新的 QPixmap 似乎覆盖了旧的 QPixmap

Question

我想在我的 GUI 上显示一些图像，首先当我单击按钮时，选择第一张图像，一切正常，我的图像显示 fitInView，但是当我想选择下一张图片，黑魔法发生了..我的第二张图片不像第一张那样在中心，在 QGraphicsView 的顶部，而且看起来旧图片的 QScenes 并没有消失，我有来自 risg 和底部的 ScrollBar，我可以滚动直到我在 QGraphicsView 上有一个空白，有什么问题？想不通。。

我的代码：

import sys
from PyQt5 import QtCore, QtGui, QtWidgets
# from PyQt4 import QtCore, QtWidgets

class Graph(QtWidgets.QGraphicsView):
        def __init__(self, parent=None):
            super(Graph, self).__init__(parent)
            scene = QtWidgets.QGraphicsScene(self)
            self.setScene(scene)
            self.pixmap = QtGui.QPixmap()
            self.m_pixmap_item = self.scene().addPixmap(self.pixmap)


        def setPixmap(self, _pixmap):
            self.pixmap = _pixmap
            # self.m_pixmap_item = self.scene().addPixmap(self.pixmap)
            self.m_pixmap_item.setPixmap(self.pixmap)
            self.fitInView(self.m_pixmap_item, QtCore.Qt.KeepAspectRatio)

        def resizeEvent(self, event):
            if not self.m_pixmap_item.pixmap().isNull():
                self.fitInView(self.m_pixmap_item, QtCore.Qt.KeepAspectRatio)
            super(Graph, self).resizeEvent(event)

主窗口部分：

class Window(QtWidgets.QWidget):
    def __init__(self):
        super(Window, self).__init__()
        self.setMinimumSize(640, 480)
        # --> Create Class ResizbleRubberBand <-> Parent: QLabel
        self.band = Graph(self)
        # --> Create buttons & functions
        self.fileOpen_btn = QtWidgets.QPushButton()
        self.create_and_format_btn(self.fileOpen_btn, self.fileOpen, 'GUI/icons/file.png', 32)
        btn_Layout = QtWidgets.QVBoxLayout()
        btn_layout_1 = QtWidgets.QHBoxLayout()
        btn_layout_1.addWidget(self.fileOpen_btn)
        btn_Layout.addLayout(btn_layout_1)
        layout = QtWidgets.QHBoxLayout(self)
        layout.setAlignment(QtCore.Qt.AlignCenter)
        layout.addWidget(self.band)
        layout.addLayout(btn_Layout)

    def create_and_format_btn(self, btn_name, btn_function, btn_icon, btn_iconsize):
        btn_name.clicked.connect(btn_function)
        btn_name.setIcon(QtGui.QIcon(btn_icon))
        btn_name.setIconSize(QtCore.QSize(btn_iconsize, btn_iconsize))

    def fileOpen(self):
        path = QtWidgets.QFileDialog.getOpenFileName(self, 'Open File')
        filename = path[0]
        self.loadImage_On_Pixmap(filename)

    def loadImage_On_Pixmap(self, file):
        f = QtGui.QPixmap(file)
        self.band.setPixmap(f)



if __name__ == '__main__':

    app = QtWidgets.QApplication(sys.argv)
    window = Window()
    # window.setGeometry(800, 100, 600, 500)
    window.show()
    sys.exit(app.exec_())

第一张图片（正常）：

第二张图片（奇怪）：

Answer 1

试试看：

from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtWidgets import QFileDialog


class PhotoViewer(QtWidgets.QGraphicsView):
    photoClicked = QtCore.pyqtSignal(QtCore.QPoint)

    def __init__(self, parent):
        super(PhotoViewer, self).__init__(parent)
        self._zoom = 0
        self._empty = True
        self._scene = QtWidgets.QGraphicsScene(self)
        self._photo = QtWidgets.QGraphicsPixmapItem()
        self._scene.addItem(self._photo)
        self.setScene(self._scene)
        self.setTransformationAnchor(QtWidgets.QGraphicsView.AnchorUnderMouse)
        self.setResizeAnchor(QtWidgets.QGraphicsView.AnchorUnderMouse)
        self.setVerticalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
        self.setHorizontalScrollBarPolicy(QtCore.Qt.ScrollBarAlwaysOff)
        self.setBackgroundBrush(QtGui.QBrush(QtGui.QColor(30, 30, 30)))
        self.setFrameShape(QtWidgets.QFrame.NoFrame)

    def hasPhoto(self):
        return not self._empty

    def fitInView(self, scale=True):
        rect = QtCore.QRectF(self._photo.pixmap().rect())
        if not rect.isNull():
            self.setSceneRect(rect)
            if self.hasPhoto():
                unity = self.transform().mapRect(QtCore.QRectF(0, 0, 1, 1))
                self.scale(1 / unity.width(), 1 / unity.height())
                viewrect = self.viewport().rect()
                scenerect = self.transform().mapRect(rect)
                factor = min(viewrect.width() / scenerect.width(),
                             viewrect.height() / scenerect.height())
                self.scale(factor, factor)
            self._zoom = 0

    def setPhoto(self, pixmap=None):
        self._zoom = 0
        if pixmap and not pixmap.isNull():
            self._empty = False
            self.setDragMode(QtWidgets.QGraphicsView.ScrollHandDrag)
            self._photo.setPixmap(pixmap)
        else:
            self._empty = True
            self.setDragMode(QtWidgets.QGraphicsView.NoDrag)
            self._photo.setPixmap(QtGui.QPixmap())
        self.fitInView()

    def wheelEvent(self, event):
        if self.hasPhoto():
            if event.angleDelta().y() > 0:
                factor = 1.25
                self._zoom += 1
            else:
                factor = 0.8
                self._zoom -= 1
            if self._zoom > 0:
                self.scale(factor, factor)
            elif self._zoom == 0:
                self.fitInView()
            else:
                self._zoom = 0

    def toggleDragMode(self):
        if self.dragMode() == QtWidgets.QGraphicsView.ScrollHandDrag:
            self.setDragMode(QtWidgets.QGraphicsView.NoDrag)
        elif not self._photo.pixmap().isNull():
            self.setDragMode(QtWidgets.QGraphicsView.ScrollHandDrag)

    def mousePressEvent(self, event):
        if self._photo.isUnderMouse():
            self.photoClicked.emit(QtCore.QPoint(event.pos()))
        super(PhotoViewer, self).mousePressEvent(event)


class Window(QtWidgets.QWidget):
    def __init__(self):
        super(Window, self).__init__()

        self.viewer = PhotoViewer(self)

        self.btnLoad = QtWidgets.QToolButton(self)
        self.btnLoad.setIcon(QtGui.QIcon('im.png'))
        self.btnLoad.setIconSize(QtCore.QSize(32, 32))
        self.btnLoad.clicked.connect(self.loadImage)

        layout = QtWidgets.QHBoxLayout(self)
        layout.addWidget(self.viewer)
        layout.addWidget(self.btnLoad)


    def loadImage(self):
        filename, _ = QtWidgets.QFileDialog.getOpenFileName(self, 'Open File')
        if filename:
            self.viewer.setPhoto(QtGui.QPixmap(filename))


if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    window = Window()
    window.setGeometry(400, 100, 640, 480)
    window.show()
    sys.exit(app.exec_())