I made a simple program that uses drawString() to draw on a JPanel that gets repainted to change the background to a random color. It works fine, other than the ~10 pixel spaces to the right side and bottom side of the JPanel, which remain the default color. I think this problem might be happening because of the way I use pack() or getPrefferedSize(). Any help or suggestions to fix this are appreciated.
Birthday.java
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
public class Birthday {
DrawString panel = new DrawString();
public Birthday() {
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(panel);
f.setTitle("Happy Birthday!");
f.setLocation(10, 10);
f.pack();
f.setVisible(true);
f.setResizable(false);
Timer timer = new Timer(500, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
panel.repaint();
}
});
timer.start();
}
public static void main(String args[]) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new Birthday();
}
});
}
}
DrawString.java
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Graphics;
import javax.swing.JPanel;
public class DrawString extends JPanel {
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
int width = getWidth();
int height = getHeight();
int x = 350;
int y = 250;
int red = random(0,255);
int green = random(0,255);
int blue = random(0,255);
Color black = new Color(0,0,0);
Color newColor = new Color(red,green,blue);
g.setColor(newColor);
g.fillRect(0,0,1000,500);
g.setColor(black);
g.setFont(new Font(null,Font.BOLD,40));
g.drawString("Happy Birthday!",x,y);
}
public static int random(int min, int max)
{
int range = max - min + 1;
int number = (int) (range * Math.random() + min);
return number;
}
#Override
public Dimension getPreferredSize() {
return new Dimension(1000, 500);
}
}
You never want to explicitly call paintComponent. Instead if you want the panel to repaint, you can call panel.repaint(), and the panel with implicitly call its own paintComponent method for you.
Don't do every thing inside the main method, you'll find you're going to run into a lot of problems with static references.
Don't use Thread.sleep(), it will block the Event Dispatch Thread., as that's where you should be running you Swing apps from. Instead use a java.swing.Timer. See this example for Timer usage.
As noted in 3, run your Swing apps from the EDT like this
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable(){
public void run() {
new MyApp();
}
});
}
Don't set the size of your frame. Instead override getPreferredSize() of your DrawingPanel and just pack() the frame.
You can center the frame by using setLocationRelativeTo(null)
Should make it a habit to use the #Override annotation to make sure you are override correctly.
Add-on to 2. What you make a habit of doing, is doing your work from the constructor, then just calling the constructor in the main. Here is a refactor of your code with all the above mentioned things fixed. You can run it.
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
public class Birthday {
DrawString panel = new DrawString();
public Birthday() {
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(panel);
f.setTitle("Happy Birthday!");
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
f.setResizable(false);
Timer timer = new Timer(500, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
panel.repaint();
}
});
timer.start();
}
public static void main(String args[]) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new Birthday();
}
});
}
}
class DrawString extends JPanel {
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
int width = getWidth();
int height = getHeight();
int x = 350;
int y = 250;
int red = random(0, 255);
int green = random(0, 255);
int blue = random(0, 255);
Color black = new Color(0, 0, 0);
Color newColor = new Color(red, green, blue);
g.setColor(newColor);
g.fillRect(0, 0, getWidth(), getHeight());
g.setColor(black);
g.setFont(new Font(null, Font.BOLD, 40));
g.drawString("Happy Birthday!", x, y);
}
public static int random(int min, int max) {
int range = max - min + 1;
int number = (int) (range * Math.random() + min);
return number;
}
#Override
public Dimension getPreferredSize() {
return new Dimension(1000, 500);
}
}
Related
I'm trying to animate a rectangle based on a coordinate determined by for-loop, inside a button. Here is my JComponent Class:
public class Rect extends JComponent {
public int x;
public int y;
public int w;
public int h;
public Rect (int x, int y, int w, int h) {
this.x = x;
this.y = y;
this.w = w;
this.h = h;
repaint();
}
#Override
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
super.paintComponent(g);
g2.setColor(Color.green);
g2.drawRect(x+15, y+15, w, h);
}
}
and here is my button and button inside JFrame class:
public class MainFrame extends JFrame {
Rect R = new Rect(15, 15, 50, 50);
JPanel lm = new JPanel();
LayoutManager lay = new OverlayLayout(lm);
JButton animate = new JButton("animate");
public MainFrame () {
setSize(1200, 700);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
lm.setLayout(lay);
lm.add(R);
}
animate.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
for (int k = 0; k < 500; k+=50) {
R = new Rect(k, k, 50, 50);
validate();
repaint();
}
}
});
}
But when I run the code and click the button, nothing happens. What's wrong?
