import java.awt.Container;
import java.awt.FlowLayout;
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.JPanel;
import javax.swing.JTextField;


public class Exercise1 extends JFrame implements ActionListener{


 private JPanel p1 = new JPanel(); //創(chuàng)建面板 
 private JPanel p2 = new JPanel(); //創(chuàng)建面板 
 private JTextField t1; //文本框1用來顯示輸入信息 
 StringBuffer str;//輸入的字符串
 JButton[] b=new JButton[10];
 JButton b1,b2,b3,b4,b5,b6;//16個按鈕
 double x,y;
 int n;
 public Exercise1() {
 
 super("假隊長的大目標(biāo)"); 
 setSize(350,300); //設(shè)置窗口大小
 setLocationRelativeTo(null); //顯示到中間 
 Container c = getContentPane(); //創(chuàng)建內(nèi)容面板對象 
 
 t1 = new JTextField(25); 
 t1.setEditable(false); //只能顯示，不能編輯 
 
 p2.add(t1); //添加文本框到面板 

 p2.setLayout(new GridLayout(3,2)); //把面扳布局為4行1列 

 str=new StringBuffer(); 
 //實例化各個按鈕 
 for(int i=0;i<10;i++) //分別為數(shù)組中0~9號的按鈕設(shè)置標(biāo)簽，并注冊監(jiān)聽器 
 { 
 String s=""+i; 
 b[i]= new JButton(s); 
 b[i].addActionListener(this); 
 } 
 b1=new JButton("+");
 b2=new JButton("-");
 b3=new JButton("*");
 b4=new JButton("/"); 
 b5=new JButton("=");
 b6=new JButton("delete"); 
 
 //添加到面板
 p1.add(b[7]);
 p1.add(b[8]);
 p1.add(b[9]);
 p1.add(b1);
 p1.add(b[4]);
 p1.add(b[5]);
 p1.add(b[6]); 
 p1.add(b2);
 p1.add(b[1]);
 p1.add(b[2]);
 p1.add(b[3]); 
 p1.add(b3);
 p1.add(b[0]);
 p1.add(b5);
 p1.add(b6);
 p1.add(b4); 
 p1.setLayout(new GridLayout(4,5,10,10)); 
 
 //注冊監(jiān)聽器 
 
 b1.addActionListener(this);
 b2.addActionListener(this);
 b3.addActionListener(this);
 b4.addActionListener(this);
 b5.addActionListener(this);
 b6.addActionListener(this);
 
 //將內(nèi)容添加到面板上然后添加到容器里
 c.add(p2); 
 c.add(p1); 
 c.setLayout(new FlowLayout()); //設(shè)置為順序布局 
 //設(shè)置窗口關(guān)閉動作 
 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //設(shè)置窗口關(guān)閉動作 
 setVisible(true); //設(shè)置為可見 
 setResizable(false); //禁止調(diào)整框架大小 
 
 }
 
 public static void main(String[] args) {
 // TODO Auto-generated method stub
 @SuppressWarnings("unused")
 Exercise1 calculate=new Exercise1();
 }


 @Override
 public void actionPerformed(ActionEvent e) {
 // TODO Auto-generated method stub 
 
 if(e.getSource()==b6){
 t1.setText("0");//清零
 t1.setHorizontalAlignment(JTextField.RIGHT);//右對齊
 str.setLength(0);
 }
 
 //Double.parseDouble 將字符串轉(zhuǎn)化為double類型
 //t1.getText().trim() 獲取字符保存后并且清除
 else if (e.getSource()==b1)//單擊加號按鈕獲得x的值并清空y的值 
 { 
 x=Double.parseDouble(t1.getText().trim()); 
 str.setLength(0); 
 y=0d; 
 n=0;
 }else if(e.getSource()==b2)//減法運算
 {
 x=Double.parseDouble(t1.getText().trim()); 
 str.setLength(0); 
 y=0d;
 n=1;
 }else if(e.getSource()==b3)//乘法運算
 {
 x=Double.parseDouble(t1.getText().trim()); 
 str.setLength(0); 
 y=0d;
 n=2;
 }else if(e.getSource()==b4)//除法運算
 {
 x=Double.parseDouble(t1.getText().trim()); 
 str.setLength(0); 
 y=0d;
 n=3;
 }else if(e.getSource()==b5)//等號
 {
 str.setLength(0);
 switch(n){
 case 0:t1.setText(""+(x+y));break;
 case 1:t1.setText(""+(x-y));break;
 case 2:t1.setText(""+(x*y));break;
 case 3:t1.setText(""+(x/y));break;
 } 
 }else{
 if(e.getSource()==b[0])
 {
 if(t1.getText().trim().equals("0"))//如果顯示屏顯示的為零不做操作 
 {} 
 else
 t1.setText(str.append(e.getActionCommand()).toString());
 t1.setHorizontalAlignment(JTextField.RIGHT); 
 y=Double.parseDouble(t1.getText().trim());
 }
 else 
 { 
 t1.setText(str.append(e.getActionCommand()).toString()); 
 t1.setHorizontalAlignment(JTextField.RIGHT); 
 y=Double.parseDouble(t1.getText().trim()); 
 }
 }
 } 
}