We Keep Coding

Background color not changing JFrame

I need help on Java Swing for GUI. I have included frame.getcontentpane().setBackground(color.cyan); to the code but frame background color doesn't change.
import javax.swing.*;
import java.awt.*;
public class LoginOne {
private static JLabel lblUsr;
private static JButton btnNext;
private static JTextField txtUsr;
private static JFrame frame;
private static JPanel panel;
public static void main(String[] args) {
frame = new JFrame("Home Page");
frame.setSize(800,600);
frame.getContentPane().setBackground(Color.cyan);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
panel = new JPanel();
frame.add(panel);
panel.setLayout(null);
lblUsr = new JLabel("Username"); //Username Label
lblUsr.setBounds(10,20,80,25);
panel.add(lblUsr);
txtUsr = new JTextField(20); //Username input field
txtUsr.setBounds(80,20,80,25);
panel.add(txtUsr);
btnNext = new JButton("Next");
btnNext.setBounds(80,90,80,25);
panel.add(btnNext);
frame.setVisible(true);
}
}

Use panel.setBackground(Color.CYAN); instead.

How to make button in one class affect text area in another?

Please help me to understand how this works. I'm having difficulties to understand how, for example, JButton in one class can alter text in JTextArea that is in another class of a same package. I've made a simple app just to ask a question here, I need this for a bigger school project where I need to implement this to work with multiple classes.
When I put everything in the same class it works but I need it in separate classes.
Here is the simple code.
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
class Button extends JPanel {
private JButton button;
private Panel panel;
public Button() {
button = new JButton("BUTTON");
panel = new Panel();
add(button);
button.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
JButton clicked = (JButton) e.getSource();
String input = clicked.getText();
panel.setTextArea(input);
//System.out.println(input);
}
});
}
}
class Panel extends JPanel {
private JTextArea textArea;
public Panel() {
setLayout(new BorderLayout());
textArea = new JTextArea();
add(textArea, BorderLayout.CENTER);
}
public JTextArea getTextArea() {
return textArea;
}
void setTextArea(String text) {
this.textArea.setText(text);
}
}
public class Java extends JFrame {
private Button dugme;
private JFrame frame;
private Panel panel;
public Java() {
frame = new JFrame();
dugme = new Button();
panel = new Panel();
//super("test");
frame.setLayout(new BorderLayout());
frame.setTitle("test");
frame.setSize(300, 400);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
frame.add(dugme, BorderLayout.NORTH);
frame.add(panel, BorderLayout.CENTER);
}
public static void main(String[] args) {
Java app = new Java();
}
}
I want action listener to alter the text in the panel, sys-out works so the listener listens the button but I can't make it to alter the text in text area.

As already mentioned by #XtremeBaumer you have two different instances of Panel class. You need to remove the secode one.
public class Button extends JPanel {
private JButton button;
private Panel panel;
public Button(Panel panel) { // we need already created instance of panel here.
this.panel = panel;
button = new JButton("BUTTON");
// panel = new Panel(); <-- this line must be deleted.
// ...
}
}
public class Java extends JFrame {
private Button dugme;
private JFrame frame;
private Panel panel;
public Java(){
frame = new JFrame();
panel = new Panel();
dugme = new Button(panel);
// ...
}
}
Please also replace the line
add(textArea, BorderLayout.CENTER);
by
add(new JScrollPane(textArea), BorderLayout.CENTER);
This allows you to get the scrool bars when text goes larger than the text ara size.
Here is your reworked example
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
class Button extends JPanel {
private JButton button;
private Panel panel;
public Button(Panel panel) {
this.panel = panel;
button = new JButton("BUTTON");
add(button);
button.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
JButton clicked = (JButton) e.getSource();
String input = clicked.getText();
panel.setTextArea(input);
//System.out.println(input);
}
});
}
}
class Panel extends JPanel {
private JTextArea textArea;
public Panel() {
setLayout(new BorderLayout());
textArea = new JTextArea();
add(new JScrollPane(textArea), BorderLayout.CENTER);
}
public JTextArea getTextArea() {
return textArea;
}
void setTextArea(String text) {
this.textArea.setText(text);
}
}
public class Java extends JFrame {
private Button dugme;
private JFrame frame;
private Panel panel;
public Java() {
frame = new JFrame();
panel = new Panel();
dugme = new Button(panel);
//super("test");
frame.setLayout(new BorderLayout());
frame.setTitle("test");
frame.setSize(300, 400);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
frame.add(dugme, BorderLayout.NORTH);
frame.add(panel, BorderLayout.CENTER);
}
public static void main(String[] args) {
Java app = new Java();
}
}

