Question

I’m building a JPanel that contains multiple fields, but according a product, the fields may vary.
There some common fields and some particular fields for each product.
Using some Interfaces, it’s possible to group the fields to build the referred JPanel with all needed fields, like this:

public class VPNProduct extends JPanel implements VPNFields{
    //use and positioning of the fields
}

interface VPNFields extends CommonFields{
    //particular VPN fields
}

interface CommonFields{
    //fields common to all products
}

My question is, there’s some best practice or technique that make it easier or more organized, including the position of the fields in the panel?

Thanks in advance.

Answer 1

There are some elegant ways of doing this. First off an interface will have your get/set methods that will access your fields. So you will have an interface for your common fields and other ones for other fields. The common fields interface (since it will be shared) should be implemented to an abstract class. This abstract class will extend JPanel and construct your JLabel, JComboBoxes …etc and lay them out in a layout manager.

Then for any other class that you would need to add more fields, you would create a Class and have it extend your abstract class (so now it is a JPanel with all common fields already created and laid out) and implement an interface with your extra fields. These extra fields you will have to create their Swing components and add them to the layout manager that currently has the common fields.

If you provide some field examples or give us a hint at the structure I could draft some code sample so you can see.

A code example showing common fields that can be use for Company and School and how we create 2 JFrames with forms all originating from 1 JPanel abstract class:

package stackoverflow.test;

public interface CommonFields {

    public void setName(String name);

    public void setLastName(String lastName);

    public void setAge(int age);

    public String getName();

    public String getLastName();

    public int getAge();
}

–

package stackoverflow.test;

public interface SchoolFields {

    public void setSchoolName(String schoolName);

    public void setGrade(int grade);

    public void setHonorsProgram(boolean isHonors);

    public String getSchoolName();

    public int getGrade();

    public boolean hasHonorsProgram();
}

–

package stackoverflow.test;

public interface CompanyFields {

    public void setCompanyName(String companyName);

    public void setJobTitle(String jobTitle);

    public void setAddress(String address);

    public String getCompanyName();

    public String getJobTitle();

    public String getAddress();
}

–

package stackoverflow.test;

import java.awt.GridLayout;

import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class AbstractJPanel extends JPanel implements CommonFields {

    private static final long serialVersionUID = 150030761086805569L;

    private JTextField nameField = null;
    private JTextField lastNameField = null;
    private JTextField ageField = null;
    private JLabel nameLabel = null;
    private JLabel lastNameLabel = null;
    private JLabel ageLabel = null;


    public AbstractJPanel() {
        super(new GridLayout(0, 2));

        nameField = new JTextField();
        lastNameField = new JTextField();
        ageField = new JTextField();

        nameLabel = new JLabel("Name: ");
        lastNameLabel =new JLabel("Last Name: ");
        ageLabel = new JLabel("Age: ");

        add(nameLabel);
        add(nameField);
        add(lastNameLabel);
        add(lastNameField);
        add(ageLabel);
        add(ageField);
    }

    public void setName(String name) {
        nameField.setText(name);
    }

    public void setLastName(String lastName) {
        lastNameField.setText(lastName);
    }

    public void setAge(int age) {
        ageField.setText(""+age);
    }

    public String getName() {
        return nameField.getText();
    }

    public String getLastName() {
        return lastNameField.getText();
    }

    public int getAge() {
        return Integer.parseInt(ageField.getText());
    }
}

–

package stackoverflow.test;

import javax.swing.JCheckBox;
import javax.swing.JLabel;
import javax.swing.JTextField;

public class SchoolPanel extends AbstractJPanel implements SchoolFields {

    private static final long serialVersionUID = -6201476099194804075L;

    private JTextField schoolNameField = null;
    private JTextField gradeField = null;
    private JCheckBox honorsCheckBox = null;
    private JLabel schoolNameLabel = null;
    private JLabel gradeLabel = null;
    private JLabel honorsLabel = null;

    public SchoolPanel() {
        super();


        schoolNameLabel = new JLabel("School Name: ");
        gradeLabel = new JLabel("Grade: ");
        honorsLabel = new JLabel("Is Honors: ");

        schoolNameField = new JTextField();
        gradeField = new JTextField();
        honorsCheckBox = new JCheckBox();

        add(schoolNameLabel);
        add(schoolNameField);
        add(gradeLabel);
        add(gradeField);
        add(honorsLabel);
        add(honorsCheckBox);
    }

    @Override
    public void setSchoolName(String schoolName) {
        schoolNameField.setText(schoolName);
    }

    @Override
    public void setGrade(int grade) {
        gradeField.setText(""+grade);
    }

    @Override
    public void setHonorsProgram(boolean isHonors) {
        honorsCheckBox.setSelected(isHonors);
    }

    @Override
    public String getSchoolName() {
        return schoolNameField.getText();
    }

    @Override
    public int getGrade() {
        return Integer.parseInt(gradeField.getText());
    }

    @Override
    public boolean hasHonorsProgram() {
        return honorsCheckBox.isSelected();
    }
}

–

package stackoverflow.test;

import javax.swing.JLabel;
import javax.swing.JTextField;

public class CompanyPanel extends AbstractJPanel implements CompanyFields {

    private static final long serialVersionUID = 7834845724312492112L;

    private JTextField companyNameField = null;
    private JTextField jobTitleField = null;
    private JTextField addressField = null;
    private JLabel companyNameLabel = null;
    private JLabel jobTitleLabel = null;
    private JLabel addressLabel = null;

    public CompanyPanel() {
        super();

        companyNameLabel = new JLabel("Company Name: ");
        jobTitleLabel = new JLabel("Job Title: ");
        addressLabel = new JLabel("Address: ");

        companyNameField = new JTextField();
        jobTitleField = new JTextField();
        addressField = new JTextField();

        super.add(companyNameLabel);
        super.add(companyNameField);
        super.add(jobTitleLabel);
        super.add(jobTitleField);
        super.add(addressLabel);
        super.add(addressField);
    }

    @Override
    public void setCompanyName(String companyName) {
        companyNameField.setText(companyName);
    }

    @Override
    public void setJobTitle(String jobTitle) {
        jobTitleField.setText(jobTitle);
    }

    @Override
    public void setAddress(String address) {
        addressField.setText(address);
    }

    @Override
    public String getCompanyName() {
        return companyNameField.getText();
    }

    @Override
    public String getJobTitle() {
        return jobTitleField.getText();
    }

    @Override
    public String getAddress() {
        return addressField.getText();
    }

}

–

package stackoverflow.test;

import java.awt.BorderLayout;

import javax.swing.JFrame;

public class MainClass {

    public MainClass() {
        JFrame frame1 = new JFrame();
        frame1.setLayout(new BorderLayout());
        frame1.add(new CompanyPanel());
        frame1.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame1.setSize(500, 500);
        frame1.setVisible(true);


        JFrame frame2 = new JFrame();
        frame2.setLayout(new BorderLayout());
        frame2.add(new SchoolPanel());
        frame2.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame2.setSize(500, 500);
        frame2.setVisible(true);
    }


    public static final void main(String ... args) {
        new MainClass();
    }
}