python3+PyQt5重新实现QT事件处理程序

本文是对《python qt gui快速编程》的第10章的例子events用python3+pyqt5进行改写，涉及到重新实现qwidget的事件处理程序。本例子涉及到上下文菜单，鼠标事件，键盘事件，可作为重新实现事件处理程序的参考。

注：在创建上下文菜单最简单的方式使用qwidget.addaction()把动作添加到窗口部件中，再把窗口部件的上下文菜单策略设置为qt.actionscontextmenu即可，但是如果像本例子一样要根据不同的状态来提供不同的选项，则要重新实现上下文菜单事件处理程序。

#!/usr/bin/env python3
import sys
from pyqt5.qtcore import (qevent, qtimer, qt)
from pyqt5.qtwidgets import (qapplication, qmenu, qwidget)
from pyqt5.qtgui import qpainter

class widget(qwidget):

  def __init__(self, parent=none):
    super(widget, self).__init__(parent)
    self.justdoubleclicked = false
    self.key = ""
    self.text = ""
    self.message = ""
    self.resize(400, 300)
    self.move(100, 100)
    self.setwindowtitle("events")
    qtimer.singleshot(0, self.givehelp) # avoids first resize msg


  def givehelp(self):
    self.text = "click to toggle mouse tracking"
    self.update()


  def closeevent(self, event):
    print("closed")


  def contextmenuevent(self, event):
    menu = qmenu(self)
    oneaction = menu.addaction("&one")
    twoaction = menu.addaction("&two")
    oneaction.triggered.connect(self.one)
    twoaction.triggered.connect(self.two)
    if not self.message:
      menu.addseparator()
      threeaction = menu.addaction("thre&e")
      threeaction.triggered.connect(self.three)
    menu.exec_(event.globalpos())


  def one(self):
    self.message = "menu option one"
    self.update()


  def two(self):
    self.message = "menu option two"
    self.update()


  def three(self):
    self.message = "menu option three"
    self.update()


  def paintevent(self, event):
    text = self.text
    i = text.find("\n\n")
    if i >= 0:
      text = text[0:i]
    if self.key:
      text += "\n\nyou pressed: {0}".format(self.key)
    painter = qpainter(self)
    painter.setrenderhint(qpainter.textantialiasing)
    painter.drawtext(self.rect(), qt.aligncenter, text)
    if self.message:
      painter.drawtext(self.rect(), qt.alignbottom|qt.alignhcenter,
               self.message)
      qtimer.singleshot(5000, self.clearmessage)
      qtimer.singleshot(5000, self.update)

  def clearmessage(self):
    self.message=""

  def resizeevent(self, event):
    self.text = "resized to qsize({0}, {1})".format(
              event.size().width(), event.size().height())
    self.update()


  def mousereleaseevent(self, event):
    if self.justdoubleclicked:
      self.justdoubleclicked = false
    else:
      self.setmousetracking(not self.hasmousetracking())
      if self.hasmousetracking():
        self.text = "mouse tracking is on.\n"+\
            "try moving the mouse!\n"+\
            "single click to switch it off"
      else:
        self.text = "mouse tracking is off.\n"+\
                      "single click to switch it on"
      self.update()


  def mousemoveevent(self, event):
    if not self.justdoubleclicked:
      globalpos = self.maptoglobal(event.pos())
      self.text = "the mouse is at\nqpoint({0}, {1}) "+\
          "in widget coords, and\n"+\
          "qpoint({2}, {3}) in screen coords".format(
          event.pos().x(), event.pos().y(), globalpos.x(),
          globalpos.y())
      self.update()


  def mousedoubleclickevent(self, event):
    self.justdoubleclicked = true
    self.text = "double-clicked."
    self.update()


  def keypressevent(self, event):
    self.key = ""
    if event.key() == qt.key_home:
      self.key = "home"
    elif event.key() == qt.key_end:
      self.key = "end"
    elif event.key() == qt.key_pageup:
      if event.modifiers() & qt.controlmodifier:
        self.key = "ctrl+pageup"
      else:
        self.key = "pageup"
    elif event.key() == qt.key_pagedown:
      if event.modifiers() & qt.controlmodifier:
        self.key = "ctrl+pagedown"
      else:
        self.key = "pagedown"
    elif qt.key_a <= event.key() <= qt.key_z:
      if event.modifiers() & qt.shiftmodifier:
        self.key = "shift+"
      self.key += event.text()
    if self.key:
      self.key = self.key
      self.update()
    else:
      qwidget.keypressevent(self, event)


  def event(self, event):
    if (event.type() == qevent.keypress and
      event.key() == qt.key_tab):
      self.key = "tab captured in event()"
      self.update()
      return true
    return qwidget.event(self, event)

if __name__ == "__main__":
  app = qapplication(sys.argv)
  form = widget()
  form.show()
  app.exec_()

运行结果：

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