Trying to use GUI, having trouble adding buttons and labels

The assignment is simple, all we need to do is have the code create a window with a red panel with a single button and label. Here is the code thus far as well as the tester class.
I got the label to display on the window, but its in a weird place. I cant get the button to display at all as well getting the background to display as red.
This is where I'm having trouble with the most:
import java.awt.Color;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class MyCustomFrame extends JFrame
{
public MyCustomFrame()
{
createComponents();
setSize(FRAME_WIDTH, FRAME_HEIGHT);
}
private void createComponents()
{
JPanel panel=new createPanel();
button=new JButton("Push Me");
label=new JLabel("This is a label");
add(button);
add(label);
}
private JButton button;
private JLabel label;
final int FRAME_WIDTH = 800;
final int FRAME_HEIGHT = 800;
public void createPanel()
{
JPanel panel=new JPanel();
panel.setBackground(Color.RED);
//button=new JButton("Push Me");
//label=new JLabel("This is a label");
}
public void createFrame()
{
JFrame frame=new JFrame();
add(frame);
frame.setVisible(true);
}
}
And this is the tester class:
import javax.swing.JFrame;
public class MyCustomFrameViewer
{
public static void main(String[] args)
{
MyCustomFrame frame = new MyCustomFrame();
frame.setTitle("My first frame");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}

You create the JPanel, panel, but add nothing to it, and then never add the panel to your JFrame. You should add your components to the JPanel, panel, and then add the panel object to your JFrame.
Note that a JPanel uses FlowLayout by default, and so it will more easily accept multiple other components without special add methods. The JFrame's contentPane uses BorderLayout which is slightly more complicated to use.

Add the panel to the frame instead of the label and button, and add the label and button to the panel...
private void createComponents()
{
JPanel panel=new createPanel();
add(panel);
button=new JButton("Push Me");
label=new JLabel("This is a label");
panel.add(button);
panel.add(label);
}
You may also want to take a look at Initial Threads and make sure you are creating your UI from within the context of the Event Dispatching Thread
Some side notes...
This scares me...
public void createFrame()
{
JFrame frame=new JFrame();
add(frame);
frame.setVisible(true);
}
You're trying to add a frame to a frame, which is an illegal operation in Swing, but thankfully, you're not actually calling it from what I can see.
Instead of using setSize(FRAME_WIDTH, FRAME_HEIGHT);, you may wish to use pack instead.

See also the tips in comments in this example:
import java.awt.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
// Don't extend frame, just use an instance
//public class MyCustomFrame extends JFrame {
public class MyCustomFrame {
private JFrame frame;
private JButton button;
private JLabel label;
private JPanel panel;
// better to override the preferred size of the component of interest
final int GAME_WIDTH = 300;
final int GAME_HEIGHT = 100;
public MyCustomFrame() {
createComponents();
// better to override the preferred size of the component of interest
//setSize(GAME_WIDTH, GAME_HEIGHT);
}
private void createComponents() {
// compilation error! createPanel() does not return anything..
//JPanel panel = new createPanel();
createPanel();
// create the frame!
createFrame();
}
private void createPanel() {
// creates a local instance
//JPanel panel = new JPanel();
panel = new JPanel() {
/* override the preferred size of the component of interest */
#Override
public Dimension getPreferredSize() {
return new Dimension(GAME_WIDTH, GAME_HEIGHT);
}
};
panel.setBackground(Color.RED);
button = new JButton("Push Me");
label = new JLabel("This is a label");
panel.add(button);
panel.add(label);
}
private void createFrame() {
// create a local instance of a JFrame that goes out of scope at end
// of method..
//JFrame frame = new JFrame();
frame = new JFrame("My first frame");
// add the panel to the frame!
frame.add(panel);
// better to use DISPOSE_ON_CLOSE
//frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
// a good way to position a GUI
frame.setLocationByPlatform(true);
// this was trying to add a JFrame to another JFrame
//add(frame);
frame.pack();
}
public final JFrame getFrame() {
return frame;
}
public static void main(String[] args) {
Runnable r = new Runnable() {
#Override
public void run() {
MyCustomFrame myFrame = new MyCustomFrame();
JFrame frame = myFrame.getFrame();
frame.setVisible(true);
}
};
// Swing GUIs should be created and updated on the EDT
// http://docs.oracle.com/javase/tutorial/uiswing/concurrency
SwingUtilities.invokeLater(r);
}
}

