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How to make JPanel fill the entire JFrame?

I am making an UI in a minecraft plugin. Everything is working, except I have a JPanel and it doesn't fill the whole JFrame. So what I want is the JPanel fill the entire JFrame even if we re-scale the window.
I use Layout manager (FlowLayout) for the JPanel.
I tried using a Layout manager for the JFrame, well it didn't solved my problem because it didn't resize the JPanel.. I tried setting the size of the JPanel to the JFrame's size, but when it's resized it doesn't scale with it.
So, how can I do this?
My plugin creates a button for every player and when I click the button it kicks the player.
My code (I can't really post less because I don't know where I need to change something):
public static JFrame f;
public static JTextField jtf;
public static JPanel jp;
public static void creategui()
{
System.out.println("GUI created.");
f = new JFrame("Players");
jp = new JPanel();
jp.setLayout(new FlowLayout(FlowLayout.LEFT));
jp.setBackground(Color.GRAY);
jtf = new JTextField("Reason");
jtf.setPreferredSize(new Dimension(200,20));
jtf.setToolTipText("Write the reason here.");
jp.setSize(new Dimension(200,200));
f.setLayout(null);
f.setSize(500,500);
f.setVisible(true);
jp.add(jtf);f.add(jp, BorderLayout.CENTER);
for (final Player p : Bukkit.getOnlinePlayers())
{
System.out.println("Looping.");
final JButton b = new JButton();
b.setName(p.getName());
b.setText(p.getName());
b.setToolTipText("Kick " + b.getText());
b.setBackground(Color.GREEN);
b.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (!b.getBackground().equals(Color.RED))
{
Bukkit.getScheduler().runTask(main, new Runnable() {
public void run() {
Bukkit.getPlayer(b.getText()).kickPlayer(jtf.getText());
b.setBackground(Color.RED);
}
});
}
}
});
jp.add(b);
System.out.println("Button added.");
}
f.add(jp, BorderLayout.CENTER);
}

The question should include an mcve reproducing the problem so we can test it.
It could look like this :
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.util.Arrays;
import java.util.List;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class Mcve {
private static List<String> players = Arrays.asList(new String[]{"Player A", "Player B"});
public static void main(String[] args) {
creategui();
}
public static void creategui()
{
JPanel jp = new JPanel();
jp.setBackground(Color.GRAY);
JTextField jtf = new JTextField("Reason");
jtf.setPreferredSize(new Dimension(200,20));
jtf.setToolTipText("Write the reason here.");
jp.setSize(new Dimension(200,200));
jp.add(jtf);
for (final String p : players)
{
final JButton b = new JButton();
b.setText(p);
b.setBackground(Color.GREEN);
b.addActionListener(e -> {
if (!b.getBackground().equals(Color.RED))
{
b.setBackground(Color.RED);
}
});
jp.add(b);
}
JFrame f = new JFrame("Players");
f.setLayout(null);
f.setSize(500,500);
f.add(jp, BorderLayout.CENTER);
f.setVisible(true);
}
}
To make the JPanel fill the entire frame simply remove this line :
f.setLayout(null);
and let the default BorderLayout manager do its work.
Here is a modified version with some additional comments:
public class Mcve {
private static List<String> players = Arrays.asList(new String[]{"Player A", "Player B"});
public static void main(String[] args) {
creategui();
}
public static void creategui()
{
JPanel jp = new JPanel();
jp.setBackground(Color.GRAY);
JTextField jtf = new JTextField("Reason");
jtf.setPreferredSize(new Dimension(200,20));
jtf.setToolTipText("Write the reason here.");
jp.setPreferredSize(new Dimension(250,200)); // set preferred size rather than size
jp.add(jtf);
for (final String p : players)
{
final JButton b = new JButton();
b.setText(p);
b.setBackground(Color.GREEN);
b.addActionListener(e -> {
if (!b.getBackground().equals(Color.RED))
{
b.setBackground(Color.RED);
}
});
jp.add(b);
}
JFrame f = new JFrame("Players");
//f.setLayout(null); null layouts are bad practice
//f.setSize(500,500); let layout managers set the sizes
f.add(jp, BorderLayout.CENTER);
f.pack();
f.setVisible(true);
}
}

A 1x1 grid layout does the job quite nicely.
window = new JFrame();
panel = new JPanel();
window.setLayout(new java.awt.GridLayout(1, 1));
window.add(panel);

Either set the layout manager for jp (the JPanel in the code you posted) to BorderLayout and add jtf (the JTextField in the code you posted) to the CENTER of jp, as in:
f = new JFrame();
jp = new JPanel(new BorderLayout());
jtf = new JTextField(30); // number of columns
jp.add(jtf, BorderLayout.CENTER);
f.add(jp, BorderLayout.CENTER);
or dispense with jp and add jtf directly to f (the JFrame in the code you posted), as in:
f = new JFrame();
jtf = new JTextField(30);
f.add(jtf, BorderLayout.CENTER);
The key is that the CENTER component of BorderLayout expands to fill the available space.

