PyQt5之QGraphics 012 简单应用QUndoCammand实现undo/redo

在文章中：https://blog.csdn.net/weixin_42837024/article/details/82184333，实现撤回和回撤功能。

上面提到的文章是用C++实现的，现在用PyQt来重写一下。

"""
有趣的事情
没有结束
2020/3/31 13:45
"""

from PyQt5.QtWidgets import (QApplication, QWidget, QUndoCommand, QUndoStack, QUndoView,
                             QGraphicsItem, QGraphicsScene, QGraphicsView,
                             QGraphicsPolygonItem, QPushButton, QAction,
                             QVBoxLayout, QHBoxLayout)
from PyQt5.QtCore import (QPoint, QPointF, QLine, QLineF,
                          QRect, QRectF, pyqtSignal, Qt, QObject)
from PyQt5.QtGui import (QPixmap, QPen, QPainter, QKeySequence,
                         QPolygon, QPolygonF, QColor, QBrush)
import random


class MyShape(QGraphicsPolygonItem):
    def __init__(self, parent=None):
        super(MyShape, self).__init__(parent)
        # self.Type = self.UserType + 1
        self.m_boxItem = QPolygonF()
        self.m_boxItem.append(QPointF(0, 0))
        self.m_boxItem.append(QPointF(30, 0))
        self.m_boxItem.append(QPointF(30, 30))
        self.m_boxItem.append(QPointF(0, 30))
        self.m_boxItem.append(QPointF(0, 0))
        self.setPolygon(self.m_boxItem)
        self.color = QColor(random.randint(0, 256), random.randint(0, 256), random.randint(0, 256))
        self.brush = QBrush(self.color)
        self.setBrush(self.brush)

        self.setFlag(QGraphicsItem.ItemIsMovable)
        self.setFlag(QGraphicsItem.ItemIsSelectable)

    # def type(self):
    #     return self.Type


class MyScene(QGraphicsScene):
    itemMoveSignal = pyqtSignal(MyShape, QPointF)

    def __init__(self):
        super(MyScene, self).__init__()
        self.m_Item = None
        self.m_oldPos = QPointF()

    def mousePressEvent(self, event):
        mousePos = QPointF(event.buttonDownScenePos(Qt.LeftButton).x(),
                           event.buttonDownScenePos(Qt.LeftButton).y())
        itemList = []
        itemList = self.items(mousePos)
        if len(itemList) > 0:
            self.m_Item = itemList[0]
        if (self.m_Item is not None) & (event.button() == Qt.LeftButton):
            self.m_oldPos = self.m_Item.pos()
        super(MyScene, self).mousePressEvent(event)

    def mouseReleaseEvent(self, event):
        if (self.m_Item is not None) & (event.button() == Qt.LeftButton):
            if self.m_oldPos != self.m_Item.pos():
                self.itemMoveSignal.emit(self.m_Item, self.m_oldPos)
            self.m_Item = None
        super(MyScene, self).mouseReleaseEvent(event)


class AddCommand(QUndoCommand):
    def __init__(self, scene):
        super(AddCommand, self).__init__()
        self.scene = scene
        self.shape = MyShape()
        self.m_initPos = QPointF(random.randint(1, 10), random.randint(1, 10))
        self.setText("add item")

    def redo(self):
        self.scene.addItem(self.shape)
        self.shape.setPos(self.m_initPos)
        self.scene.clearSelection()
        # self.update()

    def undo(self):
        self.scene.removeItem(self.shape)
        self.scene.update()


class MoveCommand(QUndoCommand):
    def __init__(self, item, oldPos):
        super(MoveCommand, self).__init__()
        self.shape = item
        self.m_oldPos = oldPos
        self.m_newPos = self.shape.pos()

    def redo(self):
        self.shape.setPos(self.m_newPos)
        self.setText("Move Item %d %d" % (self.shape.pos().x(), self.shape.pos().y()))

    def undo(self):
        self.shape.setPos(self.m_oldPos)
        # self.shape.scene().update()
        self.setText("Move Item %d %d" % (self.shape.pos().x(), self.shape.pos().y()))


class Form(QWidget):
    def __init__(self, parent=None):
        super(Form, self).__init__(parent)
        self.button = QPushButton(self)
        self.undoAction = QAction()
        self.redoAction = QAction()
        self.scene = MyScene()
        self.brush = QBrush(Qt.gray)
        self.scene.setSceneRect(QRectF(0, 0, 200, 300))
        self.scene.setBackgroundBrush(self.brush)
        self.scene.itemMoveSignal.connect(self.ShapeMoved)
        self.undoStack = QUndoStack()

        # init action
        self.undoAction = self.undoStack.createUndoAction(self, "Undo")
        self.undoAction.setShortcut(QKeySequence.Undo)

        self.redoAction = self.undoStack.createRedoAction(self, "Redo")
        self.redoAction.setShortcut(QKeySequence.Redo)

        self.addAction(self.undoAction)
        self.addAction(self.redoAction)

        # init ui
        self.button.setText("Add Shape")
        self.button.clicked.connect(self.AddItem)

        self.view = QGraphicsView()
        self.view.setScene(self.scene)

        self.vlayout = QVBoxLayout()
        self.vlayout.addWidget(self.button)
        self.vlayout.addWidget(self.view)

        self.hlayout = QHBoxLayout()
        self.undoView = QUndoView(self.undoStack)
        self.hlayout.addLayout(self.vlayout)
        self.hlayout.addWidget(self.undoView)

        self.setLayout(self.hlayout)

    def AddItem(self):
        add = AddCommand(self.scene)
        self.undoStack.push(add)

    def ShapeMoved(self, item, pos):
        move = MoveCommand(item, pos)
        self.undoStack.push(move)


if __name__ == "__main__":
    import sys
    app = QApplication(sys.argv)
    form = Form()
    form.setWindowTitle("Undo/Todo")
    form.show()
    sys.exit(app.exec_())

多谢，美美的彪。