JButtons not appearing on my JFrame

I am making a program that includes a GUI. For some reason, the JButton objects that I have created are not showing up onto my JFrame when I run the program. Here is the code:
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class ReverseAStringMain extends JPanel {
private JButton enterButton, exitButton;
private JTextField textField;
private JPanel buttonPanel;
private JTextArea textArea;
public ReverseAStringMain(){
JButton enterButton = new JButton("Enter");
JButton exitButton = new JButton("Exit");
enterButton.setPreferredSize(new Dimension(60,60));
exitButton.setPreferredSize(new Dimension(60,60));
ButtonListener listener = new ButtonListener();
enterButton.addActionListener(listener);
exitButton.addActionListener(listener);
buttonPanel = new JPanel();
buttonPanel.setPreferredSize(new Dimension(200,50));
buttonPanel.setBackground(Color.black);
buttonPanel.add(enterButton);
buttonPanel.add(exitButton);
textField = new JTextField();
textField.setSize(200, 100);
textArea = new JTextArea();
textArea.add(textField);
add(buttonPanel);
add(textField);
}
//Creating a ButtonListener class that implements the ActionListener interface
private class ButtonListener implements ActionListener{
#Override
//Overriding the ActionPerformed method of ActionListener
public void actionPerformed(ActionEvent action) {
if(action.getSource()== enterButton)
enterButton();
if(action.getSource()== exitButton)
System.exit(0);
}
}
private void enterButton() {
// TODO Auto-generated method stub
}
public static void main (String[] args){
JFrame frame = new JFrame("Raj's Reverse a String Program");
frame.setBackground(Color.white);
frame.setVisible(true);
frame.setResizable(false);
frame.setLocationRelativeTo(null);
frame.setSize(new Dimension(600,600));
//frame.pack();
frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new ReverseAStringMain());
}
}
If there are any problems or improvements I can make in my code, please let me know!

You're adding the components to your JFrame after it's visible. You should either add them to the JFrame before it's visible, or revalidate the JFrame after you add the components.

When I load your code (after making it a lot shorter in height), this is what I see:
I suspect this is more along the lines of what you expect to see.
Here is how I did it. Look carefully at:
The numbers provided to the BorderLayout constructor for white space between the panels.
The EmptyBorder for white space around the controls.
The use of pack() to shrink the GUI to the natural size.
The use of size hints in the construction of the text field and text area.
The use of a second layout - commonly known as a combined, or nested, layout.
import java.awt.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
public class ReverseAStringMain extends JPanel {
private JButton enterButton, exitButton;
private JTextField textField;
private JPanel pageTopPanel;
private JTextArea textArea;
public ReverseAStringMain(){
super(new BorderLayout(10,10));
setBorder(new EmptyBorder(5,15,5,15));
JButton enterButton = new JButton("Enter");
JButton exitButton = new JButton("Exit");
pageTopPanel = new JPanel(new FlowLayout(FlowLayout.CENTER));
pageTopPanel.setBackground(Color.black);
pageTopPanel.add(enterButton);
pageTopPanel.add(exitButton);
textField = new JTextField(5);
pageTopPanel.add(textField);
textArea = new JTextArea(4,40);
add(pageTopPanel, BorderLayout.PAGE_START);
add(textArea); // defaults to CENTER
}
public static void main (String[] args){
Runnable r = new Runnable() {
public void run() {
JFrame frame = new JFrame("XXX's Laid out Program");
frame.setBackground(Color.white);
frame.setResizable(false);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new ReverseAStringMain());
frame.pack();
frame.setVisible(true);
}
};
SwingUtilities.invokeLater(r);
}
}
General Tips
Java GUIs might have to work on a number of platforms, on different screen resolutions & using different PLAFs. As such they are not conducive to exact placement of components. To organize the components for a robust GUI, instead use layout managers, or combinations of them1, along with layout padding & borders for white space2.

