How do i link the buttons to the action listener and into the text field?

Question

okay i have no problems until the addActionListener(this) statement. i don't know where to go to link the buttons to their respective strings to be entered in the textfield

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

public class GUI extends JFrame implements ActionListener {

    private JButton one, two, three, four, five, six, seven, eight, nine, zero, point, cancel;

    private JTextField t;

    private JFrame frame;

    private String number = "";



    public GUI() {

        //creating button objects

        JButton one = new JButton("1");

        JButton two = new JButton("2");

        JButton three = new JButton("3");

        JButton four = new JButton("4");

        JButton five = new JButton("5");

        JButton six = new JButton("6");

        JButton seven = new JButton("7");

        JButton eight = new JButton("8");

        JButton nine = new JButton("9");

        JButton zero = new JButton("0");

        JButton point = new JButton(".");

        JButton cancel = new JButton("cancel");

        //call addActionListener() method

        one.addActionListener(this);

        two.addActionListener(this);

        three.addActionListener(this);

        four.addActionListener(this);

        five.addActionListener(this);

        six.addActionListener(this);

        seven.addActionListener(this);

        eight.addActionListener(this);

        nine.addActionListener(this);

        //point.addActionListener(this);

        //cancel.addActionListener(this);

        //create jframe object

        JFrame frame = new JFrame("Vendor");

        //create text field

        JTextField t = new JTextField();

        frame.setSize(400, 400);

        setVisible(true);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //remove this after creating other modules

        //creating panel object

        JPanel panel = new JPanel();

        GridLayout grid = new GridLayout(0, 3);

        panel.setLayout(grid);

        panel.setComponentOrientation(ComponentOrientation.LEFT_TO_RIGHT);

        //setting text field to the top of the frame

        add(t, BorderLayout.NORTH);

        //adding buttons to panel

        panel.add(one);

        panel.add(two);

        panel.add(three);

        panel.add(four);

        panel.add(five);

        panel.add(six);

        panel.add(seven);

        panel.add(eight);

        panel.add(nine);

        panel.add(zero);

        panel.add(point);

        panel.add(cancel);

        //adding panel to frame

        add(panel);

    }

    public void actionPerformed(ActionEvent e) {


        if (e.getSource() == one) {

            t.setText(t.getText().concat("1"));

        }

        if (e.getSource() == two) {

            t.setText(t.getText().concat("2"));

        }

        if (e.getSource() == three) {

            t.setText(t.getText().concat("3"));

        }

        if (e.getSource() == four) {

            t.setText(t.getText().concat("4"));

        }

        if (e.getSource() == five) {

            t.setText(t.getText().concat("5"));

        }

        if (e.getSource() == six) {

            t.setText(t.getText().concat("6"));

        }

        if (e.getSource() == seven) {

            t.setText(t.getText().concat("7"));

        }

        if (e.getSource() == eight) {

            t.setText(t.getText().concat("8"));

        }

        if (e.getSource() == nine) {

            t.setText(t.getText().concat("9"));

        }

        if (e.getSource() == zero) {

            t.setText(t.getText().concat("0"));

        }

        /*if(e.getSource() == point) {

     t.setText(t.getText().concat("."));

  }*/
    }

    public static void main(String[] args) {

        GUI object = new GUI();

    }
}

Answer 1

You are declaring the Buttons locally in the constructor and thereby overriding your member variables. Your member variables one, two, three... will always be null. You can write your constructor like this:

public GUI() {

    //creating button objects

    one = new JButton("1");

    two = new JButton("2");
    .
    .
    .