android - 访问 mObservables 时对 RecyclerView 适配器进行单元测试会引发 NullPointerException

Question

我的 View 模型拥有一个非常简单的 recyclerview 适配器

当我尝试向它发送消息(进而调用 notifyDatasetChanged )时，它会抛出这样的异常

java.lang.NullPointerException
at androidx.recyclerview.widget.RecyclerView$AdapterDataObservable.notifyChanged(RecyclerView.java:11996)
at

问题是 mObservers来自 AdapterDataObservable 的变量一片空白

问题是这扩展了Observable<AdapterDataObserver>反过来定义 mObservers作为

protected final ArrayList<T> mObservers = new ArrayList<T>();

所以基本上在我的适配器被实例化的那一刻，它就会调用

private final AdapterDataObservable mObservable = new AdapterDataObservable();

(顺便说一下，mObservable不为null)

反过来应该调用 mObservers = new ArrayList<T>();
有人可以解释为什么这从未被调用吗？或者是否有办法解决这个问题？

作为旁注，适配器没有被模拟，它是一个实体对象。

编辑:

这是我正在使用的测试代码:

class LoginViewModelTest {

     private lateinit var vm: LoginViewModel

        @get:Rule
        val rule = InstantTaskExecutorRule()

        @Before
        fun setUp() {

            whenever(settings.hasShownWelcome).thenReturn(false)
            whenever(settings.serverIp).thenReturn("http://127.0.0.1")

            //this is where the crash happens
            vm = LoginViewModel(settings, service, app, TestLog, TestDispatchers) { p -> permissionGranted }
        }

以下是经过测试的代码:

class LoginViewModel(private val settings: ISettings, private val service: AppService, application: Application, l: ILog, dispatchers: IDispatchers, val permissionChecker: (String) -> Boolean) :  BaseViewModel(application, l, dispatchers)

    val stepAdapter :StepAdapter

    init {
        val maxSteps = calculateSteps()
        //after this assignment, during the normal run, the stepAdapter.mObservable.mObservers is an empty array
        //during unit tests, after this assignment it is null
        stepAdapter = StepAdapter(maxSteps) 
    }

Answer 1

我通过监视适配器和 stub 修复了我的 notifyDataSetChanged .

    val spyAdapter = spyk(adapter)
    every { spyAdapter.notifyDataSetChanged() } returns Unit
    spyAdapter.changeItems(items)
    verify { spyAdapter.notifyDataSetChanged() }

请注意 changeItems来电notifyDataSetChanged内部。