java 简单计算器

最新推荐文章于 2023-04-24 14:04:14 发布

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最新推荐文章于 2023-04-24 14:04:14 发布

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文章标签： java insert constraints command string button

本文介绍了一个使用Java Swing创建的简单计算器应用程序。该计算器具备基本的数学运算功能，并通过GridBagLayout实现了灵活的界面布局。

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import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Calculator extends JFrame
{
private Container container;
private GridBagLayout layout;
private GridBagConstraints constraints;
private JTextField displayField;//计算结果显示区
private String lastCommand;//保存+,-,*,/,=命令
private double result;//保存计算结果
private boolean start;//判断是否为数字的开始

public Calculator()
{
super("Calculator");
container=getContentPane();
layout=new GridBagLayout();
container.setLayout(layout);
constraints=new GridBagConstraints();

start=true;
result=0;
lastCommand = "=";

displayField=new JTextField(20);
displayField.setHorizontalAlignment(JTextField.RIGHT);
constraints.gridx=0;
constraints.gridy=0;
constraints.gridwidth=4;
constraints.gridheight=1;
constraints.fill=GridBagConstraints.BOTH;
constraints.weightx=100;
constraints.weighty=100;
layout.setConstraints(displayField,constraints);
container.add(displayField);

ActionListener insert = new InsertAction();
    ActionListener command = new CommandAction();

addButton("Backspace",0,1,2,1,insert);
addButton("CE",2,1,1,1,insert);
addButton("C",3,1,1,1,insert);

addButton("7",0,2,1,1,insert);
addButton("8",1,2,1,1,insert);
addButton("9",2,2,1,1,insert);
addButton("/",3,2,1,1,command);

addButton("4",0,3,1,1,insert);
addButton("5",1,3,1,1,insert);
addButton("6",2,3,1,1,insert);
addButton("*",3,3,1,1,command);

addButton("1",0,4,1,1,insert);
addButton("2",1,4,1,1,insert);
addButton("3",2,4,1,1,insert);
addButton("-",3,4,1,1,command);

addButton("0",0,5,1,1,insert);
addButton("+/-",1,5,1,1,insert);//只显示"-"号,"+"没有实用价值
addButton(".",2,5,1,1,insert);
addButton("+",3,5,1,1,command);

addButton("=",0,6,4,1,command);

setSize(300,300);
setVisible(true);
}
private void addButton(String label,int row,int column,int with,int height,ActionListener listener)
{
   JButton button=new JButton(label);

   constraints.gridx=row;
   constraints.gridy=column;

   constraints.gridwidth=with;
   constraints.gridheight=height;

    constraints.fill=GridBagConstraints.BOTH;

   button.addActionListener(listener);
   layout.setConstraints(button,constraints);
   container.add(button);
}
private class InsertAction implements ActionListener
    {
       public void actionPerformed(ActionEvent event)
       {
          String input=event.getActionCommand();
          if (start)
          {
             displayField.setText("");
             start=false;

             if(input.equals("+/-"))
             displayField.setText(displayField.getText()+"-");
          }
          if(!input.equals("+/-"))
          {
           if(input.equals("Backspace"))
           {
            String str=displayField.getText();
            if(str.length()>0)
              displayField.setText(str.substring(0,str.length()-1));
            }
           else if(input.equals("CE")||input.equals("C"))
           {
            displayField.setText("0");
            start=true;
           }
           else
             displayField.setText(displayField.getText()+input);
         }
       }
    }
    private class CommandAction implements ActionListener
    {
       public void actionPerformed(ActionEvent evt)
       {
          String command=evt.getActionCommand();
          if(start)
          {
           lastCommand=command;
          }
          else
          {
          calculate(Double.parseDouble(displayField.getText()));
          lastCommand=command;
          start=true;
          }
         }
      }
   public void calculate(double x)
   {
      if (lastCommand.equals("+")) result+= x;
      else if (lastCommand.equals("-")) result-=x;
      else if (lastCommand.equals("*")) result*=x;
      else if (lastCommand.equals("/")) result/=x;
      else if (lastCommand.equals("=")) result=x;
       displayField.setText(""+ result);
    }
   public static void main(String []args)
   {
     Calculator calculator=new Calculator();
     calculator.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
   }
}