新手！编了简单计算器！为什么不行！
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
@SuppressWarnings("serial")
public class Calculator extends JFrame
{
private JTextField text;
StringBuilder str=new StringBuilder("");
double i;
double num=0;
public static void main(String[] args)
{
zys fr=new zys();
fr.setVisible(true);
}
public Calculator()
{
setTitle("计算器");
setBounds(100,100,250,200);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setResizable(false);
JPanel pan = new JPanel();
pan.setLayout(new BorderLayout(0,0));
setContentPane(pan);
JPanel pan1=new JPanel();
pan.add(pan1,BorderLayout.NORTH);
text = new JTextField();
text.setHorizontalAlignment(SwingConstants.RIGHT);
pan1.add(text);
text.setColumns(18);
JPanel pan2=new JPanel();
pan.add(pan2,BorderLayout.CENTER);
pan2.setLayout(new GridLayout(4,4,5,5));
JButton but1=new JButton("7");
pan2.add(but1);
but1.addActionListener(new NumberListener());
JButton but2=new JButton("8");
pan2.add(but2);
but2.addActionListener(new NumberListener());
JButton but3=new JButton("9");
pan2.add(but3);
but3.addActionListener(new NumberListener());
JButton but4=new JButton("+");
pan2.add(but4);
but4.addActionListener(new NumberListener());
JButton but5=new JButton("4");
pan2.add(but5);
but5.addActionListener(new NumberListener());
JButton but6=new JButton("5");
pan2.add(but6);
but6.addActionListener(new NumberListener());
JButton but7=new JButton("6");
pan2.add(but7);
but7.addActionListener(new NumberListener());
JButton but8=new JButton("-");
pan2.add(but8);
but8.addActionListener(new NumberListener());
JButton but9=new JButton("1");
pan2.add(but9);
but9.addActionListener(new NumberListener());
JButton but10=new JButton("2");
pan2.add(but10);
but10.addActionListener(new NumberListener());
JButton but11=new JButton("3");
pan2.add(but11);
but11.addActionListener(new NumberListener());
JButton but12=new JButton("*");
pan2.add(but12);
but12.addActionListener(new NumberListener());
JButton but13=new JButton("0");
pan2.add(but13);
but13.addActionListener(new NumberListener());
JButton but14=new JButton(".");
pan2.add(but14);
but14.addActionListener(new NumberListener());
JButton but15=new JButton("=");
pan2.add(but15);
but15.addActionListener(new NumberListener());
JButton but16=new JButton("/");
pan2.add(but16);
but16.addActionListener(new NumberListener());
}
class NumberListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
String stre=new String();
if(e.getActionCommand().equals("+")||e.getActionCommand().equals("-")||e.getActionCommand().equals("*")||e.getActionCommand().equals("/"))
{
stre=e.getActionCommand();
str=new StringBuilder("");
i=num;
}
str.append(String.valueOf(e.getActionCommand()));
text.setText(String.valueOf(str));
num=Double.parseDouble("str");
if(e.getActionCommand().equals("=")){
if (stre.equals("+"))
text.setText(""+(i+num));
else if (stre.equals("-"))
text.setText(""+(i-num));
else if (stre.equals("*"))
text.setText(""+(i*num));
else if (stre.equals("/"))
text.setText(""+(i/num));
}
}
}
}
[解决办法]
我改了几个地方,能运行,楼主参考一下:
import javax.swing.*;import java.awt.*;import java.awt.event.*;@SuppressWarnings("serial")public class Calculator extends JFrame{ private JTextField text; StringBuilder str=new StringBuilder(""); String stre=new String(); //设为公用。 double i; double num=0; public static void main(String[] args) { //zys fr=new zys(); Calculator fr=new Calculator(); fr.setVisible(true); } public Calculator() { ActionListener al=new NumberListener(); //让所有的按钮公用一个监听对象。 setTitle("计算器"); setBounds(100,100,250,200); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setResizable(false); JPanel pan = new JPanel(); pan.setLayout(new BorderLayout(0,0)); setContentPane(pan); JPanel pan1=new JPanel(); pan.add(pan1,BorderLayout.NORTH); text = new JTextField(); text.setHorizontalAlignment(SwingConstants.RIGHT); pan1.add(text); text.setColumns(18); JPanel pan2=new JPanel(); pan.add(pan2,BorderLayout.CENTER); pan2.setLayout(new GridLayout(4,4,5,5)); JButton but1=new JButton("7"); pan2.add(but1); but1.addActionListener(al); JButton but2=new JButton("8"); pan2.add(but2); but2.addActionListener(al); JButton but3=new JButton("9"); pan2.add(but3); but3.addActionListener(al); JButton but4=new JButton("+"); pan2.add(but4); but4.addActionListener(al); JButton but5=new JButton("4"); pan2.add(but5); but5.addActionListener(al); JButton but6=new JButton("5"); pan2.add(but6); but6.addActionListener(al); JButton but7=new JButton("6"); pan2.add(but7); but7.addActionListener(al); JButton but8=new JButton("-"); pan2.add(but8); but8.addActionListener(al); JButton but9=new JButton("1"); pan2.add(but9); but9.addActionListener(al); JButton but10=new JButton("2"); pan2.add(but10); but10.addActionListener(al); JButton but11=new JButton("3"); pan2.add(but11); but11.addActionListener(al); JButton but12=new JButton("*"); pan2.add(but12); but12.addActionListener(al); JButton but13=new JButton("0"); pan2.add(but13); but13.addActionListener(al); JButton but14=new JButton("."); pan2.add(but14); but14.addActionListener(al); JButton but15=new JButton("="); pan2.add(but15); but15.addActionListener(al); JButton but16=new JButton("/"); pan2.add(but16); but16.addActionListener(al); } class NumberListener implements ActionListener { public void actionPerformed(ActionEvent e) { //String stre=new String(); if(e.getActionCommand().equals("+")||e.getActionCommand().equals("-") ||e.getActionCommand().equals("*")|| e.getActionCommand().equals("/")) { stre=e.getActionCommand(); str=new StringBuilder(""); i=num; } else if(e.getActionCommand().equals("=")) { if (stre.equals("+")) { text.setText(""+(i+num)); stre=""; //清除原来的值. str=new StringBuilder(""); } else if (stre.equals("-")) { text.setText(""+(i-num)); stre=""; str=new StringBuilder(""); } else if (stre.equals("*")) { text.setText(""+(i*num)); stre=""; str=new StringBuilder(""); } else if (stre.equals("/")) { text.setText(""+(i/num)); stre=""; str=new StringBuilder(""); } } else //既不是"+ - * /" 又不是"=" 就是数字。 { str.append(String.valueOf(e.getActionCommand())); text.setText(String.valueOf(str)); //num=Double.parseDouble("str"); num=Double.parseDouble(str.toString()); } } }}