Develop Reference

Java GUI switching between panels on button click

I am learning Java and I have to develop an application using a GUI. I have the application working in command line already, but the GUI is driving me insane and costing me in lost hours of head banging and research which is leading nowhere. Can you please help me get the basics working so that i can develop further from there. I want to have a single frame application that can switch between frames on a button click. I created a frame and added three panels P1-P3. These are set as Card Layout (from what i read from forums). Then I added additional panels to these to which i have set colour and buttons.
'''
public class MyMainForm extends JFrame{
private JPanel P1;
private JPanel P2;
private JPanel P3;
private JButton btnFrame1;
private JButton btnFrame2;
private JButton button1;
private JTextField thisIsPanel3TextField;
private JButton btn2Frame1;
private final JFrame frame = new JFrame("MyMain Frame");
public MyMainForm() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setContentPane(P1);
pack();
setSize(1000,800);
//setLocation(null);
btnFrame1.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
P1.setVisible(false);
setContentPane(new MyMainForm().P2);
}
});
btnFrame2.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
P2.setVisible(false);
setContentPane(new MyMainForm().P3);
}
});
button1.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
P3.setVisible(false);
setContentPane(new MyMainForm().P2);
}
});
btn2Frame1.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
P1.setVisible(false);
setContentPane(new MyMainForm().P3);
}
});
}
public static void main(String[] args) {
MyMainForm MyMainForm = new MyMainForm();
MyMainForm.setVisible(true);
}
}
'''
I can display P2 or P3 with this new code example above. When i try to go from P2 or P3 back to P1 the content pane doesn't show? Do i need to revalidate the content pane for this to work? I really need to be able to go from P1 to P2

The easiest way to do this is to use a CardLayout. Just follow this example:
JFrame frame = new JFrame();
JPanel p1 = new JPanel();
p1.setBackground(Color.RED);
JPanel p2 = new JPanel();
p2.setBackground(Color.WHITE);
JPanel p3 = new JPanel();
p3.setBackground(Color.BLUE);
//Create the panel that contains the "cards".
JPanel cards = new JPanel(new CardLayout());
cards.add(p1, "Panel 1");
cards.add(p2, "Panel 2");
cards.add(p3, "Panel 3");
// Add your card container to the frame
Container pane = frame.getContentPane();
pane.add(cards, BorderLayout.CENTER);
JButton btn = new JButton("Click me!");
btn.addActionListener(new ActionListener() {
#Override
public void actionPerformed (ActionEvent e) {
CardLayout cl = (CardLayout)(cards.getLayout());
cl.next(cards);
}
});
JPanel btnPanel = new JPanel();
btnPanel.add(btn);
pane.add(btnPanel, BorderLayout.SOUTH);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(400, 400);
frame.setVisible(true);
Alternatively, you can switch to a specific panel by calling cl.show(cards, "Panel X") where X is the number of the panel. This is because the swing argument is the name I assigned to each "card" and the show method recalls panels added to CardLayout by name. For your example, each button should have a listener that uses this method to "show" its assigned panel.

Bar Chart from different class in to GUI class

I have Gui class with a JPanel and JButton. When the button is clicked i would like to display the graph in my JPanel. The Graph is in different class. Can someone help me do this please?
GUI CLASS:
public class Gui extends JFrame implements ActionListener{
JButton showGraph;
public Gui() {
super("GUI");
setSize(1200,600);
setDefaultCloseOperation(EXIT_ON_CLOSE);
showGraph = new JButton("SHOW GRAPH");
JPanel mainPanel = new JPanel();
add(mainPanel);
mainPanel.setLayout(new GridLayout(2,0,10,10));
mainPanel.setBorder(new EmptyBorder(10,10,10,10));
mainPanel.add(showGraph);
JPanel graphPanel = new JPanel();
graphPanel.setBackground(Color.yellow);
mainPanel.add(graphPanel);
showGraph.addActionListener(this);
}
public static void main (String[] args){
new Gui().setVisible(true);
}
#Override
public void actionPerformed(ActionEvent e) {
if (e.getSource() == showGraph) {
SimpleBarChart b = new SimpleBarChart();
b.getGraph();
}
}
}

Change your getGraph() method to take a JFrame and pass in this.
public void getgraph(JFrame f) {
//JFrame f = new JFrame();
f.setSize(400, 300);
... as before ...
}
Then call in actionPerformed
if (e.getSource() == showGraph) {
SimpleBarChart b = new SimpleBarChart();
b.getGraph(this);
}
You can't have a frame inside a frame. Another option would be to make getGraph() return a JPanel and then you could put the panel in your existing frame instead of updating the whole frame.

