【发布时间】：2021-06-10 23:02:01
【问题描述】：
我使用 jetpack Navigation 组件 (androidx.navigation) 创建了一个简单的两个片段示例应用程序。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, container: ViewGroup?, savedInstanceState: Bundle?): View? {
val view = inflater.inflate(R.layout.fragment_b, container, 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（第一次触摸更改文本而不导航，第二次导航返回）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，虽然whenButtonClickedTwice_NavigationHappens 通过了，但whenButtonClickedOnce_TextChangedNoNavigation 由于文本未被更改而失败，就像从未调用过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。谁能帮帮我？
【问题讨论】：
标签： android android-espresso back-button android-jetpack-navigation instrumented-test