PyQt - FigureCanvas 未显示（导航工具栏显示）

Question

I'm trying to implement Drag and Drop on a FigureCanvas. That means, I want to drag the text from the left layout and drop it to the canvas on the right. Unfortunately, even though the Navigation Toolbar is displayed, the canvas is not.

Before creating the Create_Canvas class to implement the Drag and Drop, I could display everything with no problem. I'm new to programming, I'm not sure if I wrote the Create_Canvas class right.

I also post a picture:

In case you don't have matplotlib installed.

Thanks in advance!

import sys, time

from PyQt5.QtWidgets import *
from PyQt5.QtGui import *
from PyQt5.QtCore import *

from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
from matplotlib.backends.backend_qt5agg import NavigationToolbar2QT as NavigationToolbar
from matplotlib.figure import Figure

import matplotlib.pyplot as plt
import matplotlib.cm as cm
import matplotlib.colors as mcolors
import matplotlib.colorbar as mcolorbar

import numpy as np
import pylab as pl

import random


class Example(QMainWindow):
    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        self.central_widget = QWidget()
        self.setCentralWidget(self.central_widget)
        self.editLayout = QWidget()
        self.edit = QLineEdit('chfghfghf', self)
        self.edit.setDragEnabled(True)

        self.left_layout = QVBoxLayout()
        self.left_layout.addWidget(self.edit)

        self.editLayout.setLayout(self.left_layout)

        #Create the right layout that contains the plot canvas.    
        self.plotLayout = QWidget();

        canvas = Create_Canvas(self)       

        self.button = QPushButton('Plot')

        # set the layout
        self.right_layout = QVBoxLayout()
        self.right_layout.addWidget(canvas)
        self.right_layout.addWidget(self.button)

        self.plotLayout.setLayout(self.right_layout)

        splitter_filebrowser = QSplitter(Qt.Horizontal)
        splitter_filebrowser.addWidget(self.editLayout)
        splitter_filebrowser.addWidget(self.plotLayout)
        splitter_filebrowser.setStretchFactor(1, 1)

        hbox = QHBoxLayout(self)
        hbox.addWidget(splitter_filebrowser)

        self.centralWidget().setLayout(hbox)

        self.setWindowTitle('Simple drag & drop')
        self.setGeometry(750, 100, 600, 500)


class Create_Canvas(QWidget):
    def __init__(self, parent):
        super().__init__(parent)
        self.setAcceptDrops(True)

        figure = plt.figure()
        canvas = FigureCanvas(figure)
        toolbar = NavigationToolbar(canvas, self)

        self.right_layout = QVBoxLayout()
        self.right_layout.addWidget(canvas)
        self.right_layout.addWidget(toolbar)

    def dragEnterEvent(self, e):
        print('entering')
        if e.mimeData().hasFormat('text/plain'):
            e.accept()
        else:
            e.ignore()

    def dragMoveEvent(self, e):
        print('drag moving')

    def dropEvent(self, e):
        print("dropped")


if __name__ == '__main__':

    app = QApplication(sys.argv)
    ex = Example()
    ex.show()
    app.exec_()      

Answer 1

The main point is that you need to add the canvas to a layout and add this layout to the widget. At the end you also should not forget to draw the canvas.

class Create_Canvas(QWidget):
    def __init__(self, parent):
        QWidget.__init__(self,parent)
        self.setAcceptDrops(True)

        figure = plt.figure()
        self.canvas = FigureCanvas(figure)
        toolbar = NavigationToolbar(self.canvas, self)

        self.right_layout = QVBoxLayout()
        self.right_layout.addWidget(self.canvas)
        self.right_layout.addWidget(toolbar)
        # set the layout of this widget, otherwise the elements will not be seen.
        self.setLayout(self.right_layout)
        # plot some stuff
        self.ax = figure.add_subplot(111)
        self.ax.plot([1,2,5])        
        # finally draw the canvas
        self.canvas.draw()

(This is how it would look in PyQt4, should be similar in PyQt5).

Answer 2

In PyQt5 you need to use super on the main window class to accept the drops. The dropevent function should be like this:

def dropEvent(self,e):
        """
        This function will enable the drop file directly on to the 
        main window. The file location will be stored in the self.filename
        """
        if e.mimeData().hasUrls:
            e.setDropAction(QtCore.Qt.CopyAction)
            e.accept()
            for url in e.mimeData().urls():
                if op_sys == 'Darwin':
                    fname = str(NSURL.URLWithString_(str(url.toString())).filePathURL().path())
                else:
                    fname = str(url.toLocalFile())
            self.filename = fname
            print("GOT ADDRESS:",self.filename)
            self.readData()
        else:
            e.ignore() # just like above functions  

The complete code gives this output: