一个计算器的问题:
我编写了一个计算器的程序,在编译的时候没有什么错误 但是在运行的时候却没有内容 只有标题栏 连TITLE也没有!晕!希望大家帮我看看啊!谢谢了
程序:
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.show();
}
} /**
* A frame with a calculator panel
*/
class CalculatorFrame extends JFrame
{
public CalculatorFrame()
{
setTitle("Calculator"); Container contentPane = getContentPane();
CalculatorPanel panel = new CalculatorPanel();
contenPane.add(panel);
pack();
}
}
/**
*A panel with buttons and a result display
*/
class CalculatorPanel extends JPanel
{
public CalculatorPanel()
{
setLayout(new BorderLayout()); result = 0;
lastCommand = "=";
start = true; // add the display display= new JLabel("0");
add(display,BorderLayout.NORTH); ActionListener insert = new InsertAction();
ActionListener command = new CommandAction(); //add the buttons in 4X4 grid 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);
} /**
*adds a button to the center panel.
*@param label the button label
*@param listener the button listener
*/
private void addButton(String label,ActionListener listener)
{
JButton button = new JButton(label);
button.addActionListener(listener);
panel.add(button);
} /**
*This action inserts the button action string to the
*end of the display text.
*/
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);
}
} /**
*This action executes the command that the button
*action string denotes.
*/
private class CommandAction implements ActionListener
{
public void actionPerformed(ActionEvent evt)
{
String command = evt.getActionCommand();
if(start)
{
if(command.equals("-"))
{
display.setText(command);
start=false;
}
else
lastCommand = command;
}
else
{
calculate(Double.parseDouble(display.getText()));
lastCommand = command;
start=true;
}
}
}
/**
*Carries out the pending calculation.
*@param x the value to be accumulated with the prior result.
*/
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 JLabel display;
private JPanel panel;
private double result;
private String lastCommand;
private boolean start;
}
我编写了一个计算器的程序,在编译的时候没有什么错误 但是在运行的时候却没有内容 只有标题栏 连TITLE也没有!晕!希望大家帮我看看啊!谢谢了
程序:
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.show();
}
} /**
* A frame with a calculator panel
*/
class CalculatorFrame extends JFrame
{
public CalculatorFrame()
{
setTitle("Calculator"); Container contentPane = getContentPane();
CalculatorPanel panel = new CalculatorPanel();
contenPane.add(panel);
pack();
}
}
/**
*A panel with buttons and a result display
*/
class CalculatorPanel extends JPanel
{
public CalculatorPanel()
{
setLayout(new BorderLayout()); result = 0;
lastCommand = "=";
start = true; // add the display display= new JLabel("0");
add(display,BorderLayout.NORTH); ActionListener insert = new InsertAction();
ActionListener command = new CommandAction(); //add the buttons in 4X4 grid 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);
} /**
*adds a button to the center panel.
*@param label the button label
*@param listener the button listener
*/
private void addButton(String label,ActionListener listener)
{
JButton button = new JButton(label);
button.addActionListener(listener);
panel.add(button);
} /**
*This action inserts the button action string to the
*end of the display text.
*/
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);
}
} /**
*This action executes the command that the button
*action string denotes.
*/
private class CommandAction implements ActionListener
{
public void actionPerformed(ActionEvent evt)
{
String command = evt.getActionCommand();
if(start)
{
if(command.equals("-"))
{
display.setText(command);
start=false;
}
else
lastCommand = command;
}
else
{
calculate(Double.parseDouble(display.getText()));
lastCommand = command;
start=true;
}
}
}
/**
*Carries out the pending calculation.
*@param x the value to be accumulated with the prior result.
*/
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 JLabel display;
private JPanel panel;
private double result;
private String lastCommand;
private boolean start;
}
唯一的就是你上面给的程序中有一个拼写错误contenPane.add(panel); 改为contentPane.add(panel);
我的环境java+JC
你在命令行下面javac、java一下试试看。
我在CMD中实验了下 还是那样子的 晕 怎么办啊
可以运行
鉴定完毕
LZ贴出报什么错误来啊