Hi!! I have written three classes (two of which are most relevant) and am required to construct an operating calculator.
This is the CalculatorPanel:
/*
* CalculatorPanel.java
*
* Lab 19, COMP160, 2010
*
* An alternative GUI front end for the Calculator class
*
*/
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
public class CalculatorPanel extends JPanel {
Calculator calc = new Calculator();
// an array of buttons displayed on the calculator
private JButton[] digitButtons;
// output display for the calculator
private JTextField display = new JTextField(10);
/*main method - sets up JFrame*/
public static void main(String [] args){
JFrame frame = new JFrame("Calculator");
frame.setContentPane(new CalculatorPanel());
frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
}
/* Constructor -- builds a GUI for a calculator */
public CalculatorPanel() {
/* create an array of button labels */
String[] buttonLabels = {"1", "2", "3", "4", "5", "6",
"7", "8", "9", "C", "0", "=", "+", "-", "*"};
/* Create an array of buttons. */
digitButtons = new JButton[buttonLabels.length];
/* Create an actionListener */
ButtonListener listener = new ButtonListener();
/* Create a 4 x 3 grid for placement of buttons. */
JPanel buttonGrid = new JPanel();
buttonGrid.setLayout(new GridLayout(5, 3));
/* Create a button with each button label, add it to buttonGrid,
* and register the button as a listener. */
for (int nextBut = 0; nextBut < digitButtons.length; nextBut++) {
digitButtons[nextBut] = new JButton(buttonLabels[nextBut]);
buttonGrid.add(digitButtons[nextBut]);
digitButtons[nextBut].addActionListener(listener);
}
/* Create a message for the user*/
JLabel instruct = new JLabel("Press a button");
/* add the components to this JPanel*/
setLayout(new BorderLayout());
add(instruct, BorderLayout.NORTH);
add(buttonGrid, BorderLayout.CENTER);
add(display, BorderLayout.SOUTH);
}
/* represents a listener for button presses */
private class ButtonListener implements ActionListener{
/* what to do when a button has been pressed */
public void actionPerformed(ActionEvent aE) {
JButton whichButton = (JButton) aE.getSource();
display.setText("You pressed " + whichButton.getText());
}
}
}And this the Calculator class:
/*
* Calculator.java
*
* Lab 19, COMP160, 2010
*
* A calculator class - for SIMPLE calculations like 5 + 20 =
* Large inputs will overload int, should convert to long
*/
public class Calculator {
private int currentInput; //current input
private int previousInput; // previous input
private int result; // result of calculation
private String lastOperator = ""; // keeps track of the last operator entered
/* New digit entered as integer value i - moves currentInput 1 decimal place to the left and adds i in "one's column" */
public void inDigit(int i) {
currentInput = (currentInput * 10) + i;
}
/* Operator entered + - or * */
public void inOperator(String op) {
previousInput = currentInput; // save the new input as previous to get ready for next input
currentInput = 0;
lastOperator = op; // remember which operator was entered
}
/* Equals operation sets result to previousInput + - or * currentInput (depending on lastOperator) */
public void inEquals() {
if (lastOperator.equals("+")) {
result = previousInput + currentInput;
} else if (lastOperator.equals("-")) {
result = previousInput - currentInput;
} else if (lastOperator.equals("*")) {
result = previousInput * currentInput;
}
lastOperator = ""; // reset last operator to "nothing"
}
/* Clear operation */
public void inClear() {
currentInput = 0;
previousInput = 0;
result = 0;
lastOperator = "";
}
/* returns the current result */
public String getResult() {
return Integer.toString(result); //converts int to String
}
/* returns the previous input value */
public String getPreviousInput() {
return Integer.toString(previousInput);
}
/* returns the current input value */
public String getCurrentInput() {
return Integer.toString(currentInput);
}
}There is also a CalcTextApp.java class but it's not really necessary for this.
I am having an issue with the actionPerformed() method, making button presses call methods on calc. All the instruction I've been given is:
Use "if" to work out what button has been pressed, and deal with each one appropriately. Think about how and where to display the result.
Any direction or help and I shall be forever grateful! Thanks :)
