Swing-GUI GPA Calculator

Question

I am working on an app which will get info from the user through the buttons and text frames in the MyPanel class. So far that part works. Now I want to display the courses-infos the user entered in the DisplayTable panel. I want it to update each time the add course button in the MyPanel class is pressed. I tried adding a function to DisplayTable to add a label each time the button is pressed but I could not get it to work since one is static and one is not. Any ideas on how to do that?(Or any tips on how to improve the app in general :) )

Class Main

public class Main {
    //TODO
    // PREVENT TYPE MISMATCH IN TEXT FIELDS
    // DISPLAY A TABLE OF COURSE NAMES - COURSE CREDITS - COURSE NAME AND THE GPA
    public static void main(String[] args) {
        new MyFrame();
    }
}

Class MyFrame

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class MyFrame extends JFrame{

    MainPanel mainPanel;

    MyFrame(){
        mainPanel = new MainPanel();

        this.add(mainPanel);
        this.setTitle("GPA Calculator");
        this.setResizable(false);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setSize(500,500);
        this.pack();
        this.setLocationRelativeTo(null);

        this.setVisible(true);
    }

}

Class MainPanel

import javax.swing.*;

public class MainPanel extends JPanel {

    MyPanel myPanel = new MyPanel();
    DisplayPanel displayPanel = new DisplayPanel();

    MainPanel() {
        this.add(myPanel);
        this.add(displayPanel);
    }
}

Class DisplayPanel

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

public class DisplayPanel extends JPanel {

    static JLabel addLabel = new JLabel();

    public DisplayPanel() {
        this.setPreferredSize(new Dimension(500, 500));
        this.setBackground(new Color(0xEED2CC));
        this.setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
    }

    public static void addElements(String courseName, int courseCredits, double courseGrade) {
        addLabel.setText(courseName + " " + courseCredits + " " + courseGrade);
        addLabel.setText("");
    }

}

Class MyPanel

import javax.swing.*;
import javax.swing.Timer;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.*;
import java.util.List;

public class MyPanel extends JPanel implements ActionListener{

    List<String> courseNames;
    List<Integer> courseCredits;
    List<Double> courseGrades;
    Thread thread;
    JLabel nameLabel;
    JLabel creditLabel;
    JLabel gradeLabel;
    JTextField nameField;
    JTextField creditField;
    JTextField gradeField;
    JButton calculateButton;
    JButton addCourseButton;
    JButton resetButton;
    JLabel message;


    double result = 0;
    int tempInt = 0;
    double tempDouble = 0;

    MyPanel() {

        message = new JLabel();
        message.setHorizontalAlignment(JLabel.CENTER);
        message.setFont(new Font("Helvetica Neue", Font.PLAIN, 35));
        message.setForeground(new Color(0xA1683A));
        message.setAlignmentX(JLabel.CENTER_ALIGNMENT);

        courseNames = new ArrayList();
        courseCredits = new ArrayList();
        courseGrades = new ArrayList();

        nameLabel = new JLabel();
        nameLabel.setHorizontalAlignment(JLabel.CENTER);
        nameLabel.setText("Course Name");
        nameLabel.setFont(new Font("Helvetica Neue", Font.PLAIN, 25));
        nameLabel.setForeground(new Color(0xA1683A));
        nameLabel.setAlignmentX(JLabel.CENTER_ALIGNMENT);

        nameField = new JTextField();
        nameField.setPreferredSize(new Dimension(300,30));
        nameField.setMaximumSize(nameField.getPreferredSize());

        creditLabel = new JLabel();
        creditLabel.setHorizontalAlignment(JLabel.CENTER);
        creditLabel.setText("Course Credits(ECTS)");
        creditLabel.setFont(new Font("Helvetica Neue", Font.PLAIN, 25));
        creditLabel.setForeground(new Color(0xA1683A));
        creditLabel.setAlignmentX(JLabel.CENTER_ALIGNMENT);

        creditField = new JTextField();
        creditField.setPreferredSize(new Dimension(300,30));
        creditField.setMaximumSize(creditField.getPreferredSize());

        gradeLabel = new JLabel();
        gradeLabel.setHorizontalAlignment(JLabel.CENTER);
        gradeLabel.setText("Your Grade");
        gradeLabel.setFont(new Font("Helvetica Neue", Font.PLAIN, 25));
        gradeLabel.setForeground(new Color(0xA1683A));
        gradeLabel.setAlignmentX(JLabel.CENTER_ALIGNMENT);

        gradeField = new JTextField();
        gradeField.setPreferredSize(new Dimension(300,30));
        gradeField.setMaximumSize(gradeField.getPreferredSize());


        resetButton = new JButton("Reset");
        resetButton.setAlignmentX(JLabel.CENTER_ALIGNMENT);
        resetButton.addActionListener(this);
        addCourseButton = new JButton("Add Course");
        addCourseButton.setAlignmentX(JLabel.CENTER_ALIGNMENT);
        addCourseButton.addActionListener(this);
        calculateButton = new JButton("Calculate GPA");
        calculateButton.setAlignmentX(JLabel.CENTER_ALIGNMENT);
        calculateButton.addActionListener(this);

