自定义 QGraphicsItem 删除自身 [英] Custom QGraphicsItem deletes itself

问题描述

我正在使用 PyQt 5.我有一个 QGraphicsScene，它有一个要显示的 QGraphicsObject 列表.我对 QRectF 和其他类型没有问题.但是我实现了一个自定义类，如下所示:

I am using PyQt 5. I have a QGraphicsScene that has a list with QGraphicsObject's to show. I have no problem with QRectF and other types. However I implemented a custom class as follows:

class RobotPathItem(QGraphicsItem):
def __init__(self, path):
    super().__init__()
    qpath = []
    for xy in path:
        qpath.append(QPoint(xy[0],xy[1]))
    self.path = QPolygon(qpath)

def paint(self, painter, option, qwidget = None):
    painter.drawPoints(self.path)

def boundingRect(self):
    return QRectF(0,0,520,520)

然后我将它添加到场景中:

I then add it to the scene:

self.objects[model_obj.id].append(self.scene.addItem(RobotPathItem(model_obj.actuator.get_current_path())))

这里 self.objects[model_obj.id] 是合适的列表.它确实会出现在现场.

Here self.objects[model_obj.id] is the appropriate list. It does get shown on the scene.

问题在于，在下一次迭代中，它出于某种原因从列表中删除.如果我检查

The problem is that on the very next iteration it is for some reason deleted from the list. If I check

print(self.objects[model_obj.id][-1])

我得到无"(NoneType).所有其他对象仍在列表中.错误在哪里?

I get "None" (NoneType). All other objects are still in the list. Where is the error?

推荐答案

事实证明 addItem 不像 addRect 或其他函数那样返回指针.相反，它返回 None.

Turns out addItem does not return a pointer like addRect or other functions do. Instead it returns None.

为了让上面的代码正常工作:

So for the above code to work properly:

robot_path = RobotPathItem(model_obj.actuator.get_current_path())self.scene.addItem(robot_path)self.objects[model_obj.id].append(robot_path)而不是

self.objects[model_obj.id].append(RobotPathItem(model_obj.actuator.get_current_path()))

然后执行

self.objects[model_obj.id][2].set_path(model_obj.actuator.get_current_path())

更新它

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