package hyw.calculator;

import java.awt.BorderLayout;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;

public class Calculator extends JFrame implements ActionListener {

	final String JButtonName[] = { "7", "8", "9", "+", "4", "5", "6", "-", "1", "2", "3", "×", ".", "0", "=", "÷" };
	Font font = new Font("宋体", Font.PLAIN, 17);
	JPanel p1, p2;
	JButton Jb[] = new JButton[JButtonName.length];// 创建按钮数组
	JButton ce;
	JTextField tf;

	public Calculator() {
		for (int i = 0; i < JButtonName.length; i++) {
			Jb[i] = new JButton("" + JButtonName[i]);//实例化并声明按钮名称
			Jb[i].setFont(font);// 设置字体
			Jb[i].setContentAreaFilled(false);// 设置按钮透明
			Jb[i].addActionListener(this);
		}
		p1 = new JPanel(new GridLayout(4, 4));// 设置成4X4的布 局
		for (int i = 0; i < JButtonName.length; i++) {
			p1.add(Jb[i]);
		}

		p2 = new JPanel(new BorderLayout());
		ce = new JButton("CE");
		ce.setContentAreaFilled(false);
		ce.addActionListener(this);
		tf = new JTextField("0");
		tf.setFont(font);
		p2.add(ce, "East");
		p2.add(tf, "Center");

		this.add(p2, BorderLayout.NORTH);
		this.add(p1, BorderLayout.CENTER);
		this.setVisible(true);
		this.setTitle("简易计算器");
		
		//使窗口居中
		int windowsWedth = 280;
		int windowsHeight = 300;
		int width = Toolkit.getDefaultToolkit().getScreenSize().width;
		int height = Toolkit.getDefaultToolkit().getScreenSize().height;
		this.setBounds((width - windowsWedth) / 2,
				(height - windowsHeight) / 2, windowsWedth, windowsHeight);

	}

	public void actionPerformed(ActionEvent e) {

		String label = e.getActionCommand();// 返回的是按的按钮名
		if (e.getSource() == ce)
			Reset();
		else if ("0123456789.".indexOf(label) >= 0)// 查找按钮是否为数字和"."
			RunNumber(label);
		else
			RunOperator(label);

	}
	// 是否是第一次按数字

	boolean isFirstDigit = true;

	public void RunNumber(String key) {
		if (isFirstDigit)
			tf.setText(key);// 如果是第一次按数字，覆盖文本框的内容
		else if ((key.equals(".")) && (tf.getText().indexOf(".") < 0))// 按了点并且文本框中之前没有点
			tf.setText(tf.getText() + ".");//如果按了多个".",只显示一个
		else if (!key.equals("."))
			tf.setText(tf.getText() + key);// 叠加显示在文本框中
		isFirstDigit = false;
	}

	double number = 0.0;
	String operator = "=";

	public void Reset() {// 重置
		tf.setText("0");
		isFirstDigit = true;
		operator = "=";
	}

	public void RunOperator(String key) {
		if (operator.equals("+"))
			number += Double.valueOf(tf.getText());// 将文本框中的字符串强制转化为Double类型
		else if (operator.equals("-"))
			number -= Double.valueOf(tf.getText());
		else if (operator.equals("×"))
			number *= Double.valueOf(tf.getText());
		else if (operator.equals("÷")) {
			number /= Double.valueOf(tf.getText());
		} else if (operator.equals("="))
			number = Double.valueOf(tf.getText());
		tf.setText(String.valueOf(number));
		operator = key;
		isFirstDigit = true;
	}

	public static void main(String[] args) {
		new Calculator();
	}
}