[英]How to use QPainter in a QWidget in PyQt4
我下面的代码当前打开一个空白的500x500 QMainWindow。
我只是想使用QPainter在QWidget中画一个圆。
这是我的代码:
from PyQt4 import QtCore, QtGui, Qt
from PyQt4.QtGui import QApplication, QMainWindow
import sys
class Ui_MainWindow(object):
def setupUi(self, MainWindow):
MainWindow.resize(500, 500)
self.centralwidget = QtGui.QWidget(MainWindow)
self.horizontalLayout = QtGui.QHBoxLayout(self.centralwidget)
MainWindow.setCentralWidget(self.centralwidget)
self.menubar = QtGui.QMenuBar(MainWindow)
self.menubar.setGeometry(QtCore.QRect(0, 0, 500, 22))
MainWindow.setMenuBar(self.menubar)
self.statusbar = QtGui.QStatusBar(MainWindow)
MainWindow.setStatusBar(self.statusbar)
QtCore.QMetaObject.connectSlotsByName(MainWindow)
class MyMainScreen(QMainWindow):
def __init__(self, parent=None):
QtGui.QMainWindow.__init__(self, parent)
self.ui = Ui_MainWindow() # This is from a python export from QtDesigner
self.ui.setupUi(self)
self.paintCircle()
def paintCircle(self):
self.painter = QtGui.QPainter(self)
self.painter.begin(self)
self.painter.setPen(Qt.QPen(Qt.QColor.black))
# painter.end()
self.painter.drawArc(QtCore.QRectF(250, 250, 10, 10), 0, 5760)
if __name__ == "__main__":
app = QApplication(sys.argv)
mainscreen = MyMainScreen()
mainscreen.show()
app.exec_()
我收到以下错误:
QPainter::begin: Paint device returned engine == 0, type: 1
QPainter::begin: Paint device returned engine == 0, type: 1
QPainter::setPen: Painter not active
在这种情况下,您必须重写paintEvent
函数:
from PyQt4 import QtCore, QtGui, Qt
from PyQt4.QtGui import QApplication, QMainWindow
import sys
class Ui_MainWindow(object):
def setupUi(self, MainWindow):
MainWindow.resize(500, 500)
self.centralwidget = QtGui.QWidget(MainWindow)
self.horizontalLayout = QtGui.QHBoxLayout(self.centralwidget)
MainWindow.setCentralWidget(self.centralwidget)
self.menubar = QtGui.QMenuBar(MainWindow)
self.menubar.setGeometry(QtCore.QRect(0, 0, 500, 22))
MainWindow.setMenuBar(self.menubar)
self.statusbar = QtGui.QStatusBar(MainWindow)
MainWindow.setStatusBar(self.statusbar)
QtCore.QMetaObject.connectSlotsByName(MainWindow)
class MyMainScreen(QMainWindow):
def __init__(self, parent=None):
QtGui.QMainWindow.__init__(self, parent)
self.ui = Ui_MainWindow() # This is from a python export from QtDesigner
self.ui.setupUi(self)
def paintEvent(self, event):
painter = QtGui.QPainter(self)
painter.setPen(QtGui.QPen(QtCore.Qt.red))
painter.drawArc(QtCore.QRectF(250, 250, 10, 10), 0, 5760)
if __name__ == "__main__":
app = QApplication(sys.argv)
mainscreen = MyMainScreen()
mainscreen.show()
app.exec_()
输出:
你必须使用名字
def paintEvent(self, event):
而不是def paintCircle(self):
在需要时自动运行它。
from PyQt4 import QtCore, QtGui, Qt
from PyQt4.QtGui import QApplication, QMainWindow
import sys
class Ui_MainWindow(object):
def setupUi(self, MainWindow):
MainWindow.resize(500, 500)
self.centralwidget = QtGui.QWidget(MainWindow)
self.horizontalLayout = QtGui.QHBoxLayout(self.centralwidget)
MainWindow.setCentralWidget(self.centralwidget)
self.menubar = QtGui.QMenuBar(MainWindow)
self.menubar.setGeometry(QtCore.QRect(0, 0, 500, 22))
MainWindow.setMenuBar(self.menubar)
self.statusbar = QtGui.QStatusBar(MainWindow)
MainWindow.setStatusBar(self.statusbar)
QtCore.QMetaObject.connectSlotsByName(MainWindow)
class MyMainScreen(QMainWindow):
def __init__(self, parent=None):
QtGui.QMainWindow.__init__(self, parent)
self.ui = Ui_MainWindow() # This is from a python export from QtDesigner
self.ui.setupUi(self)
def paintEvent(self, event):
self.ui.centralwidget.painter = QtGui.QPainter()
self.ui.centralwidget.painter.begin(self)
self.ui.centralwidget.painter.setPen(QtGui.QPen(QtCore.Qt.red))
self.ui.centralwidget.painter.drawArc(QtCore.QRectF(250, 250, 10, 10), 0, 5760)
self.ui.centralwidget.painter.end()
if __name__ == "__main__":
app = QApplication(sys.argv)
mainscreen = MyMainScreen()
mainscreen.show()
app.exec_()
例子画在画布上
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