python+PyQT怎么实现系统桌面时钟？

__metaclass__ = type 
#!coding= utf-8 
#http://blog.csdn.net/gatieme/article/details/17659259 
#gatieme 
 
 
import sys 
from PyQt4.QtCore import * 
from PyQt4.QtGui import * 
 
 
#-------------------------------------------------------------------------------- 
class SystemTrayIcon(QSystemTrayIcon): 
 """ 
 The systemTrayIcon which uesd to connect the clock 
 """ 
 #---------------------------------------------------------------------------- 
 def __init__(self, mainWindow, parent = None): 
  """ 
  mainWindow : the main window that the system tray icon serves to 
  """  
  super(SystemTrayIcon, self).__init__(parent) 
  self.window = mainWindow 
  self.setIcon(QIcon("heart.svg")) # set the icon of the systemTrayIcon 
   
  self.createActions( ) 
  self.createTrayMenu( ) 
   
  self.connect(self, SIGNAL("doubleClicked"), self.window, SLOT("showNormal")) 
  #self.connect(self, SIGNAL("activated( )"), self, SLOT("slot_iconActivated")) 
   
 
 def createActions(self): 
  """ 
  create some action to Max Min Normal show the window 
  """ 
  self.minimizeAction = QAction("Mi&nimize", self.window, triggered = self.window.hide) 
  self.maximizeAction = QAction("Ma&ximize", self.window, triggered = self.window.showMaximized) 
  self.restoreAction = QAction("&Restore", self.window, triggered = self.window.showNormal) 
  self.quitAction = QAction("&Quit", self.window, triggered = qApp.quit) 
     
 
 def createTrayMenu(self): 
   self.trayIconMenu = QMenu(self.window) 
   self.trayIconMenu.addAction(self.minimizeAction) 
   self.trayIconMenu.addAction(self.maximizeAction) 
   self.trayIconMenu.addAction(self.restoreAction) 
   self.trayIconMenu.addSeparator( ) 
   self.trayIconMenu.addAction(self.quitAction) 
 
   self.setContextMenu(self.trayIconMenu) 
  
 def setVisible(self, visible): 
  self.minimizeAction.setEnabled(not visible) 
  self.maximizeAction.setEnabled(not self.window.isMaximized()) 
  self.restoreAction.setEnabled(self.window.isMaximized() or not visible) 
  super(Window, self).setVisible(visible) 
 
 
 
 def closeEvent(self, event): 
  #if event.button( ) == Qt.RightButton: 
  self.showMessage("Message", 
    "The program will keep running in the system tray. To " 
    "terminate the program, choose <b>Quit</b> in the " 
    "context menu of the system tray entry.", 
    QSystemTrayIcon.Information, 5000) 
  self.window.hide( ) 
  event.ignore( ) 
 
 def slot_iconActivated(self, reason): 
  if reason == QSystemTrayIcon.DoubleClick: 
   self.wiondow.showNormal( ) 
 
 
 
#-------------------------------------------------------------------------------- 
class DigitClock(QLCDNumber): 
 """ 
 the DigitClock show a digit clock int the printer 
 """ 
  
 #---------------------------------------------------------------------------- 
 def __init__(self, parent = None): 
  """ 
  the constructor function of the DigitClock 
  """ 
  super(DigitClock, self).__init__(parent) 
  pale = self.palette( ) 
 
  pale.setColor(QPalette.Window, QColor(100, 180, 100)) 
  self.setPalette(pale) 
   
  self.setNumDigits(19) 
  self.systemTrayIcon = SystemTrayIcon(mainWindow = self) 
 
   
  self.dragPosition = None; 
  self.setWindowFlags(Qt.FramelessWindowHint | Qt.WindowStaysOnTopHint | Qt.Popup | Qt.Tool) 
  self.setWindowOpacity(1) 
   
  self.showTime( )   # print the time when the clock show 
  self.systemTrayIcon.show( ) # show the SystemTaryIcon when the clock show 
 
  self.timer = QTimer( ) 
  self.connect(self.timer, SIGNAL("timeout( )"), self.showTime) 
  self.timer.start(1000) 
   
  self.resize(500, 60) 
   
  
 #---------------------------------------------------------------------------- 
 def showTime(self): 
  """ 
  show the current time 
  """ 
  self.date = QDate.currentDate( ) 
  self.time = QTime.currentTime( ) 
  text = self.date.toString("yyyy-MM-dd") + " " + self.time.toString("hh:mm:ss") 
  self.display(text) 
 
   
 
 #---------------------------------------------------------------------------- 
 def mousePressEvent(self, event): 
  """ 
  clicked the left mouse to move the clock 
  clicked the right mouse to hide the clock 
  """ 
  if event.button( ) == Qt.LeftButton: 
   self.dragPosition = event.globalPos( ) - self.frameGeometry( ).topLeft( ) 
   event.accept( ) 
  elif event.button( ) == Qt.RightButton: 
   self.systemTrayIcon.closeEvent(event) 
 
   #self.systemTrayIcon.hide( ) 
   #self.close( ) 
 
 def mouseMoveEvent(self, event): 
  """ 
  """ 
  if event.buttons( ) & Qt.LeftButton: 
   self.move(event.globalPos( ) - self.dragPosition) 
   event.accept( ) 
  
 def keyPressEvent(self, event): 
  """ 
  you can enter "ESC" to normal show the window, when the clock is Maxmize 
  """ 
  if event.key() == Qt.Key_Escape and self.isMaximized( ): 
   self.showNormal( ) 
 
 def mouseDoubleClickEvent(self, event): 
  """ 
  """ 
  if event.buttons() == Qt.LeftButton: 
   if self.isMaximized( ): 
    self.showNormal( ) 
   else: 
    self.showMaximized( ) 
  
if __name__ == "__main__": 
 app = QApplication(sys.argv) 
  
 digitClock = DigitClock( ) 
 digitClock.show( )  
  
 sys.exit(app.exec_( ))