Galera to com um problema no código abaixo,
na linha 23 ele gera o seguinte erro:
"non-static variable this cannot be referenced from a static context. "
se alguém puder me ajudar agradeço desde já.wlu
[code]
package calculadora;
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
/**
*
-
@author Usuario
*/
public class Calculator {
/**
-
@param args the command line argumentsk
*/
public static void main(String[] args) {
// TODO code application logic here
CalculatorFrame frame = new CalculatorFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
class CalculatorFrame extends JFrame
{
public CalculatorFrame()
{
setTitle(“Calculadora”);
CalculatorPanel panel= new CalculatorPanel();
add(panel);
pack();
}
}
class CalculatorPanel extends JPanel{
public CalculatorPanel(){
setLayout(new BorderLayout());
result=0;
lastCommand = “=”;
start=true;
display = new JButton("0");
display.setEnabled(false);
add(display, BorderLayout.NORTH);
ActionListener insert = new InserAction();
ActionListener command = new CommandAction();
panel = new JPanel();
panel.setLayout(new GridLayout(4, 4));
addButton("7", insert);
addButton("8", insert);
addButton("9", insert);
addButton("/", command);
addButton("4", insert);
addButton("5", insert);
addButton("6", insert);
addButton("*", command);
addButton("1", insert);
addButton("2", insert);
addButton("3", insert);
addButton("-", command);
addButton("0", insert);
addButton(".", insert);
addButton("=", command);
addButton("+", command);
add(panel, BorderLayout.CENTER);
}
}
private void addButton(String label , ActionListener listener)
{
JButton button= new JButton(label);
button.addActionListener(listener);
panel.add(button);
}
private class InserAction implements ActionListener{
public void actionPerformed (ActionEvent event){
String input = event.getActionCommand();
if(start)
{
display.setText(" “);
start=false;
}
display.setText(display.getText()+ input);
}
}
private class CommandAction implements ActionListener{
public void actionPerformed(ActionEvent event){
String command = event.getActionCommand();
if(start)
{
if (command.equals(”-"))
{
display.setText(command);
start=false;
} else
lastCommand = command;
}else
{
calculate(Double.parseDouble(display.getText()));
lastCommand = command;
start=true;
}
}
}
public void calculate (double x)
{
if(lastCommand.equals("+"))result+= x;
else if(lastCommand.equals("+"))result+= x;
else if(lastCommand.equals("+"))result+= x;
else if(lastCommand.equals("+"))result+= x;
else if(lastCommand.equals("+"))result+= x;
display.setText(""+result);
}
private JButton display;
private JPanel panel;
private double result;
private String lastCommand;
private boolean start;
}[/code]
estas a aceber a uma variavel nao estatica…tens de definir a classe que instancia esta variavel com estatica
[code]
package calculadora;
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
/**
-
-
-
-
@author Usuario 15.
*/
public class Calculator {
/**
*/
public static void main(String[] args) {
// TODO code application logic here
CalculatorFrame frame = new CalculatorFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
static class CalculatorFrame extends JFrame {
public CalculatorFrame() {
setTitle(“Calculadora”);
CalculatorPanel panel = new CalculatorPanel();
add(panel);
pack();
}
}
static class CalculatorPanel extends JPanel {
public CalculatorPanel() {
setLayout(new BorderLayout());
result = 0;
lastCommand = “=”;
start = true;
display = new JButton("0");
display.setEnabled(false);
add(display, BorderLayout.NORTH);
ActionListener insert = new InserAction();
ActionListener command = new CommandAction();
panel = new JPanel();
panel.setLayout(new GridLayout(4, 4));
addButton("7", insert);
addButton("8", insert);
addButton("9", insert);
addButton("/", command);
addButton("4", insert);
addButton("5", insert);
addButton("6", insert);
addButton("*", command);
addButton("1", insert);
addButton("2", insert);
addButton("3", insert);
addButton("-", command);
addButton("0", insert);
addButton(".", insert);
addButton("=", command);
addButton("+", command);
add(panel, BorderLayout.CENTER);
}
}
private static void addButton(String label, ActionListener listener) {
JButton button = new JButton(label);
button.addActionListener(listener);
panel.add(button);
}
private static class InserAction implements ActionListener {
public void actionPerformed(ActionEvent event) {
String input = event.getActionCommand();
if (start) {
display.setText(" ");
start = false;
}
display.setText(display.getText() + input);
}
}
private static class CommandAction implements ActionListener {
public void actionPerformed(ActionEvent event) {
String command = event.getActionCommand();
if (start) {
if (command.equals("-")) {
display.setText(command);
start = false;
} else
lastCommand = command;
} else {
calculate(Double.parseDouble(display.getText()));
lastCommand = command;
start = true;
}
}
}
public static void calculate(double x) {
if (lastCommand.equals("+"))
result += x;
else if (lastCommand.equals("+"))
result += x;
else if (lastCommand.equals("+"))
result += x;
else if (lastCommand.equals("+"))
result += x;
else if (lastCommand.equals("+"))
result += x;
display.setText("" + result);
}
private static JButton display;
private static JPanel panel;
private static double result;
private static String lastCommand;
private static boolean start;
}[/code]
fiz algumas alteraçoes…
ai esta
Wleu Alkamavo agora compilo legal…
Acabei de postar em outro topico e posto aqui…
http://www.javafree.org/javabb/viewtopic.jbb?t=6941&Cap-2--Modificadores
Muito legal isso, da um bom conceito sobre os Modificadores em Java, que ate antes de ler isso tinha bastante duvidas, agora sumiu bastante 
Abraços