Develop Reference

How to use an ActionListener to make a JPanel Visible

I tried to make the first JPanel disappear and the second JPanel visible with the click of a JButton.
So far i only get the first JPanel to show and after clicking the JButton the Frame gets empty.
I also tried to do it with composition so i dont have to extend classes. So my bad understanding of how
composition works might be the problem. I looked into it alot but couldnt find a proper solution for my problem.
First JPanel class:
import java.awt.Color;
import java.awt.Component;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JPanel;
public class Panel1 {
JPanel firstscreenpanel = new JPanel();
JButton jButton1 = new JButton();
Panel1() {
jButton1.setBounds(300,300,400,200);
jButton1.setBackground(Color.BLACK);
jButton1.setVisible(true);
jButton1.addActionListener(new ActionListener() {
Panel2 test = new Panel2();
public void actionPerformed(ActionEvent e) {
firstscreenpanel.setVisible(false);
test.secondscreenpanel.setVisible(true);
}
});
}
public Component panelone() {
firstscreenpanel.setSize(1280, 1024);
firstscreenpanel.setLayout(null);
firstscreenpanel.setBackground(Color.BLUE);
firstscreenpanel.add(jButton1);
firstscreenpanel.setVisible(true);
return firstscreenpanel;
}
}
Second JPanel class:
import java.awt.Color;
import java.awt.Component;
import javax.swing.JButton;
import javax.swing.JPanel;
public class Panel2 {
public JPanel secondscreenpanel = new JPanel();
public JButton jButton2 = new JButton();
Panel2() {
jButton2.setBounds(100,100,400,200);
jButton2.setBackground(Color.BLACK);
jButton2.setVisible(true);
}
public Component paneltwo() {
secondscreenpanel.setSize(1280, 1024);
secondscreenpanel.setLayout(null);
secondscreenpanel.add(jButton2);
secondscreenpanel.setBackground(Color.RED);
secondscreenpanel.setVisible(false);
return secondscreenpanel;
}
}
JFrame Class:
import javax.swing.JFrame;
public class Frame1 {
public JFrame frame1 = new JFrame();
Panel1 panel1 = new Panel1();
Panel2 panel2 = new Panel2();
Frame1() {
frame1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame1.setState(JFrame.MAXIMIZED_BOTH);
frame1.setSize(1280, 1024);
frame1.setLayout(null);
frame1.add(panel1.panelone());
frame1.add(panel2.paneltwo());
frame1.setVisible(true);
}
}
Main Class:
public class MainClass {
private void showGUI() {
Frame1 jframe = new Frame1();
}
public static void main(String[] args) {
final MainClass main = new MainClass();
javax.swing.SwingUtilities.invokeLater(new Runnable()
{
public void run() {
main.showGUI();
}
});
}
}

I did not check the whole code (too bug, too many empty lines) but stopped at Panel2 test = new Panel2();
is this instance being added to some visible component? if not it will never be displayed.
Note: using a null layout manager is often not recommended, use a CardLayout or even a JTabbedPane to switch components - see tutorial A Visual Guide to Layout Managers

