Develop Reference

JPanel won't update

I've hit a problem in getting a JPanel to update.
My simple program uses a custom JPanel which displays a label and a textfield. A Jbutton on the main panel is used to replace the JPanel with a new JPanel. The initial panel shows up fine but when the button is pressed the panel is not updated with a new MyPanel. I can tell that a new object is being created as count is being incremented.
public class SwingTest extends JFrame{
private JPanel mp;
private JPanel vp;
private JButton button;
public static void main(String[] args) {
SwingTest st = new SwingTest();
}
public SwingTest() {
vp = new MyPanel();
mp = new JPanel(new BorderLayout());
mp.add(vp, BorderLayout.CENTER);
button = new JButton("Change");
button.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent ae) {
vp = new MyPanel();
vp.revalidate();
}
});
mp.add(button, BorderLayout.SOUTH);
this.add(mp);
this.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
setLocationRelativeTo(null);
setSize(250, 150);
pack();
setVisible(true);
}
}
and my custom panel....
public class MyPanel extends JPanel{
private JLabel label;
private JTextField tf;
static int count = 0;
public MyPanel(){
count++;
setLayout(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
setPreferredSize(new Dimension(400, 200));
c.gridx = 0;
c.gridy = 0;
label = new JLabel(String.valueOf(count));
tf = new JTextField(10);
add(label,c);
c.gridx = 1;
add(tf, c);
}
}

You state:
A Jbutton on the main panel is used to replace the JPanel with a new JPanel.
And yet this code:
button.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent ae) {
vp = new MyPanel();
vp.revalidate();
}
});
and yet this code does not do this at all. All it does is change the JPanel referenced by the vp variable, but has absolutely no effect on the JPanel that is being displayed by the GUI, which suggests that you're confusing reference variable with reference or object. To change the JPanel that is displayed, you must do exactly this: add the new JPanel into the container JPanel into the BorderLayout.CENTER (default) position, then call revalidate() and repaint() on the container.
e.g.,
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent ae) {
// vp = new MyPanel();
// vp.revalidate();
mp.remove(vp); // remove the original MyPanel from the GUI
vp = new MyPanel(); // create a new one
mp.add(vp, BorderLayout.CENTER); // add it to the container
// ask the container to layout and display the new component
mp.revalidate();
mp.repaint();
}
});
Or better still -- use a CardLayout to swap views.
Or better still -- simply clear the value held by the JTextField.
For more on the distinction between reference variable and object, please check out Jon Skeet's answer to this question: What is the difference between a variable, object, and reference?

background image help, JPanel, JFrame, anything?

