java图像界面开发简单实例-JButton及事件的简单应用

java图像界面开发简单实例

JButton及事件的简单应用,做一个计算器的小例子，代码如下：

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

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

/**
* 计算器实例
* @author 左杰 jdk5.0
*/
public class CalculatorFrame extends JFrame {
/**
*
*/
private static final long serialVersionUID = 1L;

public CalculatorFrame() {
setTitle("计算器");
CalculatorPanel panel = new CalculatorPanel();
add(panel);
pack();
}

public static void main(String[] args) {
CalculatorFrame frame = new CalculatorFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}

/**
* 创建显示计算器的面板
*/
class CalculatorPanel extends JPanel {
/**
*
*/
private static final long serialVersionUID = 1L;

private JButton display;//用于显示结果
private JPanel panel;//创建用于显示数字及符号按钮的面板
private double result;//用于存储计算结果
private String lastCommand;//记录点击的符号
private boolean start;//开始标志

public CalculatorPanel() {
setLayout(new BorderLayout());
result = 0;
lastCommand = "=";
start = true;

// 添加
display = new JButton("0");
display.setEnabled(false);
add(display, BorderLayout.NORTH);

//创建事件侦听对象
ActionListener insert = new InsertAction();
ActionListener command = new CommandAction();

//添加数字及符号按钮的面板面板
panel = new JPanel();
panel.setLayout(new GridLayout(4, 4));//设置面板布局为4行4列
//添加数字及符号按钮
addButton("7", insert);
addButton("8", insert);
addButton("9", insert);
addButton("/", command);

addButton("4", insert);
addButton("5", insert);
addButton("6", insert);
addButton("*", command);

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

addButton("0", insert);
addButton(".", insert);
addButton("=", command);
addButton("+", command);

add(panel, BorderLayout.CENTER);
}

/**
* 用来设置按钮及添加相应的监听
*
* @param label 按钮显示的内容
* @param listener 相应事件侦听对象
*
*/
private void addButton(String label, ActionListener listener) {
JButton button = new JButton(label);
button.addActionListener(listener);
panel.add(button);
}

/**
* 点击数字按钮事件，用于显示数字及将start标志置为false;
*/
private class InsertAction implements ActionListener {
public void actionPerformed(ActionEvent event) {
String input = event.getActionCommand();
if (start) {
display.setText("");
start = false;
}
display.setText(display.getText() + input);
}
}

/**
* 点击符号按钮事件,并进行计算
*/
private class CommandAction implements ActionListener {
public void actionPerformed(ActionEvent event) {
String command = event.getActionCommand();
//如果start为true,表示开始那么点击-号表示输入负数
if (start) {
if (command.equals("-")) {
display.setText(command);
start = false;
} else
lastCommand = command;
} else {//start为false,进行计算
calculate(Double.parseDouble(display.getText()));
lastCommand = command;
start = true;
}
}
}

/**
* 计算方法更具输入的数据和符号进行计算
*
* @param x 输入的数字
*
*/
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;
display.setText("" + result);
}
}