How do i remove an object frame jframe then add another (with code)

Question

I have written a program that paints 5 pictures onto a canvas in jframe. I have now added a jtextfield so that the user can input a number using an actionlistener.

Ideally, the number that the user enters should then produce that amount of pictures on a new canvas.

problem is, i cant remove the canvas object and add a new canvas with the new amount of pictures on it.

please help

public class TaxiFrame extends JFrame implements ActionListener {


      private JLabel L1 = new JLabel("Number of Taxis:");
      private JLabel L2 = new JLabel("Type an integer and press enter");
      private JTextField t1 = new JTextField ("            ");


    public TaxiFrame() {
        super("This is the Frame");
        setSize(600, 400);
        getContentPane().setBackground(Color.CYAN);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setLayout(new BorderLayout(10, 10));

        Random rx = new Random();
        Random ry = new Random();

        for(int i = 0; i < 5; i ++)

        {
            TaxiCanvas tax = new TaxiCanvas();
            tax.setBounds(rx.nextInt(600 - 100), ry.nextInt(400 - 100), 100, 100);
            add(tax);

        }


        JPanel p = new JPanel();     


         p.setOpaque(false);
         p.add(L1);
         getContentPane().
         add("South", p);

          p.setOpaque(false);
          p.add(t1);
          getContentPane().
          add("South", p);

          p.setOpaque(false);
          p.add(L2);
          getContentPane().
          add("South", p);

        setVisible(true);

        t1.addActionListener(this);



    }

    public static void main(String[] args) {
        new TaxiFrame();
    }


   public void actionPerformed(ActionEvent e)
    {

        if (e.getSource() == t1)
        {
            if(Integer.parseInt(t1.getText()) > 0)
            {
                    getContentPane().removeAll();
                  TaxiCanvas tax = new TaxiCanvas();           
               add(tax);
            }
        }

    }

}

thanks alot

taxi canvas code is

import java.awt.*;
import javax.swing.*;
public class TaxiCanvas extends JComponent
{
  private Taxi taxi = new Taxi();
  public void paint(Graphics g)
  {
    taxi.paint(g);

  }
}

taxi code

import java.awt.*;
public class Taxi
{
  public void paint(Graphics g)
  {


// drawing the car body
     g.setColor(Color.yellow);
     g.fillRect(0,10, 60, 15);

// drawing the wheels
     g.setColor(Color.black);
     g.fillOval(10, 20, 12, 12);     // left wheel
     g.fillOval(40, 20, 12, 12);     // right wheel

     int x[] = {10, 20, 40, 50};   // coordinate arrays for the 
     int y[] = {10, 0, 0, 10};   //   car cabin


     g.setColor(Color.yellow);
     g.fillPolygon(x, y, 4);           // drawing the cabin in yellow


     g.setColor(Color.black);
     g.drawString("20", 25, 22);
     g.drawLine(0, 25, 60, 25);

  }
  }

Answer 1

1. When removing and adding components you need to revalidate() and repaint()

2. Instead of adding and removing containers consider using a CardLayout that will "layer" your containers and let you navigate through them. See How to use CardLayout

3. Don't override the paint method of JComponent. instead override paintComponent and make sure to call super.paintComponent as not to break the paint chain and probably leaving you with paint artifacts.

4. Dont use this deprecated add("South", p); method. Instead use add(p, BorderLayout.SOUTH)

5. Trying to tax.setBounds will do nothing, as far as placement, as your layout is set (not null)

6. You are trying to add to "South" a bunch of times. Each position can only hold one component

7. When adding to BorderLayout, if you don't specify a position when adding, it will automatically get added to the CENTER. So if you try to add multiple components without specify a position, only the last component you add will be shown.

8. Swing apps should be run on the Event Dispatch Thread (EDT). You can do so by wrapping your code in your main in a SwingUtilities.invokeLater.... See more at Initial Threads

9. Honestly I have no idea what your code is attempting to do, but look at RadioDef's comment below, see if it means anything to you.

10. If you want to add multiple Taxi objects to your TaxiCanvas, see this answer where you can use a List of Taxi objects and iterate through them in the paintComponent method.

Answer 2

I implemented many of the suggestions by @peeskillet as well as cleaned up the code a little and here is the result.

import javax.swing.*;
import java.awt.event.*;
import java.util.*;
import java.awt.*;

public class TaxiFrame
extends JFrame
implements ActionListener {

    private JLabel label1 = new JLabel("Number of Taxis:");
    private JLabel label2 = new JLabel("Type an integer and press enter");
    private JTextField inputField = new JTextField(10);
    private JPanel taxiPanel = new JPanel();

    private Dimension tpSize = new Dimension(600, 400);
    private Random rand = new Random();

    public TaxiFrame() {
        super("This is the Frame");
        getContentPane().setBackground(Color.CYAN);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setLayout(new BorderLayout(10, 10));

        taxiPanel.setLayout(null);
        taxiPanel.setOpaque(false);
        taxiPanel.setPreferredSize(tpSize);
        add(taxiPanel, BorderLayout.CENTER);

        JPanel p = new JPanel();

        p.setOpaque(false);
        p.add(label1);
        p.add(inputField);
        p.add(label2);
        add(p, BorderLayout.SOUTH);

        inputField.addActionListener(this);

        inputField.setText("5");
        addNewTaxis(5);

        pack();
        setResizable(false);
        setLocationRelativeTo(null);
        setVisible(true);
    }

    private void addNewTaxis(int numTaxis) {
        for(int i = 0; i < numTaxis; i++) {
            addNewTaxi();
        }
    }

    private void addNewTaxi() {
        TaxiCanvas tc = new TaxiCanvas();
        tc.setBounds(
            rand.nextInt(tpSize.width - 100),
            rand.nextInt(tpSize.height - 100),
            100, 100
        );
        taxiPanel.add(tc);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        if(e.getSource() == inputField) {
            int numTaxis = Integer.parseInt(inputField.getText());

            if(numTaxis > 0) {
                taxiPanel.removeAll();
                addNewTaxis(numTaxis);

                taxiPanel.revalidate();
                repaint();
            }
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new TaxiFrame();
            }
        });
    }

    public static class TaxiCanvas
    extends JComponent {
        private Taxi taxi = new Taxi();

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            taxi.paint(g);
        }
    }

    public static class Taxi {
        public void paint(Graphics g) {
            // drawing the car body
            g.setColor(Color.yellow);
            g.fillRect(0,10, 60, 15);

            // drawing the wheels
            g.setColor(Color.black);
            g.fillOval(10, 20, 12, 12); // left wheel
            g.fillOval(40, 20, 12, 12); // right wheel

            int x[] = {10, 20, 40, 50}; // coordinate arrays for the 
            int y[] = {10, 0, 0, 10};   //   car cabin

            g.setColor(Color.yellow);
            g.fillPolygon(x, y, 4);     // drawing the cabin in yellow

            g.setColor(Color.black);
            g.drawString("20", 25, 22);
            g.drawLine(0, 25, 60, 25);
        }
    }
}

Please don't accept this answer, I just wanted to show they were good suggestions and show the working code. There were many small Swing-related bugs but otherwise the code works.