PyQt5: chapter10-画一个所需大小的圆

实例

1. 创建基于Dialog without Buttons模板窗口
2. 添加Label部件，其text为Click the mouse and drag it to draw a  circle of the desired size
3. 保存为demoDrawCircle.ui
4. 使用pyuic生成demoDrawCircle.py
5. 创建callDrawCircle.py

import sys
from PyQt5.QtWidgets import QDialog,QApplication
from PyQt5.QtGui import QPainter
from cookbook_200505.demoDrawCircle import *

class MyForm(QDialog):
    def __init__(self):
        super().__init__()
        self.ui=Ui_Dialog()
        self.ui.setupUi(self)
        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)
        rect=QtCore.QRect(self.pos1[0],self.pos1[1],width,height)
        startAngle=0
        arcLength=360*16
        qp.drawArc(rect,startAngle,arcLength)
        qp.end()
    def mousePressEvent(self,event):
        if event.buttons()&QtCore.Qt.LeftButton:
            self.pos1[0],self.pos1[1]=event.pos().x(),event.pos().y()
    def mouseReleaseEvent(self,event):
        self.pos2[0],self.pos2[1]=event.pos().x(),event.pos().y()
        self.update()
if __name__=="__main__":
    app=QApplication(sys.argv)
    w=MyForm()
    w.show()
    sys.exit(app.exec())