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OK button and String not showing up on JPanel

I am trying to make a panel showing a printed statement "Hello World!" and an OK button. Neither will show up on the panel and I have no idea why. I started with a block of code that was supposed to create just a blank popup. The blank popup worked great. I can't add the string or button and see them. I have tried calling paintComponent. I have tried adding the content to the panel. Does anyone know what I am missing?
Here is my code
package painting;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class SwingPaintDemo1 {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
private static class SwingPaintDemo extends JPanel{
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawString("Hello World!", 20,30);
}
}
private static void createAndShowGUI() {
System.out.println("Created GUI on EDT? "+
SwingUtilities.isEventDispatchThread());
JFrame f = new JFrame("Swing Paint Demo");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setSize(250,250);
f.setVisible(true);
JButton okbutton = new JButton("OK");
ButtonHandler listener = new ButtonHandler();
okbutton.addActionListener(listener);
SwingPaintDemo displayPanel = new SwingPaintDemo();
JPanel content = new JPanel();
content.setLayout(new BorderLayout());
content.add(displayPanel, BorderLayout.CENTER);
content.add(okbutton, BorderLayout.SOUTH);
}
private static class ButtonHandler implements ActionListener{
public void actionPerformed(ActionEvent e) {
System.exit(0);
}
}
}

You forgot to add the JPanel to the JFrame. Just add the following line at the bottom of your createAndShowGUI() method:
f.add(content);
I would also recommend moving your f.setVisible(true); line to the bottom of the method just to be safe. When you make the frame visible, the component tree is set up to take into account all the components added to the JFrame. If you add more components after that, you will need to do either manually revalidate the tree or do something that triggers an automatic revalidation. I'm assuming you're not revalidating your tree anywhere, so you should move f.setVisible(true); to after all the components are added.

Multiple Buttons doing something

I am still learning how to code in java and I could use a bit of help right now.
This is the current code I wrote. As you can see, it's a simple panel with a bunch of buttons and a slider. I want to make a different console output whenever I hit a different button. So if I hit Back, it's supposed to write Back in the console. If I scroll a bit on the slider, it's supposed to write the new value in the console. Stuff like that. I know it has to be done with actionListener and actionPerformed but after some experimenting I couldn't get it to work.
import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Gui implements ActionListener {
// Adding all the goods
JFrame frame;
JPanel panel;
JButton endButton;
JButton backButton;
JButton calcButton;
JSlider maxIterations;
JLabel view;
Gui() {
// General
this.frame = new JFrame("Trying my best, I swear");
this.frame.setSize(500, 500);
this.frame.setVisible(true);
this.panel = new JPanel();
// Buttons
this.backButton = new JButton("Back");
this.calcButton = new JButton("Calc");
this.endButton = new JButton("End");
this.panel.add(this.endButton);
this.panel.add(this.calcButton);
this.panel.add(this.backButton);
this.frame.add(this.panel);
// Label
JLabel label1 = new JLabel();
label1.setText("Space Holer");
panel.add(label1);
// Slider
JSlider slider = new JSlider(JSlider.HORIZONTAL, 0, 30, 15);
panel.add(slider);
slider.setMinorTickSpacing(2);
slider.setMajorTickSpacing(5);
slider.setPaintTicks(true);
slider.setPaintLabels(true);
// Make the buttons do something
this.endButton.addActionListener(this);
}
public void actionPerformed(ActionEvent ae) {
System.out.println("End");
}
public static void main(String[] args) {
#SuppressWarnings("unused")
Gui m = new Gui();
}
}

You could...
Take advantage of the actionCommand property of the button, which is set to the ActionEvent when it's created. If you don't supply an actionCommand to the button yourself, it will default to the text value, so you could do something like
public class ButtonActionHandler implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
switch (e.getActionCommand()) {
case "Back":
System.out.println("Back");
break;
case "Calc":
System.out.println("Calc");
break;
case "End":
System.out.println("End");
break;
}
}
}
This is good if the ActionListener is external to the class where the buttons are defined, because you won't have access to the button references. It's also good, because you could have a number of buttons (including toolbar buttons and menu items) which do the same thing
You could...
Make use of the ActionListener's source property
public class ButtonActionHandler implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
if (e.getSource() == backButton) {
System.out.println("Back");
} else if (e.getSource() == calcButton) {
System.out.println("Calc");
} else if (e.getSource() == endButton) {
System.out.println("End");
}
}
}
This is useful if the ActionListener in defined as a inner class to the parent class from where the buttons are defined
You could...
Use an anonymous class registered directly against the button...
endButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println("End");
}
});
This is good where the button does a single, isolated task
You could...
Make use of the Action API which allows you to define a self contained unit of work, which can be used by buttons to configure themselves completely from it. This is useful where you have a repeated action which can be executed from different locations of the UI, like a "open file" action contained in the menu bar, tool bar and some wizard. You can even use it with the key bindings API for extended functionality
See How to use actions for more details