This is not the best implementation, but it is simple enough for you to follow. I modified your code to create a frame containing your original two panels (although those panel classes are not necessary - as I explained in a comment on your posted solution), and a button to toggle visibility on the panels. I am using a regular JButton and not a JToggleButton also not the best use of the class, but simply for you to understand.
The Action Listener is added to the button on the frame. Notice that my action listener does not create new instances of anything. That was part of the original problem. Since the button is a member of the frame class like the panels 1 and 2, it has access to them directly. SO, in the listener, all I need to do is "toggle" the visibility of each of the panels.
public class Frame1 extends JFrame {
private Panel1 panel1 = new Panel1();
private Panel2 panel2 = new Panel2();
private JPanel btnPanel = new JPanel();
private JButton button = new JButton("Toggle");
public Frame1() {
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
boolean visible = panel1.isVisible();
panel1.setVisible(!visible);
panel2.setVisible(visible);
}
});
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setState(JFrame.MAXIMIZED_BOTH);
setSize(1280, 1024);
btnPanel.setSize(400, 100);
btnPanel.add(button);
setLayout(null);
add(panel1);
add(panel2);
add(btnPanel);
}
}
public class Panel1 extends JPanel {
public Panel1() {
setBounds(100,100,400,200);
setBackground(Color.RED);
setVisible(true);
}
}
public class Panel2 extends JPanel {
public Panel2() {
setBounds(100,100,400,200);
setBackground(Color.BLACK);
setVisible(false);
}
}
public class MainClass {
private void showGUI() {
Frame1 jframe = new Frame1();
jframe.setVisible(true);
}
public static void main(String[] args) {
final MainClass main = new MainClass();
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
main.showGUI();
}
});
}
}

You can fix your program by passing a reference of your frame to your panel1. See my example below.
Frame class
import javax.swing.*;
public class Frame1 {
private JFrame frame = new JFrame();
private Panel1 panel1;
private Panel2 panel2;
Frame1() {
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setState(JFrame.MAXIMIZED_BOTH);
frame.setSize(1280, 1024);
frame.setLayout(null);
panel1 = new Panel1(this);
frame.add(panel1.getPanel());
panel2 = new Panel2();
frame.add(panel2.getPanel());
frame.setVisible(true);
}
public Panel2 getPanel2() {
return panel2;
}
}
Panel1 class
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Panel1 {
private JPanel panel = new JPanel();
private Frame1 frame1;
private JButton jButton1 = new JButton();
public Panel1(Frame1 frame1) {
this.frame1 = frame1;
panel.setSize(1280, 1024);
panel.setLayout(null);
panel.setBackground(Color.BLUE);
panel.add(jButton1);
panel.setVisible(true);
jButton1.setBounds(300,300,400,200);
jButton1.setBackground(Color.BLACK);
jButton1.setVisible(true);
jButton1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
panel.setVisible(false);
frame1.getPanel2().getPanel().setVisible(true);
}
});
}
public JPanel getPanel() {
return panel;
}
}
Panel2 class
import javax.swing.*;
import java.awt.*;
public class Panel2 {
private JButton jButton2 = new JButton();
private JPanel panel = new JPanel();
public Panel2() {
panel.setSize(1280, 1024);
panel.setLayout(null);
panel.add(jButton2);
panel.setBackground(Color.RED);
panel.setVisible(false);
jButton2.setBounds(100,100,400,200);
jButton2.setBackground(Color.BLACK);
jButton2.setVisible(true);
}
public JPanel getPanel() {
return panel;
}
}

I solved my problem by adding "public static" to "Panel2 panel2 = new Panel2();"
And then i just used:
"Frame1.panel2.secondscreenpanel.setVisible(true);"
inside the JButton ActionListener.
Its now working but i guess thats a bad way of doing it. Because i heard that using to much static isnt that good. But i dont now why yet.

Refresh JFrame? Java Swing

I don't know how to resolve this case:
I have a JFrame with JPanel on it. I added two JButtons to this JPanel.
Class MainFrame
import java.awt.Color;
import javax.swing.JFrame;
public class MainFrame extends JFrame{
public MainFrame(){
this.setSize(100,100);
MainPanel panel = new MainPanel();
this.add(panel);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setVisible(true);
}
}
and MainPanel with two buttons
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JPanel;
public class MainPanel extends JPanel implements ActionListener{
JButton button, example;
public MainPanel(){
this.setLayout(new BorderLayout());
JButton button = new JButton("New");
button.addActionListener(this);
JButton example = new JButton("example");
this.add(button, BorderLayout.NORTH);
this.add(example, BorderLayout.CENTER);
}
#Override
public void actionPerformed(ActionEvent event) {
if (event.getSource().equals(button)){
example.setEnabled(false);
example.setBackground(Color.yellow);
}
}
}
and start class Main
public class Main {
public static void main (String[] args){
MainFrame frame = new MainFrame();
}
}
What should I do to change background color second button?

