放大和缩小小部件

Question

如何在小部件上使用键输入制作缩放效果？该小部件位于滚动区域内，并且有一些使用QPainter制作的图纸，这些图纸会随着用户输入而更改。缩放会影响滚动条的长度，越近，条形就越小。最低级别的缩放应使滚动条与小部件区域一样大，以便可以可视化小部件中的所有内容。

地雷危险系数：

from PyQt5 import QtCore, QtWidgets
from PyQt5.QtWidgets import QWidget
from PyQt5.QtCore import Qt
from PyQt5.QtGui import QPainter, QPen, QColor
import sys

class Diedrico(QWidget):
def __init__(self, parent):
super().__init__(parent)
def paintEvent(self, event):
qp = QPainter(self)
qp.setPen(QPen(QColor(Qt.black), 5))
qp.drawRect(500, 500, 1000, 1000)

class UiVentana(QtWidgets.QMainWindow):
def __init__(self, parent=None):
super(UiVentana, self).__init__(parent)
self.resize(520, 520)
self.widget_central = QtWidgets.QWidget(self)
scrol = QtWidgets.QScrollArea(self.widget_central)
scrol.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOn)
scrol.setGeometry(QtCore.QRect(10, 10, 500, 500))
scrol.setWidgetResizable(False)
contenido = QtWidgets.QWidget()
contenido.setGeometry(QtCore.QRect(0, 0, 2000, 2000))
scrol.setWidget(contenido)
self.Diedrico = Diedrico(contenido)
self.Diedrico.setGeometry(QtCore.QRect(0, 0, 2000, 2000))
self.setCentralWidget(self.widget_central)

if __name__ == "__main__":
app = QtWidgets.QApplication(sys.argv)
ui = UiVentana()
ui.show()
sys.exit(app.exec_())

Answer 1

你为什么要重新发明轮子？与其想要实现缩放功能的逻辑，不如使用已经这样做的类。在这种情况下，一个不错的选择是将 QGraphicsView 与 QGraphicsScene 一起使用：

注： 快捷键标准"放大"和"缩小"分别与 Ctrl ++和Ctrl+-相关联。

from PyQt5 import QtCore, QtGui, QtWidgets

class Diedrico(QtWidgets.QWidget):
def paintEvent(self, event):
qp = QtGui.QPainter(self)
pen = QtGui.QPen(QtGui.QColor(QtCore.Qt.black), 5)
qp.setPen(pen)
qp.drawRect(500, 500, 1000, 1000)

class UiVentana(QtWidgets.QMainWindow):
factor = 1.5
def __init__(self, parent=None):
super(UiVentana, self).__init__(parent)
self._scene = QtWidgets.QGraphicsScene(self)
self._view = QtWidgets.QGraphicsView(self._scene)
self._diedrico = Diedrico()
self._diedrico.setFixedSize(2000, 2000)
self._scene.addWidget(self._diedrico)
self.setCentralWidget(self._view)
QtWidgets.QShortcut(
QtGui.QKeySequence(QtGui.QKeySequence.ZoomIn),
self._view,
context=QtCore.Qt.WidgetShortcut,
activated=self.zoom_in,
)
QtWidgets.QShortcut(
QtGui.QKeySequence(QtGui.QKeySequence.ZoomOut),
self._view,
context=QtCore.Qt.WidgetShortcut,
activated=self.zoom_out,
)
@QtCore.pyqtSlot()
def zoom_in(self):
scale_tr = QtGui.QTransform()
scale_tr.scale(UiVentana.factor, UiVentana.factor)
tr = self._view.transform() * scale_tr
self._view.setTransform(tr)
@QtCore.pyqtSlot()
def zoom_out(self):
scale_tr = QtGui.QTransform()
scale_tr.scale(UiVentana.factor, UiVentana.factor)
scale_inverted, invertible = scale_tr.inverted()
if invertible:
tr = self._view.transform() * scale_inverted
self._view.setTransform(tr)

if __name__ == "__main__":
import sys
app = QtWidgets.QApplication(sys.argv)
ui = UiVentana()
ui.show()
sys.exit(app.exec_())

---

更新：

如果要分别对放大和缩小使用+和-，只需将快捷方式更改为：

QtWidgets.QShortcut(
QtGui.QKeySequence(QtCore.Qt.Key_Plus), # <---
self._view,
context=QtCore.Qt.WidgetShortcut,
activated=self.zoom_in,
)
QtWidgets.QShortcut(
QtGui.QKeySequence(QtCore.Qt.Key_Minus), # <---
self._view,
context=QtCore.Qt.WidgetShortcut,
activated=self.zoom_out,
)