如何让我的动作侦听器与我的计算方法进行通信以将文本输出到我的 GUI？

Question

I have been tasked with creating a GUI application that will take a 3 digit input and return the sum, reverse, and array of that number. I have created all of my variables and GUI components and laid them out, but I am now stuck when it comes to doing the calculation and returning the answers to the GUI.

package lab02;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class Lab02 extends JFrame implements ActionListener
{

   Container content = this.getContentPane();
   SpringLayout layout = new SpringLayout();
   JLabel lblNum = new JLabel("Enter a 3-digit number:");
   JLabel lblSum = new JLabel("Sum:");
   JLabel lblReverse = new JLabel("Reverse:");
   JLabel lblArray = new JLabel("Array:");
   JLabel lblTheSum = new JLabel("");
   JLabel lblTheReverse = new JLabel("");
   JLabel lblTheArray = new JLabel("");
   JLabel lblTextColor = new JLabel("Text color:");
   JButton btnComp = new JButton("Compute");
   JTextField tfInput = new JTextField(5);

   public Lab02()
   {
      content.setLayout(layout);
      this.CreateWindow();
      content.add(lblNum);
      layout.putConstraint(SpringLayout.NORTH, lblNum, 25, SpringLayout.NORTH, content);
      layout.putConstraint(SpringLayout.WEST, lblNum, 25, SpringLayout.WEST, content);

      content.add(lblSum);
      layout.putConstraint(SpringLayout.NORTH, lblSum, 60, SpringLayout.NORTH, content);
      layout.putConstraint(SpringLayout.WEST, lblSum, 25, SpringLayout.WEST, content);

      content.add(lblReverse);
      layout.putConstraint(SpringLayout.NORTH, lblReverse, 95, SpringLayout.NORTH, content);
      layout.putConstraint(SpringLayout.WEST, lblReverse, 25, SpringLayout.WEST, content);

      content.add(lblArray);
      layout.putConstraint(SpringLayout.NORTH, lblArray, 130, SpringLayout.NORTH, content);
      layout.putConstraint(SpringLayout.WEST, lblArray, 25, SpringLayout.WEST, content);

      content.add(lblTextColor);
      layout.putConstraint(SpringLayout.NORTH, lblTextColor, 165, SpringLayout.NORTH, content);
      layout.putConstraint(SpringLayout.WEST, lblTextColor, 25, SpringLayout.WEST, content);

      content.add(lblTheSum);
      layout.putConstraint(SpringLayout.NORTH, lblTheSum, 60, SpringLayout.NORTH, content);
      layout.putConstraint(SpringLayout.WEST, lblTheSum, 175, SpringLayout.WEST, content);

      content.add(lblTheReverse);
      layout.putConstraint(SpringLayout.NORTH, lblTheReverse, 95, SpringLayout.NORTH, content);
      layout.putConstraint(SpringLayout.WEST, lblTheReverse, 175, SpringLayout.WEST, content);

      content.add(lblTheArray);
      layout.putConstraint(SpringLayout.NORTH, lblTheArray, 130, SpringLayout.NORTH, content);
      layout.putConstraint(SpringLayout.WEST, lblTheArray, 175, SpringLayout.WEST, content);

      content.add(btnComp);
      layout.putConstraint(SpringLayout.NORTH, btnComp, 200, SpringLayout.NORTH, content);
      layout.putConstraint(SpringLayout.WEST, btnComp, 150, SpringLayout.WEST, content);

      content.add(tfInput);
      layout.putConstraint(SpringLayout.NORTH, tfInput, 25, SpringLayout.NORTH, content);
      layout.putConstraint(SpringLayout.WEST, tfInput, 175, SpringLayout.WEST, content);

      btnComp.addActionListener(this);
   }

   public void CreateWindow()
   {
      this.setVisible(true);
      this.setSize(400, 300);
      this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      this.setTitle("Lab02");
   }