Java - Blank window

I am newbie to Java. My following code give me a blank window.
Anyone can help me with what is going on ?
I am thinking that the error is at the ActionListeners.
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setTitle("Listeners");
frame.setSize(400, 200);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
frame.setLayout(new BorderLayout());
JTextArea txtArea = new JTextArea();
HelloActionListener hlisten = new HelloActionListener(txtArea);
JButton bl = new JButton("TOP");
bl.addActionListener((ActionListener) hlisten);
JButton b2 = new JButton("LEFT");
ActionListener rightListener = (ActionEvent e) -> {
txtArea.setText("Yes,let's go Left");
};
b2.addActionListener(rightListener);
JButton b3 = new JButton("RIGHT");
b3.addActionListener((ActionEvent e) -> {
txtArea.setText("Sorry, we cant go Right");
});
JButton b4 = new JButton("Bottom");
b4.addActionListener((ActionListener) hlisten);
frame.add(bl, BorderLayout.PAGE_START);
frame.add(b2, BorderLayout.LINE_START);
frame.add(b3, BorderLayout.LINE_END);
frame.add(b4, BorderLayout.PAGE_END);
frame.add(txtArea, BorderLayout.CENTER);
frame.setVisible(true);
}

Say you want to put "Hello" in your text area when the top button is pressed. Then you need to define your HelloActionListener as below:
private static class HelloActionListener implements ActionListener {
private JTextArea textArea;
public HelloActionListener(JTextArea textArea) {
this.textArea = textArea;
}
#Override
public void actionPerformed(ActionEvent e) {
textArea.setText("Hello");
}
}
The rest of your code is kind of messy but should work, however, you don't need to make the frame to be visible twice.
UPDATE
But I do think your code should be something like this:
public class MyApplication extends JFrame {
public MyApplication() {
setTitle("Listeners");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(new BorderLayout());
JTextArea txtArea = new JTextArea();
HelloActionListener hlisten = new HelloActionListener(txtArea);
JButton bl = new JButton("TOP");
bl.addActionListener(hlisten);
JButton b2 = new JButton("LEFT");
ActionListener rightListener = e -> {
txtArea.setText("Yes,let's go Left");
};
b2.addActionListener(rightListener);
JButton b3 = new JButton("RIGHT");
b3.addActionListener(e -> {
txtArea.setText("Sorry, we cant go Right");
});
JButton b4 = new JButton("Bottom");
b4.addActionListener(hlisten);
add(bl, BorderLayout.PAGE_START);
add(b2, BorderLayout.LINE_START);
add(b3, BorderLayout.LINE_END);
add(b4, BorderLayout.PAGE_END);
add(txtArea, BorderLayout.CENTER);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
JFrame frame = new MyApplication();
frame.pack();
frame.setVisible(true);
});
}
private class HelloActionListener implements ActionListener {
private JTextArea textArea;
public HelloActionListener(JTextArea textArea) {
this.textArea = textArea;
}
#Override
public void actionPerformed(ActionEvent e) {
JButton button = (JButton) e.getSource();
textArea.setText("Hello from " + button.getText());
}
}
}

There is no need for the first frame.setVisible(true); in your code - you are calling that again right at the end. But your panels are all zero size. You need to call frame.pack(); before you set it visible. Note also that all of that (the GUI stuff) should be done from the Event Dispatch Thread, not from your main thread.

JScrollPane does not work on JPanel

I have a frame that contains a mainPanel. This last will add other commandPanels (each one contains a button and a textField) Dynamically. the problem is that the JScrollPane does not appear to let me use the unseen commandPanels even if the mainPanel is full.
The below picture shows my case.
To initialize the window I wrote below code:
frame = new JFrame();
frame.setBounds(100, 100, 962, 639);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(null);
mainPanel = new JPanel();
mainPanel.setBounds(264, 6, 692, 500);
mainPanel.setLayout(new BoxLayout(mainPanel, BoxLayout.Y_AXIS));
scroll = new JScrollPane();
scroll.getViewport().add(mainPanel);
frame.getContentPane().add(scroll);
and the method that add dynamically the new commandPanels is:
public void loadCommandPanel(String commandName)
{
CommandPanel newCommandPanel = new CommandPanel();
newCommandPanel.getCommandBtn().setText(commandName);
mainPanel.add(newCommandPanel);
scroll.getViewport().add( newCommandPanel );
mainPanel.add( scroll, BorderLayout.EAST);
frame.add( mainPanel);
...
}
Any help to get the scrollPane, will be much more than appreciated.

scroll.getViewport().add(mainPanel); is not how you use JViewport or JScrollPane; instead you should using something like this:
scroll.getViewport().setView(newCommandPanel);
or
scroll.setViewportView(newCommandPanel);
Take a look at How to Use Scroll Panes for more details.
Note also, this doesn't makes sense:
CommandPanel newCommandPanel = new CommandPanel();
newCommandPanel.getCommandBtn().setText(commandName);
mainPanel.add(newCommandPanel);
scroll.getViewport().add( newCommandPanel );
You add newCommandPanel to mainPanel, then promptly add it to another container (albeit incorrectly).
A component can only reside on a single parent; the moment you add it to another container, it is automatically removed from the previous container.

