我有一个Box2D世界,需要过滤碰撞,我在那里有三个实体,汽车,行人和建筑物。可以在found here处告诉我一个新问题。我终于设法过滤掉了碰撞,当汽车撞到行人时它会起作用,但是当汽车撞到建筑物时,我得到一个错误,即“ NoneType不可下标”我该如何解决?谢谢
CAR_CATEGORY = 0x0002
PEDESTRIAN_CATEGORY = 0x0004
BUILDING_CATEGORY = 0x0008
CAR_GROUP = 2
PEDESTRIAN_GROUP = -4
BUILDING_GROUP = 8
class myContactListener(b2ContactListener):
def handle_contact(self, contact, began):
# A contact happened -- see if a wheel hit a
# ground area
fixture_a = contact.fixtureA
fixture_b = contact.fixtureB
body_a, body_b = fixture_a.body, fixture_b.body
ud_a, ud_b = body_a.userData, body_b.userData
pedestrian_contact = None
car_contact = None
building_contact = None
for ud in (ud_a, ud_b):
obj = ud['obj']
if isinstance(obj, Car):
car_contact = obj
elif isinstance(obj, Pedestrian):
pedestrian_contact = obj
elif isinstance(obj, Building):
building_contact = obj
if car_contact is not None and pedestrian_contact is not None:
if began:
print("Shame on you, you killed an innocent pedestrian!!!")
elif car_contact is not None and building_contact is not None:
if began:
print("BOOMMM")
def __init__(self):
b2ContactListener.__init__(self)
def BeginContact(self, contact):
self.handle_contact(contact, True)
def EndContact(self, contact):
pass
def PreSolve(self, contact, oldManifold):
pass
def PostSolve(self, contact, impulse):
pass
box2world = world(contactListener=myContactListener(),gravity =(0.0, 0.0), doSleep =True)
如何解决该错误?任何帮助表示赞赏
由于您的代码只有一个subscription(一种使用[]
括号),该错误消息表示您可能需要在执行ud
之前检查None
的ud['obj']
对象,例如:
if ud is None:
continue
同一错误消息可以在任何python解释器中触发,如下所示:
>>> a = None[0]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'NoneType' object is not subscriptable
>>>
documentation官方定义了订阅:
6.3.2。订阅
订阅将选择一个序列项(字符串,元组或列表)或映射(字典)对象:
订阅:::主要“ [” expression_list“]”
主要对象必须评估为支持订阅的对象(例如列表或字典)。用户定义的对象可以支持通过定义getitem()方法进行订阅。
...并继续定义支持订阅的对象的内置类型。