Need to add ActionListener to all buttons,
calcButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println("calcButton");
// calculation for slider.
}
});
backButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println("backButton");
}
});
then u get the different console output.

Call setVisible on jframe after you placed all components into it.
Add ActionListener to each button. Add ChangeListener to slider as it cannot have ActionListener.
See full code:
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSlider;
public class Gui implements ActionListener {
// Adding all the goods
JFrame frame;
JPanel panel;
JButton endButton;
JButton backButton;
JButton calcButton;
JSlider maxIterations;
JLabel view;
Gui() {
// General
this.frame = new JFrame("Trying my best, I swear");
this.frame.setSize(500, 500);
this.panel = new JPanel();
// Buttons
this.backButton = new JButton("Back");
this.calcButton = new JButton("Calc");
this.endButton = new JButton("End");
this.panel.add(this.endButton);
this.panel.add(this.calcButton);
this.panel.add(this.backButton);
this.frame.add(this.panel);
// Label
JLabel label1 = new JLabel();
label1.setText("Space Holer");
panel.add(label1);
// Slider
JSlider slider = new JSlider(JSlider.HORIZONTAL, 0, 30, 15);
panel.add(slider);
slider.setMinorTickSpacing(2);
slider.setMajorTickSpacing(5);
slider.setPaintTicks(true);
slider.setPaintLabels(true);
// Make the buttons do something
this.endButton.addActionListener(this);
this.backButton.addActionListener(this);
this.calcButton.addActionListener(this);
slider.addChangeListener(e -> {
Object source = e.getSource();
if (source instanceof JSlider) {
int value = ((JSlider) source).getValue();
System.out.println(value);
}
});
frame.pack();
this.frame.setVisible(true);
}
public void actionPerformed(ActionEvent ae) {
Object source = ae.getSource();
if (source instanceof JButton) {
String text = ((JButton) source).getText();
System.out.println(text);
}
}
public static void main(String[] args) {
#SuppressWarnings("unused")
Gui m = new Gui();
}
}

No idea how to run the graphics depending on a radio button?

So I have 1 class, with a radio button and 1 class, that will create an applet depending on the outcome of the Radio Button. I don't know how to make the graphics run depending on an if/else statement. All help will be greatly appreciated.
Radio Button Class:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class RadioButton extends JPanel {
static JFrame frame;
JLabel pic;
RadioListener myListener = null;
protected JRadioButton displacement;
protected JRadioButton accel;
protected JRadioButton time;
public RadioButton() {
// Create the radio buttons
displacement = new JRadioButton("Displacement");
displacement.setMnemonic(KeyEvent.VK_N);
displacement.setSelected(true);
//Displacement Button, set to automatically be clicked
accel = new JRadioButton("Acceleration");
accel.setMnemonic(KeyEvent.VK_A);
accel.setActionCommand("acceleration");
//Acceleration Button
time = new JRadioButton("Change in time");
time.setMnemonic(KeyEvent.VK_S);
time.setActionCommand("deltaT");
//The change in time button
// Creates the group of buttons
ButtonGroup group = new ButtonGroup();
group.add(displacement);
group.add(accel);
group.add(time);
myListener = new RadioListener();
displacement.addActionListener(myListener);
accel.addActionListener(myListener);
time.addActionListener(myListener);
// Set up the picture label
pic = new JLabel(new ImageIcon(""+"numbers" + ".jpg")); //Set the Default Image
pic.setPreferredSize(new Dimension(177, 122));
// Puts the radio buttons down
JPanel panel = new JPanel();
panel.setLayout(new GridLayout(0, 1));
panel.add(displacement);
panel.add(accel);
panel.add(time);
setLayout(new BorderLayout());
add(panel, BorderLayout.WEST);
add(pic, BorderLayout.CENTER);
setBorder(BorderFactory.createEmptyBorder(40,40,40,40));
}
//Listening to the buttons
class RadioListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
pic.setIcon(new ImageIcon(""+e.getActionCommand()
+ ".jpg"));
}
}
public static void main(String s[]) {
frame = new JFrame("∆x = Vavg * time");
frame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {System.exit(0);}
});
frame.getContentPane().add(new RadioButton(), BorderLayout.CENTER);
frame.pack();
frame.setVisible(true);
}
}
If/Else Statements class:
import java.lang.Object;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.*;
public class RadioButtonMain extends RadioButton {
public static void main(String [ ] args) {
new RadioButtonMain().doMain();
}
public void doMain() {
if ( displacement.isSelected()) {
//option 1 for applet
}
if ( accel.isSelected()) {
//Option 2 for applet
}
else {
//Option 3 for applet
}
}
}
How would I get the graphics to run based on whether or not the variables accel and displacement are pressed? Thanks.

