How to find a button source in AWT (calculator homework)
We were asked to make a simple GUI calculator, I used getSource() to detect the buttons, cause that's what they taught us. It works by typing the 1st and 2nd value then choosing the operation, it worked. But I made a mistake, because what they want us to do is that the numbers should also be buttons, just like a real calculator. so how do i get the value of each button using getSource()? like when I press button 1 and 2 is equal to 3. heres what ive done
import java.awt.*;
import java.awt.event.*;
public class SimpleCalculator implements ActionListener
{
// containers
private Frame f;
private Panel p1, p2, p3, p4;
// components
private Label l1, l2, l3;
private TextField tf1, tf2, tf3;
private Button bAdd, bSub, bMul, bDiv, bClear;
public SimpleCalculator()
{
f = new Frame("My First GUI App");
p1 = new Panel();
p2 = new Panel();
p3 = new Panel();
p4 = new Panel();
l1 = new Label("First: ");
l2 = new Label("Second: ");
l3 = new Label("Result: ");
tf1 = new TextField(15);
tf2 = new TextField(15);
tf3 = new TextField(15);
bAdd = new Button("+");
bSub = new Button("-");
bMul = new Button("*");
bDiv = new Button("/");
bClear = new Button("C");
}
public void launchFrame()
{
// use default layout manager of the Panel (FlowLayout)
p1.add(l1);
p1.add(tf1);
p2.add(l2);
p2.add(tf2);
p3.add(l3);
p3.add(tf3);
p4.add(bAdd);
p4.add(bSub);
p4.add(bMul);
p4.add(bDiv);
p4.add(bClear);
// change the layout manager of the Frame,
// use GridLayout(4, 1)
f.setLayout(new GridLayout(4, 1));
f.add(p1);
f.add(p2);
f.add(p3);
f.add(p4);
f.pack();
f.setVisible(true);
// register event handlers
bAdd.addActionListener(this);
bSub.addActionListener(this);
bMul.addActionListener(this);
bDiv.addActionListener(this);
bClear.addActionListener(this);
f.addWindowListener(new MyCloseButtonHandler());
}
// override the actionPerformed method
public void actionPerformed(ActionEvent ae)
{
Object source = ae.getSource();
double num1, num2, result = 0.0;
if (tf1.getText() != null && tf2.getText() != null)
{
num1 = Double.parseDouble(tf1.getText());
num2 = Double.parseDouble(tf2.getText());
if (source == bAdd)
result = num1 + num2;
else if (source == bSub)
result = num1 - num2;
else if (source == bMul)
result = num1 * num2;
else if (source == bDiv)
result = num1 / num2;
else if (source == bClear)
{
tf1.setText("0.0");
tf2.setText("0.0");
tf3.setText("0.0");
}
else {}
// tf3.setText(new Double(result).toString());
tf3.setText("" + result);
}
}
private class MyCloseButtonHandler extends WindowAdapter
{
public void windowClosing(WindowEvent we)
{
System.exit(0);
}
}
public static void main(String args[])
{
SimpleCalculator sc = new SimpleCalculator();
sc.launchFrame();
}
}
Solution 1:
I would tend to have each button for the numbers, as well as each button for operands, add text to a text field that is the 'Input/Output'.
Also have a button = (equals). When the = button is activated, call the ScriptEngine to evaluate the content of the I/O text field and write the result back to it.
E.G.
= 
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
import java.util.ArrayList;
// script package introduced in Java 1.6
import javax.script.ScriptEngineManager;
import javax.script.ScriptEngine;
import javax.script.ScriptException;
class ScriptEngineCalculator implements ActionListener, KeyListener {
private final JTextField io = new JTextField(15);
private final ArrayList<JButton> controls = new ArrayList<>();
private final JPanel ui = new JPanel(new BorderLayout(2, 2));
private ScriptEngine engine;
ScriptEngineCalculator() {
initUI();
}
public final void initUI() {
// obtain a reference to the JS engine
engine = new ScriptEngineManager().getEngineByExtension("js");
JPanel text = new JPanel(new GridLayout(0, 1, 3, 3));
ui.add(text, BorderLayout.PAGE_START);
Font font = io.getFont();
font = font.deriveFont(font.getSize() * 1.8f);
io.setFont(font);
io.setHorizontalAlignment(SwingConstants.TRAILING);
io.setFocusable(false);
text.add(io);
JPanel buttons = new JPanel(new GridLayout(4, 4, 2, 2));
ui.add(buttons, BorderLayout.CENTER);
String[] keyValues = {
"7", "8", "9", "/",
"4", "5", "6", "*",
"1", "2", "3", "-",
"0", ".", "C", "+"
};
for (String keyValue : keyValues) {
addButton(buttons, keyValue);
}
JButton equals = new JButton("=");
configureButton(equals);
ui.add(equals, BorderLayout.LINE_END);
ui.setBorder(new EmptyBorder(5, 5, 5, 5));
}
public JComponent getUI() {
return ui;
}
public void addButton(Container c, String text) {
JButton b = new JButton(text);
configureButton(b);
c.add(b);
}
public void configureButton(JButton b) {
Font f = b.getFont();
b.setFont(f.deriveFont(f.getSize() * 1.5f));
b.addActionListener(this);
b.addKeyListener(this);
controls.add(b);
}
public void calculateResult() {
try {
Object result = engine.eval(io.getText());
if (result == null) {
io.setText("Output was 'null'");
} else {
io.setText(result.toString());
}
} catch (ScriptException se) {
io.setText(se.getMessage());
}
}
@Override
public void actionPerformed(ActionEvent ae) {
String command = ae.getActionCommand();
switch (command) {
case "C":
io.setText("");
break;
case "=":
calculateResult();
break;
default:
io.setText(io.getText() + command);
break;
}
}
private JButton getButton(String text) {
for (JButton button : controls) {
String s = button.getText();
if (text.endsWith(s)
|| (s.equals("=")
&& (text.equals("Equals") || text.equals("Enter")))) {
return button;
}
}
return null;
}
/* START - Because I hate mice. */
@Override
public void keyPressed(KeyEvent ke) { }
@Override
public void keyReleased(KeyEvent ke) {
String s = KeyEvent.getKeyText(ke.getKeyCode());
JButton b = getButton(s);
if (b != null) {
b.requestFocusInWindow();
b.doClick();
}
}
@Override
public void keyTyped(KeyEvent ke) { }
/* END - Because I hate mice. */
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
ScriptEngineCalculator sc = new ScriptEngineCalculator();
JFrame f = new JFrame("Calculet");
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
f.setContentPane(sc.getUI());
f.pack();
f.setMinimumSize(f.getSize());
f.setLocationByPlatform(true);
f.setVisible(true);
});
}
}
Solution 2:
You can check if your source is a Button (not actually nessesary since you should know it is only called from a button) and then type cast to a button and use .getText()
String sourceText;
if (ae.getSource() instanceof Button) {
sourceText = ((Button)ae.getSource()).getText();
}