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Reusing a Button in Java Makes Nothing Display

I am really new to GUI programming in Java so please forgive me if this code is really basic. In short, I want to have 2 panels that are the same design. After I press the "A" button on the panel 1, I want to make panel 2 appear with the same design. Making the GUI efficient or pretty doesn't currently matter to me. I just want it to work. I have parts of the code listed below.
JButton buttonA = new JButton("a");
JButton buttonB = new JButton("b");
JButton buttonC = new JButton("c");
JButton buttonD = new JButton("d");
JPanel pan1 = new JPanel();
JPanel pan2 = new JPanel();
setTitle ("Test");
setSize (640, 640);
setResizable(false);
GridLayout grid1 = new GridLayout();
setLayout (grid1);
FlowLayout flow1 = new FlowLayout();
pan1.setLayout (flow1);
pan1.add(buttonA);
pan1.add(buttonB);
pan1.add(buttonC);
pan1.add(buttonD);
buttonA.addActionListener(this);
buttonB.addActionListener(this);
buttonC.addActionListener(this);
buttonD.addActionListener(this);
FlowLayout flow2 = new FlowLayout();
pan2.setLayout (flow2);
pan2.add(buttonA);
pan2.add(buttonB);
pan2.add(buttonC);
pan2.add(buttonD);
add(pan1);
add(pan2);
pan1.setVisible(true);
pan2.setVisible(false);
setVisible(true);
public void actionPerformed(ActionEvent event) {
if (command.equals("a")){//i want to show the panel 2 after button a is pressed
System.out.println("HelloA");
pan1.setVisible(false);
pan2.setVisible(true);
}
Currently, it just shows nothing in the window. Any help guys?

Short answer is, you can't.
Long answer is, a component can only reside on a single parent. Adding a component to a second container will automatically remove it from the first container before its added to the new one.
Instead, you will need to create individual buttons for both containers.
Also, understand that BorderLayout can't support what you're trying to do, it will only manage one component at a time (in each of the 5 available positions)
A better solution would be to make use of the CardLayout which is designed to facilitate the action you are trying to achieve

buttons to change card in cardlayout

I have 2 panels in my frame, 1 is for buttons (I want to use radioButton, but for now it is easier using buttons) and the other one is for the card layout panel. My plan is to shuffle the chad when I press specific button. Like the move button will show me the move panel card. Move panel card has x0 label and text field, Line panel card has x0 and x1 both label and text field.
There are 2 classes, 1 is for the buttonpanel = Buttons
the other one is for the cards = PanelMiddle
Here's my code:
public class PanelMiddle{
JPanel controlPanel = new JPanel();
CardLayout cl = new CardLayout();
JPanel movePanel = new JPanel();
JPanel linePanel = new JPanel();
JLabel x0Label = new JLabel("x0");
JTextField x0TextField = new JTextField(3);
JLabel x1Label = new JLabel("x1");
JTextField x1TextField = new JTextField(3);
public PanelMiddle(){
controlPanel.setLayout(cl);
//move panel
movePanel.setLayout(new GridLayout (1,2));
movePanel.add(x0Label);
movePanel.add(x0TextField);
controlPanel.add(movePanel,"Move"); //add the keyword Move to show the move card
//line panel
linePanel.setLayout(new GridLayout (2,2));
//linePanel.add(x0Label);
linePanel.add(x1Label);
//linePanel.add(x0TextField);
linePanel.add(x1TextField);
controlPanel.add(linePanel,"Line"); // add the keyword Line to show the line card
}
}
In the other class I have:
public class Buttons extends PanelMiddle{
JPanel buttonPanel = new JPanel();
JButton moveB = new JButton ("Move");
JButton lineB = new JButton ("Line");
public Buttons(){
buttonPanel.setLayout(new GridLayout (2,1));
buttonPanel.add(moveB);
buttonPanel.add(lineB);
action();
}
public void action(){
moveB.addActionListener((e) -> {
cl.show(controlPanel,"Move");
});
lineB.addActionListener((e) -> { cl.show(controlPanel,"Line");});
}
}
The result that I got is weird. It doesn't show fully my panel. But when I tried commenting all the line panel, it works. Does someone have a fix here?
NB: Im sorry I dont know how to edit the text here so its a little bit messy.
edit 1 : as guleryuz says, I commented out the x0Label and x0TextField from the line panel

in swing component hierarchy a component can only be added to one container, you are adding x0Label and x0TextField two both panels. so when you add x0Labe two second panel (linePanel) it will be removed from movePanel (same case for x0TextField) so movePanel becomes empty.
more details here