EDIT: I run the frame inside my main class like this:
public class OrImage {
public static void main(String[] args) throws Exception
SwingUtilities.invokeLater(new Runnable() {
public void run() {
MainFrame mf = new MainFrame();
mf.setVisible(true);
}
});
}
}
I changed the code of class MainFrame such that when you press the animate button, something happens, but I don't know if that is what you want to happen.
I did not change class Rect and I added main() method to MainFrame just to keep everything in one class.
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.LayoutManager;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.OverlayLayout;
public class MainFrame extends JFrame {
Rect R = new Rect(15, 15, 50, 50);
JPanel lm = new JPanel();
LayoutManager lay = new OverlayLayout(lm);
JButton animate = new JButton("animate");
public MainFrame () {
setSize(1200, 700);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
lm.setLayout(lay);
lm.add(R);
animate.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
for (int k = 0; k < 500; k+=50) {
R = new Rect(k, k, 50, 50);
lm.add(R);
}
lm.revalidate();
lm.repaint();
}
});
add(lm, BorderLayout.CENTER);
add(animate, BorderLayout.PAGE_END);
setLocationByPlatform(true);
setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(() -> new MainFrame());
}
}
The main change is in method actionPerformed(). You need to add R to the JPanel. You need to call revalidate() on the JPanel because you have changed the number of components that it contains. And after calling revalidate() you should call repaint() (again, on the JPanel) to make it redraw itself.
This is how it looks before pressing animate.
And this is how it looks after pressing animate
EDIT
As requested – with animation.
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.LayoutManager;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.OverlayLayout;
import javax.swing.Timer;
public class MainFrame extends JFrame {
Rect R = new Rect(15, 15, 50, 50);
JPanel lm = new JPanel();
LayoutManager lay = new OverlayLayout(lm);
JButton animate = new JButton("animate");
private int x;
private int y;
private Timer timer;
public MainFrame () {
setSize(1200, 700);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
lm.setLayout(lay);
lm.add(R);
timer = new Timer(500, event -> {
if (x < 500) {
lm.remove(R);
x += 50;
y += 50;
R = new Rect(x, y, 50, 50);
lm.add(R);
lm.revalidate();
lm.repaint();
}
else {
timer.stop();
}
});
timer.setInitialDelay(0);
animate.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
timer.start();
}
});
add(lm, BorderLayout.CENTER);
add(animate, BorderLayout.PAGE_END);
setLocationByPlatform(true);
setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(() -> new MainFrame());
}
}
I had to implement a JFrame with the size of 500 x 500 pixels that should have a 9 x 9 "field" of circles, but as you can see in the picture the distance between the first line of ovals and the second line of ovals is not equal.
The diameter should be 20 pixel and the distance between the center of one oval to another oval should be 40 pixel, but I don't know if I did this correctly:
import javax.swing.JFrame;
import java.awt.Graphics;
import java.awt.Color;
public class KreisFrame extends JFrame {
public KreisFrame() {
//Set JFrame size
setSize(500,500);
//Make JFrame visible
setVisible(true);
}
public void paint(Graphics g) {
super.paint(g);
g.setColor(Color.GREEN);
g.fillRect(0, 0, 500, 500);
for (int j = 0; j < 500; j += 60){
for (int i = 0; i < 500; i += 60) {
// draw circle
g.drawOval(i, 20, 20, 20);
g.drawOval(i, j, 20, 20);
// fill circle
g.fillOval(i, 20, 20, 20);
g.fillOval(i, j, 20, 20);
g.setColor(Color.BLUE);
}
}
}
public static void main(String[]args) {
KreisFrame myframe = new KreisFrame();
}
}
Can someone tell me what I did wrong?