        //spacing and adding the elements
        this.add(Box.createRigidArea(new Dimension(0,20)));
        this.add(nameLabel);
        this.add(Box.createRigidArea(new Dimension(0,10)));
        this.add(nameField);
        this.add(Box.createRigidArea(new Dimension(0,20)));
        this.add(creditLabel);
        this.add(Box.createRigidArea(new Dimension(0,10)));
        this.add(creditField);
        this.add(Box.createRigidArea(new Dimension(0,20)));
        this.add(gradeLabel);
        this.add(Box.createRigidArea(new Dimension(0,10)));
        this.add(gradeField);
        this.add(Box.createRigidArea(new Dimension(0,20)));
        this.add(addCourseButton);
        this.add(Box.createRigidArea(new Dimension(0,5)));
        this.add(calculateButton);
        this.add(Box.createRigidArea(new Dimension(0,5)));
        this.add(resetButton);
        this.add(Box.createRigidArea(new Dimension(0,30)));
        this.add(message);
        this.setPreferredSize(new Dimension(500, 500));
        this.setBackground(new Color(0xEED2CC));
        this.setLayout(new BoxLayout(this,BoxLayout.Y_AXIS));
    }

    //calculate the GPA
    public double calculateGPA(){
        for (Integer courseCredit : courseCredits) {
            tempInt += courseCredit;
        }
        for(int i = 0; i<courseGrades.size();i++){
            tempDouble += courseGrades.get(i) * courseCredits.get(i);
        }
        return tempDouble/tempInt;
    }

    //create labels to display on the table
    public void createLabel(){

    }

    @Override
    public void actionPerformed(ActionEvent e) throws NumberFormatException {

        if(e.getSource().equals(addCourseButton)){

            //add items from the textFields to lists
            String tempText = nameField.getText();
            int tempCredit = Integer.parseInt(creditField.getText());
            double tempGrade = Double.parseDouble(gradeField.getText());
            courseNames.add(tempText);
            courseCredits.add(tempCredit);
            courseGrades.add(tempGrade);

            //set textFields to empty
            nameField.setText("");
            creditField.setText("");
            gradeField.setText("");

            //display a message for 3 seconds
            thread = new Thread();
            thread.start();
            message.setText("Course Added Successfully!");
            Timer timer = new Timer(3000, a -> message.setText(null));
            timer.setRepeats(false);
            timer.start();

            //add to table panel
            DisplayPanel.addElements(){

            }

        }

        //calculate the GPA, initialize the display panel
        //to display the courses names-credits-results and the gpa
        //as a table
        if(e.getSource().equals(calculateButton)){
            result = calculateGPA();
            message.setText(result + "");
        }

        //clear the lists,text fields and the message
        //get rid of the table panel
        if(e.getSource().equals(resetButton)){
            courseNames.clear();
            courseGrades.clear();
            courseCredits.clear();
            nameField.setText("");
            creditField.setText("");
            gradeField.setText("");
            message.setText(null);
        }
    }
}

- Why have this as static: static JLabel addLabel = new JLabel(); - DisplayTable: cannot find this in the source code. — N Sarj, Jan 21 '22 at 16:09

N Sarj · Accepted Answer · 2022-01-22T17:09:25.110

1

You appear to have used static without need.

static JLabel addLabel = new JLabel();

Make the above non-static, (ideally also make private)

public static void addElements

Make the above non static also, rename to something like setLabelText

DisplayPanel displayPanel = new DisplayPanel();
MyPanel myPanel = new MyPanel(displayPanel);

As shown above, pass displayPanel as a parameter to myPanel. Obviously in MyPanel, you would have one more instance variable:

DisplayPanel displayPanel;

which would be initialized in the constructor, using the constructor argument.

In MyPanel#actionPerformed, instead of:

//add to table panel
DisplayPanel.addElements(){
}

do:

displayPanel.addElements(....);

or rather

displayPanel.setLabelText(...);

invoke the DisplayPanel#setLabelText method on grade calculation and resetting also.

Also invoke the

Finally, remove line:

addLabel.setText("");

If you want DisplayPanel, why then also have the following?

public void createLabel(){

edited Jan 22 '22 at 17:09

answered Jan 21 '22 at 16:29

N Sarj

374
3
11

Thank you for your help. My reasoning for createLabel function was that each time the button was pressed it would create a new JLabel with the info, then that label would be added to the DisplayPanel. – learningJava2020 Jan 21 '22 at 21:18
Followed your advice and got rid of the errors on compiling. But I still can not figure out how to make the label texts print to the displayLabel. I'm guessing it's something about updating the panel. – learningJava2020 Jan 21 '22 at 21:47
1

You will need to invoke repaint on the JPANEL, when handling the action on the button. See https://stackoverflow.com/questions/33441787/how-to-use-the-repaint-method-in-java-swing and https://stackoverflow.com/questions/1097366/java-swing-revalidate-vs-repaint let me know if you need more help with that. – N Sarj Jan 22 '22 at 08:37
https://pastebin.com/MkYn4J2Z I tried calling the setLabelText method from the MyPanel class, and what the actual function is supposed to do is update the panel and display the text for each element in the passed lists when the button is clicked, But still could not update even with revalidate and repaint – learningJava2020 Jan 22 '22 at 10:04
Hi, after a lot of tinkering I found the culprit. There are two mistakes. 1. You wrote `MyPanel(DisplayPanel displayPanel) { ` `this.displayPanel = new DisplayPanel();` You need to keep the panel passed as a parameter, not instantiate a new one. Otherwise, you are doing actions on the wrong component. 2. You're using a layout that is causing the panel to be out of view. Make the window resizable, add some default text on the label. Then tinker to see where the panel is located. – N Sarj Jan 22 '22 at 17:07

Swing-GUI GPA Calculator

1 Answers1