java懸浮窗效果

import   java.awt.*; 
import   java.awt.event.MouseEvent; 

import   javax.swing.JFrame; 
import   javax.swing.JLabel; 
import   javax.swing.event.MouseInputAdapter; 

public   class   UndecoratedFrame   extends   JFrame 
{ 
private   static   final   int   TITLE_HEIGHT   =   20; 

public   UndecoratedFrame()   throws   HeadlessException 
{ 
super(); 
setUndecorated(true); 

MouseHandler   ml   =   new   MouseHandler(); 
addMouseListener(ml); 
addMouseMotionListener(ml); 
} 

public   UndecoratedFrame(String   title)   throws   HeadlessException 
{ 
super(title); 
setUndecorated(true); 

MouseHandler   ml   =   new   MouseHandler(); 
addMouseListener(ml); 
addMouseMotionListener(ml); 
} 

public   Insets   getInsets() 
{ 
return   new   Insets(TITLE_HEIGHT,   1,   1,   1); 
} 

public   void   paint(Graphics   g) 
{ 
super.paint(g); 
g.setColor(new   Color(0,   0,   128)); 
g.drawRect(0,   0,   getWidth()-1,   getHeight()-1); 
g.fillRect(0,   0,   getWidth(),   TITLE_HEIGHT); 

FontMetrics   fm   =   g.getFontMetrics(); 
g.setColor(Color.white); 
g.drawString(getTitle(),   2,   (TITLE_HEIGHT   -   fm.getHeight())   /   2   +   fm.getAscent()); 
} 

private   class   MouseHandler   extends   MouseInputAdapter 
{ 
private   Point   point; 

public   void   mousePressed(MouseEvent   e) 
{ 
if   (e.getY()   <=   TITLE_HEIGHT)   { 
this.point   =   e.getPoint(); 
} 
} 

public   void   mouseDragged(MouseEvent   e) 
{ 
if   (point   !=   null)   { 
setCursor(Cursor.getPredefinedCursor(Cursor.MOVE_CURSOR)); 

Point   p   =   e.getPoint(); 
int   dx   =   p.x   -   point.x; 
int   dy   =   p.y   -   point.y; 

int   x   =   getX(); 
int   y   =   getY(); 
setLocation(x   +   dx,   y   +   dy); 
} 
} 

public   void   mouseReleased(MouseEvent   e) 
{ 
point   =   null; 
setCursor(Cursor.getDefaultCursor()); 
} 
} 

public   static   void   main(String[]   args) 
{ 
JFrame   f   =   new   UndecoratedFrame( "Undecorated   Frame "); 
f.getContentPane().add(new   JLabel( "Hello   World! ",   JLabel.CENTER),   BorderLayout.CENTER); 
f.setSize(400,   400); 
f.setLocationRelativeTo(null); 
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
f.setVisible(true); 
} 

}