I want to make a background image for a game I'm designing but I cant figure out the right way to get the effect I want, I want a background that can be seen behind text etc. basically having the background cover the whole JFrame / JPanel not just one section of the layout (e.g. BorderLayout.Center) I think it does this anyway but if it does do that how do I make the background for those transparent to see the background which is behind...
Confusing i know but I hope someone here understands what I am trying to do and can help... this is my current code. I have been playing around with the background so dont read to much in how i have written it.
import javax.swing.*;
import javax.swing.border.*;
import java.awt.*;
public class GamePanel extends JPanel {
private JTextPane playertext;
private JTextField wealthstring, currentwealth;
public GamePanel() {
super();
setLayout(new BorderLayout());
setBackground(Game.getBackgroundColor());
Border raised = BorderFactory.createRaisedBevelBorder();
Border lowered = BorderFactory.createLoweredBevelBorder();
setBorder(BorderFactory.createCompoundBorder(new EmptyBorder(4, 4, 4, 4), (BorderFactory.createCompoundBorder(raised, lowered))));
add(northpanel(), BorderLayout.NORTH);
add(eastpanel(), BorderLayout.EAST);
}
private JLabel northpanel() {
Font northfont = new Font("Engravers MT", Font.BOLD, 12);
ImageIcon banner = new ImageIcon("images/banner.png", "North Background");
playertext = new JTextPane();
playertext.setFont(northfont);
playertext.setEditable(false);
playertext.setText("Player: \n" + Game.getName());
playertext.setBackground(Game.getBackgroundColor());
playertext.setBorder(new EmptyBorder(10,10,10,10));
wealthstring = new JTextField("Money: ");
wealthstring.setFont(northfont);
wealthstring.setEditable(false);
wealthstring.setHorizontalAlignment(wealthstring.RIGHT);
wealthstring.setBorder(null);
wealthstring.setBackground(Game.getBackgroundColor());
currentwealth = new JTextField();
currentwealth.setFont(northfont);
currentwealth.setEditable(false);
currentwealth.setHorizontalAlignment(wealthstring.RIGHT);
currentwealth.setBackground(Game.getBackgroundColor());
currentwealth.setBorder(null);
String wealthrounded = String.format("%.2f", Game.getMoney());
currentwealth.setText(wealthrounded);
JPanel wealthtext = new JPanel();
wealthtext.setLayout(new GridLayout(2, 1));
wealthtext.setBackground(Game.getBackgroundColor());
wealthtext.setBorder(new EmptyBorder(10,10,10,10));
wealthtext.add(wealthstring);
wealthtext.add(currentwealth);
JLabel northpanel = new JLabel();
northpanel.setLayout(new BorderLayout());
northpanel.setIcon(banner);
northpanel.add(new JSeparator(), BorderLayout.PAGE_END);
northpanel.add(playertext, BorderLayout.WEST);
northpanel.add(wealthtext, BorderLayout.EAST);
return northpanel;
}
private JPanel eastpanel() {
JButton tab1 = new JButton("Tab 1");
JButton tab2 = new JButton("Tab 2");
JButton tab3 = new JButton("Tab 3");
JPanel easttabs = new JPanel();
easttabs.setLayout(new GridLayout(1, 3));
easttabs.add(tab1);
easttabs.add(tab2);
easttabs.add(tab3);
JPanel eastpanels = new JPanel();
eastpanels.setLayout(new BorderLayout());
eastpanels.setBackground(Game.getBackgroundColor());
eastpanels.add(easttabs, BorderLayout.NORTH);
return eastpanels;
}
}

So if you already have a JPanel that has your image as Background and you want to add another panel over it with your components you can use Opacity to achieve this. Only the components added to this panel will be visible. Here's the code :
import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JPanel;
public class TransparentPane extends JPanel {
public TransparentPane() {
setOpaque(false);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0f));
g2d.setColor(getBackground());
g2d.fill(getBounds());
g2d.dispose();
}
}

Create a class that extends from JPanel and in its paint method draw an image over it.
Now create a class the extends from JFrame and in its constructor set its contentpane to the object of that JPanel class like below. Now you can add components to jframe.
class SimpleTest extends JFrame {
JButton btn = new JButton("A Game");
public SimpleTest() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setContentPane(new CPane());
getContentPane().setBackground(Color.red);
getContentPane().add(btn, BorderLayout.NORTH);
setSize(new Dimension(300, 300));
setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new SimpleTest();
}
});
}
}
class CPane extends JPanel {
Image back;
public void paintComponent(Graphics g) {
super.paintComponent(g);
try {
back = ImageIO.read(getClass().getResource("back.jpg"));
} catch (Exception ex) {
}
g.drawImage(back, 0, 0, this);
}
}
If you want to make a jpanel transparent then do
panel.setOpaque(false);

