My problem is that when i use
public void paint(Graphics g)
{}
Method to draw a String as
g.drawString("hello java",0,0);
My full code is
import javax.swing.*;
import java.awt.*;
class test
extends JFrame
{
public void testing()
{
setSize(500,500);
show();
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public void paint(Graphics g)
{ super.paint(g);
g.drawString("HELLO JAVA");
}
public static void main(String arg[])
{
test t=new test();
t.testing();
} }
In JFrame i am getting a black screen without hello java being drawn
Please help me
Thanks in advance
To display the inherited frame correctly, the paint method in the inherited class should contain the call of super.paint():
class MyFrame extends JFrame {
public void paint(Graphics g) {
super.paint(g);
g.drawString("hello java", 50, 50);
}
}
EDIT (painting in the panel):
import java.awt.*;
import javax.swing.*;
public class CustomPaint {
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
JFrame frame = new JFrame("CustomPaint");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new MyPanel());
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
});
}
}
class MyPanel extends JPanel {
public Dimension getPreferredSize() {
return new Dimension(320, 240);
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
String msg = "HELLO JAVA";
g2.setPaint(Color.BLUE);
int w = (getWidth() - g.getFontMetrics().stringWidth(msg)) / 2;
g2.drawString(msg, w, getHeight() / 2);
}
}
Related
package drawinglinebymethods;
import java.awt.*;
import javax.swing.JFrame;
public class DrawingLineByMethods extends Frame {
public JFrame f=new JFrame();
void fra_size()
{
f.setSize(450, 300);
}
void fra_visible()
{
f.setVisible(true);
}
void fra_title()
{
f.setTitle(" java frame");
}
void exit()
{
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public void line(Graphics g) {
g.drawLine(10, 10, 20, 300);
}
public static void main(String[] args) {
DrawingLineByMethods obj = new DrawingLineByMethods();
obj.fra_size();
obj.fra_title();
obj.fra_visible();
obj.fra_exit();
obj.line(g); // <-- error here
}
}
Your question suggests that you are not yet clear on how graphics and drawing works in Swing GUI's. Some suggestions for you:
Don't have your class extend java.awt.Frame as this makes no sense. You're not creating an AWT Frame window and have no need of this.
Create a class that extends JPanel and draw in its paintComponent method as the Swing painting tutorials (link now added) show you.
You never call drawing code directly but rather it is indirectly called by the JVM.
If you want to draw from outside of the GUI itself, then draw to a BufferedImage, one that is then displayed within the GUI.
Don't use a Graphics object obtained by calling getGraphics() on a GUI component as the object thus obtained will not persist, and this risks you creating unstable graphics or worse -- throwing a NullPointerException.
For example:
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import javax.swing.*;
#SuppressWarnings("serial")
public class LineDraw extends JPanel {
private static final int PREF_W = 450;
private static final int PREF_H = 300;
public LineDraw() {
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// use rendering hints to draw smooth lines
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// do drawing here
g.drawLine(10, 10, 20, 300);
}
private static void createAndShowGui() {
LineDraw mainPanel = new LineDraw();
JFrame frame = new JFrame("Line Draw");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
createAndShowGui();
});
}
}
If you want to add lines as the program runs, again, use a BufferedImage that is drawn within the JPanel's paintComponent method. When you need to add a new line to the GUI, extract the Graphics or Graphics2D object from the BufferedImage using getGraphics() or createGraphics() respectively (it's OK to do this), draw with this Graphics object, dispose of the Graphics object, and repaint the GUI. For example in the code below, I draw a new line when the button is pressed by adding code within the JButton's ActionListener (actually its AbstractAction which is similar to an ActionListener but more powerful):
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.image.BufferedImage;
import javax.swing.*;
#SuppressWarnings("serial")
public class LineDraw extends JPanel {
private static final int PREF_W = 450;
private static final int PREF_H = 300;
private BufferedImage img;
private int yDistance = 20;
private int deltaY = 10;
public LineDraw() {
img = new BufferedImage(PREF_W, PREF_H, BufferedImage.TYPE_INT_ARGB);
add(new JButton(new DrawLineAction("Draw Line", KeyEvent.VK_D)));
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// draw the buffered image here
if (img != null) {
g.drawImage(img, 0, 0, this);
}
// use rendering hints to draw smooth lines
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// do drawing here
g.drawLine(10, 10, 20, 300);
}
public void drawNewLines() {
Graphics2D g2 = img.createGraphics();
g2.setColor(Color.BLACK);
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
yDistance += deltaY;
g2.drawLine(10, 10, yDistance, PREF_H);
g2.dispose();
repaint();
}
private class DrawLineAction extends AbstractAction {
public DrawLineAction(String name, int mnemonic) {
super(name); // give button its text
putValue(MNEMONIC_KEY, mnemonic); // alt-hot key for button
}
#Override
public void actionPerformed(ActionEvent e) {
drawNewLines();
}
}
private static void createAndShowGui() {
LineDraw mainPanel = new LineDraw();
JFrame frame = new JFrame("Line Draw");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
createAndShowGui();
});
}
}
Line is a non-static method, the only way to call it from a static method (main here) is to have an instance of the class.
I am trying to fill JFrame with a JPanel and colour that JPanel, but for some reason I get a border on the bottom right edges.
My code:
public class Main extends JFrame {
public MyPanel myPanel = new MyPanel();
public static void main(String args[])
{
Main main = new Main();
main.init();
}
public void init()
{
this.setSize(300,400);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setContentPane(myPanel);
this.setVisible(true);
}
#Override
public void paint(Graphics g)
{
myPanel.paintComponents(g);
}
class MyPanel extends JPanel
{
#Override
public void paintComponents(Graphics g)
{
g.fillRect(0, 0, getWidth(), getHeight());
}
}
}
Shows:
You're short-circuiting the paint chain with this method
#Override
public void paint(Graphics g) {
myPanel.paintComponents(g);
}
This isnt really doing anything useful so you can remove it. Also you need to override paintComponent rather than paintComponents in MyPanel
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.fillRect(0, 0, getWidth(), getHeight());
}
Aside:
You could have simply created a panel and called setBackground to get this functionality
I don't understand why my code isn't working, trying to print a rectangle in my JFrame, but keep ending up with an error on f.add(p);.
import javax.swing.*;
import java.awt.*;
public class SPEL{
public void paintComponent(Graphics g){
g.drawRect(50,75,100,50);
}
public static void main(String[] args) {
JFrame f = new JFrame();
f.setSize(400, 300);
f.setLocation(100,100);
f.setTitle("SPEL");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
SPEL p = new SPEL();
f.add(p);//error
f.setVisible(true);
}
}
You forgot to extends something, for example:
public class SPEL extends JPanel {
You can add #Override to reduce the chance of this kind of mistake
#Override
public void paintComponent(Graphics g){
try this! :
import javax.swing.*;
import java.awt.*;
#SuppressWarnings("serial")
public class SPEL extends JPanel {
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.setPaint(Color.red);
Rectangle b = new Rectangle(50, 75, 100, 50);
g2d.draw(b);
g2d.fill(b);
}
public static void main(String[] args) {
JFrame f = new JFrame();
f.setSize(400, 300);
f.setLocation(100, 100);
f.setTitle("SPEL");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
SPEL p = new SPEL();
f.add(p);
f.setVisible(true);
}
}
extends JPanle
#Override
Using Graphics2D
g2d.fill(Shape s)
I want to make the JFrame transparent, but the image on top of it to be non-transparent. This is what I have now:
Does anyone know a way to make only the JFrame transparent?
Here's my code:
import javax.swing.*;
import java.awt.*;
import com.sun.awt.AWTUtilities;
import static java.awt.GraphicsDevice.WindowTranslucency.*;
public class SplashDemo extends JFrame
{
public SplashDemo()
{
setUndecorated(true);
setSize(200, 200);
add(new JLabel(new ImageIcon("puppy2.png")));
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
setVisible(true);
setOpacity(0.85f);
}
public static void main(String[] args)
{
new SplashDemo();
}
}
Basically, you need to make a transparent window and a translucent content pane. This will mean anything added to the content pane will continue to be rendered without additional alphering...
public class TranscluentWindow {
public static void main(String[] args) {
new TranscluentWindow();
}
public TranscluentWindow() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (Exception ex) {
}
JWindow frame = new JWindow();
frame.setAlwaysOnTop(true);
frame.addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
if (e.getClickCount() == 2) {
SwingUtilities.getWindowAncestor(e.getComponent()).dispose();
}
}
});
frame.setBackground(new Color(0,0,0,0));
frame.setContentPane(new TranslucentPane());
frame.add(new JLabel(new ImageIcon(ImageIO.read(getClass().getResource("/Puppy.png")))));
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
} catch (IOException ex) {
ex.printStackTrace();
}
}
});
}
public class TranslucentPane extends JPanel {
public TranslucentPane() {
setOpaque(false);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.setComposite(AlphaComposite.SrcOver.derive(0.85f));
g2d.setColor(getBackground());
g2d.fillRect(0, 0, getWidth(), getHeight());
}
}
}
First coord in this case should be 0,0 and not 8,30. What am i doing wrong(i am using NetBeans)
import java.awt.Color;
import java.awt.Graphics;
public class TEST extends javax.swing.JFrame {
#Override
public void paint(Graphics g){
super.paint(g);
g.setColor(Color.blue);
g.drawRect(8, 30, 200, 200);
repaint();
}}
Add a JPanel to the frame and paint in that. The frame's coordinates include the decorations (title bar, borders, etc.). It would look something like this:
public class Test extends JFrame {
public static void main(String[] args) {
new Test();
}
private Test() {
add(new MyPanel());
setDefaultCloseOperation(EXIT_ON_CLOSE);
setSize(600, 600);
setVisible(true);
}
private class MyPanel extends JPanel {
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.blue);
g.drawRect(8, 30, 200, 200);
}
}
}
Also, don't call repaint(); in paint();. That will cause an infinite loop and will freeze the entire program.
The problem is your paint(..) method is not taking into account the JFrame Insets by calling getInsets which as docs state:
If a border has been set on this component, returns the border's
insets.
this code works fine:
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;
public class Test {
public Test() {
createAndShowGui();
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new Test();
}
});
}
private void createAndShowGui() {
JFrame frame = new JFrame() {
#Override
public void paint(Graphics g) {
super.paint(g);
g.setColor(Color.blue);
g.drawRect(0 + getInsets().left, 0 + getInsets().top, 200, 200);
}
};
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
}
}
however this is not best practice.
Rather add JPanel to JFrame and override paintComponent(Graphics g) of JPanel dont forget call to super.paintComponent(g) as first call in the overridden method and than draw there (dont forget to override getPreferredSize() and return correct Dimensions so the JPanel will fit its drawing/graphic content) this problem will no longer persist as JPanel is added at correct co-ordinates on contentPane like so:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class Test {
public Test() {
createAndShowGui();
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new Test();
}
});
}
private void createAndShowGui() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel panel = new JPanel() {
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.addRenderingHints(new RenderingHints(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY));
g2d.setColor(Color.blue);
g2d.drawRect(0, 0, 200, 200);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(300, 300);
}
};
frame.add(panel);
frame.pack();
frame.setVisible(true);
}
}
The above includes Graphics2D and RenderingHints i.e anti-aliasing. Just for some better looking drawings :)