//file: Calculator.java import java.awt.*; import java.awt.event.*; import javax.swing.*; public class Calculator extends JPanel implements ActionListener { GridBagConstraints gbc = new GridBagConstraints( ); JTextField theDisplay = new JTextField( ); public Calculator( ) { gbc.weightx = 1.0; gbc.weighty = 1.0; gbc.fill = GridBagConstraints.BOTH; ContainerListener listener = new ContainerAdapter( ) { public void componentAdded(ContainerEvent e) { Component comp = e.getChild( ); if (comp instanceof JButton) ((JButton)comp).addActionListener(Calculator.this); } }; addContainerListener(listener); gbc.gridwidth = 4; addGB(this, theDisplay, 0, 0); // make the top row JPanel topRow = new JPanel( ); topRow.addContainerListener(listener); gbc.gridwidth = 1; gbc.weightx = 1.0; addGB(topRow, new JButton("C"), 0, 0); gbc.weightx = 0.33; addGB(topRow, new JButton("%"), 1, 0); gbc.weightx = 1.0; addGB(topRow, new JButton("+"), 2, 0 ); gbc.gridwidth = 4; addGB(this, topRow, 0, 1); gbc.weightx = 1.0; gbc.gridwidth = 1; // make the digits for(int j=0; j for(int i=0; i addGB(this, new JButton("" + ((2-j)*3+i+1) ), i, j+2); // -, x, and divide addGB(this, new JButton("-"), 3, 2); addGB(this, new JButton("x"), 3, 3); addGB(this, new JButton("\u00F7"), 3, 4); // make the bottom row JPanel bottomRow = new JPanel( ); bottomRow.addContainerListener(listener); gbc.weightx = 1.0; addGB(bottomRow, new JButton("0"), 0, 0); gbc.weightx = 0.33; addGB(bottomRow, new JButton("."), 1, 0); gbc.weightx = 1.0; addGB(bottomRow, new JButton("="), 2, 0); gbc.gridwidth = 4; addGB(this, bottomRow, 0, 5); } void addGB(Container cont, Component comp, int x, int y) { if ((cont.getLayout( ) instanceof GridBagLayout) == false) cont.setLayout(new GridBagLayout( )); gbc.gridx = x; gbc.gridy = y; cont.add(comp, gbc); } public void actionPerformed(ActionEvent e) { if (e.getActionCommand( ).equals("C")) theDisplay.setText(""); else theDisplay.setText(theDisplay.getText( ) + e.getActionCommand( )); } public static void main(String[] args) { JFrame f = new JFrame("Calculator"); f.addWindowListener(new WindowAdapter( ) { public void windowClosing(WindowEvent e) { System.exit(0); } }); f.setSize(200, 250); f.setLocation(200, 200); f.setContentPane(new Calculator( )); f.setVisible(true); } }
