FragmentScenario无法正常工作

Question

我使用的结构几乎与Google示例相同：GithubBrowserSample。

此字段注入到我的Fragment类中：

@Inject
lateinit var viewModelFactory: ViewModelProvider.Factory

val viewModel: TrainingListViewModel by viewModels {
    viewModelFactory
}

在我所有的片段测试中，我得到了这个错误，该错误对应于通过注入实例化的字段：

java.lang.RuntimeException: kotlin.UninitializedPropertyAccessException: lateinit property viewModelFactory has not been initialized
at androidx.test.runner.MonitoringInstrumentation.runOnMainSync(MonitoringInstrumentation.java:441)
at androidx.test.core.app.ActivityScenario.onActivity(ActivityScenario.java:564)
at androidx.fragment.app.testing.FragmentScenario.internalLaunch(FragmentScenario.java:300)
at androidx.fragment.app.testing.FragmentScenario.launchInContainer(FragmentScenario.java:282)
at com.maximesarrato.lafayapp.ui.training.TrainingListFragmentTest.init(TrainingListFragmentTest.kt:213)
at java.lang.reflect.Method.invoke(Native Method)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at androidx.test.internal.runner.junit4.statement.RunBefores.evaluate(RunBefores.java:76)
at org.junit.rules.TestWatcher$1.evaluate(TestWatcher.java:55)
at org.junit.rules.TestWatcher$1.evaluate(TestWatcher.java:55)
at org.junit.rules.TestWatcher$1.evaluate(TestWatcher.java:55)
at org.junit.rules.RunRules.evaluate(RunRules.java:20)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at androidx.test.ext.junit.runners.AndroidJUnit4.run(AndroidJUnit4.java:104)
at org.junit.runners.Suite.runChild(Suite.java:128)
at org.junit.runners.Suite.runChild(Suite.java:27)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
at androidx.test.internal.runner.TestExecutor.execute(TestExecutor.java:56)
at androidx.test.runner.AndroidJUnitRunner.onStart(AndroidJUnitRunner.java:392)
at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:2189)
Caused by: kotlin.UninitializedPropertyAccessException: lateinit property viewModelFactory has not been initialized
at com.maximesarrato.lafayapp.ui.training.TrainingListFragment.getViewModelFactory(TrainingListFragment.kt:41)
at com.maximesarrato.lafayapp.ui.training.TrainingListFragment$viewModel$2.invoke(TrainingListFragment.kt:49)
at com.maximesarrato.lafayapp.ui.training.TrainingListFragment$viewModel$2.invoke(TrainingListFragment.kt:39)
at androidx.lifecycle.ViewModelLazy.getValue(ViewModelProvider.kt:52)
at androidx.lifecycle.ViewModelLazy.getValue(ViewModelProvider.kt:41)
at com.maximesarrato.lafayapp.ui.training.TrainingListFragment.getViewModel(Unknown Source:7)
at com.maximesarrato.lafayapp.ui.training.TrainingListFragmentTest$init$$inlined$launchFragmentInContainer$1.instantiate(FragmentScenario.kt:114)
at androidx.fragment.app.testing.FragmentScenario$1.perform(FragmentScenario.java:310)
at androidx.fragment.app.testing.FragmentScenario$1.perform(FragmentScenario.java:301)
at androidx.test.core.app.ActivityScenario.lambda$onActivity$2$ActivityScenario(ActivityScenario.java:551)
at androidx.test.core.app.ActivityScenario$$Lambda$4.run(Unknown Source:4)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:462)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at android.app.Instrumentation$SyncRunnable.run(Instrumentation.java:2207)
at android.os.Handler.handleCallback(Handler.java:883)
at android.os.Handler.dispatchMessage(Handler.java:100)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)

当我使用FragmentScenario设置片段时会发生这种情况：

viewModel = mock(TrainingListViewModel::class.java)

val scenario = launchFragmentInContainer(themeResId = R.style.Theme_LafayWorkbook) {
    TrainingListFragment().apply {
        appExecutors = countingAppExecutors.appExecutors
        viewModelFactory = ViewModelUtil.createFor(viewModel)
    }
}

dataBindingIdlingResourceRule.monitorFragment(scenario)
scenario.onFragment { fragment ->
    Navigation.setViewNavController(fragment.requireView(), navController)
    fragment.binding.trainingListRv.itemAnimator = null
    fragment.disableProgressBarAnimations()
}

但是当我在使用FragmentScenario之前设置Fragment时，它可以工作：

viewModel = mock(TrainingListViewModel::class.java)
val trainingListFragment = TrainingListFragment()
trainingListFragment.viewModelFactory = ViewModelUtil.createFor(viewModel)
trainingListFragment.appExecutors = countingAppExecutors.appExecutors

trainingListFragment.viewLifecycleOwnerLiveData.observeForever { viewLifecycleOwner ->
    if (viewLifecycleOwner != null) {
        Navigation.setViewNavController(trainingListFragment.requireView(), navController)
    }
}

val scenario = launchFragmentInContainer(themeResId = R.style.Theme_LafayWorkbook) {
    trainingListFragment
}