You should really subclass a JPanel, not the JFrame. And all of this should be done on the EventDispatchThread, not the main thread. Further, don't use "magic" numbers like 500, 20, and 40. Here's a solution that paints the entire panel, regardless of what size it is (note that there is no provision here for having a border on the panel).
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class Kreis extends JPanel {
protected int dia = 20;
protected int sep = 40;
public Kreis() {
// Set JFrame size
setPreferredSize(new Dimension(500, 500));
setBackground(Color.green);
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Dimension d = getSize();
g.setColor(Color.BLUE);
for (int y = 0; y < d.height; y += sep) {
for (int x = 0; x < d.width; x += sep) {
// draw circle
g.fillOval(x, y, dia, dia);
}
}
}
public static void main(final String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
// Create and set up the window.
JFrame jf = new JFrame();
Kreis panel = new Kreis();
jf.add(panel);
jf.pack();
jf.setVisible(true);
jf.addWindowListener(new WindowAdapter() {
#Override
public void windowClosing( WindowEvent arg0) {
System.exit(0);
}
});
}
});
}
}
I am practicing to draw a ball in the Panel and show the ball's coordinate when the ball is dragged.
This is my first time to practice a drawing exercise(?)
This is my code.
import java.awt.*;
import java.awt.event.*;
public class MovingBall extends Frame {
Panel ballPanel = new Panel();
Label ballLabel = new Label();
Panel coordinatePanel = new Panel();
Label coordinateLabel = new Label();
int x0=0,y0 =0, x=20,y=30;
int nowX, nowY;
Label nowXcoordinateLabel = new Label("Now X :"+nowX);
Label nowYcoordinateLabel = new Label("Now Y :"+nowY);
MovingBall(){
setLayout(new GridLayout(1,1));
ballPanel.add(ballLabel); coordinatePanel.add(coordinateLabel);
add(ballPanel);
add(coordinatePanel);
ballPanel.setBackground(Color.white);
coordinatePanel.setBackground(Color.LIGHT_GRAY);
nowXcoordinateLabel.setBackground(Color.WHITE);
nowYcoordinateLabel.setBackground(Color.WHITE);
coordinatePanel.add(nowXcoordinateLabel);
coordinatePanel.add(nowYcoordinateLabel);
setVisible(true);
setSize(400,400);
MouseMotionListener ml = new MouseMotionAdapter(){
public void mouseDragged(MouseEvent e){
Point p = new Point();
nowX = (int) p.getX();
nowY = (int) p.getY();
}
};
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent we) {
dispose();
}
}
);
}
public void paintComponent(Graphics2D gg){
// super.paintComponents(gg);
ballPanel.paintComponents(gg);
gg.setColor(Color.BLUE);
gg.fillOval(x0, y0, 10, 10);
}
public static void main(String[]arg){
MovingBall mb = new MovingBall();
}
}
I have two problems
I used fillOval and paintComponent to draw and display a ball but I don't see that on the screen. Why?
Any idea how to move the ball if I want to move that using mouseDragged? Do I need some thread?
Let's start with
Frame doesn't have a paintComponent method, so nothing is ever going to call it.