   @Override
   public void actionPerformed(ActionEvent e)
   {
      int num = Integer.parseInt(tfInput.getText());
      this.sumTheDigits(num);
      this.reverseTheOrder(num);
      this.createArrayFrom(num);

   }

   public String sumTheDigits(int num)
   {

      int one;
      int two;
      int three;
      int sum;

      one = num % 10;
      two = (num/10) % 10;
      three = num / 100;
      sum = one + two + three;

      String strSum = String.valueOf(sum);

      return strSum;
   }

    public String reverseTheOrder(int num)
   {
      int first;
      int second;
      int third;

      first = num / 100;
      second = (num/10) % 10;
      third = num % 10;

      StringBuffer s = new StringBuffer(3);

      s.append(third);
      s.append(second);
      s.append(first);

      String reverse = s.toString();

      return reverse;
   }

     public int[] createArrayFrom(int num)
   {

      int first;
      int second;
      int third;
      int[] array = new int[3];

      first = num / 100;
      second = (num/10) % 10;
      third = num % 10;

      array[0] = first;
      array[1] = second;
      array[2] = third;

      return array;
   }

   public static void main(String[] args)
   {
      Lab02 gui = new Lab02();
   }



}

Answer 1

You get your action listener to communicate with your GUI by using a model / view / controller pattern. Lots of people have said as much. I'm going to show you in practice how you separate your code into a model, a view, and a controller.

I tried not to modify your code too much. Frankly, a spring layout is useless, in my opinion.

Anyway, here's the GUI.

Here are the changes I made, in no particular order.

1. I created a Lab02Model class and moved all your calculations into this class.

2. I created a Lab02Listener class and moved the action listener code into that class.

3. I started your GUI by calling the SwingUtilities invokeLater method. This ensures that your GUI is created and executed on the Event Dispatch Thread.

4. I used a JFrame. There's no need to extend a Swing component unless you intend to override one of the component methods.

5. I moved most of your field definitions into the constructor of Lab02. You only make fields class fields if they need to be referenced in more than one place in the class.

6. I added lots of getter methods so one class could get values from another class. Pay attention to these methods. This is how you communicate between classes.

Anyway, here's my code.

import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Arrays;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.SpringLayout;
import javax.swing.SwingUtilities;

public class Lab02 {

    private JLabel lblTheSum = new JLabel("");
    private JLabel lblTheReverse = new JLabel("");
    private JLabel lblTheArray = new JLabel("");

    private JTextField tfInput = new JTextField(5);

    public Lab02() {
        JFrame frame = new JFrame("Lab02");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Container content = frame.getContentPane();

        SpringLayout layout = new SpringLayout();
        JLabel lblNum = new JLabel("Enter a 3-digit number:");
        JLabel lblSum = new JLabel("Sum:");
        JLabel lblReverse = new JLabel("Reverse:");
        JLabel lblArray = new JLabel("Array:");
        JLabel lblTextColor = new JLabel("Text color:");
        JButton btnComp = new JButton("Compute");

        content.setLayout(layout);
        content.add(lblNum);
        layout.putConstraint(SpringLayout.NORTH, lblNum, 25, SpringLayout.NORTH, content);
        layout.putConstraint(SpringLayout.WEST, lblNum, 25, SpringLayout.WEST, content);

        content.add(lblSum);
        layout.putConstraint(SpringLayout.NORTH, lblSum, 60, SpringLayout.NORTH, content);
        layout.putConstraint(SpringLayout.WEST, lblSum, 25, SpringLayout.WEST, content);

        content.add(lblReverse);
        layout.putConstraint(SpringLayout.NORTH, lblReverse, 95, SpringLayout.NORTH, content);
        layout.putConstraint(SpringLayout.WEST, lblReverse, 25, SpringLayout.WEST, content);

        content.add(lblArray);
        layout.putConstraint(SpringLayout.NORTH, lblArray, 130, SpringLayout.NORTH, content);
        layout.putConstraint(SpringLayout.WEST, lblArray, 25, SpringLayout.WEST, content);

