[java]ItemEvent事件：简单计算器

代码：

Example9_8.java

public class Example9_8
{
	public static void main(String args[]){
		WindowOperation win = new WindowOperation();
		win.setBounds(100,100,390,360);
		win.setTitle("简单计算器");
	}
}

WindowOperation.java

import java.awt.*;
import javax.swing.*;
import java.io.*;
public class WindowOperation extends JFrame
{
	JTextField inputNumberOne,inputNumberTwo;
	JComboBox choiceFuhao;
	JTextArea textShow;
	JButton button;
	OperatorListener operator;
	ComputerListener computer;
	public WindowOperation()
	{
		init();
		setVisible(true);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}
	void init(){
		setLayout(new FlowLayout());
		inputNumberOne = new JTextField(5);
		inputNumberTwo = new JTextField(5);
		choiceFuhao= new JComboBox();
		button=new JButton("计算");
		choiceFuhao.addItem("选择运算符号:");
		String [] a={"+","-","*","/"};
		for(int i=0;i<a.length;i++){
			choiceFuhao.addItem(a[i]);
		}
		textShow=new JTextArea(9,30);
		operator=new OperatorListener();
		computer=new ComputerListener();
		operator.setJComboBox(choiceFuhao);
		operator.setWorkTogether(computer);
		computer.setJTextFieldOne(inputNumberOne);
		computer.setJTextFieldTwo(inputNumberTwo);
		computer.setJTextArea(textShow);
		choiceFuhao.addItemListener(operator);
		button.addActionListener(computer);
		add(inputNumberOne);
		add(choiceFuhao);
		add(inputNumberTwo);
		add(button);
		add(new JScrollPane(textShow));
	}
}

OperatorListener.java

import java.awt.event.*;
import javax.swing.*;
public class OperatorListener implements ItemListener
{
	JComboBox choice;
	ComputerListener workTogether;
	public void setJComboBox(JComboBox box){
		choice =box;
	}
	public void setWorkTogether(ComputerListener computer){
		workTogether=computer;
	}
	public void itemStateChanged(ItemEvent e){
		String fuhao= choice.getSelectedItem().toString();
		workTogether.setFuhao(fuhao);
	}
}

ComputerListener.java

import java.awt.event.*;
import javax.swing.*;
public class ComputerListener implements ActionListener
{
	JTextField inputNumberOne,inputNumberTwo;
	JTextArea textShow;
	String fuhao;
	public void setJTextFieldOne(JTextField t){
		inputNumberOne=t;
	}
	public void setJTextFieldTwo(JTextField t){
		inputNumberTwo=t;
	}
	public void setJTextArea(JTextArea area){
		textShow = area;
	}
	public void setFuhao(String s){
		fuhao=s;
	}
	public void actionPerformed(ActionEvent e){
		try{
			double number1=Double.parseDouble(inputNumberOne.getText());
			double number2=Double.parseDouble(inputNumberTwo.getText());
			double result =0;
			if(fuhao.equals("+")){
				result=number1+number2;
			}
			else if(fuhao.equals("-")){
				result=number1-number2;
			}
			else if(fuhao.equals("/")){
				result=number1/number2;
			}
			else if(fuhao.equals("*")){
				result=number1*number2;
			}
			textShow.append(number1+" "+fuhao+" "+number2+" = "+result+"\n");
		}
		catch(Exception exp){
			textShow.append("\n请输入数字字符\n");
		}
	}

}

运行截图：