In java awt or swing when you want to change painting of some component you usually have to override the method paint(Graphics g) (in awt) or paintComponent(Graphics g) (in swing).
This is usually (maybe allways - I'm not sure) done when you are creating the component for example:
JPanel jPanel = new JPanel() {
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
//... my implementation of paint, some transfromations, rotation, etc
}
};
Imagine that you have container of components which could for example consists of some JLabels, some JTextFields, some image. Which will be all put on one component.
By container I mean you have some list or map with ids or some similar structure in which are all components you will put on one JFrame.
The question is if I can change the painting method after creating with all of the components which are in this list in the moment when all of them are already created. For example I want do the rotation action (rotate), which is defined in Graphisc2D, with all of them.
So basicaly what I want is that I throught the list of componets I have and say:
"All of you (components) which are in the list will be rotated by some angle". Is that possible? If yes how?
Edit:
This is my not correctly working solution:
graphicalDisplayPanel = new JPanel() {
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g2d = (Graphics2D) g;
g2d.rotate(Math.PI, anchorx, anchory);
}
#Override
public void paintChildren(Graphics g) {
super.paintChildren(g);
Graphics2D g2d2 = (Graphics2D) g;
g2d2.rotate(Math.PI, anchorx, anchory);
}
};
JFrame jFrame = JFrame();
// ... setting dimension, position, visible etc for JFrame, it works correctly nonrotated
jFrame.setContentPane(graphicalDisplayPanel);
I have not tested this, but it seems like it would work. A JComponent's paint() method calls:
paintComponent(co);
paintBorder(co);
paintChildren(co);
where co is a Graphics object. In theory you create an image, retrieve the graphics object and then pass that into paintChildren(). you will have to call paintComponent() and paintBorder() yourself, if you do this. Then, just rotate the image and draw it into your component. You may have to crop the image or resize your component accordingly for this to work. It might look something like this:
BufferedImage myImage;
#Override
public void paint(Graphics g){
myImage = new BufferedImage(getWidth(), getHeight(), BufferedImage.TRANSLUCENT);
//using a transparent BufferedImage might not be efficient in your case
Graphics myGraphics = myImage.getGraphics();
super.paintComponent(g);
super.paintBorder(g);
super.paintChildren(myGraphics);
//rotation code here
// ...
//draw children onto your component
g.drawImage(myImage, 0, 0,getWidth(), getHeight(), null);
}
I hope I didn't make any mistakes, please let me know if this works.
So basicaly what I want is that I throught the list of componets I have and say: "All of you (components) which are in the list will be rotated by some angle".
If you want to rotate panel and therefore all the components on the panel as a single using then you need to do the custom painting in the paintComponent() method.
If you want to rotate, for example, individual images that each have a different angle of rotation then you can again do this in the paintComponent(...) method and change the angle for each component.
Or, in this second case you can use the Rotated Icon class. In this case the Icon is just added to a JLabel. Then you can change the degrees of rotation and repaint the label, so there is no custom painting (except in the Icon itself).
Related
I want to update an image in Java Swing and tried two different methods of rendering these images.
Define a JLabel and set the icon of it
Override the paintComponent(Graphics g) function in a custom JPanel and call g.drawImage(img, 0, 0, null)
Rendering the first image works as expected in both ways, but if I'm trying to update the image, it doesn't replace but renders one layer above which is a problem, because the images I want to render are semi-transparent, so you can see the others through.
I'm already using the repaint() method.
Method 1
public void setImage(Image img) {
this.backgroundLabel.setIcon(new ImageIcon(img));
this.repaint();
}
Method 2
public void setImage(Image img) {
this.img = img;
this.repaint();
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawImage(img, 0, 0, null);
}
I'm thankful for any tips! <3
The first thing line in paintComponent(Graphics g) should be
super.paintComponent(g);
This clears the panel, does any background painting if necessary, and any other support functions from the overridden paintComponent method. Otherwise, you will keep drawing images over the previous ones without first clearing them.
For anyone in the future with the same problem, here is the answer I came up with.
I didn't repainted the full frame, but only the JPanel.
I had to add
frame.repaint();
in setImage().
The below code is to display a triangle in applet.But it does not work for me. If i pass Graphics g instead of Graphics2D g then it works fine.But i want to know what the mistake i am doing while using Graphics g. I am new to java and learning from some online tutorials. So please correct my program and tell me what mistake i am doing.
import javax.swing.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class Vehicle extends JFrame {
final int WIDTH = 900;
int HEIGHT = 650;
public void init() {
setSize(WIDTH, HEIGHT);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(true);
}
public void paint(Graphics2D g) {
Graphics2D g2 = (Graphics2D) g;
Dimension d = getSize();
System.out.println(d);
int[] yPoints={150,250,250};
int[] xPoints={200,150,250};
g2.setColor(Color.green);
g2.drawPolygon(xPoints, yPoints, 3);
g2.drawRect(100, 100, 100, 100);
g2.setColor(Color.red);
g2.fillPolygon(xPoints, yPoints, 3);
}
public static void main(String[] args) {
Vehicle v= new Vehicle();
v.init();
}
}
The method paint(Graphics g) is defined in java.awt.Component. This is more or less legacy code. However, this API hasn't changed for a long time and is inherited by modern Swing components, such as JFrame.
You can't simply change the method signature (in your case to paint(Graphics2D g)), you have to live with the signature defined by the API.
So, in your case, the paint(Graphics2D g) does not override the API method paint(Graphics g), and thus is not called when updating the JFrame. Nothing is painted.
Change your code like this:
----------------%<----------------------
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(true);
}
public void paint(Graphics g) { // <-- Change from Graphics2D to Graphics
Graphics2D g2 = (Graphics2D) g;
Dimension d = getSize();
System.out.println(d);
int[] yPoints={150,250,250};
int[] xPoints={200,150,250};
---------------->%----------------------
Take a good look at what your program is doing before looking for assistance. (Not scolding you, just trying to help for the future.)
You have public void paint(Graphics2D g), which, as Petersen stated, is not a method in the JFrame class. A good trick to use to check if your methods in swing will do what tutorials say they will do is to put #Override above the method. If it errors, it means that method is not in JFrame or whatever superclass you have. Otherwise, it is overriding the method.
Additionally, another flag would be the next line: Graphics2D g2 = (Graphics2D) g;
Here you're casting a Graphics2D object as a Graphics2D object... which should never need to happen.. haha
If you are just getting started with swing and Graphics2D I suggest learning some of the Panels systems and other low-level things like drawImage or drawString, if you haven't done so already.
Working with Java2D it often helps to imagine your application as an animation. Imagine that at one point one specific frame(I am talking about animation frames okay) is drawn on the screen. When some event occurs we replace this frame with another frame incorporating the change much like the way cartoons or animation movies are built. How we draw animation frames? How do we switch between frames?
Java API provides a paint(graphics g) method for its components to be drawn. And then to update the same component you really call repaint() which simply calls paint(Graphics g) again and displays any changes on to the screen. This API method has a strict signature that we shall follow. It is paint(Graphics g). But Graphics2D is much like a cool kid on the block that provides more functionality because Graphics was too old(legacy) and not cool anymore. So how do we do this because paint(Graphics g) only accepts Graphics not Graphics2D? Graphics2D is a subclass of Graphics okay.
Protocol is simple,
Use the legacy paint(Graphics g) method of every component.
Once we have used super.paint(Graphics g) (if needed) ,we can typecast the Graphic object that we were using for legacy purposes to Graphics2D to get enhance functionality.(you have done this step right)
Problem with your code:
It is only the signature. Java and the repaint() expect the method to be paint(Graphics g) but you have changed the signature and now the above protocol (or contract) is broken. The idea is to keep the contract(by not changing the signature) and then typecast and override to add extended features. Java is not able to find paint(Graphics g) and so repaint() will not also find paint(Graphics g).
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);
}
}
I'm making my first simple game, that looks like Space Invaders.
I have used paint for drawing my hero on my JPanel. Now I guess if it's possible, in a simple way, to add a background image on my JPanel.
ImageIcon img = new ImageIcon(this.getClass().getResource("back.gif"));
Image image = img.getImage();
setDoubleBuffered(true);
hero = new Hero("hbarrel.gif",350,500);
public void paint(Graphics g) {
super.paint(g);
Graphics2D g2d = (Graphics2D)g;
g2d.drawImage(hero.getImage(), hero.getX(), hero.getY(), this);
g2d.drawImage(image,0,0,this);
// Toolkit.getDefaultToolkit().sync();
g.dispose();
}
So, this is it: I tried to use my background img as hero img, and it works! but when I use the code above it only paints my hero img.... so it isn't a resource position issue.
Override paintComponent(Graphics) method and use Graphics.drawImage() to do that in your own custom component.
Well, try to paint the background image first and then the hero so that you have hero above background image
I'm using a custom JLayeredPane.
I have several Shapes which needed to be drawn on different layers in the JLayeredPane.
To test this I create a JPanel and ask its graphics. Then I draw a test rectangle on that JPanel (preparing the graphics) and in my paintComponent method from the JLayeredPane I finally draw everything. But this fails (NullPointerException).
public class MyCustomPanel extends JLayeredPane {
// test
JPanel testpane;
Graphics g2;
// test
// constructor
public MyCustomPanel() {
testpane = new JPanel();
this.add(testpane, new Integer(14));
g2 = testpane.getGraphics();
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g2.drawRect(10, 10, 300, 300);
}
}
// run:
//Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
// at view.MyCustomPanel.paintComponent(MyCustomPanel.java:65)
Why can't I draw on such a JPanel from within my JLayeredPane? I can draw directly on my JLayeredPane from within my paintComponent method but that's on the default Panel from the JLayeredPane. I need to create and draw on several layers which are added in my JLayeredPane.
What am I doing wrong? :s
You should use g2 casting the Graphics that is passed to you:
Graphics2D g2 = (Graphics2D)g;
Why don't you try decoupling things?
class InnerPanel extends JPanel
{
public void paint(Graphics g)
{
Graphics2D g2 = (Graphics2D)g;
g2.drawRect(....);
}
}
class MyLayered extends JLayeredPane()
{
MyLayered()
{
this.add(new InnerPanel(), 14);
}
}
this makes more sense..
Also because you are trying to do something that doesn't agree with Swing behaviour.
Swing will care by itself to call the appropriate paint methods over things that must be displayed, and to go with this protocol you should tell Graphics objects what to draw when Swing asks it to your objects (calling the paint) method, not when you want to do it.
In this way whenever Swing wants to draw your JLayeredPane you just draw things on a Graphic object of other things without considering that Swing will call their appropriate methods when it's the right time to do so.
In conclusion: you can't draw something on a Graphic object when you want it. You can do it just inside methods invoked by Swing, because otherwise Graphics of these objects doesn't mean anything
The variable g2 is probably null because you set it in the constructor, not when drawing. Instead, use the "g" that was passed in.
You can only get a legitimate Graphics from a component that is currently being painted. Otherwise, it's not valid. At the point you're requesting it, the MyCustomPanel() isn't being displayed, and neither is testpane.