PyQt：是否可以 drag/drop QGridLayout 中的 QWidgets 来重新排列它们？

Question

我正在寻找一种方法来创建可以 dragged/dropped 重新排列顺序的图形网格。我的第一次尝试是使用 QDockWidgets，因为它们允许 drag/drop，但是它们在许多其他方面受到限制。是否可以在 QGridLayout 中实现此功能？

现在我有一个带有 3x3 matplotlib 小部件的 QGridLayout。

这是所需布局结果的示例。

示例代码：

import sys
from PyQt5 import QtWidgets
from matplotlib.figure import Figure
from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg as FigureCanvas
import random

from PyQt5.QtWidgets import QGridLayout, QVBoxLayout, QHBoxLayout, QScrollArea, QWidget, QDialog, QApplication, QFrame

class IndicSelectWindow(QDialog):
    def __init__(self, parent=None):
        super(IndicSelectWindow, self).__init__(parent=parent)
        self.resize(1000, 800)

        self.layout = QtWidgets.QHBoxLayout(self)
        self.scrollArea = QScrollArea(self)
        self.scrollArea.setWidgetResizable(True)
        self.scrollAreaWidgetContents = QWidget()
        self.gridLayout = QGridLayout(self.scrollAreaWidgetContents)
        self.scrollArea.setWidget(self.scrollAreaWidgetContents)
        self.layout.addWidget(self.scrollArea)

        for i in range(3):
             for j in range(3):
                 self.Frame = QFrame(self)
                 self.Frame.setStyleSheet("background-color: white;")
                 self.Frame.setFrameStyle(QFrame.Panel | QFrame.Raised)
                 self.Frame.setLineWidth(2)
                 self.layout = QHBoxLayout(self.Frame)

                 self.figure = Figure()  # a figure to plot on
                 self.canvas = FigureCanvas(self.figure)
                 self.ax = self.figure.add_subplot(111)  # create an axis
                 data = [random.random() for i in range(10)]
                 self.ax.plot(data, '*-')  # plot data
                 self.canvas.draw()  # refresh canvas

                 self.layout.addWidget(self.canvas)

                 Box = QVBoxLayout()

                 Box.addWidget(self.Frame)

                 self.gridLayout.addLayout(Box, i, j)
                 self.gridLayout.setColumnStretch(i % 3, 1)
                 self.gridLayout.setRowStretch(j, 1)

if __name__ == '__main__':
    app = QApplication(sys.argv)
    w = IndicSelectWindow()
    w.show()
    sys.exit(app.exec_())

Answer 1

这里是一个实现，将交换 drag/drop 中涉及的项目的位置。 3 个主要步骤是：

(1) 重新实现mousePressEvent，根据鼠标坐标获取LayoutItem的索引。

(2) 重新实现 mouseMoveEvent 以设置 FigureCanvas 的 QDrag。

(3) 重新实现 dropEvent 以交换布局中的目标项。

由于 matplotlib 小部件吸收鼠标事件，您还需要重新实现 eventFilter 来检测它们。

import sys, random
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from matplotlib.figure import Figure
from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg as FigureCanvas

class IndicSelectWindow(QDialog):

    def __init__(self, parent=None):
        super(IndicSelectWindow, self).__init__(parent=parent)
        self.resize(1000, 800)

        self.target = None
        self.setAcceptDrops(True)
        self.layout = QHBoxLayout(self)
        self.scrollArea = QScrollArea(self)
        self.scrollArea.setWidgetResizable(True)
        self.scrollAreaWidgetContents = QWidget()
        self.gridLayout = QGridLayout(self.scrollAreaWidgetContents)
        self.scrollArea.setWidget(self.scrollAreaWidgetContents)
        self.layout.addWidget(self.scrollArea)

        for i in range(3):
            for j in range(3):
                self.Frame = QFrame(self)
                self.Frame.setStyleSheet("background-color: white;")
                self.Frame.setFrameStyle(QFrame.Panel | QFrame.Raised)
                self.Frame.setLineWidth(2)
                self.layout = QHBoxLayout(self.Frame)

                self.figure = Figure()  # a figure to plot on
                self.canvas = FigureCanvas(self.figure)
                self.ax = self.figure.add_subplot(111)  # create an axis
                data = [random.random() for i in range(10)]
                self.ax.plot(data, '*-')  # plot data
                self.canvas.draw()  # refresh canvas
                self.canvas.installEventFilter(self)

                self.layout.addWidget(self.canvas)

                Box = QVBoxLayout()

                Box.addWidget(self.Frame)

                self.gridLayout.addLayout(Box, i, j)
                self.gridLayout.setColumnStretch(i % 3, 1)
                self.gridLayout.setRowStretch(j, 1)

    def eventFilter(self, watched, event):
        if event.type() == QEvent.MouseButtonPress:
            self.mousePressEvent(event)
        elif event.type() == QEvent.MouseMove:
            self.mouseMoveEvent(event)
        elif event.type() == QEvent.MouseButtonRelease:
            self.mouseReleaseEvent(event)
        return super().eventFilter(watched, event)

    def get_index(self, pos):
        for i in range(self.gridLayout.count()):
            if self.gridLayout.itemAt(i).geometry().contains(pos) and i != self.target:
                return i

    def mousePressEvent(self, event):
        if event.button() == Qt.LeftButton:
            self.target = self.get_index(event.windowPos().toPoint())
        else:
            self.target = None

    def mouseMoveEvent(self, event):
        if event.buttons() & Qt.LeftButton and self.target is not None:
            drag = QDrag(self.gridLayout.itemAt(self.target))
            pix = self.gridLayout.itemAt(self.target).itemAt(0).widget().grab()
            mimedata = QMimeData()
            mimedata.setImageData(pix)
            drag.setMimeData(mimedata)
            drag.setPixmap(pix)
            drag.setHotSpot(event.pos())
            drag.exec_()

    def mouseReleaseEvent(self, event):
        self.target = None

    def dragEnterEvent(self, event):
        if event.mimeData().hasImage():
            event.accept()
        else:
            event.ignore()

    def dropEvent(self, event):
        if not event.source().geometry().contains(event.pos()):
            source = self.get_index(event.pos())
            if source is None:
                return

            i, j = max(self.target, source), min(self.target, source)
            p1, p2 = self.gridLayout.getItemPosition(i), self.gridLayout.getItemPosition(j)

            self.gridLayout.addItem(self.gridLayout.takeAt(i), *p2)
            self.gridLayout.addItem(self.gridLayout.takeAt(j), *p1)


if __name__ == '__main__':
    app = QApplication(sys.argv)
    w = IndicSelectWindow()
    w.show()
    sys.exit(app.exec_())

PyQt：是否可以 drag/drop QGridLayout 中的 QWidgets 来重新排列它们？

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