我正在尝试使用 python 和 matplotlib 创建一个 Qt4 应用程序，但我陷入了一种行为，这对我来说不是很清楚。
这个应用程序有一个 QMdiArea，它保存了在各个子窗口中动态创建的图形。一切似乎都工作正常，但之前在绘制数据时定义的艺术家挑选事件。显然，在 MainWindow 类中创建 QMdiAreaSubWindow 实例时，“pick_event”mpl_connection 被清除了。
奇怪的是，如果在 MainWinddow 应用程序之外执行同一段代码。
我编写了代码的简化版本以重现该行为，也许有人可以告诉我我做错了什么。
干杯!
#!/usr/bin/python
import sys
from PyQt4.QtGui import QWidget, QPushButton, QMainWindow, QMdiArea, QVBoxLayout, QApplication
from PyQt4.QtCore import Qt
from pylab import *
from matplotlib.backends.backend_qt4agg import (
FigureCanvasQTAgg as FigureCanvas,
NavigationToolbar2QTAgg as NavigationToolbar)
from matplotlib.backend_bases import key_press_handler
class MyMainWindow(QMainWindow):
""" Defines a simple MainWindow with a QPushButton that plots a Random Wave Fucntion
which must be shown in a Window within a QMdiArea Widget.
"""
def __init__(self, parent=None):
"""
"""
super(MyMainWindow,self).__init__(parent)
self.setWidgets()
def setWidgets(self, ):
""" Createsthe QPushButton and QMdiArea Widgets, organising them in
QVBoxLayout as a central Widget of the MainWindow
"""
vBox = QVBoxLayout()
mainFrame = QWidget()
self._plotGraphButton = QPushButton("Plot Graph")
self._plotGraphButton.clicked.connect(self.plotRandom)
self._mdiArea = QMdiArea()
vBox.addWidget(self._plotGraphButton)
vBox.addWidget(self._mdiArea)
mainFrame.setLayout(vBox)
self.setCentralWidget(mainFrame)
# This is the function called when the Plot Graph Button is pressed
#and where the Picking event does not work.
# When the button is pressed a new window with the plot is shown, but
#it is not possible to drag the rectangle patch with the mouse.
def plotRandom(self, ):
""" Generates and Plots a random wave function (+noise) embedding into a
QMdiAreaSubWindow.
"""
print "Plotting!!"
x = linspace(0,10,1000)
w = rand(1)*10
y = 100*rand(1)*sin(2*pi*w*x)+rand(1000)
p = PlotGraph(x,y)
child = self._mdiArea.addSubWindow(p.plotQtCanvas())
child.show()
class PlotGraph(object):
"""
"""
def __init__(self, x,y):
""" This class plots the data and encapsulates the figure instance in a FigureCanvasQt4Agg,
which can be used to create a QMdiArea SubWindow.
A rectangle patch is added to the plot and linked to the methods that
can drag it horizontally in the graph.
Arguments:
- `x`: Data
- `y`: Data
"""
self._x = x
self._dx = x[1]-x[0]
self._y = y
def _createPlotWidget(self, ):
""" Creates a figure and a NavigationBar organising them vertically into a QWidget,
which can be used by a QMdiArea.addSubWindow method.
"""
self._mainFrame = QWidget()
self._fig = figure(facecolor="white")
self._canvas = FigureCanvas(self._fig)
self._canvas.setParent(self._mainFrame)
self._canvas.setFocusPolicy(Qt.StrongFocus)
# Standard NavigationBar and button press management
self._mplToolbar = NavigationToolbar(self._canvas, self._mainFrame)
self._canvas.mpl_connect('key_press_event', self.on_key_press)
# Layouting
vbox = QVBoxLayout()
vbox.addWidget(self._canvas) # the matplotlib canvas
vbox.addWidget(self._mplToolbar)
self._mainFrame.setLayout(vbox)
def plotQtCanvas(self, ):
""" Plots data using matplotlib, adds a draggable Rectangle and connects the dragging
methods to the mouse events
"""
self._createPlotWidget()
ax = self._fig.add_subplot(111)
ax.plot(self._x,self._y)
ax.set_xlim(self._x[0],self._x[-1])
ax.set_ylim(-max(self._y)*1.1,max(self._y)*1.1)
xlim = ax.get_xlim()
ylim = ax.get_ylim()
wd = (xlim[1]-xlim[0])*0.1
ht = (ylim[1]-ylim[0])
rect = Rectangle((xlim[0],ylim[0]),wd,ht,alpha=0.3,color="g",picker=True)
ax.add_patch(rect)
# Connecting Events to Rectangle dragging methods
self._canvas.mpl_connect("pick_event",self.on_pick)
self._canvas.mpl_connect("button_release_event",self.on_release)
return self._mainFrame
def on_pick(self,event):
""" Manages the Artist Picking event. This method register which
Artist was picked and connects the rectOnMove method to the mouse
motion_notify_event SIGNAL.
Arguments:
- `event`:
"""
if isinstance(event.artist, Rectangle):
rectWd = event.artist.get_width()
if event.mouseevent.button == 1:
self._dragged = event.artist
self._id = self._canvas.mpl_connect("motion_notify_event",self.rectOnMove)
def rectOnMove(self, event):
""" After being picked, updates the new position of the Artist.
Arguments:
- `event`:
"""
rectWd = self._dragged.get_width()
if event.xdata:
i = event.xdata
n2 = rectWd/2.0
if i>=n2 and i<(self._x[-1]-n2):
self._dragged.set_x(i-n2)
self._canvas.draw()
def on_release(self,event):
""" When the mouse button is released, simply disconnect the
SIGNAL motion_notify_event and the rectOnMove method.
Arguments:
- `event`:
"""
self._canvas.mpl_disconnect(self._id)
def on_key_press(self, event):
# implement the default mpl key press events described at
# http://matplotlib.org/users/navigation_toolbar.html#navigation-keyboard-shortcuts
key_press_handler(event, self._canvas, self._mplToolbar)
if __name__ == '__main__':
qApp = QApplication(sys.argv)
MainWindow = MyMainWindow()
# By calling the piece of code bellow everything works fine and the
# the rectangle patch can be dragged, as expected.
# This piece of code "theoretically" does the same thing as the
# method plotRandom() defined in the class MyMainWindow.
print "Plotting!!"
x = linspace(0,10,1000)
w = rand(1)*10
y = 100*rand(1)*sin(2*pi*w*x)
####################################################################
p = PlotGraph(x,y)
child = MainWindow._mdiArea.addSubWindow(p.plotQtCanvas())
child.show()
MainWindow.show()
sys.exit(qApp.exec_())