trans_three.java

这是我在北大青鸟的第一学期的一个毕业设计

import java.awt.*;

import javax.swing.*;
import javax.swing.border.BevelBorder;
import javax.swing.event.*;
import java.awt.event.*;
import java.util.*;

class TransparentBackground extends JComponent
              implements ComponentListener, WindowFocusListener,Runnable {

    private JFrame frame;
    private Image background;
    private long lastupdate = 0;
    public boolean refreshRequested = true;

    public TransparentBackground(JFrame frame) {
        this.frame = frame;
        updateBackground( );
        frame.addComponentListener(this);
        frame.addWindowFocusListener(this);
        new Thread(this).start( );
    }

    /**
     * @todo  获取背景图片
     *
     */
    public void updateBackground( ) {
      try {
        Robot rbt = new Robot( );
        Toolkit tk = Toolkit.getDefaultToolkit( );
        Dimension dim = tk.getScreenSize( );
        background = rbt.createScreenCapture(
        new Rectangle(0,0,(int)dim.getWidth( ),
                          (int)dim.getHeight( )));
      } catch (Exception ex) {
        ex.printStackTrace( );
      }
    }
    /**
     * @todo 通过当前frame的大小和位置在 background背景中截取图
     *       作为当前frame的背景图片
     */
    public void paintComponent(Graphics g) {
      Point pos = this.getLocationOnScreen( );
      Point offset = new Point(-pos.x,-pos.y);
      g.drawImage(background,offset.x,offset.y,null);
    }


    public void componentShown(ComponentEvent evt) { repaint( ); }
    public void componentResized(ComponentEvent evt) { repaint( ); }
    public void componentMoved(ComponentEvent evt) { repaint( ); }
    public void componentHidden(ComponentEvent evt) { }
    public void windowGainedFocus(WindowEvent evt) { refresh( ); }
    public void windowLostFocus(WindowEvent evt) { refresh( ); }

    /**
     * @todo  用上面获取的图片更新背景
     *
     */
    public void refresh( ) {
      if(frame.isVisible( )) {
          repaint( );
          refreshRequested = true;
          lastupdate = new Date( ).getTime( );
      }
    }


    public void run( ) {
      try {
          while(true) {
              Thread.sleep(250);
              long now = new Date( ).getTime( );
              if(refreshRequested &&
                  ((now - lastupdate) > 1000)) {
                  if(frame.isVisible( )) {
                      Point location = frame.getLocation( );
                      frame.setVisible(false );
                      updateBackground( );
                      frame.setVisible(true );
                  frame.setLocation(location);
                      refresh( );
                  }
                  lastupdate = now;
                  refreshRequested = false;
                  }
              }
          } catch (Exception ex) {
             ex.printStackTrace( );
          }
      }

}