Question

Class SampleFiveA extends JPanel. This contains textfields, one below the other, each of which has a label on the left. All textfields will be of the same width and positioned against the right border of the panel. SampleFiveA has only one constructor that accepts the following three parameters:

ArrayList names,
ArrayList values,
int cols

I so far created the sample username password screen in GUI but now I have a problem implementing an ArrayList in JPanel one for User Name and the other for password. Kind of stuck there for hours now cant find a proper example to do it. Below is the code I commented what I need to be done using ArrayList.

public class SampleFiveA extends JPanel {


ArrayList<String> names = new ArrayList<String>(); //the text for the labels
ArrayList<String> values = new ArrayList<String>(); // the initial contents of the text fields
int col ; //the number of columns used to set the width of each textfield


public SampleFiveA()
{
        JPanel p = new JPanel();
        p.setLayout(new GridLayout(2,2)); 

        JLabel lab1 = new JLabel("User Name", JLabel.LEFT);         
        p.add(lab1 = new JLabel("User Name"));
        JTextField txt1 = new JTextField("User Name", JTextField.RIGHT);
        p.add(txt1= new JTextField());



        JLabel lab2 = new JLabel("Password ", JLabel.LEFT);            
        p.add(lab2 = new JLabel("Password"));
        JPasswordField txt2 = new JPasswordField("*****",JPasswordField.RIGHT );
        p.add(txt2 = new JPasswordField());



      //  names.add(lab1,lab2);// Not right but I want to put the label text to this arrayList
      //  values.add(txt1,txt2);// 


        add(p);
};



public static void main(String[] args) 
{


JFrame frame = new JFrame();
frame.getContentPane().add(new SampleFiveA());

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(200,200);
frame.setVisible(true);


};
};

Answer 1

Here’s a start for you.

It adds a FocusListener to the text fields and makes sure that the content of the ArrayList is updated with the current value when the text field looses focus.

import java.awt.GridLayout;
import java.awt.event.*;
import java.util.ArrayList;

import javax.swing.*;

public class Main extends JPanel {

    ArrayList<String> names = new ArrayList<String>(); // the text for the
                                                       // labels
    ArrayList<String> values = new ArrayList<String>(); // the initial contents
                                                        // of the text fields
    int col; // the number of columns used to set the width of each textfield

    public Main() {
        JPanel p = new JPanel();
        p.setLayout(new GridLayout(2, 2));

        names = new ArrayList<String>();
        values = new ArrayList<String>();


        JLabel lab1 = new JLabel("User Name", JLabel.LEFT);
        p.add(lab1);
        JTextField txt1 = new JTextField("User Name", JTextField.RIGHT);
        p.add(txt1);

        names.add(lab1.getText());
        values.add(txt1.getText());

        JLabel lab2 = new JLabel("Password ", JLabel.LEFT);
        p.add(lab2);
        JPasswordField txt2 = new JPasswordField("*****", JPasswordField.RIGHT);
        p.add(txt2);
        names.add(lab2.getText());
        values.add(txt2.getText());


        // names.add(lab1,lab2);// Not right but I want to put the label text to
        // this arrayList
        // values.add(txt1,txt2);//
        txt1.addFocusListener(new ArrayListFocusListener(txt1, values, 0));
        txt2.addFocusListener(new ArrayListFocusListener(txt2, values, 1));

        add(p);


        // Start a thread to print the content of the list for 10 seconds
        new Thread() {
            public void run() {
                for (int i = 0; i < 10; i++) {
                    try {
                        sleep(1000);
                    } catch (InterruptedException e) {
                    }
                    System.out.println(values);
                }
            }
        }.start();


    };



    public static void main(String[] args) {

        JFrame frame = new JFrame();
        frame.getContentPane().add(new Main());

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(200, 200);
        frame.setVisible(true);

    };

    class ArrayListFocusListener implements FocusListener {
        JTextField textField;
        ArrayList<String> backingList;
        int myIndex;

        public ArrayListFocusListener(JTextField textField,
                ArrayList<String> backingList, int myIndex) {
            this.textField = textField;
            this.backingList = backingList;
            this.myIndex = myIndex;
        }

        public void focusGained(FocusEvent e) {
        }

        @Override
        public void focusLost(FocusEvent e) {
            backingList.set(myIndex, textField.getText());
        }

    }
};