片段方案无法按预期工作

Question

我使用的架构与Google示例几乎相同：GithubBrowserSample。

这个字段被注入到我的Fragment类中：

@Inject
lateinit var viewModelFactory: ViewModelProvider.Factory
val viewModel: TrainingListViewModel by viewModels {
viewModelFactory
}

在我所有的碎片测试中，我都得到了这个错误，它对应于一个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)

当我用FragmentScenario:这样设置我的片段时，就会发生这种情况

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()
}

但当我在使用FragmentScenario之前设置Fragment时，它是有效的：

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()
}
}
}

你们知道为什么会发生这种事吗？我该怎么解决？我真的很挣扎：(

Answer 1

您遇到的问题是由变量阴影引起的。

当你写这个代码

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)不是使用上面使用mock创建的viewModel变量，而是使用TrainingListFragment中的viewModel变量**。这是因为您使用的是apply { }，这意味着代码应用的范围是片段本身——它实际上就像您的代码在片段本身中一样，所以viewModel实际上是TrainingListViewModel.this.viewModel。

这就是为什么你的错误信息显示

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()，即从您的instantiate块中访问viewModel属性。

最简单的解决方案是为mock viewModel使用不同的变量名，而不是使用相同的名称viewModel。如果它被命名为mockViewModel，那么它调用ViewModelUtil.createFor(mockViewModel)将正确地引用您的mock ViewModel，因为您的片段中不会有任何具有相同名称的变量。

另一种选择是使用also而不是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和apply一样，总是返回原始对象-您的TrainingListFragment(这是正确的，也是您想要返回的(。

然而，当使用also时，您必须命名正在操作的变量(这里我使用fragment而不是默认的it(，如果您想引用片段变量中的某些内容，则需要特别使用fragment.viewModel。同样，在没有任何名称阴影的情况下，在本例中，viewModel将指向作用域中唯一的viewModel变量——您的mock ViewModel。