Even if it did, position 0x0 would paint the circle under the frame's borders, so you wouldn't see it
You should be getting the Point from the MouseEvent, not from the new Point object you've created
It's not the responsibility of the frame to manage the mouse dragged or painting, the frame is responsible for providing the initial container onto which everything else added
From that, you should move the functionality of the painting and mouse dragged management to it's own class. This provides you with two things, first, a surface onto which you can paint, and which will contained within the frame borders and the mouse events will automatically be converted to the panels context (0x0 will be the top left corner of the panel)
This raises the question about how to update the labels. Well, you could take a leaf from the AWT API and use a simple observer pattern to generate events when the coordinates are changed, for example
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Label;
import java.awt.Panel;
import java.awt.Point;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.awt.event.MouseMotionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.ArrayList;
import java.util.EventObject;
import java.util.List;
public class MovingBall extends Frame {
BallPane ballPanel = new BallPane();
Label ballLabel = new Label();
int x0 = 0, y0 = 0, x = 20, y = 30;
int nowX, nowY;
Label nowXcoordinateLabel = new Label("Now X :" + nowX);
Label nowYcoordinateLabel = new Label("Now Y :" + nowY);
MovingBall() {
setLayout(new BorderLayout());
ballPanel.add(ballLabel);
add(ballPanel);
ballPanel.setBackground(Color.white);
nowXcoordinateLabel.setBackground(Color.WHITE);
nowYcoordinateLabel.setBackground(Color.WHITE);
setVisible(true);
setSize(400, 400);
addWindowListener(new WindowAdapter() {
#Override
public void windowClosed(WindowEvent e) {
dispose();
}
});
Panel coordinates = new Panel(new FlowLayout());
coordinates.add(nowXcoordinateLabel);
coordinates.add(nowYcoordinateLabel);
coordinates.setBackground(Color.LIGHT_GRAY);
add(coordinates, BorderLayout.SOUTH);
ballPanel.addCoordinateListene(new CoordinateListener() {
#Override
public void coordinatesChanged(CoordinateEvent evt) {
nowXcoordinateLabel.setText("Now X: " + evt.getCoordinate().getX());
nowYcoordinateLabel.setText("Now X: " + evt.getCoordinate().getY());
revalidate();
repaint();
}
});
}
public static void main(String[] arg) {
MovingBall mb = new MovingBall();
}
public class CoordinateEvent extends EventObject {
private final Point p;
public CoordinateEvent(Object source, Point p) {
super(source);
this.p = p;
}
public Point getCoordinate() {
return p;
}
}
public interface CoordinateListener {
public void coordinatesChanged(CoordinateEvent evt);
}
public class BallPane extends Panel {
int x0 = 0, y0 = 0, x = 20, y = 30;
private List<CoordinateListener> coordinateListeners;
public BallPane() {
MouseMotionListener ml = new MouseMotionAdapter() {
public void mouseDragged(MouseEvent e) {
x0 = (int) e.getX();
y0 = (int) e.getY();
fireCoordinateChange(new Point(e.getPoint()));
repaint();
}
};
addMouseMotionListener(ml);
coordinateListeners = new ArrayList<>(5);
}
#Override
public void paint(Graphics g) {
super.paint(g);
g.setColor(Color.BLUE);
g.fillOval(x0, y0, 10, 10);
}
public void addCoordinateListene(CoordinateListener listener) {
coordinateListeners.add(listener);
}
public void removeCoordinateListene(CoordinateListener listener) {
coordinateListeners.remove(listener);
}
protected void fireCoordinateChange(Point p) {
CoordinateEvent evt = new CoordinateEvent(this, p);
for (CoordinateListener listener : coordinateListeners) {
listener.coordinatesChanged(evt);
}
}
}
}
Make your class extending Panel and make it ready to drawing with overriding paint method and add the MouseMotionListener to listining your panel.Get X and Y coordinates for using in paint method, at last add your drawing panel to Frame.
