Swing實現計算器GUI

package swing;

import java.awt.BorderLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextArea;
/**


@author He Jinlong
@version 2.0 第一個版本沒有使用網格布局，顯示出來的效果很糟糕，通過使用網格布局，終于實現了想要的結果
*/
public class NewCalculator extends JFrame {
// 定義菜單欄
 private JMenuBar bar;
 private JMenu mune;
 private JMenuItem itemhelp;
 private JMenuItem itemcaculater;
 // 建立2個大的容器
 private JPanel textPanel;// 存放顯示屏的容器
 private JPanel btnPanel;// 存放按鈕的容器
 private GridBagLayout gb;// 定義網格布局
 private GridBagConstraints gbc;// 定義網格的布局的大管家
 private JButton btn[] = new JButton[18];// 定義按鈕數組
 private JTextArea textArea;// 定義顯示屏
 private String btnStr[] = new String[18];// 定義按鈕內容
/**

構造方法，用來初始化計算器
*/
public NewCalculator() {
 init();
 addComponent();
 setJMenuBar(bar);
 setResizable(false);
 setLocation(500, 220);
 setTitle("我的計算器");
 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 setVisible(true);
 setSize(240, 300);
}
/**

初始化各個小組件
*/
public void init() {
 bar = new JMenuBar();
mune = new JMenu("幫助");
itemhelp = new JMenuItem("幫助");
 itemcaculater = new JMenuItem("關于計算機");
 itemhelp.addActionListener(menuListener);
 itemcaculater.addActionListener(menuListener);
textPanel = new JPanel();
 btnPanel = new JPanel();
gb = new GridBagLayout();
 gbc = new GridBagConstraints();
gbc.gridwidth = 1;
 gbc.gridheight = 1;
 gbc.fill = GridBagConstraints.BOTH;
 gbc.insets = new Insets(2, 2, 2, 2);
 gbc.gridx = 0;
 gbc.gridy = 0;
textArea = new JTextArea(3, 20);
 btnStr = new String[] { "  c ", "  EDL ", "  * ", "  / ", "  1 ",

     "  2 ", "  3 ", "  + ", "  4 ", "  5 ", "  6 ", "  - ", "  7 ",
     "  8 ", "  9 ", "  = ", "  0 ", "  . " };

for (int i = 0; i < btn.length; i++) {

 btn[i] = new JButton(btnStr[i]);
 btn[i].addActionListener(buttonListener);

}
}
/**

將各個小組件添加到容器中
*/
public void addComponent() {
 textArea.setEditable(false);
 textPanel.add(textArea);
btnPanel.setLayout(gb);
 for (int i = 0; i < btn.length; i++) {

 int x = 1;
 if (i == 15) {
     gbc.gridheight = 2;
 } else if (i == 17) {
     gbc.gridwidth = 2;
 }
 gb.setConstraints(btn[i], gbc);
 btnPanel.add(btn[i]);
 gbc.gridwidth = 1;
 gbc.gridheight = 1;
 gbc.gridx += x;
 if ((i + 1) % 4 == 0) {
     gbc.gridx = 0;
     gbc.gridy += 1;
 }


}
add(BorderLayout.NORTH, textPanel);
add(BorderLayout.CENTER, btnPanel);
bar.add(mune);
mune.add(itemhelp);
 mune.add(itemcaculater);
}
// 實例化一個監聽器，用來監聽按鈕點擊事件
private ActionListener buttonListener = new ActionListener() {
@Override
 public void actionPerformed(ActionEvent e) {

 String str = ((JButton) e.getSource()).getText();
 JOptionPane.showMessageDialog(null, "You clicked " + str
         + " button");

}
};
// 同上，用來監聽菜單上的點擊事件
private ActionListener menuListener = new ActionListener() {
@Override
 public void actionPerformed(ActionEvent e) {

 String str = ((JMenuItem) e.getSource()).getText();
 JOptionPane.showMessageDialog(null, "You clicked " + str
         + " button");

}
};
public static void main(String[] args) {
 new NewCalculator();
}
}</pre>