Generally, you want to set the frame visible After adding components
JFrame frame = new JFrame("Raj's Reverse a String Program");
frame.setBackground(Color.white);
frame.setResizable(false);
frame.setLocationRelativeTo(null);
frame.setSize(new Dimension(600,600));
//frame.pack();
frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(new ReverseAStringMain());
frame.setVisible(true); <<------
Also, it is better practice to use .pack() insteack of .setSize(), so you had it right in the commented out //.pack()
If you wanted to set a size to the panel, you would override the getPreferredSize() like this
public Dimension getPreferredSize() {
return new Dimension(300, 300); // or whatever size you want
}
When you .pack(), this preferred size will be respected by the frame.
Also, not, setting the size of the JTextField won't work. What you want to do is pass it an integer value for the number of character spaces, like this
textField = new JTextField(20);
See an edited version of your program, with all the above mentioned points. One thing I also did was get rid of all your .setPreferredSizes. You will see the difference
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class ReverseAStringMain extends JPanel {
private JButton enterButton, exitButton;
private JTextField textField;
private JPanel buttonPanel;
private JTextArea textArea;
public ReverseAStringMain() {
JButton enterButton = new JButton("Enter");
JButton exitButton = new JButton("Exit");
//enterButton.setPreferredSize(new Dimension(60, 60));
//exitButton.setPreferredSize(new Dimension(60, 60));
ButtonListener listener = new ButtonListener();
enterButton.addActionListener(listener);
exitButton.addActionListener(listener);
buttonPanel = new JPanel();
//buttonPanel.setPreferredSize(new Dimension(200, 50));
buttonPanel.setBackground(Color.black);
buttonPanel.add(enterButton);
buttonPanel.add(exitButton);
textField = new JTextField(20);
//textField.setSize(200, 100); /// <<-----------
textArea = new JTextArea();
textArea.add(textField);
add(buttonPanel);
add(textField);
}
public Dimension getPreferredSize() {
return new Dimension(600, 600);
}
// Creating a ButtonListener class that implements the ActionListener
// interface
private class ButtonListener implements ActionListener {
#Override
// Overriding the ActionPerformed method of ActionListener
public void actionPerformed(ActionEvent action) {
if (action.getSource() == enterButton)
enterButton();
if (action.getSource() == exitButton)
System.exit(0);
}
}
private void enterButton() {
// TODO Auto-generated method stub
}
public static void main(String[] args) {
JFrame frame = new JFrame("Raj's Reverse a String Program");
frame.setBackground(Color.white);
frame.getContentPane().add(new ReverseAStringMain());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}
Have a look at the Swing tutorial trail for more information on creating GUIs with Swing.

Try to add the buttonPanel to a Container, like this. And extend JFrame instead
Container contentpane = getContentPane();
contentPane.add(buttonPanel);

TitledBorder around JTextField

In java, when I use a TitledBorder around a JTextField, part of the JTextField spills over the TitledBorder in all directions. Is there a way to prevent this?

If you replace the border of the textfield with a TitledBorder you lose the natural border of the field. The solution is to create a CompoundBorderthat combines the TitledBorder with the border of the field:
JTextField field = new JTextField(10);
field.setBorder(new CompoundBorder(BorderFactory.createTitledBorder("Title"), field.getBorder()));
However the TitledBorder still inherits the background color of the textfield.
Another solution is to embed the textfield in a JPanel and put the TitledBorder on the panel:
JTextField field = new JTextField(10);
JPanel borderPanel = new JPanel();
borderPanel.setBorder(BorderFactory.createTitledBorder("Title"));
borderPanel.add(field);

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class AA
{
public static void main(String[] args)
{
FrameCreator Frame= new FrameCreator();
Frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Frame.setVisible(true);
}
}
class FrameCreator extends JFrame
{
public FrameCreator()
{
int height=100;
int width=300;
setSize(width,height);
setLocation(0,0);
setTitle("TextField example");
showPanel=new JPanel();
textFieldPanel=new JPanel();
label=new JLabel("Sentence");
label.setFont(new Font("Serif",Font.PLAIN,12));
showPanel.add(label);
add(showPanel, BorderLayout.CENTER);
textfield=new JTextField("Sentence", 20);
textfield.setBorder(BorderFactory.createTitledBorder("Name"));
textfield.addActionListener(
new ActionListener()
{
public void actionPerformed(ActionEvent evento1)
{
String sentence=textfield.getText();
label.setText(sentence);
}
});
textFieldPanel.add(textfield);
add(textFieldPanel, BorderLayout.SOUTH);
}
JLabel label;
JPanel showPanel, textFieldPanel;
String sentence;
JTextField textfield;
}
I have used textfield.setBorder(BorderFactory.createTitledBorder("Name"));