如何解决android jetpack 导航仪器测试在返回导航时失败
我使用 jetpack Navigation
组件 (androidx.navigation
) 创建了一个简单的两片段示例应用。第一个片段导航到第二个片段,它使用 OnBackpresseddispatcher
覆盖后退按钮行为。
活动布局
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="@dimen/Box_inset_layout_padding"
tools:context=".navigationcontroller.NavigationControllerActivity">
<fragment
android:name="androidx.navigation.fragment.NavHostFragment"
android:id="@+id/nav_host"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:navGraph="@navigation/nav_graph" />
</LinearLayout>
片段A:
class FragmentA : Fragment() {
lateinit var buttonNavigation: Button
override fun onCreateView(inflater: LayoutInflater,container: ViewGroup?,savedInstanceState: Bundle?): View? {
val view = inflater.inflate(R.layout.fragment_a,container,false)
buttonNavigation = view.findViewById<Button>(R.id.button_navigation)
buttonNavigation.setonClickListener { Navigation.findNavController(requireActivity(),R.id.nav_host).navigate(R.id.fragmentB) }
return view
}
}
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".navigationcontroller.FragmentA">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="fragment A" />
<Button
android:id="@+id/button_navigation"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="go to B" />
</LinearLayout>
片段B:
class FragmentB : Fragment() {
override fun onCreateView(inflater: LayoutInflater,savedInstanceState: Bundle?): View? {
val view = inflater.inflate(R.layout.fragment_b,false)
requireActivity().onBackpresseddispatcher.addCallback(object : OnBackpressedCallback(true) {
override fun handleOnBackpressed() {
val textView = view.findViewById<TextView>(R.id.textView)
textView.setText("backbutton pressed,press again to go back")
this.isEnabled = false
}
})
return view
}
}
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".navigationcontroller.FragmentA">
<TextView
android:id="@+id/textView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="fragment B" />
</FrameLayout>
当我手动测试应用程序时,FragmentB 中后退按钮的预期行为(第一次触摸在没有导航的情况下更改文本,第二次向后导航)工作正常。 我添加了仪器测试来检查 FragmentB 中的后退按钮行为,这就是问题开始出现的地方:
class NavigationControllerActivityTest {
lateinit var fragmentScenario: FragmentScenario<FragmentB>
lateinit var navController: TestNavHostController
@Before
fun setUp() {
navController = TestNavHostController(ApplicationProvider.getApplicationContext())
fragmentScenario = FragmentScenario.launchInContainer(FragmentB::class.java)
fragmentScenario.onFragment(object : FragmentScenario.FragmentAction<FragmentB> {
override fun perform(fragment: FragmentB) {
Navigation.setViewNavController(fragment.requireView(),navController)
navController.setLifecycleOwner(fragment.viewLifecycleOwner)
navController.setonBackpresseddispatcher(fragment.requireActivity().getonBackpresseddispatcher())
navController.setGraph(R.navigation.nav_graph)
// simulate backstack from prevIoUs navigation
navController.navigate(R.id.fragmentA)
navController.navigate(R.id.fragmentB)
}
})
}
@Test
fun whenButtonClickedOnce_TextChangednoNavigation() {
Espresso.pressBack()
onView(withId(R.id.textView)).check(matches(withText("backbutton pressed,press again to go back")))
assertEquals(R.id.fragmentB,navController.currentDestination?.id)
}
@Test
fun whenButtonClickedTwice_NavigationHappens() {
Espresso.pressBack()
Espresso.pressBack()
assertEquals(R.id.fragmentA,navController.currentDestination?.id)
}
}
不幸的是,当 whenButtonClickedTwice_NavigationHappens
通过时,whenButtonClickedOnce_TextChangednoNavigation
由于文本未更改而失败,就像从未调用 OnBackpressedCallback
一样。由于应用程序在手动测试期间运行良好,因此测试代码肯定有问题。有人可以帮我吗?
