小弟做一個計算器的Java文檔: import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Caculator extends Panel
{
static JFrame frame;
static Panel subpanel;
static String add="+";
static String subtract="-";
static String multiply="*";
static String divide="/";
TextField num1textfield,num2textfield,resulttextfield;
Button equalbutton;
ButtonGroup group;
JRadioButton addbutton,subtractbutton,multiplybutton,dividebutton;
public Caculator()
{
num1textfield=new TextField(5);
num2textfield=new TextField(5);
resulttextfield=new TextField(5);
equalbutton=new Button("=");
buttonlistener bnlistener=new buttonlistener();
equalbutton.addActionListener(bnlistener); addbutton=new JRadioButton(add);
addbutton.setActionCommand(add); subtractbutton=new JRadioButton(subtract);
subtractbutton.setActionCommand(subtract); multiplybutton =new JRadioButton(multiply);
multiplybutton.setActionCommand(multiply); dividebutton=new JRadioButton(divide);
dividebutton.setActionCommand(divide); group=new ButtonGroup();
group.add(addbutton);
group.add(subtractbutton);
group.add(multiplybutton);
group.add(dividebutton);
addbutton.setSelected(true);
subpanel=new Panel();
subpanel.setLayout(new GridLayout(4,1));
subpanel.add(addbutton);
subpanel.add(subtractbutton);
subpanel.add(multiplybutton);
subpanel.add(dividebutton); super.add(num1textfield);
super.add(subpanel);
super.add(num2textfield);
super.add(equalbutton);
super.add(resulttextfield); }
class buttonlistener implements ActionListener
{ public void actionPerformed (ActionEvent e)
{ Double n1=new Double(num1textfield.getText());
Double n2=new Double(num2textfield.getText());
double num1,num2,num3;
num1=n1.doubleValue();
num2=n2.doubleValue();
num3=0;
String cmd=group.getSelection().getActionCommand();
if (cmd==add)
num3=num1+num2;
else if (cmd==subtract)
num3=num1-num2;
else if (cmd==multiply)
num3=num1*num2;
else if (cmd==divide)
num3=num1/num2;
Double n3=new Double(num3);
resulttextfield.setText(n3.toString());
resulttextfield.select(0,0);
}
}
public static void main(String args[])
{
try
{
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
}
catch (Exception exe)
{
System.err.println("Error loading L&p:" + exe);
} Caculator panel=new Caculator();
frame=new JFrame("Caculator");
frame.addWindowListener(new WindowAdapter () {
public void windowClosing(WindowEvent e){ System.exit(0);}
});
frame.getContentPane.add("Center",panel);
frame.pack();
frame.setVisible(true);
}}
編譯之後發現提示:frame.getContentPane.add("Center",panel);
can not resolve symbol
symbol: variable getContentPane
location: class javax.swing.JFrame
frame.getContentPane.add("Center",panel);請問大俠如何修正啊
import java.awt.event.*;
import javax.swing.*;
public class Caculator extends Panel
{
static JFrame frame;
static Panel subpanel;
static String add="+";
static String subtract="-";
static String multiply="*";
static String divide="/";
TextField num1textfield,num2textfield,resulttextfield;
Button equalbutton;
ButtonGroup group;
JRadioButton addbutton,subtractbutton,multiplybutton,dividebutton;
public Caculator()
{
num1textfield=new TextField(5);
num2textfield=new TextField(5);
resulttextfield=new TextField(5);
equalbutton=new Button("=");
buttonlistener bnlistener=new buttonlistener();
equalbutton.addActionListener(bnlistener); addbutton=new JRadioButton(add);
addbutton.setActionCommand(add); subtractbutton=new JRadioButton(subtract);
subtractbutton.setActionCommand(subtract); multiplybutton =new JRadioButton(multiply);
multiplybutton.setActionCommand(multiply); dividebutton=new JRadioButton(divide);
dividebutton.setActionCommand(divide); group=new ButtonGroup();
group.add(addbutton);
group.add(subtractbutton);
group.add(multiplybutton);
group.add(dividebutton);
addbutton.setSelected(true);
subpanel=new Panel();
subpanel.setLayout(new GridLayout(4,1));
subpanel.add(addbutton);
subpanel.add(subtractbutton);
subpanel.add(multiplybutton);
subpanel.add(dividebutton); super.add(num1textfield);
super.add(subpanel);
super.add(num2textfield);
super.add(equalbutton);
super.add(resulttextfield); }
class buttonlistener implements ActionListener
{ public void actionPerformed (ActionEvent e)
{ Double n1=new Double(num1textfield.getText());
Double n2=new Double(num2textfield.getText());
double num1,num2,num3;
num1=n1.doubleValue();
num2=n2.doubleValue();
num3=0;
String cmd=group.getSelection().getActionCommand();
if (cmd==add)
num3=num1+num2;
else if (cmd==subtract)
num3=num1-num2;
else if (cmd==multiply)
num3=num1*num2;
else if (cmd==divide)
num3=num1/num2;
Double n3=new Double(num3);
resulttextfield.setText(n3.toString());
resulttextfield.select(0,0);
}
}
public static void main(String args[])
{
try
{
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
}
catch (Exception exe)
{
System.err.println("Error loading L&p:" + exe);
} Caculator panel=new Caculator();
frame=new JFrame("Caculator");
frame.addWindowListener(new WindowAdapter () {
public void windowClosing(WindowEvent e){ System.exit(0);}
});
frame.getContentPane.add("Center",panel);
frame.pack();
frame.setVisible(true);
}}
編譯之後發現提示:frame.getContentPane.add("Center",panel);
can not resolve symbol
symbol: variable getContentPane
location: class javax.swing.JFrame
frame.getContentPane.add("Center",panel);請問大俠如何修正啊
解决方案 »
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