Appengine Cloud Endpoints：获取模型对象方法的NPE

I'm using Cloud Endpoints to retrieve data from appengine to android. Using the generated library I retrieve a list of objects. This appears to work fine, and if I log the object I see the json. However if I use a getX() on the object I get a NPE. Java GAE 1.8.7. Doing this in an AsycTask in activity.

我正在使用Cloud Endpoints从appengine检索数据到android。使用生成的库我检索对象列表。这似乎工作正常，如果我记录对象，我看到了json。但是如果我在对象上使用getX（），我会得到一个NPE。 Java GAE 1.8.7。在AsycTask活动中执行此操作。

        Builder builder = new Builder(AndroidHttp.newCompatibleTransport(),
                new GsonFactory(), null);
        MyObjectOperations service = builder.build().myobject();
        MyObjectCollection tmp = null;

        GetMyObjects it = service.getMyObjects();
        tmp = it.execute();
        listOfMyObjects = tmp.getItems();

        MyObject test=listOfMyObjects.get(0);
        test.getMyField();     //NPE here - on every field

What could cause this?? The listOfMyObjects is the correct size. I have used this client lib before and it worked. Now it is an updated version. Any help would be great!

有什么可能导致这个？ listOfMyObjects的大小正确。我之前使用过这个客户端库并且它有效。现在它是一个更新版本。任何帮助都会很棒！

1 个解决方案

#1

If your listOfMyObjects is not an instance of ArrayList<> or some other Iterable, the get(0) will return null, as the list isn't indexed. So, even if the list has n items, it doesn't have a specific nth item, as they're not ordered.

如果listOfMyObjects不是ArrayList <>或其他Iterable的实例，则get（0）将返回null，因为列表未编入索引。因此，即使列表中有n个项目，它也没有特定的第n个项目，因为它们没有被订购。

Create an ArrayList like this:

像这样创建一个ArrayList：

listOfMyObjects = new ArrayList<myObject>(tmp.getItems());

Then get(0) should work.

然后得到（0）应该工作。

#1