Teste

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<3; j++) for(int i=0; i<3; 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)