiguration gfConf = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration();
img = new BufferedImage(view.getWidth(), view.getHeight(), BufferedImage.TYPE_INT_ARGB);
}
Graphics2D g2d = img.createGraphics();
view.paint(g2d);
Image scaled = img.getScaledInstance(getWidth(), getHeight(), 0);
g.drawImage(scaled, 0, 0, null);
}
EDIT 5
It seems like others are having trouble recreating the exact problem. I would ask people to run the code pasted here. When I first run this example I see the following:
Neither the JScrollNavigator or the JMenuBar have been painted; these frame areas are transparent.
After resizing I see the following:
The JMenuBar has still not been painted and it appears that the JPanel was at some point rendered at (0,0) (where the JMenuBar should be). The view.paint call within paintComponent is the direct cause of this.

Summary: The original JScrollNavigator uses the Swing opacity property to render a convenient green NavBox over a scaled thumbnail of the component in an adjacent JScrollPane. Because it extends JPanel, the (shared) UI delegate's use of opacity conflicts with that of the scrollable component. The images seen in edit 5 above typify the associated rendering artifact, also shown here. The solution is to let NavBox, JScrollNavigator and the scrollable component extend JComponent, as suggested in the second addendum below. Each component can then manage it's own properties individually.
I see no unusual rendering artifact with your code as posted on my platform, Mac OS X, Java 1.6. Sorry, I don't see any glaring portability violations.
A few probably irrelevant, but perhaps useful, observations.
Even if you use setSize(), appropriately in this case, you should still pack() the enclosing Window.
f.pack();
f.setSize(300, 200);
For convenience, add() forwards the component to the content pane.
f.add(nav, BorderLayout.WEST);
Prefer StringBuilder to StringBuffer.
Consider ComponentAdapter in place of ComponentListener.
Addendum: As suggested here, I got somewhat more flexible results using RenderingHints instead of getScaledInstance() as shown below. Adding a few icons makes it easier to see the disparate effect on images and text.
editPane.insertIcon(UIManager.getIcon("OptionPane.errorIcon"));
editPane.insertIcon(UIManager.getIcon("OptionPane.warningIcon"));
...
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Component view = jScrollPane.getViewport().getView();
BufferedImage img = new BufferedImage(view.getWidth(),
view.getHeight(), BufferedImage.TYPE_INT_ARGB);
Graphics2D off = img.createGraphics();
off.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
off.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
RenderingHints.VALUE_INTERPOLATION_BICUBIC);
view.paint(off);
Graphics2D on = (Graphics2D)g;
on.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
on.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
RenderingHints.VALUE_INTERPOLATION_BICUBIC);
on.drawImage(img, 0, 0, getWidth(), getHeight(), null);
}
Addendum secundum: It looks like the JPanel UI delegate is not cooperating. One workaround is to extend JComponent so that you can control opacity. It's only slightly more work to manage the backgroundColor. NavBox and JScrollNavigator are also candidates for a similar treatment.
jsp.setViewportView(new JComponent() {
{
setBackground(Color.red);
setBorder(BorderFactory.createLineBorder(Color.BLACK, 16));
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(getBackground());
g.fillRect(0, 0, getWidth(), getHeight());
}
#Override
public Dimension getPreferredSize() {
return new Dimension(300, 300);
}
});

I am also not sure what you mean by corruption, but I noticed that the resampled image is much nicer if you specify Image.SCALE_SMOOTH as the rescaling hint:
Image scaled = img.getScaledInstance(getWidth(), getHeight(), Image.SCALE_SMOOTH);
Maybe this is what you are looking for...

