import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class Calculator extends Frame {
    
    private double value = 0.0;
    private String fuhao = "";
    private String valueString = "0";
    private int flag = 0;
    
    Button[] b = new Button[18];
    JPanel jp = new JPanel();
    JTextField tf = new JTextField("0", 20);
    
    public static void main(String[] args) {
        Calculator cal = new Calculator();
        cal.launchframe();
    }

    public void launchframe() {
        this.setTitle("计算器 V1.0");
        this.setVisible(true);
        this.setResizable(false);
        this.setBounds(450, 150, 230, 320);

        jp.setLayout(new GridLayout(5, 4));
        this.add(jp);
        Draw();

        MenuBar mb = new MenuBar();
        this.setMenuBar(mb);
        Menu m1 = new Menu("文件");
        Menu m2 = new Menu("帮助");
        mb.add(m1);
        mb.add(m2);
        MenuItem mi11 = new MenuItem("保存结果");
        MenuItem mi12 = new MenuItem("退出");
        MenuItem mi2 = new MenuItem("关于计算器");
        m1.add(mi11);
        m1.add(mi12);
        m2.add(mi2);
        mi11.addActionListener(new Mb1());
        mi12.addActionListener(new Mb1());
        mi2.addActionListener(new Mb2());
        this.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });
    }

    public void Draw() {
        String str[] = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "+",
                "-", "*", "/", ".", "%", "C", "=", };
        for (int i = 0; i < b.length; i++) {
            b[i] = new Button(str[i]);
            jp.add(b[i]);
            b[i].addActionListener(new Btn());
        }
        this.add(tf, BorderLayout.NORTH);

    }

    public class Btn implements ActionListener {

        public void actionPerformed(ActionEvent e) {
            String s = e.getActionCommand();

            if ("0123456789".indexOf(s) != -1) {
                if (flag == 1) {
                    flag = 2;//第二次输入数字的时候修改flag的值,影响=号
                    valueString = "0";
                }
                if (s.equals(".") && valueString.indexOf(".") == -1) {
                    valueString += s;
                } else {
                    valueString += s;//数字赋值
                    }
                if (valueString.startsWith("0")) {
                    valueString = valueString.substring(1);//覆盖初始时的0
                }
            } else if ("+-*/".indexOf(s) != -1) {
                if (flag == 0) {
                    flag = 1;//第一次输入数字修改flag的值
                    value = Double.parseDouble(valueString);//value里保存valueString里第一次输入的数值
            } else if (flag == 2) {
                    jisuan(valueString, value, fuhao);
                    flag = 1;    
                }
                fuhao = s;
            } else if ("=".equals(s)) {
                if (flag == 2) {
                    jisuan(valueString, value, fuhao);
                }
                flag = 0;//初始化
            } else if ("C".equals(s)) {
                value = 0.0;
                fuhao = "";
                valueString = "0";
                flag = 0;
            }
            showValueString();
            
        }
    }
    private void showValueString() {
        tf.setText(valueString);
        
    }

    private void jisuan(String valueString, double value, String fuhao) {
        double v = Double.parseDouble(valueString);
        double sum = 0;
        if (fuhao == "+") {
            sum = v + value;
        } else if (fuhao == "-") {
            sum = v - value;
        } else if (fuhao == "*") {
            sum = v * value;
        } else if (fuhao == "/") {
            sum = v % value;
        }
        valueString = sum + "";
        System.out.println(sum);
    }

    class Mb1 implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            System.exit(0);
        }
    }

    class Mb2 extends JFrame implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            JOptionPane.showMessageDialog(null,
                    "", "信息",
                    JOptionPane.PLAIN_MESSAGE);
        }
    }
}