GUI, JComboBox and opening a new window

I am new to Java and especially new to GUI and it's super confusing to me right now.
I'm making a program for class that is supposed to have a menu (JComboBox I'm assuming) that opens a new window when an option is selected. I am just working on the first option where you click "The Matrix" and a new window pops up with two buttons called "Red Pill" & "Blue Pill" and thats where I've hit a wall.
I got to the point where I am able to create a new window (not sure if this is even the right route to take for opening the new window) but, When I try to add Buttons to the new pop up window nothing shows up....
Thanks for any help or pointers in the right direction!
public class MultiForm extends JFrame{
private JComboBox menu;
private JButton bluePill;
private JButton redPill;
private static String[] fileName = {"", "The Matrix", "Another Option"};
public MultiForm() {
super("Multi Form Program");
setLayout(new FlowLayout());
menu = new JComboBox(fileName);
add(menu);
TheHandler handler = new TheHandler();
menu.addActionListener(handler);
}
private class TheHandler implements ActionListener{
public void actionPerformed(ActionEvent event) {
********************************************************************
//Create a new window when "The Matrix" is clicked in the JCB
JFrame newFrame = new JFrame();
JPanel panel = new JPanel();
newFrame.setLayout(new FlowLayout());
newFrame.setSize(500, 300);
newFrame.setDefaultCloseOperation(newFrame.EXIT_ON_CLOSE);
Icon bp = new ImageIcon(getClass().getResource("Blue Pill.png"));
bluePill = new JButton("Blue Pill", bp);
newFrame.add(bluePill);
Icon rp = new ImageIcon(getClass().getResource("Red Pill.png"));
redPill = new JButton("Red Pill", rp);
newFrame.add(redPill);
add(panel);
newFrame.setVisible(true);
}
}
public static void main(String[] args) {
MultiForm go = new MultiForm();
go.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
go.setSize(400, 200);
go.setVisible(true);
}
}

I tried doing newFrame.add(BluePill) and it created a button that was the size of the entire window and it would not allow me to add both buttons that way
That's because the frame uses a BorderLayout by default. Unless you specify otherwise, the component's will be added to the CENTER position, BUT, BorderLayout will only allow a single component to be managed at each of the it's five available positions, so you are only seeing the last component you added.
See How to Use BorderLayout for more details
so I figured that wasn't the correct way
It's the right approach, you just need to use a layout manager which can accommodate more components or change the position which you are adding the buttons
In this little example, I've just use a FlowLayout, but you can use what ever is going to give you the effect you desire
JFrame newFrame = new JFrame();
newFrame.setLayout(new FlowLayout());
newFrame.setDefaultCloseOperation(newFrame.EXIT_ON_CLOSE);
bluePill = new JButton("Blue Pill");
newFrame.add(bluePill);
redPill = new JButton("Red Pill");
newFrame.add(redPill);
newFrame.pack();
newFrame.setVisible(true);
As a general rule of thumb, I don't like adding components like this directly to a top level container, I prefer to use a intermediate container, like a JPanel, this gives me more possibilities for re-use, but that's me.
You should also only make the frame visible when it's actually ready, otherwise you may find that some times, the components won't show up
See Laying Out Components Within a Container for more details

You are not using the getContentPane() method from the new JFrame.
You have to actually use getContentPane() first because you're not adding any component to the JFrame itself but to an intermediate "panel".
JFrame newFrame = new JFrame();
JPanel panel = new JPanel();
newFrame.setSize(300, 200);
newFrame.setDefaultCloseOperation(newFrame.EXIT_ON_CLOSE);
bluePill = new JButton("Blue Pill");
panel.add(bluePill);
redPill = new JButton("Red Pill");
panel.add(redPill);
newFrame.getContentPane().add(panel);
newFrame.setVisible(true);
You'll have to add a Layout to the JPanel or/and the JFrame and play with the sizes of the component but with this you're on the right path.
I always put the setVisible method a the end, after adding all the components to the frame.

You made some mistakes.
add(bluePill);
will not do what you want, even if it would, it would still be wrong.
(sounds weird, but I'll explain it)
First the "right" way to do it:
//Create a new window when "The Matrix" is clicked in the JCB
JFrame newFrame = new JFrame();
newFrame.setSize(300, 200);
newFrame.setDefaultCloseOperation(newFrame.EXIT_ON_CLOSE);
bluePill = new JButton("Blue Pill");
newFrame.getContentPane().add(bluePill);
redPill = new JButton("Red Pill");
newFrame.getContentPane().add(redPill);
newFrame.setVisible(true);
Notice I added "newFrame", because you were calling the method of MultiForm.
That's because "add()" is the same as "this.add()" and "this" points to MultiForm. Check it with this line if you want:
System.out.println(this.toString());
The "getContentPane()" is best explained with this image:
You were adding it directly to the JFrame (I don't even know what exactly happens then).
It is also good practice to set the frame visible when it is ready to be visible. Your frame did not contain anything when you made it visible.
Now to the JPanel. A JPanel can hold some elements like JButton,etc. and it can also have a layout. Since you didn't use the JPanel at all, i removed the line from your code. You can still add the JPanel to your ContentPane and add a Layout to the JPanel. (You can also add JPanels to JPanels to create complex layouts)
I hope this was clear for you.

JTabbedPane in JPanel?

