QPainter没有画

Question

I'm trying to draw some lines with QPainter with variable self.lines but it doesn't do it. When I'm trying to draw anything else, but I pass numbers by hand, everything goes smoothly. Here's my code:

import sys, os
from math import pi
from PyQt5.QtWidgets import (QApplication, QWidget, QPushButton, QMenuBar, QMenu, QAction, QHBoxLayout, QFileDialog)
from PyQt5.QtGui import (QPainter, QPen)
from PyQt5.QtCore import (Qt, QPoint, QLineF)

class MainWindow(QWidget):
    def __init__(self):
        super().__init__()

        self.coords, self.graph, self.used, self.tin, self.fup, self.con_points = [], [], [], [], [], []
        self.num_of_peaks, self.circle_size, self.timer = 0, 40, 0
        self.algo_starts, self.from_file = False, False
        self.graph_config, self.graph_new = None, None

        self.lines = []

        self.setGeometry(300, 300, 1000, 500)
        self.move(QApplication.desktop().screen().rect().center()-self.rect().center())
        self.setWindowTitle("con point")

        self.menubar = QMenuBar(self)
        self.filemenu = self.menubar.addMenu("File")
        self.newfile = self.filemenu.addAction("New")
        self.openfile = self.filemenu.addAction("Open")
        self.savefile = self.filemenu.addAction("Save")
        self.exitfile = self.filemenu.addAction("Exit")

        self.filemenu.triggered[QAction].connect(self.ProcessTrigger)

        self.startalgobtn = QPushButton("Start", self)
        self.startalgobtn.setGeometry(self.width()-self.startalgobtn.width(), self.menubar.height(),self.startalgobtn.width(), self.startalgobtn.height())
        self.startalgobtn.setVisible(False)

        self.exitbtn = QPushButton("Exit", self)
        self.exitbtn.setGeometry(self.width()-self.startalgobtn.width(), self.menubar.height() + self.exitbtn.height(),self.startalgobtn.width(),
                                 self.startalgobtn.height())
        self.exitbtn.setVisible(False)
        self.exitbtn.clicked.connect(self.Exit)

        self.show()

    def ProcessTrigger(self, q):
        if q == self.newfile: self.NewFile()
        if q == self.openfile: self.OpenFile()
        if q == self.savefile: self.SaveFile()
        if q == self.exitfile: self.Exit()

    def paintEvent(self, a0):
        self.paint_teritory = QPainter(self)
        self.paint_teritory.setRenderHint(QPainter.Antialiasing)
        self.paint_teritory.setBackground(Qt.white)
        self.paint_teritory.setBrush(Qt.black)
        self.paint_teritory.setPen(QPen(Qt.black, 2, Qt.SolidLine))
        self.paint_teritory.drawEllipse(40, 40, 40, 40)
        self.paint_teritory.drawLines(self.lines)

        self.paint_teritory.end()

    def NewFile(self):
        return

    def OpenFile(self):
        self.from_file = True
        self.graph_config = QFileDialog.getOpenFileName(self, "Open File", os.getcwd(), "Text Files (*.txt)")[0]
        self.ReadGraph()

    def SaveFile(self):
        return

    def Exit(self): QApplication.instance().quit()

    def ReadGraph(self):
        if self.from_file:
            with open(self.graph_config) as f: self.graph_config = f.readlines()

            self.num_of_peaks = int(self.graph_config[0])
            self.graph = [[] for x in range(self.num_of_peaks)]

            i = 1
            while self.graph_config[i] != "COORDS\n":
                line = self.graph_config[i].split()
                if len(line) == 1: self.graph[int(line[0])-1] = []
                else: self.graph[int(line[0])-1] = sorted(list(map(int, line[1::])))
                i += 1

            i += 1
            for x in range(i, len(self.graph_config)):
                self.coords.append(list(map(int, self.graph_config[i].split())))

        for i in self.graph:
            for j in i:
                self.lines.append(
                    QLineF(QPoint(self.coords[self.graph.index(i)][0], self.coords[self.graph.index(i)][1]),
                           QPoint(self.coords[j - 1][0], self.coords[j - 1][1])))
        self.conf_yes = True

        self.startalgobtn.setVisible(True)
        self.exitbtn.setVisible(True)

if __name__ == "__main__":
    app = QApplication(sys.argv)
    con_point_app = MainWindow()
    sys.exit(app.exec_())

So, as I said, when I'm trying to draw with self.lines nothing happens but when I'm drawing a circle with self.paint_teritory.drawEllipse(40, 40, 40, 40) , it actually appears.