Simple code : UPDATED
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridLayout;
import java.awt.Label;
import java.awt.Panel;
import java.awt.RenderingHints;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
public class TestClass extends Panel {
/**
*
*/
private static final long serialVersionUID = 1L;
Panel ballPanel = new Panel();
Label ballLabel = new Label();
Panel coordinatePanel = new Panel();
Label coordinateLabel = new Label();
int nowX, nowY;
Label nowXcoordinateLabel = new Label("Now X :");
Label nowYcoordinateLabel = new Label("Now Y :");
TestClass() {
coordinatePanel.add(coordinateLabel);
nowXcoordinateLabel.setBackground(Color.WHITE);
nowYcoordinateLabel.setBackground(Color.WHITE);
nowXcoordinateLabel.setPreferredSize(new Dimension(100, 25));
nowYcoordinateLabel.setPreferredSize(new Dimension(100, 25));
coordinatePanel.setPreferredSize(new Dimension(400, 30));
coordinatePanel.setBackground(Color.LIGHT_GRAY);
coordinatePanel.add(nowXcoordinateLabel);
coordinatePanel.add(nowYcoordinateLabel);
MouseAdapter ml = new MouseAdapter() {
#Override
public void mouseMoved(MouseEvent e) {
nowXcoordinateLabel.setText("Now X :" + e.getX());
nowYcoordinateLabel.setText("Now Y :" + e.getY());
nowX = e.getX();
nowY = e.getY();
repaint();
super.mouseMoved(e);
}
};
setLayout(new GridLayout(1, 1));
setBackground(Color.WHITE);
addMouseMotionListener(ml);
setVisible(true);
setSize(400, 400);
}
#Override
public void paint(Graphics g) {
Graphics2D gg = (Graphics2D) g;
gg.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
gg.setColor(Color.BLUE);
gg.fillOval(nowX, nowY, 20, 20);
}
public static void main(String[] arg) {
TestClass mb = new TestClass();
Frame frame = new Frame("Test drawing");
frame.addWindowListener(new WindowAdapter() {
#Override
public void windowClosing(WindowEvent e) {
frame.dispose();
super.windowClosing(e);
}
});
frame.setLayout(new GridLayout(1, 1));
frame.add(mb);
frame.add(mb.coordinatePanel);
frame.setSize(800, 600);
frame.setVisible(true);
}
}
To get the position of the mouse instead of:
nowX = (int) p.getX();
Write this:
nowX = (int) e.getX();
You also need to redraw the oval every time the user triggers a Mouse Drag event
Current state:
I have a JPanel object which contains complex components(3D-canvas written by myself).
Problem:
There is two screen devices now. I want to use one for control, another just for display, just like PowerPoint. How can I display this JPanel on another screen efficiently(static view is enough, but I want it to reflect the change on control screen?
What I have tried:
I have tried to draw the static picture to another JPanel every 200ms.
Graphics2D g2 = (Graphics2D) contentPanel.getGraphics();
g2.translate(x, y);
g2.scale(scale, scale);
displayPanel.paintAll(g2);
Notes: contentPanel is in a JFrame of display screen, displayerPanel is the panel I want to copy
But I get a problem that the display screen flicker so seriously that I can not accept this...Is it the problem of my CPU or graphics card? Or is these any efficient method I can use? Please help, thanks so much!
And here is the MCVE (sorry, this is my first time asking question in stackoverflow, but I am touched by your helps! Thanks again!)
import javax.swing.*;
import java.awt.*;
import java.util.*;
import java.util.Timer;
public class DisplayWindow {
private static JFrame frame = new JFrame();
private static JPanel contentPanel = new JPanel();
private static JPanel displayPanel = null;
private static Timer timerDisplay = null;
static {
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setBounds(50, 50, 1366, 768);
frame.getContentPane().add(contentPanel);
frame.setVisible(true);
if (timerDisplay == null) {
timerDisplay = new java.util.Timer();
timerDisplay.schedule(new DisplayAtFixedRate(), 1000, 250);
}
}
public static void display(JPanel panel) {
displayPanel = panel;
}
private static class DisplayAtFixedRate extends TimerTask {
#Override
public void run() {
if (displayPanel != null && displayPanel.getWidth() != 0) {
double windowWidth = frame.getWidth();
double windowHeight = frame.getHeight();
double panelWidth = displayPanel.getWidth();
double panelHeight = displayPanel.getHeight();
double scale = Math.min(windowWidth / panelWidth, windowHeight / panelHeight);
int x = (int) (windowWidth - panelWidth * scale) / 2;
int y = (int) (windowHeight - panelHeight * scale) / 2;
Graphics2D g2 = (Graphics2D) contentPanel.getGraphics();
g2.translate(x, y);
g2.scale(scale, scale);
displayPanel.paintAll(g2);
}
}
}
public static void main(String[] args) {
JFrame controlFrame = new JFrame();
controlFrame.setBounds(50, 50, 1366, 768);
JPanel controlPanel = new JPanel();
controlFrame.getContentPane().add(controlPanel, BorderLayout.CENTER);
controlPanel.add(new JLabel("Hello Stackoverflow!"));
controlFrame.setVisible(true);
DisplayWindow.display(controlPanel);
}
}
Here is an example for you:
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTree;
import javax.swing.SwingUtilities;
import javax.swing.Timer;
import javax.swing.WindowConstants;
public class PaintImage {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
startUI();
}
});
}
private static void startUI() {
final JFrame mainFrm = new JFrame("Main");
final JFrame paintFrame = new JFrame("Copy");
mainFrm.add(new JScrollPane(new JTree()), BorderLayout.WEST);
mainFrm.add(new JScrollPane(new JTextArea("Write your text here...")), BorderLayout.CENTER);
mainFrm.pack();
mainFrm.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
mainFrm.setLocationRelativeTo(null);
final JLabel label = new JLabel("");
paintFrame.add(label);
paintFrame.setSize(mainFrm.getSize());
paintFrame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
mainFrm.setVisible(true);
paintFrame.setVisible(true);
final Timer t = new Timer(200, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
final Image img = getScreenShot(mainFrm.getContentPane());
label.setIcon(new ImageIcon(img));
}
});
t.start();
}
public static BufferedImage getScreenShot(Component component) {
final BufferedImage image = new BufferedImage(
component.getWidth(),
component.getHeight(),
BufferedImage.TYPE_INT_RGB
);
// call the Component's paint method, using
// the Graphics object of the image.
