软帝学院教你用java编写计算器（二）

软帝学院教你用java编写计算器（二）

import java.awt.BorderLayout;

import java.awt.GridBagLayout;

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.JOptionPane;

import javax.swing.JPanel;

import javax.swing.JTextField;

public class Calculator extends JFrame implements ActionListener {

  JTextField result;

  int calculate_type=0;

  Calculator(){

 JPanel jp;

 JButton jb;

 jp= new JPanel();

 jp.setLayout(new BorderLayout());

 result = new JTextField();

 result.setEditable(false);

 jp.add(result,BorderLayout.NORTH);//窗口中间添加数字按钮、清空、退格、小数点按钮

 JPanel keyPanel = new JPanel();

 keyPanel.setLayout(new GridLayout(5,3));

 jb = new JButton("1");

 keyPanel.add(jb);

 jb.addActionListener(this);

 jb = new JButton("2");

 keyPanel.add(jb);

 jb.addActionListener(this);

 jb = new JButton("3");

 keyPanel.add(jb);

 jb.addActionListener(this);

 jb = new JButton("4");

 keyPanel.add(jb);

 jb.addActionListener(this);

 jb = new JButton("5");

 keyPanel.add(jb);

 jb.addActionListener(this);

 jb = new JButton("6");

 keyPanel.add(jb);

 jb.addActionListener(this);

 jb = new JButton("7");

 keyPanel.add(jb);

 jb.addActionListener(this);

 jb = new JButton("8");

 keyPanel.add(jb);

 jb.addActionListener(this);

 jb = new JButton("9");

 keyPanel.add(jb);

 jb.addActionListener(this);

 jb = new JButton("0");

 keyPanel.add(jb);

 jb.addActionListener(this);

 jb = new JButton("C");

 keyPanel.add(jb);

 jb.addActionListener(this);

 jb = new JButton("退格");

 keyPanel.add(jb);

 jb.addActionListener(this);

 jb = new JButton(".");

 keyPanel.add(jb);

 jb.addActionListener(this);

 jb = new JButton("=");

 keyPanel.add(jb);

 jb.addActionListener(this);

 jb = new JButton("CE");

 keyPanel.add(jb);

 jb.addActionListener(this);

 jp.add(keyPanel,BorderLayout.CENTER);

 JPanel operatorpJPanel = new JPanel();

 operatorpJPanel.setLayout(new GridLayout(4,1));

 jb = new JButton("+");

 operatorpJPanel.add(jb);

 jb.addActionListener(this);

 jb = new JButton("-");

 operatorpJPanel.add(jb);

 jb.addActionListener(this);

 jb = new JButton("*");

 operatorpJPanel.add(jb);

 jb.addActionListener(this);

 jb = new JButton("/");

 operatorpJPanel.add(jb);

 jb.addActionListener(this);

 jp.add(operatorpJPanel,BorderLayout.EAST);

 setContentPane(jp);

 setTitle("计算器");

 setSize(340,260);

 setVisible(true);

 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

  }

     public void  actionPerformed(ActionEvent e){

    String cmd =e.getActionCommand();

    String c =result.getText();

    if (cmd.equals("C")) {

result.setText("");

}

    else if (cmd.equals("退格")) {

if (c.length()>0) {

String slast = c.substring(c.length() -1);

if (slast.equals("+") || slast.equals("-") || slast.equals("*")  || slast.equals("/")) {

calculate_type = 0;//如果删除了运算符，将计算类型恢复为未确定状态

}

result.setText(c.substring(0,c.length() -1));

}

else if (cmd.compareTo("0")>=0 && cmd.compareTo("9")<=0) {

result.setText(c+cmd);

}

else if (cmd.equals(".")) {

result.setText(c+cmd);

}

else if (cmd.equals("+") || cmd.equals("-") || cmd.equals("*") || cmd.equals("/") ) {

if (calculate_type ==0) {

result.setText(c+cmd);

judgeCalculateType(cmd);//判断计算类型

}

else {//自上次计算完成后，第二次点击运算符，触发计算

calculate();

result.setText(result.getText()+cmd);

judgeCalculateType(cmd);//判断计算类型

}

}

else if (cmd.equals("=")) {//点击=进行计算

try {

} catch (Exception exp) {

JOptionPane.showMessageDialog(this, "输入错误，请检查输出或重新启动程序");

}

}

}

     }

   //判断计算类型

private void judgeCalculateType(String cmd) {

    if (cmd.equals("+"))

calculate_type =1;//记录运算类型

else if (cmd.equals("-"))

calculate_type =2;

else if(cmd.equals("*"))

calculate_type =3;

else

calculate_type =4;

}

//完成计算功能

   private void calculate() {

double rt,op1,op2;

String c = result.getText();

int pos;

char ops[] ={'+','-','*','/'};//查找运算符位置

pos =c.indexOf(ops[calculate_type-1]);//以运算符位置为分界点，分离出两个待计算的数

op1 = Double.parseDouble(c.substring(0,pos));

    op2 = Double.parseDouble(c.substring(pos+1));

    switch (calculate_type) {

case 1:

rt = op1+op2;

break;

case 2:

rt = op1-op2;

break;

case 3:

rt = op1*op2;

break;

case 4:

rt = op1/op2;

break;

default:

 rt =0;

}

    result.setText("" +rt);//显示计算结果

    calculate_type =0;//准备记录下次计算的类型

}

public static void main(String[] args) {

new Calculator();

}

}