You have your button variables defined twice, once as an instance variable and once as a local variable.
Get rid of the local variable:
//JButton example = new JButton("example");
example = new JButton("example");
Now your ActionListener code can reference the instance variable.

In your example:
JButton button, example; // <-- Here, you create your two (protected) variables
public MainPanel(){
this.setLayout(new BorderLayout());
JButton button = new JButton("New"); // <-- And here, you create a local variable
button.addActionListener(this);
JButton example = new JButton("example"); // <-- Here, another local variable
this.add(button, BorderLayout.NORTH);
this.add(example, BorderLayout.CENTER);
}
#Override
public void actionPerformed(ActionEvent event) {
if (event.getSource().equals(button)){
example.setEnabled(false);
example.setBackground(Color.yellow);
}
}

JButton not resizing with setMaximumSize()?

I have been trying to learn Buttons but it refuses to resize. Button1 (code below) just takes up the whole screen. I have seen other posts who's problem was that they didn't use
setMaximumSize();
but I'm using it and it still isn't working! I didn't make a JPanel yet. Here is my JFrame:
import java.awt.Dimension;
import javax.swing.JButton;
import javax.swing.JFrame;
public class Frame extends JFrame {
private JButton button1;
private JButton button2;
public Frame()
{
button1 = new JButton("Hello button1");
button2 = new JButton("Hello button2");
button2.setMaximumSize(new Dimension(100,100));
button1.setMaximumSize(new Dimension(100,100));
add(button2);
add(button1);
}
}
My main class is plain and simple:
import javax.swing.JFrame;
import javax.swing.JPanel;
public class Panel extends JPanel{
public static void main(String args [])
{
Frame frame = new Frame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(500, 500);
frame.setVisible(true);
}
}

It's because the frame('s contentPane) has a BorderLayout by default. You add the buttons to BorderLayout.CENTER, so the layout manager ignores the minimum-, preferred- and maximumSize.
I just want them to come up small and side by side
For that you could use a simple FlowLayout. (And if you want them to be centered on the frame, a parent JPanel with a GridBagLayout)
If you want a custom width & height for the buttons, override their getPreferredSize method. Overriding this method is safer than calling setPreferredSize.
Example:
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class Example {
public Example() {
JButton button1 = new JButton("Hello button1");
JButton button2 = new JButton("Hello button2") {
#Override
public Dimension getPreferredSize() {
int width = super.getPreferredSize().width;
return new Dimension(width, width);
}
};;
JPanel buttonPanel = new JPanel();
buttonPanel.add(button1);
buttonPanel.add(button2);
JPanel contentPanel = new JPanel(new GridBagLayout());
contentPanel.add(buttonPanel);
JFrame frame = new JFrame();
frame.setContentPane(contentPanel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(400, 400);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
new Example();
}
});
}
}

I added a flowlayout and changed setMaximumSize to setPreferredSize. That should fix your problem.
Here try this:
import java.awt.Dimension;
import javax.swing.JButton;
import javax.swing.JFrame;
public class Frame extends JFrame {
private JButton button1;
private JButton button2;
public Frame()
{
button1 = new JButton("Hello button1");
button2 = new JButton("Hello button2");
button2.setPreferredSize(new Dimension(100,100));
button1.setPreferredSize(new Dimension(100,100));
add(button2);
add(button1);
}
}
<----now the other class--->
import java.awt.FlowLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class Panel extends JPanel{
public static void main(String args [])
{
Frame frame = new Frame();
frame.setLayout(new FlowLayout());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(500, 500);
frame.setVisible(true);
}
}

