python - 为什么带有自定义绘画的小部件不可见？

Question

所以我正在尝试使用自定义小部件构建一个简单的 PyQt 应用程序。然而，画家不画任何东西。如果我注释掉第 44-45 行 ( label = QLabel('Map');box.addWidget(label))，我可以看到一个大的彩色矩形。但是，当我尝试在矩形上方添加标签时，矩形不再显示。

我想我可能用错了画家，但我不确定。

我是 PyQt 的新手，对我的编码风格或逻辑的任何评论也将不胜感激。

from PyQt5.QtCore import Qt
from PyQt5.QtGui import QPainter, QColor
from PyQt5.QtWidgets import (QMainWindow,
                               QWidget,
                               QFrame,
                               QDesktopWidget,
                               QGridLayout,
                               QLabel,
                               QTextEdit,
                               QSplitter,
                               QVBoxLayout,
                               QApplication)


class Simulator(QMainWindow):
    def __init__(self):
        super().__init__()

        self.stdout = QTextEdit()
        self.stderr = QTextEdit()
        self.exec = QTextEdit()

        self.frame = QFrame()
        self.setCentralWidget(self.frame)
        self.screen = QDesktopWidget().screenGeometry()
        self.setGeometry(self.screen)
        self.grid = QGridLayout()
        self.frame.setLayout(self.grid)
        self.map = SimulatedFieldMap()

        # -- setting splitters
        splitter_r = QSplitter(Qt.Vertical)
        splitter_l = QSplitter(Qt.Vertical)
        splitter_h = QSplitter(Qt.Horizontal)
        splitter_h.addWidget(splitter_l)
        splitter_h.addWidget(splitter_r)
        # --------------

        # -- top left --
        frame = QFrame()
        box = QVBoxLayout()
        frame.setLayout(box)
        splitter_l.addWidget(frame)
        label = QLabel('Map')
        box.addWidget(label)
        box.addWidget(self.map)
        # ------

        # -- bottom left --
        box = QVBoxLayout()
        frame = QFrame()
        frame.setLayout(box)
        box.addWidget(QLabel('Exec'))
        box.addWidget(self.exec)
        splitter_l.addWidget(frame)
        # -------

        # -- top right --
        box = QVBoxLayout()
        frame = QFrame()
        frame.setLayout(box)
        splitter_r.addWidget(frame)
        box.addWidget(QLabel('STDOUT'))
        box.addWidget(self.stdout)
        # -------

        # -- bottom right --
        box = QVBoxLayout()
        frame = QFrame()
        frame.setLayout(box)
        splitter_r.addWidget(frame)
        box.addWidget(QLabel('STDERR'))
        box.addWidget(self.stderr)
        # -------

        self.grid.addWidget(splitter_h, 0, 0)
        splitter_h.setSizes((self.screen.width() * 0.7, self.screen.width() * 0.3))
        splitter_l.setSizes((self.screen.height() * 0.7, self.screen.height() * 0.3))
        splitter_r.setSizes((self.screen.height() * 0.7, self.screen.height() * 0.3))


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

    def paintEvent(self, event):
        qp = QPainter()
        qp.begin(self)
        self.paintMap(qp)
        qp.end()

    def paintMap(self, qp):
        qp.setBrush(QColor(200, 162, 200))  # lilac
        qp.setPen(QColor(200, 162, 200))
        geo = self.geometry()
        qp.drawRect(geo)


if __name__ == '__main__':
    app = QApplication([])
    app.setStyle('Fusion')
    sim = Simulator()
    sim.show()
    status = app.exec_()
    exit(status)

我在 macOS 10.13.5 上使用 Python3.7。

标签： pythonpyqtpyqt5qpainterpython-3.7

Answer 1

绘制小部件时，使用内部坐标，但geometry()它是相对于父级的坐标，因此您不应该使用它，而应该使用rect().