解决方法
FragmentB 的 OnBackPressedCallback
被忽略的原因是 OnBackPressedDispatcher
对待它的 OnBackPressedCallback
的方式。它们作为命令链运行,这意味着最近注册的启用的事件将“吃掉”事件,因此其他人不会收到它。因此,最近在 FragmentScenario.onFragment()
内注册的回调(由 lifecycleOwner
启用,因此每当 Fragment 至少处于生命周期 STARTED
状态时。由于在测试期间按下后退按钮时 Fragment 是可见的,回调始终在当时启用),将优先于之前在 FragmentB.onCreateView()
中注册的回调。
因此,必须在执行 TestNavHostController
之前添加 FragmentB.onCreateView()
的回调。
这会导致@Before方法的测试代码发生变化:
@Before
fun setUp() {
navController = TestNavHostController(ApplicationProvider.getApplicationContext())
fragmentScenario = FragmentScenario.launchInContainer(FragmentB::class.java,initialState = Lifecycle.State.CREATED)
fragmentScenario.onFragment(object : FragmentScenario.FragmentAction<FragmentB> {
override fun perform(fragment: FragmentB) {
navController.setLifecycleOwner(fragment.requireActivity())
navController.setOnBackPressedDispatcher(fragment.requireActivity().getOnBackPressedDispatcher())
navController.setGraph(R.navigation.nav_graph)
// simulate backstack from previous navigation
navController.navigate(R.id.fragmentA)
navController.navigate(R.id.fragmentB)
}
})
fragmentScenario.moveToState(Lifecycle.State.RESUMED)
fragmentScenario.onFragment(object : FragmentScenario.FragmentAction<FragmentB> {
override fun perform(fragment: FragmentB) {
Navigation.setViewNavController(fragment.requireView(),navController)
}
})
}
最重要的变化是在 CREATED
状态(而不是默认的 RESUMED
)下启动 Fragment,以便能够在 onCreateView()
之前修改它。
另外,请注意 Navigation.setViewNavController()
在将片段移动到 onFragment()
状态后在单独的 RESUMED
中运行 - 它接受 View
参数,因此不能在 {{1} 之前使用}}
如果您要测试您的 OnBackPressedCallback
逻辑,最好直接执行此操作,而不是尝试测试 Navigation 与默认 Activity 的 OnBackPressedDispatcher
之间的交互。
这意味着您希望通过注入 OnBackPressedDispatcher
来打破 Activity 的 requireActivity().onBackPressedDispatcher
(OnBackPressedDispatcher
) 和 Fragment 之间的硬依赖关系,从而允许您提供测试特定实例:
class FragmentB(val onBackPressedDispatcher: OnBackPressedDispatcher) : Fragment() {
override fun onCreateView(inflater: LayoutInflater,container: ViewGroup?,savedInstanceState: Bundle?): View? {
val view = inflater.inflate(R.layout.fragment_b,container,false)
onBackPressedDispatcher.addCallback(object : OnBackPressedCallback(true) {
override fun handleOnBackPressed() {
val textView = view.findViewById<TextView>(R.id.textView)
textView.setText("backbutton pressed,press again to go back")
this.isEnabled = false
}
})
return view
}
}
这允许您拥有生产代码 provide a FragmentFactory:
class MyFragmentFactory(val activity: FragmentActivity) : FragmentFactory() {
override fun instantiate(classLoader: ClassLoader,className: String): Fragment =
when (loadFragmentClass(classLoader,className)) {
FragmentB::class.java -> FragmentB(activity.onBackPressedDispatcher)
else -> super.instantiate(classLoader,className)
}
}
// Your activity would use this via:
override fun onCreate(savedInstanceState: Bundle?) {
supportFragmentManager.fragmentFactory = MyFragmentFactory(this)
super.onCreate(savedInstanceState)
// ...
}
这意味着您可以编写如下测试:
class NavigationControllerActivityTest {
lateinit var fragmentScenario: FragmentScenario<FragmentB>
lateinit var onBackPressedDispatcher: OnBackPressedDispatcher
lateinit var navController: TestNavHostController
@Before
fun setUp() {
navController = TestNavHostController(ApplicationProvider.getApplicationContext())
// Create a test specific OnBackPressedDispatcher,// giving you complete control over its behavior
onBackPressedDispatcher = OnBackPressedDispatcher()
// Here we use the launchInContainer method that
// generates a FragmentFactory from a constructor,// automatically figuring out what class you want
fragmentScenario = launchFragmentInContainer {
FragmentB(onBackPressedDispatcher)
}
fragmentScenario.onFragment(object : FragmentScenario.FragmentAction<FragmentB> {
override fun perform(fragment: FragmentB) {
Navigation.setViewNavController(fragment.requireView(),navController)
navController.setGraph(R.navigation.nav_graph)
// Set the current destination to fragmentB
navController.setCurrentDestination(R.id.fragmentB)
}
})
}
@Test
fun whenButtonClickedOnce_FragmentInterceptsBack() {
// Assert that your FragmentB has already an enabled OnBackPressedCallback
assertTrue(onBackPressedDispatcher.hasEnabledCallbacks())
// Now trigger the OnBackPressedDispatcher
onBackPressedDispatcher.onBackPressed()
onView(withId(R.id.textView)).check(matches(withText("backbutton pressed,press again to go back")))
// Check that FragmentB has disabled its Callback
// ensuring that the onBackPressed() will do the default behavior
assertFalse(onBackPressedDispatcher.hasEnabledCallbacks())
}
}
这避免了测试 Navigation 的代码,而是专注于测试您的代码,特别是您与 OnBackPressedDispatcher
的交互。
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