        content.add(lblTextColor);
        layout.putConstraint(SpringLayout.NORTH, lblTextColor, 165, SpringLayout.NORTH, content);
        layout.putConstraint(SpringLayout.WEST, lblTextColor, 25, SpringLayout.WEST, content);

        content.add(lblTheSum);
        layout.putConstraint(SpringLayout.NORTH, lblTheSum, 60, SpringLayout.NORTH, content);
        layout.putConstraint(SpringLayout.WEST, lblTheSum, 175, SpringLayout.WEST, content);

        content.add(lblTheReverse);
        layout.putConstraint(SpringLayout.NORTH, lblTheReverse, 95, SpringLayout.NORTH, content);
        layout.putConstraint(SpringLayout.WEST, lblTheReverse, 175, SpringLayout.WEST, content);

        content.add(lblTheArray);
        layout.putConstraint(SpringLayout.NORTH, lblTheArray, 130, SpringLayout.NORTH, content);
        layout.putConstraint(SpringLayout.WEST, lblTheArray, 175, SpringLayout.WEST, content);

        content.add(btnComp);
        layout.putConstraint(SpringLayout.NORTH, btnComp, 200, SpringLayout.NORTH, content);
        layout.putConstraint(SpringLayout.WEST, btnComp, 150, SpringLayout.WEST, content);

        content.add(tfInput);
        layout.putConstraint(SpringLayout.NORTH, tfInput, 25, SpringLayout.NORTH, content);
        layout.putConstraint(SpringLayout.WEST, tfInput, 175, SpringLayout.WEST, content);

        Lab02Model lab02Model = new Lab02Model();
        btnComp.addActionListener(new Lab02Listener(this, lab02Model));

        frame.setSize(400, 300);
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public void updateGUI(String sumText, String reverseText, int[] array) {
        lblTheSum.setText(sumText);
        lblTheReverse.setText(reverseText);
        lblTheArray.setText(Arrays.toString(array));
    }

    public JTextField getTfInput() {
        return tfInput;
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Lab02();
            }
        });
    }

    public class Lab02Listener implements ActionListener {

        private Lab02 lab02;
        private Lab02Model lab02Model;

        public Lab02Listener(Lab02 lab02, Lab02Model lab02Model) {
            this.lab02 = lab02;
            this.lab02Model = lab02Model;
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            int num = Integer.parseInt(lab02.getTfInput().getText());
            lab02Model.calculateValues(num);
            lab02.updateGUI(lab02Model.getDigitSum(), lab02Model.getReverseOrder(), lab02Model.getNumArray());
        }

    }

    public class Lab02Model {

        private int[] numArray;

        private String reverseOrder;
        private String digitSum;

        public void calculateValues(int num) {
            this.digitSum = sumTheDigits(num);
            this.reverseOrder = reverseTheOrder(num);
            this.numArray = createArrayFrom(num);
        }

        public int[] getNumArray() {
            return numArray;
        }

        public String getReverseOrder() {
            return reverseOrder;
        }

        public String getDigitSum() {
            return digitSum;
        }

        public String sumTheDigits(int num) {

            int one;
            int two;
            int three;
            int sum;

            one = num % 10;
            two = (num / 10) % 10;
            three = num / 100;
            sum = one + two + three;

            String strSum = String.valueOf(sum);

            return strSum;
        }

        public String reverseTheOrder(int num) {
            int first;
            int second;
            int third;

            first = num / 100;
            second = (num / 10) % 10;
            third = num % 10;

            StringBuffer s = new StringBuffer(3);

            s.append(third);
            s.append(second);
            s.append(first);

            String reverse = s.toString();

            return reverse;
        }

        public int[] createArrayFrom(int num) {

            int first;
            int second;
            int third;
            int[] array = new int[3];

            first = num / 100;
            second = (num / 10) % 10;
            third = num % 10;

            array[0] = first;
            array[1] = second;
            array[2] = third;

            return array;
        }
    }

}