这是我的测试的源代码：

@RunWith(AndroidJUnit4::class)
class TrainingListFragmentTest {
    @Rule
    @JvmField
    val executorRule = TaskExecutorWithIdlingResourceRule()

    @Rule
    @JvmField
    val countingAppExecutors = CountingAppExecutorsRule()

    @Rule
    @JvmField
    val dataBindingIdlingResourceRule = DataBindingIdlingResourceRule()

    private val navController = mock<NavController>()
    private val trainingsLiveData = MutableLiveData<Resource<List<Training>>>()
    private val isPremiumLiveData = MutableLiveData<PremiumAccount>()
    private val trainingDeletedLiveData = MutableLiveData<Event<Boolean>>()
    private val navigateToCreateTrainingLiveData = MutableLiveData<Event<Boolean>>()
    private val navigateToExerciseListLiveData = MutableLiveData<Event<Training>>()
    private lateinit var viewModel: TrainingListViewModel

    @Before
    fun init() {
        viewModel = mock(TrainingListViewModel::class.java)
        val trainingListFragment = TrainingListFragment()
        trainingListFragment.viewModelFactory = ViewModelUtil.createFor(viewModel)
        trainingListFragment.appExecutors = countingAppExecutors.appExecutors

        trainingListFragment.viewLifecycleOwnerLiveData.observeForever { viewLifecycleOwner ->
            if (viewLifecycleOwner != null) {
                Navigation.setViewNavController(trainingListFragment.requireView(), navController)
            }
        }

        `when`(viewModel.trainingsLiveData).thenReturn(trainingsLiveData)
        `when`(viewModel.isPremium).thenReturn(isPremiumLiveData)
        `when`(viewModel.trainingDeleted).thenReturn(trainingDeletedLiveData)
        `when`(viewModel.navigateToCreateTraining).thenReturn(navigateToCreateTrainingLiveData)
        `when`(viewModel.navigateToExerciseList).thenReturn(navigateToExerciseListLiveData)

        val scenario = launchFragmentInContainer(themeResId = R.style.Theme_LafayWorkbook) {
            trainingListFragment
        }
        dataBindingIdlingResourceRule.monitorFragment(scenario)
        scenario.onFragment { fragment ->
            Navigation.setViewNavController(fragment.requireView(), navController)
            fragment.binding.trainingListRv.itemAnimator = null
            fragment.disableProgressBarAnimations()
        }
    }

}

你们对为什么会这样以及如何解决这个问题有想法吗？我真的在为此苦苦挣扎：（

Answer 1

您遇到的问题是由于variable shadowing。

编写此代码时

viewModel = mock(TrainingListViewModel::class.java)

val scenario = launchFragmentInContainer(themeResId = R.style.Theme_LafayWorkbook) {
    TrainingListFragment().apply {
        appExecutors = countingAppExecutors.appExecutors
        viewModelFactory = ViewModelUtil.createFor(viewModel)
    }
}

ViewModelUtil.createFor(viewModel)是not，而不是使用您在上面的viewModel中创建的mock变量，而是在viewModel中使用了TrainingListFragment变量**。这是因为您使用的是apply { }，这意味着代码所适用的范围是片段本身-有效地就像您的代码位于该片段本身内一样，因此viewModel实际上是TrainingListViewModel.this.viewModel。

这就是您的错误消息说的原因

at com.maximesarrato.lafayapp.ui.training.TrainingListFragment.getViewModel(Unknown Source:7)
at com.maximesarrato.lafayapp.ui.training.TrainingListFragmentTest$init$$inlined$launchFragmentInContainer$1.instantiate(FragmentScenario.kt:114)

您正在调用getViewModel()，即从viewModel块中访问instantiate属性。

最简单的解决方案是为模拟viewModel使用不同的变量名称，而不是使用相同的名称viewModel。如果将其命名为mockViewModel，则它的调用ViewModelUtil.createFor(mockViewModel)将正确引用您的模拟ViewModel，因为片段中将没有任何同名变量。

另一个选项是使用also代替apply：

viewModel = mock(TrainingListViewModel::class.java)

val scenario = launchFragmentInContainer(themeResId = R.style.Theme_LafayWorkbook) {
    TrainingListFragment().also { fragment ->
        fragment.appExecutors = countingAppExecutors.appExecutors
        fragment.viewModelFactory = ViewModelUtil.createFor(viewModel)
    }
}

[also，与apply一样，总是返回原始对象-您的TrainingListFragment（这是正确的以及您要返回的内容）。

但是，当使用also时，必须命名要操作的变量（这里我使用fragment而不是默认的it），如果要引用，则需要专门使用fragment.viewModel片段变量中的某些内容。同样，在没有任何名称隐藏的情况下，在这种情况下，viewModel将指向作用域中唯一的viewModel变量-您的模拟ViewModel。