component.paint( image.getGraphics() ); // alternately use .printAll(..)
return image;
}
}
Origin of method getScreenShot is here
The painting can be done by passing the displayPanel to draw itself.
class DuplicatePanel extends JPanel {
private final JPanel displayPanel;
DuplicatePanel(JPanel displayPanel) {
this.displayPanel = displayPanel;
}
#Override
public void paintComponent(Graphics g) {
displayPanel.paintComponent(g);
}
}
To trigger the repaints, like repaint(50L) either use a SwingTimer or your own manual repaints.
How do I make my JFrame match the size of the JPanel which holds the dynamically sized content?
I have created two simple class snippets if anyone could guide me through them.
Class1 : CanvasExample.java
import java.awt.Dimension;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class CanvasExample {
public static void main(String[] args) {
JPanelEx dataOut = new JPanelEx();
SwingUtilities.invokeLater(new Runnable() {
public void run() {
JFrame f = new JFrame("Title!");
f.setMinimumSize(new Dimension(200,100));
f.getContentPane().add(dataOut);
f.pack();
f.setVisible(true);
}
});
}
}
Class 2: JPanelEx.java
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class JPanelEx extends JPanel {
public JPanelEx() {
super(new FlowLayout());
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawString("Hello1", 10, 10);
g.drawString("Hello2", 10, 30);
g.drawString("Hello3", 10, 50);
g.drawString("Hello4", 10, 70);
g.drawString("Hello5", 10, 90);
g.drawString("Hello6", 10, 110);
g.drawString("Hello7", 10, 130);
g.drawString("Hello8", 10, 150);
g.drawString("Hello9", 10, 170);
g.drawString("Hello10", 10, 190);
g.dispose();
}
}
Current Output :
Expected Output :
I understand similar question might have been asked many times but I scanned through and couldn't get a clear solution. Any help is appreciated.
Your JPanelEx will need to provide size hints to allow the layout management system to determine how best the component should be laid out and the amount of space the content needs
Also, don't call dispose on Graphics contexts you didn't create!
As an example...
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import java.awt.FontMetrics;
import java.awt.Graphics;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new JPanelEx());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class JPanelEx extends JPanel {
private int numElements = 10;
public JPanelEx() {
super(new FlowLayout());
}
#Override
public Dimension getPreferredSize() {
FontMetrics fm = getFontMetrics(getFont());
int width = 0;
int height = fm.getHeight() * numElements;
for (int index = 0; index < numElements; index++) {
width = Math.max(width, fm.stringWidth("Hello" + index));
}
return new Dimension(width, height);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
int x = 0;
int y = 0;
FontMetrics fm = g.getFontMetrics();
for (int index = 0; index < numElements; index++) {
g.drawString("Hello" + index, x, y + fm.getAscent());
y += fm.getHeight();
}
}
}
}
Also see Laying Out Components Within a Container for more details about the layout manager API