Remember, a GUI is an event driven environment, things don't run within a linear manner. Instead of trying run a method yourself, you need to use a callback or listener of some kind which will tell you when the state of the program/buttons change...
When the JRadioButton actionPerformed event is raised, you need to call another method which provides information about what has occurred. You can then override these methods in your RadioButtonMain class and take action when they are called
This is very similar to an Observer Pattern

Opening a textpane in the same form on a Button click

I am trying to design a basic editor type of GUI in Java using Swing. I have a menu item named New clicking on which I want a blank text area to fill up the GUI. My code is as folows :
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class UI extends JFrame {
private JMenuBar bar;
private JMenu menu;
private JMenuItem item;
private JTextPane tp;
public UI() {
setLayout(new FlowLayout());
bar = new JMenuBar();
setJMenuBar(bar);
menu = new JMenu("File");
bar.add(menu);
item = new JMenuItem("New");
menu.add(item);
item.addActionListener(new xyz());
}
public class xyz implements ActionListener {
public void actionPerformed(ActionEvent arg0) {
JTextPane tp = new JTextPane();
add(tp);
}
}
public static void main(String args[]) {
// do the rest of the stuffs
}
}
However, even on clicking on the New, I do not get the textPane on the same frame. Can someone please explain.

use JTextPane#setText("") instead of to create a new JTextPane
otherwise you have to notify Container with (re)validate() and repaint()

The text-panes should probably be added to a JTabbedPane if this app. supports multiple documents. If it is intended for 'single document', put the text pane onto the frame at start-up.

Internal JFrames

I want to know how to show an internal frame in swing. That means,when a JFrame is needed, normally what I do is,
new MyJFrame().setVisible(true);
Let's say the previous form should be displayed as well. And when this new frame is displayed,another new icon is displayed on the task bar.(it sounds like two separate applications run in one application) I want to avoid showing that icon and display both frames as they are in one application. Thank you

..want to avoid showing that icon and display both frames as they are in one application.
Another solution is to put the 2nd and subsequent free floating elements in a JDialog.
E.G. of using both a frame and dialog to hold extra content.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class FrameTest {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
initGui();
}
});
}
public static void initGui() {
final JFrame f = new JFrame("Frame Test");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel gui = new JPanel(new GridLayout(0,1,5,5));
final Content c = new Content();
JButton frame = new JButton("Frame");
frame.addActionListener( new ActionListener() {
public void actionPerformed(ActionEvent ae) {
JFrame f2 = new JFrame("Content");
f2.add(c.getContent());
f2.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
f2.pack();
f2.setLocationByPlatform(true);
f2.setVisible(true);
}
});
gui.add(frame);
JButton dialog = new JButton("Dialog");
dialog.addActionListener( new ActionListener() {
public void actionPerformed(ActionEvent ae) {
JDialog d = new JDialog(f);
d.add(new Content().getContent());
d.pack();
d.setLocationByPlatform(true);
d.setVisible(true);
}
});
gui.add(dialog);
f.add(gui);
f.pack();
f.setVisible(true);
}
}
class Content {
public Component getContent() {
JPanel p = new JPanel();
p.add(new JLabel("Hello World!"));
return p;
}
}

You have one JFrame for an application.
You can display multiple JPanels within a JFrame.
Or, as trashgod pointed out, you can have multiple JInternalFrames within a JDesktopFrame.