MDI 中的 PyQt4 子窗口。检查哪个子窗口处于活动状态

Question

在下面的可执行代码中你可以创建更多的子窗口。但是，当我从一个子窗口切换到另一个子窗口时，我希望程序检测哪个子窗口当前处于活动状态。图像，我们打开了两个子窗口。一个子窗口我们称之为 A，另一个子窗口我们称之为 B。它们都已经打开了。子窗口 A 已激活，现在我切换到子窗口 B。class Custom_Window() 怎么会告诉我 "I am here and I am currently active"？。

更新

import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *

class Custom_Window(QWidget) :  
   def __init__(self, parent = None) :
      super(Custom_Window, self) .__init__(parent)

      # print here in this class, that itself is currently active,
      # because this window is a subwindow, so its inherits from class
      # QMdiSubWindow(). I want this subwindow itself tell me
      # whether its activated or not. BUT I don't know how to
      # solve this idea.

   def changeEvent(self, event):

      print "event", event
      print "type", type(self.parent())
      print "Status", self.parent().isActiveWindow()

      if event.type() == QEvent.WindowActivate:
         if self.parent().isActiveWindow():
            print "is currently active."
         else: print "I am passive"

class MainWindow(QMainWindow) :
   count = 0

   def __init__(self, parent = None) :
      super(MainWindow, self) .__init__(parent)
      self.mdi = QMdiArea()
      self.setCentralWidget(self.mdi)
      bar = self.menuBar()

      file = bar.addMenu("File")
      file.addAction("New")
      file.addAction("cascade")
      file.addAction("Tiled")
      file.triggered[QAction].connect(self.windowaction)
      self.setWindowTitle("MDI demo")

   def windowaction(self, q) :
       custom_window = Custom_Window()
       print "triggered"

       if q.text() == "New" :
           MainWindow.count = MainWindow.count+1
           sub = QMdiSubWindow()
           sub.setWidget(Custom_Window() )
           sub.setWindowTitle("subwindow"+str(MainWindow.count) )
           self.mdi.addSubWindow(sub)
           sub.show()

       if q.text() == "cascade" :
           self.mdi.cascadeSubWindows()

       if q.text() == "Tiled" :
           self.mdi.tileSubWindows()

def main() :
   app = QApplication(sys.argv)
   ex = MainWindow()
   ex.show()
   sys.exit(app.exec_() )

if __name__ == '__main__':
   main()

Answer 1

QMdiArea show you which APIs to use. There is a subWindowActivated 信号的 Qt 文档就是为此目的而设计的，因此只需将插槽连接到它即可：

class Custom_Window(QWidget) :

    def handleActivationChange(self, subwindow):
        if subwindow is self.parent():
            print 'activated:', self
        else:
            print 'deactivated:', self

...

       self.mdi.subWindowActivated.connect(
          sub.widget().handleActivationChange)

MDI 中的 PyQt4 子窗口。检查哪个子窗口处于活动状态

PyQt4 Subwindow in MDI. Check which subwindow is active

qt4

pyqt4

python-2.7