Simple PySide/PyQt QPropertyAnimation

markbaas

Hi,

I'm struggling to get an animation working. It seems that animation outside of my class work fine, however as soon as I run them from withing the class, they refuse to start. Can anyone tell me what's wrong with my code:

@import sys

from PySide import QtCore, QtGui

class Pixmap(QtCore.QObject):
def init(self, pix):
super(Pixmap, self).init()

    if type(pix) == type(""):
        pix = QtGui.QPixmap(pix)

    self.pixmap_item = QtGui.QGraphicsPixmapItem(pix)
    self.pixmap_item.setCacheMode(QtGui.QGraphicsItem.DeviceCoordinateCache)

def set_pos(self, pos):
    self.pixmap_item.setPos(pos)

def get_pos(self):
    return self.pixmap_item.pos()
    
def get_opacity(self):
    return self.pixmap_item.opacity()
    
def set_opacity(self, opacity):
    self.pixmap_item.setOpacity(opacity)

pos = QtCore.Property(QtCore.QPointF, get_pos, set_pos)
opacity = QtCore.Property(float, get_opacity, set_opacity)

"""
Sets up the subclassed QGraphicsView
"""
class ImageWidget(QtGui.QGraphicsView):
LastPanPoint = None
CurrentCenterPoint = None

def __init__(self, parent=None):
    super(ImageWidget, self).__init__(parent)
    
    self.setRenderHints(QtGui.QPainter.Antialiasing | QtGui.QPainter.SmoothPixmapTransform)
    
    # set-up the scene
    self.scene = QtGui.QGraphicsScene()
    self.setScene(self.scene)
    
    
def loadImage(self, f):
    # Load image
     pixmap = Pixmap(f)
    item = pixmap.pixmap_item
    item.setOpacity(0)
    self.scene.addItem(item)
    
    anim = QtCore.QPropertyAnimation(pixmap, "opacity")
    anim.setDuration(10000)
    anim.setStartValue(0.0)
    anim.setEndValue(1.0)
    anim.setEasingCurve(QtCore.QEasingCurve.InOutBack)
    QtCore.QTimer.singleShot(1000, anim, QtCore.SLOT("start()"))
    QtCore.QObject.connect(anim, QtCore.SIGNAL("finished()"), anim, QtCore.SLOT("deleteLater()"))

if name == "main":
a = QtGui.QApplication(sys.argv)
view = ImageWidget()
view.setGeometry(100,100, 900, 600)
view.loadImage(sys.argv[1])

view.show()
a.exec_()@

madjar

Hi

This answer may be a little help but I hope it helps someone nevertheless.

In ImageWidget.loadImage, you create anim as a local variable. That means it's going to be garbage collected at the end of th call : as soon as the call is over, the animation is deleted, and won't have any effect.

There is two ways to solve the problem :

Define anim as an object attribute (@self.anim = …@)
Set anim as a child of the current object, so that it keeps a reference to anim and prevent the garbage collection (@anim = QtCore.QPropertyAnimation(pixmap, "opacity", self)@)

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Simple PySide/PyQt QPropertyAnimation