I have made some changes and it works perfectly now. For those who want the same thing here's my code:
import ...
public class mainUserInterface {
private JFrame frame;
private JPanel mainPanel;
private JPanel commandsPanel;
private JScrollPane commandsScrollPane;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
mainUserInterface window = new mainUserInterface();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public mainUserInterface() {
initialize();
}
private void initialize() {
frame = new JFrame("CommandsExecutor");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setPreferredSize(new Dimension(1000, 700));
mainPanel = new JPanel(new BorderLayout(5,5));
mainPanel.setBorder( new TitledBorder("") );
commandsPanel = new JPanel();
commandsPanel.setLayout(new BoxLayout(commandsPanel, BoxLayout.Y_AXIS));
for(int i=0; i<15;i++){
commandsPanel.add(new CommandPanel());
}
commandsScrollPane = new JScrollPane(commandsPanel);
mainPanel.add(commandsScrollPane,BorderLayout.CENTER);
frame.setContentPane(mainPanel);
frame.pack();
frame.setVisible(true);
}
}
and Here's the commandPanel class:
import ...
public class CommandPanel extends JPanel {
private JTextField commandResult;
private JButton commandBtn;
public CommandPanel()
{
this.setLayout( new BorderLayout(10,10));
this.setBorder( new TitledBorder("Command:") );
this.setMaximumSize(new Dimension(692,60));
this.setMinimumSize(new Dimension(692,60));
commandBtn = new JButton("Execute");
commandBtn.setMaximumSize(new Dimension(137, 34));
commandBtn.setMinimumSize(new Dimension(137, 34));
this.add(commandBtn, BorderLayout.WEST);
commandResult = new JTextField();
commandResult.setMaximumSize(new Dimension(518, 34));
commandResult.setMinimumSize(new Dimension(518, 34));
this.add(commandResult, BorderLayout.CENTER);
}
public JTextField getCommandResult() {
return commandResult;
}
public JButton getCommandBtn() {
return commandBtn;
}
public void setCommandResult(JTextField commandResult) {
this.commandResult = commandResult;
}
public void setCommandBtn(JButton commandBtn) {
this.commandBtn = commandBtn;
}
}
Thanks for all who answered my question, it really helped.

How do I add a class in to a JPanel?

This is the JPanel
public class DisplayBoard {
public static void main (String[] args) {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//The main panel
JPanel main = new JPanel();
main.setPreferredSize(new Dimension(600,800) );
main.setLayout(new BorderLayout());
//The title panel
JPanel title = new JPanel();
title.setPreferredSize(new Dimension(400, 120));
title.setBackground(Color.YELLOW);
JLabel test1 = new JLabel("Title goes here");
title.add(test1);
//The side bar panel
JPanel sidebar = new JPanel();
sidebar.setPreferredSize(new Dimension(200, 800));
sidebar.add(AddSubtract);
sidebar.setBackground(Color.GREEN);
JLabel test2 = new JLabel("Sidebar goes here");
sidebar.add(test2);
//The panel that displays all the cards
JPanel cardBoard = new JPanel();
cardBoard.setPreferredSize(new Dimension(400,640) );
//adding panels to the main panel
main.add(cardBoard, BorderLayout.CENTER);
main.add(title, BorderLayout.NORTH);
main.add(sidebar, BorderLayout.WEST);
frame.setContentPane(main);
frame.pack();
frame.setVisible(true);
}
}
and I want to add this class into the sidebar panel
public class AddSubtract {
int Number = 0;
private JFrame Frame = new JFrame("Math");
private JPanel ContentPane = new JPanel();
private JButton Button1 = new JButton("Add");
private JButton Button2 = new JButton("Subtract");
private JLabel Num = new JLabel ("Number: " + Integer.toString (Number));
public AddSubtract() {
Frame.setContentPane(ContentPane);
ContentPane.add(Button1);
ContentPane.add(Button2);
ContentPane.add(Num);
Button1.addActionListener(new Adding());
Button2.addActionListener(new Subtracting());
}
public class Adding implements ActionListener {
public void actionPerformed(ActionEvent e) {
Number++;
Num.setText ("Number: " + Integer.toString (Number));
}
}
public class Subtracting implements ActionListener {
public void actionPerformed(ActionEvent e) {
Number--;
Num.setText ("Number: " + Integer.toString (Number));
}
}
public void launchFrame(){
Frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Frame.pack();
Frame.setVisible(true);
}
public static void main(String args[]){
AddSubtract Test = new AddSubtract();
Test.launchFrame();
}
}
Can someone explain to me how I can do this ?
I have a feeling that this is not going to work, but I really want to learn the way to do it.

This definately is not going to work. For starters, you have two main() methods. Second, if you want to add a class to your Frame, it should extend from JComponent. Basically, your code should look like this:
public class MainFrame extends JFrame {
public MainFrame() {
this.add(new MainPanel())
//insert all settings here.
}
}
public class MainPanel extends JPanel {
public MainPanel() {
this.add(new AddSubtract());
this.add(/*more panels*/)
}
}
public class AddSubtract extends JPanel {
public AddSubtract() {
//add buttons and stuff here
}
}
and variables do NOT start with capitals.
Edit: And when you have some JFrame, it's usually best to have a main() method with just one line:
public static void main(String[] args) {
new MainFrame();
}
just set the settings and configuration of the JFrame in the constructor.