pyqt QTreeView 为空时显示文本

class QTreeView(QTreeView):

    def __init__(self, parent=None):

        super(QTreeView, self).__init__(parent)

    def paintEvent(self,event):

        if self.model() and self.model().rowCount() > 0:

            super().paintEvent(event)

        else:

            painter = QtGui.QPainter (self.viewport())

            # If no items draw a text in the center of the viewport.

            self.viewport()

            text = "There are no elements in this view"

            textRect = painter.fontMetrics().boundingRect(text)

            textRect.moveCenter(self.viewport().rect().center())

            painter.drawText(textRect, Qt.AlignCenter, text)