如何在 PyQt5 中通过拖放来绘制矩形并调整其形状

2022-01-12 00:00:00 python pyqt pyqt5 qpainter qmouseevent

问题描述

我正在尝试通过拖放在 PyQt5 创建的 GUI 上绘制一个矩形.我设法做到了，但是释放鼠标左键时会绘制矩形.

I'm trying to draw a rectangle on GUI created by PyQt5 by drag and drop. I managed to do that, but the rectangle is drawn when the mouse left key is released.

我想做的就是这样link:

  • 按下鼠标左键时，开始绘制矩形.
  • 拖动时，通过鼠标移动调整矩形形状.
  • 松开鼠标左键后，确定矩形形状.

我该如何实现呢?提前致谢.

How can I implement this? Thanks in advance.

这是我的代码.

# -*- coding: utf-8 -*-

import sys
from PyQt5 import QtWidgets, QtCore
from PyQt5.QtGui import QPainter

class MyWidget(QtWidgets.QWidget):
    def __init__(self):
        super().__init__()
        self.setGeometry(30,30,600,400)
        self.pos1 = [0,0]
        self.pos2 = [0,0]
        self.show()

    def paintEvent(self, event):
        width = self.pos2[0]-self.pos1[0]
        height = self.pos2[1] - self.pos1[1]     

        qp = QPainter()
        qp.begin(self)           
        qp.drawRect(self.pos1[0], self.pos1[1], width, height)        
        qp.end()

    def mousePressEvent(self, event):
        self.pos1[0], self.pos1[1] = event.pos().x(), event.pos().y()
        print("clicked")

    def mouseReleaseEvent(self, event):
        self.pos2[0], self.pos2[1] = event.pos().x(), event.pos().y()
        print("released")
        self.update()

if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    window = MyWidget()
    window.show()
    app.aboutToQuit.connect(app.deleteLater)
    sys.exit(app.exec_())

解决方案

你不必使用mouseReleaseEvent函数，而是每次调用的mouseMoveEvent函数鼠标移动了，我修改了代码让它更简单.

You do not have to use the mouseReleaseEvent function, but the mouseMoveEvent function that is called each time the mouse is moved, and I have modified the code to make it simpler.

class MyWidget(QtWidgets.QWidget):
    def __init__(self):
        super().__init__()
        self.setGeometry(30,30,600,400)
        self.begin = QtCore.QPoint()
        self.end = QtCore.QPoint()
        self.show()

    def paintEvent(self, event):
        qp = QtGui.QPainter(self)
        br = QtGui.QBrush(QtGui.QColor(100, 10, 10, 40))  
        qp.setBrush(br)   
        qp.drawRect(QtCore.QRect(self.begin, self.end))       

    def mousePressEvent(self, event):
        self.begin = event.pos()
        self.end = event.pos()
        self.update()

    def mouseMoveEvent(self, event):
        self.end = event.pos()
        self.update()

    def mouseReleaseEvent(self, event):
        self.begin = event.pos()
        self.end = event.pos()
        self.update()

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