Java - combobox height changes with frame height

I have a frame which contains a vertical toolbar with a combobox and some buttons. The combobox takes up the maximum height it can in the toolbar. Why? And how to solve this? Is there a way to fix the size of the combobox?
The code:
import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JToolBar;
import javax.swing.border.BevelBorder;
public class Clipping extends JPanel {
public Clipping()
{
setLayout(new BorderLayout());
JToolBar toolbar = new JToolBar(JToolBar.VERTICAL);
CreateToolBarButtons(toolbar);
toolbar.setFloatable(false);
toolbar.setBorder(new BevelBorder(BevelBorder.RAISED));
add(toolbar, BorderLayout.WEST);
}
private static void CreateToolBarButtons(JToolBar toolbar)
{
String[] cboList = {"Line", "Polygon"};
JComboBox cboDraw = new JComboBox(cboList);
JButton btnClip = new JButton("Set clip area");
JButton btnClear = new JButton("Clear");
toolbar.add(cboDraw);
toolbar.addSeparator();
toolbar.add(btnClip);
toolbar.addSeparator();
toolbar.add(btnClear);
}
public static void main(String[] args)
{
CreateFrame();
}
private static void CreateFrame()
{
JFrame frame = new JFrame("Clipping");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new Clipping());
frame.setSize(500,500);
frame.setVisible(true);
}
}

JToolbar uses a BoxLayout and JComboBox has an issue with it. See this question for a solution. Rather than creating a subclass, try to just setMaximumSize on the combo box with the height that you like.

Adding a jTextArea to JPanel from within the Panel

So, I am creating a new Canvas (JPanel) class: Canvas canvas = new Canvas(); and then I am calling a method on that class: canvas.addTextBox();
Now, from within this Canvas class, I want to add a new jTextArea to the Canvas. I tried using the code below but it isn't showing up. Not sure what I am doing wrong. Thanks!
class Canvas extends JPanel {
public Canvas() {
this.setOpaque(true);
//this.setBackground(Color.WHITE);
}
public void addTextBox() {
final JTextArea commentTextArea = new JTextArea(10, 10);
commentTextArea.setLineWrap(true);
commentTextArea.setLineWrap(true);
commentTextArea.setWrapStyleWord(true);
commentTextArea.setVisible(true);
}
}
Full Code
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import javax.swing.JFrame;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JTextArea;
public class UMLEditor {
public static void main(String[] args) {
JFrame frame = new UMLWindow();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setBounds(30, 30, 1000, 700);
frame.getContentPane().setBackground(Color.white);
frame.setVisible(true);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}
class UMLWindow extends JFrame {
Canvas canvas = new Canvas();
private static final long serialVersionUID = 1L;
public UMLWindow() {
addMenus();
}
public void addMenus() {
getContentPane().add(canvas);
JMenuBar menubar = new JMenuBar();
JMenuItem newTextBox = new JMenuItem("New Text Box");
newTextBox.setMnemonic(KeyEvent.VK_E);
newTextBox.setToolTipText("Exit application");
newTextBox.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent event) {
canvas.addTextBox();
}
});
menubar.add(newTextBox);
setJMenuBar(menubar);
setSize(300, 200);
setLocationRelativeTo(null);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
}
class Canvas extends JPanel {
public Canvas() {
this.setOpaque(true);
//this.setBackground(Color.WHITE);
}
public void addTextBox() {
final JTextArea commentTextArea = new JTextArea(10, 10);
commentTextArea.setLineWrap(true);
commentTextArea.setLineWrap(true);
commentTextArea.setWrapStyleWord(true);
commentTextArea.setVisible(true);
}
}

The addTextBox method only creates a JTextArea. It never adds it to the JPanel
You will need to add the following line to addTextBox method:
add( commentTextArea );
In case the JFrame which contains your components is already visible on screen when the addTextBox method is called, you need to invalidate the container as well. Simply add
revalidate();
repaint();