Qpainter Draw Line Between Two Widgets

I have a layout, and I am going to add a button to this layout (by clicking on the add button). Everytime I add a button, I wanna draw a line between Previous button and new butto

Solution 1:

The logic is similar: Trace the events and changes (such as creating and destroying widgets) and then use the information to get the information to draw the lines:

import functools
import sys

from PyQt5.QtCore import QEvent, QLine
from PyQt5.QtGui import QPainter
from PyQt5.QtWidgets import QApplication, QPushButton, QVBoxLayout, QWidget


class Drawer:
    def __init__(self):
        self._lines = []

    @property
    def lines(self):
        return self._lines

    @lines.setter
    def lines(self, l):
        self._lines = l[:]
        self.update()

    def paintEvent(self, event):
        painter = QPainter(self)
        for line in self.lines:
            painter.drawLine(line)


class Example(QWidget, Drawer):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.initUI()

    def initUI(self):
        self.AddButton = QPushButton("Add")
        self.AddButton.clicked.connect(self.addbuttonwithline)

        self.vbox = QVBoxLayout(self)
        self.vbox.addWidget(self.AddButton)

        self.setGeometry(300, 300, 300, 150)
        self.setWindowTitle("Buttons")

        self.buttons = []

    def addbuttonwithline(self):
        button = QPushButton("delete")
        button.clicked.connect(functools.partial(self.remove_button, button))
        button.installEventFilter(self)
        self.vbox.addWidget(button)
        self.buttons.append(button)
        self.recalculate_position()

    def remove_button(self, button):
        self.buttons.remove(button)
        button.deleteLater()
        self.recalculate_position()

    def recalculate_position(self):
        lines = []
        for last_button, next_button in zip(self.buttons, self.buttons[1:]):
            l = QLine(last_button.pos(), next_button.pos())
            lines.append(l)
        self.lines = lines

    def eventFilter(self, o, e):
        if e.type() == QEvent.Move and o in self.buttons:
            self.recalculate_position()
        return super().eventFilter(o, e)


if __name__ == "__main__":

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