I was able to reproduce your problem and get you the result your looking for. The problem is that the drawing of the image wasn't complete by the time you were repainting again, so only portions of the image were being painted. To fix this, add this field to your JScrollNavigator class (as a lock):
/** Lock to prevent trying to repaint too many times */
private boolean blockRepaint = false;
When we repaint the component, this lock will be activated. It won't be released until we have been able to successfully paint the panel - then another paint can be executed.
The paintComponent needs to be changed to abide by the lock and use a ImageObserver when painting your navigation panel.
#Override
protected void paintComponent(final Graphics g) {
super.paintComponent(g);
if(!blockRepaint){
final Component view = (Component)jScrollPane.getViewport().getView();
BufferedImage img = new BufferedImage(view.getWidth(), view.getHeight(), BufferedImage.TYPE_INT_ARGB);
Graphics2D g2d = img.createGraphics();
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// Paint JScrollPane view to off-screen image and then scale.
// It is this action that causes the display corruption!
view.paint(g2d);
ImageObserver io = new ImageObserver() {
#Override
public boolean imageUpdate(Image img, int infoflags, int x, int y,int width, int height) {
boolean result = true;
g.drawImage(img, 0, 0, null);
if((infoflags & ImageObserver.FRAMEBITS) == ImageObserver.FRAMEBITS){
blockRepaint = false;
result = false;
}
return result;
}
};
Image scaled = img.getScaledInstance(getWidth(), getHeight(), 0);
blockRepaint = g.drawImage(scaled, 0, 0, io);
}
}

draw buffered image ontop of another buffered image

my goal is to draw some bufferedimage onto another. then all this stuff draw onto some other bufferedimage and so on. And finally draw this on top of a panel.
For now i'm trying to draw bufferedimage onto panel and nothing works. My bufferedimage looks completely white:
public class Main2 {
public static void main(String[] args) {
JFrame frame = new JFrame("asdf");
final JPanel panel = (JPanel) frame.getContentPane();
frame.setSize(500,500);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
panel.addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
somepaint(panel);
}
});
}
private static void somepaint(JPanel panel) {
BufferedImage image = new BufferedImage(200,200,BufferedImage.TYPE_INT_ARGB);
image.getGraphics().setColor(Color.red);
image.getGraphics().fillRect(0, 0, 200, 200);
Graphics2D graphics = (Graphics2D) panel.getGraphics();
graphics.setColor(Color.magenta);
graphics.fillRect(0, 0, 500, 500);
graphics.drawImage(image, null, 0, 0); // draws white square instead of red one
}
}
thanks

Re:
private static void somepaint(JPanel panel) {
BufferedImage image = new BufferedImage(200,200,BufferedImage.TYPE_INT_ARGB);
image.getGraphics().setColor(Color.red);
image.getGraphics().fillRect(0, 0, 200, 200);
Graphics2D graphics = (Graphics2D) panel.getGraphics();
This is not how you draw inside of a JPanel or JComponent.
Don't call getGraphics() on a component as the Graphics object returned will be short-lived, and anything drawn with it will not persist. Instead do your JPanel's drawing inside of its paintComponent(Graphics G) method override. You will need to create a class that extends JPanel in order to override paintComponent(...).
Most importantly, to see how to do Swing graphics correctly, don't guess. You'll want to read the Swing Graphics Tutorials first as it will require you to toss out some incorrect assumptions (I know that this is what I had to do to get it right).

You need to rectify your parameters in the drawImage() call. Change this:
graphics.drawImage(image, null, 0, 0);
to
graphics.drawImage(image, 0, 0,null);
Check the Java docs for more details.

Background Image in JTextPane

How do I set a background image to a JTextPane - some sort of a watermark.
I tried this option - creating a child class of JTextPane and use the paint method to draw the image.
But then the text is displayed "below" the image than above.
Is there any "standard" or "well known" way to do this?
(BTW, I tried (something silly?) making the content type "text/html", and setting the image as the background image of a <div> but it did not help.)

Here's a working example:
import javax.swing.*;
import java.awt.*;
public class ScratchSpace {
public static void main(String[] args) {
JFrame frame = new JFrame("");
final MyTextPane textPane = new MyTextPane();
frame.add(textPane);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
private static class MyTextPane extends JTextPane {
public MyTextPane() {
super();
setText("Hello World");
setOpaque(false);
// this is needed if using Nimbus L&F - see http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6687960
setBackground(new Color(0,0,0,0));
}
#Override
protected void paintComponent(Graphics g) {
// set background green - but can draw image here too
g.setColor(Color.GREEN);
g.fillRect(0, 0, getWidth(), getHeight());
// uncomment the following to draw an image
// Image img = ...;
// g.drawImage(img, 0, 0, this);
super.paintComponent(g);
}
}
}
The important things to note:
your component must not be opaque...
so setOpaque(false);
override paintComponent(Graphics g), not paint.
paint your background, with an image
or drawing BEFORE calling
super.paintComponent(g);
If you want to master this stuff, I recommend reading "Filthy Rich Clients", a book all about how to bend Swing to your will.

Try changing the paint code to this.
public void paint(Graphics g)
{
g.setXORMode(Color.white);
g.drawImage(image,0, 0, this);
super.paint(g);
}
This would make your image to be painted before the text is rendered by the actual component's paint method.

Hmm., put a background image to the JFrame/JPanel containg the JTextPane,.. and keep the JTextPane transparent to some level.

Paint background of JPanel

How can I tell the paint method to draw background on JPanel only and not on the entire JFrame.
My JFrame size is bigger than the JPanel. When I try to paint a grid background for the JPanel, the grid seems to be painted all over the JFrame instead of just the JPanel.
Here parts of the code:
public class Drawing extends JFrame {
JPanel drawingPanel;
...........
public Drawing (){
drawingPanel = new JPanel();
drawingPanel.setPreferredSize(new Dimension(600,600));
}
public void paint(Graphics g)
{
super.paintComponents(g);
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
paintBackground(g2); //call a METHOD to paint the for JPANEL
}
private void paintBackground(Graphics2D g2)
{
g2.setPaint(Color.GRAY);
for (int i = 0; i < drawingPanel.getSize().width; i += 300)
{
Shape line = new Line2D.Float(i, 0, i, drawingPanel.getSize().height);
g2.draw(line);
}
for (int i = 0; i < drawingPanel.getSize().height; i += 300)
{
Shape line = new Line2D.Float(0, i, drawingPanel.getSize().width, i);
g2.draw(line);
}
} //END private void paintBackground(Graphics2D g2)
}

If you want to do painting on the JPanel then override the JPanel, not the JFrame.
You should be overriding the paintComponent() method of JPanel. Read the section from the Swing tutorial on Custom Painting for a working example.

camickr is correct. So:
public class Drawing extends JFrame {
JPanel drawingPanel;
...........
public Drawing (){
drawingPanel = new MyPanel();
drawingPanel.setPreferredSize(new Dimension(600,600));
add(drawingPanel);
}
}
public class MyPanel extends JPanel {
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
myBackgroundRoutine(g2);
}
}
You need to strictly separate your drawing from different components. Swing is already
managing subcomponents, so there is absolutely no need to implement drawings in your
Panel in the Frame (calling paintComponents() is a severe error).
And you should never override paint(), because only paintComponent()
is used in Swing. Don't mix both until you absolutely know what you are doing.

super.paintComponents(g);
I would suggest as your first point of investigation.

The code you posted is not complete, it's missing how the panel is added to the JFrame and which LayoutManager is being used.
The code seams to be correct. Are you sure the JPanel is not occupying the whole JFrame? Add a System.out.println(drawingPanel.getSize()) to check this.
If you are using the BorderLayout, the default for JFrame, and has just added the panel without any constraint, the panel will use the whole area. The PreferredSize is ignored.
Try this, just for testing:
public Drawing (){
drawingPanel = new JPanel();
drawingPanel.setPreferredSize(new Dimension(600,600)); // ignored
drawingPanel.setBounds(0, 0, 600, 600); // location and size
setLayout(null);
add(drawingPanel);
}
but IMO this is not the best or correct way to do it. I would prefer to override the paintComponent() method from the JPanel, as suggested by Thorsten and camickr.
But it will still use the whole area of the JFrame until other Component is added to the JFrame or the LayoutManager changed.

You should override the JPanel, not the JFrame to do painting. You can override the paintComponent() method of the JPanel