请教等号问题

[sc4496642]

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Calculator
{
public static void main(String[] args)
{
CalculatorFrame frame=new CalculatorFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}

class CalculatorFrame extends JFrame
{
public CalculatorFrame()
{

setTitle("Calculator");

//add panel to frame
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 InsertAction();
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("=",insert);
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 InsertAction 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;
}




==========================================
上面是JAVA源代码。


这个是一个计算器的程序。但是等于号不好用。

就是假如我要算9*8 的话 ，一定要输入 9*8/ 或者9*8-或者9*8+或者9*8*才可以。输出72。

如果输入9*8=的话 ，那么输出的是9==，如果再按下-号，那么就会出现错误。

诚心请教高手帮忙解决。怎么样才能输入9*8= 输出72。

谢谢了。

[cyazhang]

up

[liujiaqwer]

个人觉得 addButton("=",insert); 应该改成 addButton("=",command);

[huoyin]

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Calculator {
public static void main(String[] args) {
CalculatorFrame frame = new CalculatorFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}

class CalculatorFrame extends JFrame {
public CalculatorFrame() {

setTitle("Calculator");

// add panel to frame
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 InsertAction();
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); //insert换为command就好了
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 InsertAction 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;
}

[sc4496642]

谢谢3楼 和2楼的高人。。真的感谢。