So I fixed it somehow, this is the code:
public static void creategui()
{
System.out.println("GUI created.");
f = new JFrame("Players");
jp = new JPanel();
jp.setBackground(Color.GRAY);
jp.setSize(200,200);
jtf = new JTextField(30);
jtf.setToolTipText("Write the reason here.");
jp.add(jtf);
for (final Player p : Bukkit.getOnlinePlayers())
{
System.out.println("Looping.");
final JButton b = new JButton();
b.setName(p.getName());
b.setText(p.getName());
b.setToolTipText("Kick " + b.getText());
b.setBackground(Color.GREEN);
b.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (!b.getBackground().equals(Color.RED))
{
Bukkit.getScheduler().runTask(main, new Runnable() {
public void run() {
getplr(b.getText()).kickPlayer(jtf.getText());
b.setBackground(Color.RED);
}
});
}
}
});
jp.add(b);
System.out.println("Button added.");
}
f.setLayout(new BorderLayout());
f.add(jp, BorderLayout.CENTER);
f.setSize(500,500);
f.pack();
f.setVisible(true);
}

Adding a JScrollPane to an existing JPanel

I am trying to add a JScrollPane (createTeamScrollPane) to a JPanel (createTeamPanel) that I have. I have a frame, with a BorderLayout with the NORTH portion being used by a JPanel called tabMenu, and then the CENTER portion I would like my 'createTeamPanel' to have this scrolling ability as it will have more content than what I can fit on the screen at once. I am then adding both panels to the frame. Currently the code as is runs but the window appears blank. Once resizing the window, I then see the 3 buttons in the NORTH portion of my frame (why is this happening?) and when I click on 'Create Team' it brings up the list of JLabels and JButtons I expect but I don't see any scrolling bars?
public static void main (String args[]) {
JFrame frame = new JFrame();
frame.setTitle("v0.01");
frame.setSize(800, 800);
//frame.setLayout(null);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel mainPanel = new JPanel();
mainPanel.setLayout(new BorderLayout());
JPanel tabMenu = new JPanel();
JPanel createTeamPanel = new JPanel();
createTeamPanel.setLayout(new BoxLayout(createTeamPanel, BoxLayout.Y_AXIS));
createTeamPanel.setSize(800, 700);
createTeamPanel.setVisible(showCreateTeamPanel);
createTeamPanel.setBackground(Color.gray);
JScrollPane createTeamScrollPane = new JScrollPane(createTeamPanel);
createTeamScrollPane.setBounds(50, 50, 200, 500);
createTeamScrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
createTeamScrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
createTeamScrollPane.setPreferredSize(new Dimension(500,500));
//createTeamPanel.add(createTeamScrollPane);
List<Player> teamList = MockTeams.initTeam();
int xcoord = 100;
int ycoord = 50;
for(Player player : teamList) {
JLabel label = new JLabel(player.getName());
label.setBounds(xcoord, ycoord, Constants.buttonWidth, Constants.buttonHeight);
JButton addToTeamBtn = new JButton("Add to team");
addToTeamBtn.setBounds(xcoord + 100, ycoord, Constants.buttonWidth, Constants.buttonHeight);
addToTeamBtn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
myTeam.add(player);
addToTeamBtn.setEnabled(false);
}
});
createTeamPanel.add(label);
//createTeamFrame.add(label);
createTeamPanel.add(addToTeamBtn);
//createTeamFrame.add(addToTeamBtn);
ycoord += 50;
}
JButton createTeamBtn = new JButton("Create Team");
createTeamBtn.setBounds(0,0,150,20);
createTeamBtn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
//Hide/Show Create team panel
if (!showCreateTeamPanel) {
showCreateTeamPanel = true;
createTeamPanel.setVisible(showCreateTeamPanel);
} else {
showCreateTeamPanel = false;
createTeamPanel.setVisible(showCreateTeamPanel);
}
}
});
JButton manageTeamBtn = new JButton("Team Statistics");
manageTeamBtn.setBounds(100,150,150,40);
JButton resetBtn = new JButton("Reset Season");
resetBtn.setBounds(100,200,150,40);
tabMenu.add(createTeamBtn);
tabMenu.add(manageTeamBtn);
tabMenu.add(resetBtn);
mainPanel.add(tabMenu, BorderLayout.NORTH);
mainPanel.add(createTeamPanel, BorderLayout.CENTER);
frame.add(mainPanel);
}
Expected result is to see a scrolling ability on the createTeamPanel but it is not there.

