helloframe.java

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package hello;

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

public class HelloFrame extends JFrame {
  JPanel contentPane; 
  BorderLayout borderLayout1 = new BorderLayout();

  //打开窗口的主方法
  public static void main(String[] args) {
    HelloFrame frame = new HelloFrame();
    //取得屏幕大小    
    Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
    //取得窗口大小    
    Dimension frameSize = frame.getSize();
    //使窗口居中对齐
    frame.setLocation( (screenSize.width - frameSize.width) / 2,
                      (screenSize.height - frameSize.height) / 2);
    frame.setVisible(true);
  }
  
  //类的构造器
  public HelloFrame() {
    try {
      jbInit();
    }
    catch(Exception e) {
      e.printStackTrace();
    }
  }

  //初始化窗口的方法
  private void jbInit() throws Exception  {
    contentPane = (JPanel) this.getContentPane();
    contentPane.setLayout(borderLayout1);
    this.setSize(new Dimension(400, 300));
    this.setTitle("Hello窗口程序");
  }

  //当窗口关闭时清空内存
  protected void processWindowEvent(WindowEvent e) {
    if (e.getID() == WindowEvent.WINDOW_CLOSING) {
      System.exit(0);
    }
  }
}