How to retrieve a swing form values

I have two swing Frames. Frame one will contain a button.when we click the button we will get another frame which will have the five lables(which are the varibles of a class.) with the textfields beside, and a submit button. user will enter the values and clicks submit butoon.
My question is how can retrieve the values from that Frame two when user clicks submit button .i have the code like blelow.
public class Form extends JFrame implements ActionListener {
JPanel panel = new JPanel();
JFrame frame = new JFrame("New frame");
JPanel panel2 = new JPanel();
JButton button = new JButton("add");
JButton button2 = new JButton("Submit");
JLabel label;
JTextField textfield;
public Form() {
setLayout(new BorderLayout());
panel.setLayout(new BoxLayout(panel, BoxLayout.PAGE_AXIS));
panel.setPreferredSize(new Dimension(300, 200));
button.addActionListener(this);
add(panel, BorderLayout.CENTER);
add(button, BorderLayout.SOUTH);
}
public static void main(String[] a) {
Form s = new Form();
s.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
s.pack();
s.setVisible(true);
}
#Override
public void actionPerformed(ActionEvent arg0) {
dispose();
panel2.setLayout(new FlowLayout());
panel2.setPreferredSize(new Dimension(1000, 1000));
final Field[] fields = Employee.class.getFields();
for (Field temp : fields) {
label = new JLabel(temp.getName());
label.setBounds(20, 50, 100, 20);
textfield = new JTextField(20);
textfield.setBounds(140, 50, 100, 20);
panel2.add(label);
panel2.add(textfield);
}
frame.add(panel2);
frame.setSize(290, 300);
frame.setVisible(true);
button2.setSize(20, 30);
frame.add(button2, BorderLayout.SOUTH);
repaint();
revalidate();
button2.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
}
});
}
}

Start by taking a look at The Use of Multiple JFrames, Good/Bad Practice?
Instead of using a second frame, you should use a modal dialog, which, when made visible, will halt your programs execution at that point until it's disposed, at which time it will return and you can extract the values you want from it.
See How to Make Dialogs for more details

BorderLayout not working JFrame

For some reason I can't get the BorderLayout to set the way it's supposed to. Just would like to know where I'm going wrong.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class ColorFactory extends JFrame
{
final int width = 500;
final int height = 300;
private JPanel buttonPanel;
private JPanel radioButtonPanel;
private JLabel msgChangeColor;
public ColorFactory()
{
setTitle("Color Factory");
setSize(width, height);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(new BorderLayout());
createTopPanel();
add(buttonPanel, BorderLayout.NORTH);
createBottomPanel();
add(radioButtonPanel, BorderLayout.SOUTH);
msgChangeColor = new JLabel("Top buttons change the panel color and bottom radio buttons change the text color.");
add(msgChangeColor, BorderLayout.CENTER);
pack();
}
private void createTopPanel()
{
buttonPanel = new JPanel();
setLayout(new FlowLayout());
JButton redButton = new JButton("Red");
redButton.setBackground(Color.RED);
redButton.addActionListener(new ButtonListener());
redButton.setActionCommand("R");
JButton orangeButton = new JButton("Orange");
orangeButton.setBackground(Color.ORANGE);
orangeButton.addActionListener(new ButtonListener());
orangeButton.setActionCommand("O");
JButton yellowButton = new JButton("Yellow");
yellowButton.setBackground(Color.YELLOW);
yellowButton.addActionListener(new ButtonListener());
yellowButton.setActionCommand("Y");
buttonPanel.add(redButton);
buttonPanel.add(orangeButton);
buttonPanel.add(yellowButton);
}
private void createBottomPanel()
{
radioButtonPanel = new JPanel();
setLayout(new FlowLayout());
JRadioButton greenRadioButton = new JRadioButton("Green");
greenRadioButton.setBackground(Color.GREEN);
greenRadioButton.addActionListener(new RadioButtonListener());
greenRadioButton.setActionCommand("G");
JButton blueRadioButton = new JButton("Blue");
blueRadioButton.setBackground(Color.BLUE);
blueRadioButton.addActionListener(new RadioButtonListener());
blueRadioButton.setActionCommand("B");
JButton cyanRadioButton = new JButton("Cyan");
cyanRadioButton.setBackground(Color.CYAN);
cyanRadioButton.addActionListener(new RadioButtonListener());
cyanRadioButton.setActionCommand("C");
radioButtonPanel.add(greenRadioButton);
radioButtonPanel.add(blueRadioButton);
radioButtonPanel.add(cyanRadioButton);
}
private class ButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
String actionColor = e.getActionCommand();
if(actionColor.equals("R"))
{
buttonPanel.setBackground(Color.RED);
radioButtonPanel.setBackground(Color.RED);
}
if(actionColor.equals("O"))
{
buttonPanel.setBackground(Color.ORANGE);
radioButtonPanel.setBackground(Color.ORANGE);
}
if(actionColor.equals("Y"))
{
buttonPanel.setBackground(Color.YELLOW);
radioButtonPanel.setBackground(Color.YELLOW);
}
}
}
private class RadioButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
String actionTextColor = e.getActionCommand();
if(actionTextColor.equals("G"))
{
msgChangeColor.setForeground(Color.GREEN);
}
if(actionTextColor.equals("B"))
{
msgChangeColor.setForeground(Color.BLUE);
}
if(actionTextColor.equals("C"))
{
msgChangeColor.setForeground(Color.CYAN);
}
}
}
public static void main(String[] args)
{
ColorFactory run = new ColorFactory();
run.setVisible(true);
}
}

The problem is you are changing the layout manager for the frame when you create your top and bottom panels...
private void createTopPanel() {
buttonPanel = new JPanel();
setLayout(new FlowLayout()); // <--- This is call setLayout on the frame
This is why it's dangerous to...
Extend from something like JFrame directly...
Dynamically build components
It's all to easy to lose context and start effecting components you didn't actually want to...

Another problem (besides the one posted by MadProgrammer) is that you add your components to the JFrame itself.
You should add content to the content pane of the frame which you can get by calling JFrame.getContentPane().
Example:
JFrame f = new JFrame("Test");
Container c = f.getContentPane();
c.add(new JButton("In Center"), BorderLayout.CENTER);
c.add(new JButton("At the Bottom"), BorderLayout.SOUTH);
c.add(new JButton("At the Top"), BorderLayout.NORTH);
c.add(new JButton("On the Left"), BorderLayout.WEST);
c.add(new JButton("On the Right"), BorderLayout.EAST);
You can set/change the content panel by calling JFrame.setContentPane(). The default content panel already has BorderLayout so you don't even need to change it nor to set a new panel.

Put a JTextfield on a JPanel?

Why the textfield is not appearing on my panel which is inside my frame?
I mean is there some additional action necessary to make the components of the panel
visible?
I hope somebody can help me....
public class example1 {
public static void main(String[] args) {
JFrame tt=new TT();
}
}
class TT extends JFrame {
JTextField textField;
JPanel panel;
JButton button1;
JButton button2;
public TT() {
setSize(300, 300);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
setTitle("Bla Blubb");
setResizable(false);
setLayout(null);
panel=new JPanel();
panel.setBounds(5, 5, 290, 290);
add(panel);
textField=new JTextField();
textField.setBounds(5, 5, 280, 50);
panel.add(textField);
setVisible(true);
}
}

import java.awt.FlowLayout;
import javax.swing.*;
class TT extends JFrame {
JTextField textField;
JPanel panel;
JButton button1;
JButton button2;
public TT() {
//setSize(300, 300); // better to use pack() (after components added)
//setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // better to use
setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
//setLocationRelativeTo(null); // better to use..
setLocationByPlatform(true);
setTitle("Bla Blubb");
setResizable(false);
//setLayout(null); // better to use layouts with padding & borders
// set a flow layout with large hgap and vgap.
panel = new JPanel(new FlowLayout(SwingConstants.LEADING, 10, 10));
// panel.setBounds(5, 5, 290, 290); // better to pack()
add(panel);
//textField = new JTextField(); // suggest a size in columns
textField = new JTextField(8);
//textField.setBounds(5, 5, 280, 50); // to get height, set large font
textField.setFont(textField.getFont().deriveFont(50f));
panel.add(textField);
pack(); // make the GUI the minimum size needed to display the content
setVisible(true);
}
public static void main(String[] args) {
// GUIS should be constructed on the EDT.
JFrame tt = new TT();
}
}