Here's the file I use to test: https://drive.google.com/file/d/1V4I2okeoE7K_hoClfllYLvFXB78Cjxyh/view?usp=sharing

And that's instruction how to make one for this program: https://drive.google.com/open?id=1EPxlxUPxH3oWaYJdi9N3RVtC7WPokOCU

Answer 1

The problem is that you are generating a line where the start and end points are the same, so this is invalid and PyQt creates a null QLine.

Also draw lines can be laborious, the most advisable in this case is to use QPainterPath as I show below:

import sys, os
from math import pi
from PyQt5.QtWidgets import (QApplication, QWidget, QPushButton, QMenuBar, QMenu, QAction, QHBoxLayout, QFileDialog)
from PyQt5.QtGui import (QPainter, QPen, QPainterPath)
from PyQt5.QtCore import (Qt, QPointF, QLineF)

class MainWindow(QWidget):
    def __init__(self):
        super().__init__()

        self.algo_starts, self.from_file = False, False
        self.graph_config, self.graph_new = None, None

        self.paths = []

        self.setGeometry(300, 300, 1000, 500)
        self.move(QApplication.desktop().screen().rect().center()-self.rect().center())
        self.setWindowTitle("con point")

        self.menubar = QMenuBar(self)
        self.filemenu = self.menubar.addMenu("File")
        self.newfile = self.filemenu.addAction("New")
        self.openfile = self.filemenu.addAction("Open")
        self.savefile = self.filemenu.addAction("Save")
        self.exitfile = self.filemenu.addAction("Exit")

        self.filemenu.triggered[QAction].connect(self.ProcessTrigger)

        self.startalgobtn = QPushButton("Start", self)
        self.startalgobtn.setGeometry(self.width()-self.startalgobtn.width(), self.menubar.height(),self.startalgobtn.width(), self.startalgobtn.height())
        self.startalgobtn.setVisible(False)

        self.exitbtn = QPushButton("Exit", self)
        self.exitbtn.setGeometry(self.width()-self.startalgobtn.width(), self.menubar.height() + self.exitbtn.height(),self.startalgobtn.width(),
                                 self.startalgobtn.height())
        self.exitbtn.setVisible(False)
        self.exitbtn.clicked.connect(self.Exit)

        self.show()

    def ProcessTrigger(self, q):
        if q == self.newfile: self.NewFile()
        if q == self.openfile: self.OpenFile()
        if q == self.savefile: self.SaveFile()
        if q == self.exitfile: self.Exit()

    def paintEvent(self, a0):
        painter = QPainter(self)
        painter.setRenderHint(QPainter.Antialiasing)
        painter.setBackground(Qt.white)
        painter.setBrush(Qt.black)
        painter.setPen(QPen(Qt.black, 2, Qt.SolidLine))
        painter.drawEllipse(40, 40, 40, 40)
        painter.setBrush(Qt.NoBrush)
        for path in self.paths:
            painter.drawPath(path)

    def NewFile(self):
        return

    def OpenFile(self):
        self.from_file = True
        self.graph_config = QFileDialog.getOpenFileName(self, "Open File", os.getcwd(), "Text Files (*.txt)")[0]
        self.ReadGraph()

    def SaveFile(self):
        return

    def Exit(self): QApplication.instance().quit()

    def ReadGraph(self):
        if self.from_file:
            with open(self.graph_config) as f: data = f.readlines()
            num_of_peaks, *info = data
            ix = info.index("COORDS\n")
            vertices_raw = info[:ix]
            coords_raw = info[ix+1:]
            vertices = [list(map(int, vertice.split())) for vertice in vertices_raw]
            coords = [list(map(int, coord.split())) for coord in coords_raw] 

            for vertice in vertices:
                path = QPainterPath()
                for i, p in enumerate(vertice):

                    point = QPointF(*coords[i])
                    if i == 0:
                        path.moveTo(point)
                    else:
                        path.lineTo(point)
                self.paths.append(path)

            self.update()

        self.conf_yes = True

        self.startalgobtn.setVisible(True)
        self.exitbtn.setVisible(True)

if __name__ == "__main__":
    app = QApplication(sys.argv)
    con_point_app = MainWindow()
    sys.exit(app.exec_())