Fixed: I was able to add the JScrollPane to the mainPanel with:
mainPanel.add(createTeamScrollPane, BorderLayout.CENTER);

JButton not responsive - have to click twice

I created a GUI using java swing and in a specific situation, the JButton is unresponsive and I have to click it twice. On the click, it takes the info in the textArea and sends it to a TextParser class to be parsed. If I type more stuff in the area after, and click the evaluateButton, it doesn't respond and I have to click it again to work. Does anyone know if this is a known bug or how I can fix this?
The code for the class is as follows.
/**
* Add the components to the GUI.
* #param pane - the pane for the GUI
*/
public static void addComponentsToPane(Container pane) {
pane.setLayout(new BorderLayout());
JPanel instructionsPanel = new JPanel();
JLabel instructions = new JLabel("Enter the email text below");
instructionsPanel.setBackground(Color.LIGHT_GRAY);
instructionsPanel.add(instructions);
pane.add(instructionsPanel, BorderLayout.NORTH);
JPanel textAreaPanel = new JPanel();
textAreaPanel.setBackground(Color.LIGHT_GRAY);
final JTextArea textArea = new JTextArea();
textArea.setBackground(Color.WHITE);
textArea.setMinimumSize(new Dimension(400,350));
textArea.setMaximumSize(new Dimension(400,350));
textArea.setPreferredSize(new Dimension(400,350));
textArea.setLineWrap(true);
Border border = BorderFactory.createLineBorder(Color.BLACK);
textArea.setBorder(border);
textArea.setMinimumSize(new Dimension(500, 200));
textArea.setFont(new Font("Serif", Font.PLAIN, 16));
textAreaPanel.add(textArea);
pane.add(textAreaPanel, BorderLayout.CENTER);
JPanel scoringPanel = new JPanel();
JButton evaluateButton = new JButton("Evaluate Email");
final JLabel scoreLabel = new JLabel("");
JButton uploadFileBtn = new JButton("Upload File");
JButton importTermsBtn = new JButton("Import Terms");
scoringPanel.add(evaluateButton);
scoringPanel.add(uploadFileBtn);
scoringPanel.add(importTermsBtn);
scoringPanel.add(scoreLabel);
pane.add(scoringPanel, BorderLayout.SOUTH);
evaluateButton.addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
try {
String email = textArea.getText();
TextParser textParser = new TextParser(email);
double score = textParser.parse();
scoreLabel.setText(score+"");
} catch (Exception ex) {
System.out.println(ex);
}
}
});
uploadFileBtn.addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
scoreLabel.setText("Feature not yet available.");
}
});
importTermsBtn.addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
DatabaseInput d = new DatabaseInput();
d.main(null);
}
});
}
/**
* Create the GUI and show it.
*/
private static void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("EmailGUI");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//frame.setLocationRelativeTo(null);
frame.setPreferredSize(new Dimension(500,500));
frame.setTitle("Email Text Input");
frame.setResizable(true);
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
frame.setSize(screenSize.width, screenSize.height);
//Set up the content pane.
addComponentsToPane(frame.getContentPane());
//Display the window.
frame.pack();
frame.setVisible(true);
}
My main method just calls createAndShowGUI(). I am new to StackOverflow so if I need to give more or less information in my post please let me know!

As Reimeus and Jason C said in the comments, I should have been using ActionListener which works perfectly.

Adding ActionListeners to JPanel

This questions has been asked a few times but mine is a little different. I created a small application and in the view I added a few JPanels to a JFrame. I then try to add actionListeners in the controller which is where the problem happened.
The code below gives me the following error:
The method addActionListener(new ActionListener(){})
is undefined for the type JPanel
The view class
public class MainMenuGUI {
JTabbedPane tabbedPane = new JTabbedPane();
JPanel findUserPanel;
JPanel deleteUserPanel;
JPanel addUserPanel;
JFrame frame = new JFrame();
JPanel tabbedPanel = new JPanel();
//Controller class for tabbedPanel
ControllerTabbedPane listen = new ControllerTabbedPane(this);
//Controller class for findUserPanel
FindUserPanelController findUserController = new FindUserPanelController(findUserPanel);
public MainMenuGUI() {
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(400, 400);
findUserPanel = createFindUserPanel();
deleteUserPanel = createDeleteUserPanel();
addUserPanel = createAddUserPanel();
tabbedPane.addTab("Find User", findUserPanel);
tabbedPane.addTab("Delete User", deleteUserPanel);
tabbedPane.addTab("Add User", addUserPanel);
tabbedPanel.add(tabbedPane);
frame.add(tabbedPanel);
frame.pack();
// opens frame in the center of the screen
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
JPanel createFindUserPanel() {
findUserPanel = new JPanel();
findUserPanel.setPreferredSize(new Dimension(300, 300));
findUserPanel.setLayout(new GridLayout(5, 7));
JLabel firstlbl = new JLabel("First Name");
JLabel lastlbl = new JLabel("Last Name");
JLabel addresslbl = new JLabel("Address");
JLabel agelbl = new JLabel("Age");
JTextField firstNametxt = new JTextField(15);
JTextField lastNametxt = new JTextField(15);
JTextField addresstxt = new JTextField(30);
JTextField age = new JTextField(3);
JButton btn = new JButton("Submit");
JScrollPane window = new JScrollPane();
window.setViewportBorder(new LineBorder(Color.RED));
window.setPreferredSize(new Dimension(150, 150));
findUserPanel.add(firstlbl);
findUserPanel.add(firstNametxt);
findUserPanel.add(lastlbl);
findUserPanel.add(lastNametxt);
findUserPanel.add(addresslbl);
findUserPanel.add(addresstxt);
findUserPanel.add(agelbl);
findUserPanel.add(age);
findUserPanel.add(window, BorderLayout.CENTER);
findUserPanel.add(btn);
return findUserPanel;
}
Controller Class
public class ControllerTabbedPane {
MainMenuGUI mainMenuGUI;
int currentTabbedIndex = 0;
ControllerTabbedPane(MainMenuGUI mainMenuGUI){
this.mainMenuGUI = mainMenuGUI;
addTabbedPaneListeners();
}
private void addTabbedPaneListeners() {
mainMenuGUI.tabbedPane.addChangeListener(new ChangeListener() {
#Override
public void stateChanged(ChangeEvent ce) {
currentTabbedIndex = mainMenuGUI.tabbedPane.getSelectedIndex();
System.out.println("Current tab is:" + currentTabbedIndex);
}
});
}
/*ERROR saying The method addActionListener(new ActionListener(){})
is undefined for the type JPanel*/
private void findPanelListeners() {
mainMenuGUI.findUserPanel.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
}
});
}

This is the way to achieve your request:
JPanel panel1 = new JPanel();
JPanel panel2 = new JPanel();
JButton bt1 = new JButton();
JButton bt2 = new JButton();
panel1.add(bt1);
panel2.add(bt2);
bt1.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println("Bt1 on panel1 pressed");
}
});
bt2.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println("Bt2 on panel2 pressed");
}
});
You can modify variables or other objects into the listeners to store which panel was "pressed".

I think its not possible to add addActionListner() to JPanel
Instead
You can use,
JPanel p1=new JPanel();
p1.addMouseListener(this);
And override
public void mouseClicked(MouseEvent me)
{
int x=me.getX();
int y=me.getY();
System.out.println(x+","+y);
//By using x AND y you can identify the panel
}
NB: extends MouseAdapter

Adding buttons below JTextArea

I am trying to add two buttons below the JTextArea using the Eclipse WindowBuilder, but I can't. I tried to change the layout, but I couldn't find a way to add buttons where I want and to re-size the JTextArea in an easy way.
public TestScrollPane03() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
JTextArea textArea = new JTextArea(100, 50);
JScrollPane scrollPane = new JScrollPane(textArea);
JFrame frame = new JFrame("Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(scrollPane);
frame.setSize(200, 200);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
How would I go about adding buttons below my original textArea?

You need to have two panels, one for your textArea, and one for your input (in this case buttons). I think something like this is what you are looking for:
public class Test
{
public static void createFrame()
{
EventQueue.invokeLater(new Runnable()
{
#Override
public void run()
{
JFrame frame = new JFrame("Test");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
JPanel panel = new JPanel();
panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
panel.setOpaque(true);
JTextArea textArea = new JTextArea(15, 50);
textArea.setWrapStyleWord(true);
textArea.setEditable(false);
textArea.setFont(Font.getFont(Font.SANS_SERIF));
JScrollPane scroller = new JScrollPane(textArea);
scroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
scroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
JPanel inputpanel = new JPanel();
inputpanel.setLayout(new FlowLayout());
JTextField input = new JTextField(20);
JButton button = new JButton("Enter");
DefaultCaret caret = (DefaultCaret) textArea.getCaret();
caret.setUpdatePolicy(DefaultCaret.ALWAYS_UPDATE);
panel.add(scroller);
inputpanel.add(input);
inputpanel.add(button);
panel.add(inputpanel);
frame.getContentPane().add(BorderLayout.CENTER, panel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
frame.setResizable(false);
input.requestFocus();
}
});
}
public static void main(String... args)
{
createFrame();
}
}
If you want your frame to look more like those of the OS you are running on, you can add .setLookAndFeel() before you make the frame visible:
try
{
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (Exception e) {
e.printStackTrace();
}
What adding the UIManager looks like (notably a bit smaller):