I have a simple problem when I want to add tabs in my jpanel. The alignment of the tabs get horizontal instead of vertical, wich looks like crap =/.
It looks like this:
If I discard the panel instead and add the tabbedPane directly to the frame, everything works fine.
If you uncomment the three lines of code and remove the getContentPane().add(jtp); you can reproduce my probleme.
working Code:
public class TabbedPane extends JFrame
{
public TabbedPane()
{
setTitle("Tabbed Pane");
setSize(300, 300); // set size so the user can "see" it
JTabbedPane jtp = new JTabbedPane();
// JPanel panel = new JPanel();//uncomment all three lines
// panel.add(jtp);
// getContentPane().add(panel);
getContentPane().add(jtp);//remove me
JPanel jp1 = new JPanel();// This will create the first tab
JPanel jp2 = new JPanel();// This will create the second tab
JLabel label1 = new JLabel();
label1.setText("This is Tab 1");
jp1.add(label1);
jtp.addTab("Tab1", jp1);
jtp.addTab("Tab2", jp2);
JButton test = new JButton("Press");
jp2.add(test);
setVisible(true); // otherwise you won't "see" it
}
public static void main(String[] args)
{
TabbedPane tab = new TabbedPane();
}
}
Thanks a lot!

If I discard the panel instead and add the tabbedPane directly to the frame, everything works fine.
The default layout of JPanel is FlowLayout, which "lets each component assume its natural (preferred) size." The default layout of JFrame is BorderLayout, the CENTER of which ignores preferred size. In either case, invoking setSize() precludes the layout from functioning initially; re-size the frame to see the effect. Instead, use pack(), which "Causes this Window to be sized to fit the preferred size and layouts of its subcomponents."
setDefaultCloseOperation(EXIT_ON_CLOSE);
pack();
setVisible(true); // otherwise you won't "see" it

There are many things I would change in that code, starting with the recommendations of #trashgod. OTOH this is the minimal change needed in order to stretch the tabbed pane to the width/height of the parent container.
// give the panel a layout that will stretch components to available space
JPanel panel = new JPanel(new GridLayout());//uncomment all three lines
panel.add(jtp);
getContentPane().add(panel);
//getContentPane().add(jtp);//remove me
For more details see this answer.

Well firstly you can try this:
JPanel panel = new JPanel();//uncomment all three lines
panel.setLayout(new GridLayout());
JPanel jp1 = new JPanel();// This will create the first tab
JPanel jp2 = new JPanel();// This will create the second tab
JLabel label1 = new JLabel();
label1.setText("This is Tab 1");
jp1.add(label1);
jtp.addTab("Tab1", jp1);
jtp.addTab("Tab2", jp2);
JButton test = new JButton("Press");
jp2.add(test);
getContentPane().add(jtp);
and in the main:
TabbedPane tab = new TabbedPane();
tab.pack();
tab.setVisible(true);
May I suggest using MigLayout to set layouts, it will make your life easier. Hope it helps.

Try GridbagLayout. Once you have mastered it, you can design UI of any sort with this layout.

I agree with prasanth regarding the use of GridBagLayout
I have gone through this problem once and I solved it by adding the JTabbedPaneto the panel via GridBagLayout, make sure you add the JTabbedPane using the ipadx and ipady according to your requirements in your GridBagConstraints object
e.g.
JPanel myPanel=new JPanel();
myPanel.setLayout(new GridBagLayout());
JTabbedPane jTP=new JTabbedPane();
jTP.add("Tab1",new JPanel());//substitute your component instead of "new JPanel"
GridBagConstraints myConstraints=new GridBagConstraints();
myConstraints.ipadx=400;//streches the component being added along x axis - 200 px on both sides
myConstraints.ipady=600;//streches the component being added along y axis - 200 px on both sides
myPanel.add(jTP,myConstraints);
You can adjust both these properties according to what is perfect for your need

Java - how to add panel in bottom-to-top order?

Is there any way that I could add panels in bottom-to-top order?..
I've tried some layout managers, but still i couldn't get it..
need help.
JPanel mainpanel = new JPanel();
JPanel panel_1 = new JPanel();
JPanel panel_2 = new JPanel();
JPanel panel_3 = new JPanel();
mainpanel.add(panel_1);
mainpanel.add(panel_2);
mainpanel.add(panel_3);
mainpanel.add(panel_4);
mainpanel.add(panel_5);
mainpanel.add(panel_n);

You should be able to specify an index for adding the panel. Ie:
mainpanel.add(panel_1, 0);
mainpanel.add(panel_2, 0);
mainpanel.add(panel_3, 0);
This will always add each panel in the first position.

MigLayout works here as well - and increases maintainabilty:
JPanel mainpanel = new JPanel(new MigLayout();
private void addPanel(JPanel newPanel) {
mainpanel.add(newPanel, "dock north");
}

Add the panel in order, In which order you want to display in the frame.
Let p1,p2,p3 are the subv-panels and p is main panel.
You want order of panel as folowing : p2,p3,p1
p.add(p2);
p.add(p3);
p.add(p1);
then finally add it to your frame.
I think this will help you.