java非常简单的问题（用swing做计算器）

王兰花 2018-05-09 05:40:33

package src.test;

import java.awt.*;

import javax.swing.*;

import java.awt.event.*;

public class examplethree extends JFrame {

	JTextField inputField;

	JPanel p1=new JPanel();

	JPanel p2=new JPanel();

	double result;//计算结果

	String symbol;//运算符号

	public void addButton(String a, ActionListener cc){ 

		JButton button = new JButton(a);

		button.addActionListener(cc);

		p2.add(button);

	}

	public examplethree(){ 

		JMenuBar menubar=new JMenuBar();

		this.setJMenuBar(menubar);

		JMenu menu1=new JMenu("简单");

		JMenu menu2=new JMenu("完整");

		JMenu menu3=new JMenu("科学");

		menubar.add(menu1);

		menubar.add(menu2);

		menubar.add(menu3);

		symbol="=";

		this.setTitle("计算器");

		this.setSize(200, 300);

		this.setDefaultCloseOperation(EXIT_ON_CLOSE);

		this.setVisible(true);      

		inputField = new JTextField(20);

		p1.add(inputField);

		this.add(p1,BorderLayout.NORTH);

		p2.setLayout(new GridLayout(4, 4 , 6, 6));

		class Action1 implements ActionListener{

			public void actionPerformed(ActionEvent e){

				String input=e.getActionCommand();

				inputField.setText(inputField.getText()+input);

			}

		}

		class Action2 implements ActionListener{

			public void actionPerformed(ActionEvent e){

				String input=e.getActionCommand();

				symbol = input;

				result =Double.parseDouble(inputField.getText());

				if(symbol.equals("+")){

					inputField.setText(" ");

					result +=Double.parseDouble(input);

				}

				else if(symbol.equals("-")){

					result -=Double.parseDouble(inputField.getText()); 

				}

				else if(symbol.equals("*")){

					result *=Double.parseDouble(inputField.getText()); 

				}

				else if(symbol.equals("/")){

					result /=Double.parseDouble(inputField.getText()); 

				}else{

						result =Double.parseDouble(inputField.getText());

				 }

				inputField.setText(result+"");

				

			}

		}

		class Action3 implements ActionListener{

			public void actionPerformed(ActionEvent e){

				String input=e.getActionCommand();

				if(input.equals("C")){

					inputField.setText("0");

				}

			}

		}

		menu2.addActionListener(new ActionListener(){

			public void actionPerformed(ActionEvent e){

				JPanel panel1=new JPanel();

				JLabel label=new JLabel("wobu",JLabel.CENTER);

				label.setFont(new Font("宋体",Font.PLAIN,20));

				panel1.add(label);

				panel1.setVisible(true); 

			}

		});

		Action1 a1 = new Action1();

		Action2 a2 = new Action2();

		Action3 a3 = new Action3();

		this.addButton("7",a1);

		this.addButton("8",a1);

		this.addButton("9",a1);

		this.addButton("+",a2);

		this.addButton("4",a1);

		this.addButton("5",a1);

		this.addButton("6",a1);

		this.addButton("-",a2);

		this.addButton("1",a1);

		this.addButton("2",a1);

		this.addButton("3",a1);

		this.addButton("*",a2);

		this.addButton("0",a1);

		this.addButton("C",a3);

		this.addButton("=",a2);

		this.addButton("/",a2);

		this.add(p2,BorderLayout.SOUTH);

		this.pack(); 

		

	}//构造方法

	public static void main(String[] args){

		new examplethree();

	}

}

可能逻辑有错误可是我找不出来了，运行加法运算只显示后面输入的·数字，求解

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我自横刀香甜笑 2018-05-11

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跟你的减号的处理一样的就可以了。。。。。

我自横刀香甜笑 2018-05-11

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引用 3 楼 sinat_33854637 的回复:

[quote=引用 2 楼 lye2000000_super 的回复:] if(symbol.equals("+")){ inputField.setText(" "); result +=Double.parseDouble(input); } 因为你解析的是加号。。。。。。

我是先实现加法的啊，运行加法运算只显示后面输入的·数字这里不懂呢[/quote] class Action2 implements ActionListener{ public void actionPerformed(ActionEvent e){ String input=e.getActionCommand(); symbol = input; result =Double.parseDouble(inputField.getText()); if(symbol.equals("+")){ inputField.setText(" "); result +=Double.parseDouble(input); } else if(symbol.equals("-")){ result -=Double.parseDouble(inputField.getText()); } else if(symbol.equals("*")){ result *=Double.parseDouble(inputField.getText()); } else if(symbol.equals("/")){ result /=Double.parseDouble(inputField.getText()); }else{ result =Double.parseDouble(inputField.getText()); } inputField.setText(result+""); } } 把红色的地方改成result +=Double.parseDouble(inputField.getText()); 你在把加号解析成数字，自然会报错不出结果了。实际上是出了异常了。所以不出结果。

王兰花 2018-05-10