from PyQt5 import QtCore, QtGui, QtWidgets


class Simulator(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()

        self.stdout = QtWidgets.QTextEdit()
        self.stderr = QtWidgets.QTextEdit()
        self.exec = QtWidgets.QTextEdit()

        self.frame = QtWidgets.QFrame()
        self.setCentralWidget(self.frame)

        self.grid = QtWidgets.QGridLayout(self.frame)
        self.map = SimulatedFieldMap()

        # -- setting splitters
        splitter_r = QtWidgets.QSplitter(QtCore.Qt.Vertical)
        splitter_l = QtWidgets.QSplitter(QtCore.Qt.Vertical)
        splitter_h = QtWidgets.QSplitter(QtCore.Qt.Horizontal)
        splitter_h.addWidget(splitter_l)
        splitter_h.addWidget(splitter_r)
        # --------------

        # -- top left --
        frame = QtWidgets.QFrame()
        box = QtWidgets.QVBoxLayout(frame)
        splitter_l.addWidget(frame)
        label = QtWidgets.QLabel('Map')
        box.addWidget(label)
        box.addWidget(self.map)
        # ------

        # -- bottom left --
        frame = QtWidgets.QFrame()
        box = QtWidgets.QVBoxLayout(frame)
        box.addWidget(QtWidgets.QLabel('Exec'))
        box.addWidget(self.exec)
        splitter_l.addWidget(frame)
        # -------

        # -- top right --
        frame = QtWidgets.QFrame()
        box = QtWidgets.QVBoxLayout(frame)
        splitter_r.addWidget(frame)
        box.addWidget(QtWidgets.QLabel('STDOUT'))
        box.addWidget(self.stdout)
        # -------

        # -- bottom right --
        frame = QtWidgets.QFrame()
        box = QtWidgets.QVBoxLayout(frame)
        splitter_r.addWidget(frame)
        box.addWidget(QtWidgets.QLabel('STDERR'))
        box.addWidget(self.stderr)
        # -------

        screen = QtWidgets.QDesktopWidget().screenGeometry()

        self.grid.addWidget(splitter_h, 0, 0)
        splitter_h.setSizes((screen.width() * 0.7, screen.width() * 0.3))
        splitter_l.setSizes((screen.height() * 0.7, screen.height() * 0.3))
        splitter_r.setSizes((screen.height() * 0.7, screen.height() * 0.3))


class SimulatedFieldMap(QtWidgets.QWidget):
    def __init__(self):
        super().__init__()

    def paintEvent(self, event):
        qp = QtGui.QPainter(self)
        self.paintMap(qp)

    def paintMap(self, qp):
        qp.setBrush(QtGui.QColor(200, 162, 200))  # lilac
        qp.setPen(QtGui.QColor(200, 162, 200))
        qp.drawRect(self.rect())


if __name__ == '__main__':
    import sys

    app = QtWidgets.QApplication(sys.argv)
    app.setStyle('Fusion')
    sim = Simulator()
    sim.showMaximized()
    sys.exit(app.exec_())

---

更新：如果您希望将其放置在某个位置，则不应将其放置在布局中，但标签必须是地图的子级，并用于move()建立相对于地图左上角的位置。

# -- top left --
frame = QtWidgets.QFrame()
box = QtWidgets.QVBoxLayout(frame)
box.addWidget(self.map)
splitter_l.addWidget(frame)
label = QtWidgets.QLabel('Map', self.map)
label.move(0, 100)    
# ------

更新：问题是由 QLabel 的垂直 sizePolicyQSizePolicy::Preferred导致它扩展，一个简单的解决方案是将其更改为QSizePolicy::Maximum，因此根据字体计算正确的高度。

# -- top left --
frame = QtWidgets.QFrame()
box = QtWidgets.QVBoxLayout(frame)
splitter_l.addWidget(frame)
label = QtWidgets.QLabel('Map')
sp = label.sizePolicy()
sp.setVerticalPolicy(QtWidgets.QSizePolicy.Maximum)
label.setSizePolicy(sp)
box.addWidget(label)
box.addWidget(self.map)
# ------