This calculator should reside in a class called Calculator, which extends JFrame
ID: 3855228 • Letter: T
Question
This calculator should reside in a class called Calculator, which extends JFrame. To add listeners to buttons, you should use the anonymous class strategy we discussed in lecture. For this basic calculator for the buttons, you should simply add ActionListeners. The calculator should look like the one below. The dimensions are 160 times 260. The text area should not be editable, it should only display information from the button presses Being a postfix calculator, the first operation button you click will perform the selected operation on whatever input was entered and zero (the initial value for some variable in which to save input, say, currentResult). Thus, entering 20 * 10 +, the result should be 10 ((O * 20) + 10). Entering 20 * 10 + 30 should result in 300. Entering 1020 *. on the other hand, should return 200 (0 + 10) * 20)Explanation / Answer
HI,
Please find below the java calculator program that extends JFrame-
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
class Calculator extends JFrame {
private final Font BIGGER_FONT = new Font("monspaced",
Font.PLAIN, 20);
private JTextField textfield;
private boolean number = true;
private String equalOp = "=";
private CalculatorOp op = new CalculatorOp();
public Calculator() {
textfield = new JTextField("0", 12);
textfield.setHorizontalAlignment(JTextField.RIGHT);
textfield.setFont(BIGGER_FONT);
ActionListener numberListener = new NumberListener();
String buttonOrder = "1234567890 ";
JPanel buttonPanel = new JPanel();
buttonPanel.setLayout(new GridLayout(4, 4, 4, 4));
for (int i = 0; i < buttonOrder.length(); i++) {
String key = buttonOrder.substring(i, i+1);
if (key.equals(" ")) {
buttonPanel.add(new JLabel(""));
} else {
JButton button = new JButton(key);
button.addActionListener(numberListener);
button.setFont(BIGGER_FONT);
buttonPanel.add(button);
}
}
ActionListener operatorListener = new OperatorListener();
JPanel panel = new JPanel();
panel.setLayout(new GridLayout(4, 4, 4, 4));
String[] opOrder = {"+", "-", "*", "/","=","C"};
for (int i = 0; i < opOrder.length; i++) {
JButton button = new JButton(opOrder[i]);
button.addActionListener(operatorListener);
button.setFont(BIGGER_FONT);
panel.add(button);
}
JPanel pan = new JPanel();
pan.setLayout(new BorderLayout(4, 4));
pan.add(textfield, BorderLayout.NORTH );
pan.add(buttonPanel , BorderLayout.CENTER);
pan.add(panel , BorderLayout.EAST );
this.setContentPane(pan);
this.pack();
this.setTitle("Calculator");
this.setResizable(false);
}
private void action() {
number = true;
textfield.setText("0");
equalOp = "=";
op.setTotal("0");
}
class OperatorListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
if (number) {
action();
textfield.setText("0");
} else {
number = true;
String displayText = textfield.getText();
if (equalOp.equals("=")) {
op.setTotal(displayText);
} else if (equalOp.equals("+")) {
op.add(displayText);
} else if (equalOp.equals("-")) {
op.subtract(displayText);
} else if (equalOp.equals("*")) {
op.multiply(displayText);
} else if (equalOp.equals("/")) {
op.divide(displayText);
}
textfield.setText("" + op.getTotalString());
equalOp = e.getActionCommand();
}
}
}
class NumberListener implements ActionListener {
public void actionPerformed(ActionEvent event) {
String digit = event.getActionCommand();
if (number) {
textfield.setText(digit);
number = false;
} else {
textfield.setText(textfield.getText() + digit);
}
}
}
public class CalculatorOp {
private int total;
public CalculatorOp() {
total = 0;
}
public String getTotalString() {
return ""+total;
}
public void setTotal(String n) {
total = convertToNumber(n);
}
public void add(String n) {
total += convertToNumber(n);
}
public void subtract(String n) {
total -= convertToNumber(n);
}
public void multiply(String n) {
total *= convertToNumber(n);
}
public void divide(String n) {
total /= convertToNumber(n);
}
private int convertToNumber(String n) {
return Integer.parseInt(n);
}
}
}
Regards.
Vinay