Java GUI——一个简单的计算器

Java课的一次GUI作业，写了一个简单的计算器，支持加减乘除连续运算。代码很少，一百多行吧。

运行起来是这样子的

上面那个文本框就很奇怪，可能是用了setLayout的缘故，用setSize好像对它不起作用。不管它了，就这样吧2333。

贴个代码

package calculator;

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


public class Calculator extends JFrame implements ActionListener{
	private final String[] KEYS = {"√","C","⬅","÷","7","8","9","×","4","5","6","＋","1","2","3","-","±",".","0","＝"};
	private JButton keys[] = new JButton[KEYS.length];   //按钮
	private JTextField resultText = new JTextField("0");  //文本框
	private boolean firstDigit = true; //数字首位未按下标记
	private String operator ;
	private double lastNum = 0;
	
	
	//构造函数
	public Calculator(String title){
		super(title);
		initialize();
	}
	//初始化界面
	private void initialize() {
		
		JPanel keyPanel = new JPanel();
		keyPanel.setLayout(new GridLayout(5,4,3,3));  //网络布局 5行4列 间隔3个像素
		for(int i =0; i < KEYS.length; i++) {
			keys[i] = new JButton(KEYS[i]);
			keyPanel.add(keys[i]);
			keys[i].addActionListener(this);
			//数字键和算符键用颜色区分开
			if("0123456789.".indexOf(KEYS[i]) >= 0) keys[i].setForeground(Color.blue);
			else keys[i].setForeground(Color.RED);
		}
		this.add(keyPanel);
		resultText.setHorizontalAlignment(JTextField.RIGHT);
		resultText.setEditable(false);
		resultText.setBackground(Color.white);
		this.add("North", resultText);
		this.setVisible(true);
		this.pack();
		this.setBounds(500, 300, 400, 400);
	}
	
	@Override
	public void actionPerformed(ActionEvent e) {    //根据不同事件源选择相应操作
		// TODO Auto-generated method stub
        // 获取事件源的标签  
        String label = e.getActionCommand();  
        if (label.equals("⬅")) {  
            handleBackspace();  
        } else if (label.equals("C")) {  
            handleC();  
        } else if ("0123456789.".indexOf(label) >= 0) {  
            handleNumber(label);  
        } else {  
            handleOperator(label);  
        }  
	}
	
	//退格
    private void handleBackspace() {  
        String text = resultText.getText();  
        int i = text.length();  
        if (i > 0) {  
            // 退格
            text = text.substring(0, i - 1);  
            if (text.length() == 0) {  
                // 如果文本没有了内容，则初始化计算器的各种值  
                resultText.setText("0");  
                firstDigit = true;  
                operator = "";  
            } else {  
                // 显示新的文本  
                resultText.setText(text);  
            }  
        }  
    }  
    //数字键
    private void handleNumber(String key) {  
        if (firstDigit) {  
            // 数字的第一位
            resultText.setText(key);  
        } else if ((key.equals(".")) && (resultText.getText().indexOf(".") < 0)) {  
            // 输入的是小数点，小数点附在结果文本框的后面  
            resultText.setText(resultText.getText() + ".");  
        } else if (!key.equals(".")) {  
            // 输入的是数字，将数字附在结果文本框的后面  
            resultText.setText(resultText.getText() + key);  
        }  
        firstDigit = false;  
    }  
  
    //归零
    private void handleC() {  
        // 初始化
        resultText.setText("0");  
        firstDigit = true;  
        operator = "";  
    }  
    //算符键
    private void handleOperator(String key) {
    	double x = getNumberFromText(); //当前文本框中的操作数
    	if(key.equals("±")) {
    		x = x * (-1);
    	}
    	else if(key.equals("√"))
    	{
    		x = Math.sqrt(x);
    	}
    	else if(!key.equals("＝"))   //按下的是双目运算符e
    	{
    		lastNum = x;   //存下第一个操作数
    		operator = key;  //存下操作符
    		//System.out.println(key);
    	}
    	else {
    		System.out.println(operator);
    		if(operator.equals("＋")) {
    			x += lastNum;
    		}
    		else if(operator.equals("-")) {
    			x = lastNum - x;
    		}
    		else if(operator.equals("×")) {
    			x *= lastNum;
    		}
    		else if(operator.equals("÷"))
    		{
    			if(x==0.0)
    			{
    				resultText.setText("Error");
    				return ;
    			}
    			else
    				x = lastNum/x;
    		}
    		
    	}
		firstDigit = true;
    	setText(x);
    }
    
    //更新文本框显示
    private void setText(double res)
    {
        long t1;  
        double t2;  
        t1 = (long) res;  
        t2 = res - t1;  
        if (t2 == 0) {  
            resultText.setText(String.valueOf(t1));  
        } else {  
            resultText.setText(String.valueOf(res));  
        }  
    }
    //从文本框中获取数值
    private double getNumberFromText() {  
        double result = 0;  
        try {  
            result = Double.valueOf(resultText.getText()).doubleValue(); 
        } catch (NumberFormatException e) {  
        }  
        return result;  
    }  
	
	public static void main(String[] args) {
		Calculator cal = new Calculator("计算器");
	}
}