Question

I am very new to Java AWT. My question header must seem ridiculous to you, sorry about that. In my application I have three buttons which display different threads when clicked on. Now I want to add maybe a button or checkboxes or choicelist, etc when clicked on a particular button. For eg, if I click on yes button, it should display a choice list, something like that. How do I achieve something like that? Here is my code so far:

import java.awt.Button;

import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;


public class AppWindow extends Frame implements ActionListener{
    String keymsg = "Test message";
    String mousemsg = "Nothing";
    int mouseX=30, mouseY=30;
    String msg;
    public AppWindow(){
        //addKeyListener(new MyKeyAdapter(this));
        //addMouseListener(new MyMouseAdapter(this));
        addWindowListener(new MyWindowAdapter());
    }

    public void paint(Graphics g){
        g.drawString(msg, 150, 100);
    }

    //Here the window is created:

    public static void main(String args[]){
        AppWindow appwin = new AppWindow();

        appwin.setSize(new Dimension(300,200));
        appwin.setTitle("My first AWT Application");
        appwin.setLayout(new FlowLayout(FlowLayout.LEFT));
        appwin.setVisible(true);

        Button yes,no,maybe;
        yes = new Button("yes");
        no = new Button("no");
        maybe = new Button("maybe");

        appwin.add(yes);
        appwin.add(no);
        appwin.add(maybe);

        yes.addActionListener(appwin);
        no.addActionListener(appwin);
        maybe.addActionListener(appwin);


    }

    @Override
    public void actionPerformed(ActionEvent ae) {
        // TODO Auto-generated method stub
        String str = ae.getActionCommand();
        if(str.equals("yes")){
            msg = "You pressed Yes";
        }
        if(str.equals("no")){
            msg = "You pressed No";
        }
        if(str.equals("maybe")){
            msg = "You pressed Maybe";
        }

        repaint();
    }


}


class MyWindowAdapter extends WindowAdapter {
    public void windowClosing(WindowEvent we){
        System.exit(0);
    }
}

Answer 1

Points describing what you should be doing :

• As already mentioned by others, better to use Swing over AWT, since Swing is more advanced.
• As much as possible, always try to Paint on top of a JPanel or a
  JComponent, instead of Painting right on top of your JFrame, by
  overriding the paintComponent(Graphics g) method of the said
  JComponent/JPanel
• Never call setVisible(true) on the JFrame until and unless it’s
  size has been established. So in general terms, this has to be the
  last call, once you are done adding components to the JFrame and
  the size of the JFrame has been realized by the LayoutManager.
• Inside your actionPerformed(...), instead of writing all if
statement blocks, you should adhere to the if-else if statement
blocks. The benefit of this, over the former is that, at any given
  time, only one event will be fired, hence once the said condition is
  satisfied, you don’t want your code to keep checking other
  conditions, which in general is really not a good programming
  practice, IMHO.
• MOST IMPORTANT THING : Never make calls like pack()/setVisible(…) from within the main method, such calls belong
  to the Event Dispatch Thread, and must be done on the same. Please
  read Concurrency in Swing for more detail.

Have a look at the example program, for better understanding.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class ComponentExample
{
    private CustomPanel drawingBoard;
    private JPanel contentPane;
    private JButton yesButton;
    private JButton noButton;
    private JButton maybeButton;
    private JComboBox cbox;
    private ActionListener buttonAction = new ActionListener()
    {
        @Override
        public void actionPerformed(ActionEvent ae)
        {
            JButton button = (JButton) ae.getSource();

            if (cbox.isShowing())
                    contentPane.remove(cbox);

            if (button == yesButton)
            {
                drawingBoard.setText("You Pressed YES.");           
                contentPane.add(cbox, BorderLayout.PAGE_END);               
            }
            else if (button == noButton)
                drawingBoard.setText("You Pressed NO.");
            else if (button == maybeButton)
                drawingBoard.setText("You Pressed MAYBE.");             

            /*
             * revalidate()/repaint() is needed
             * when the JComponent is added or
             * removed from the already 
             * visible Container.
             */
            contentPane.revalidate();
            contentPane.repaint();
        }
    };

    public ComponentExample()
    {
        cbox = new JComboBox(
                    new String[]{"I GOT IT"
                               , "I STILL HAD DOUBT"});
    }

    private void displayGUI()
    {
        JFrame frame = new JFrame("Component Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        contentPane = new JPanel();
        contentPane.setOpaque(true);
        contentPane.setBackground(Color.DARK_GRAY);
        contentPane.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
        contentPane.setLayout(new BorderLayout(5, 5));

        JPanel buttonPanel = new JPanel();
        buttonPanel.setOpaque(true);
        buttonPanel.setBackground(Color.WHITE);

        yesButton = new JButton("YES");
        yesButton.addActionListener(buttonAction);
        noButton = new JButton("NO");
        noButton.addActionListener(buttonAction);
        maybeButton = new JButton("MAY BE");
        maybeButton.addActionListener(buttonAction);
        buttonPanel.add(yesButton);
        buttonPanel.add(noButton);
        buttonPanel.add(maybeButton);

        contentPane.add(buttonPanel, BorderLayout.PAGE_START);

        drawingBoard = new CustomPanel();
        contentPane.add(drawingBoard, BorderLayout.CENTER);

        frame.setContentPane(contentPane);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String... args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            public void run()
            {
                new ComponentExample().displayGUI();
            }
        });
    }
}

class CustomPanel extends JPanel
{
    private String msg;

    public CustomPanel()
    {
        msg = "";
        setOpaque(true);
        setBackground(Color.WHITE);
    }

    public void setText(String msg)
    {
        this.msg = msg;
        repaint();
    }

    @Override
    public Dimension getPreferredSize()
    {
        return (new Dimension(300, 300));
    }

    @Override
    protected void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        g.drawString(msg, getWidth() / 3, getHeight() / 3);
    }
}