如何在儀器測驗中啟動具有安全引數的片段？

下面我有一個測驗類，旨在單獨啟動一個片段并測驗 navController 的導航能力。

第一次測驗，landingToGameFragmentTest()完美運行！

第二個測驗啟動一個片段，該片段取決于要傳遞給它的安全引數。除此之外，我認為它們的執行方式沒有任何區別。

// Declare navController at top level so it can be accessed from any test in the class
private lateinit var navController: TestNavHostController

// Use Generic type with fragment as upper bound to pass any type of FragmentScenario
private fun <T : Fragment> init(scenario: FragmentScenario<T>) {

    // Create a test navController
    navController = TestNavHostController(
        ApplicationProvider.getApplicationContext()
    )

    scenario.onFragment { fragment ->
        // Link navController to its graph
        navController.setGraph(R.navigation.nav_graph)
        // Link fragment to its navController
        Navigation.setViewNavController(fragment.requireView(), navController)
    }
}

@Test
fun landingToGameFragmentTest() {

    init(launchFragmentInContainer<LandingFragment>(themeResId = THEME))

    // Click button to navigate to GameFragment
    onView(withId(R.id.button_start_game))
        .perform(click())

    assertEquals("Navigation to GameFragment failed",
        R.id.gameFragment,
        navController.currentDestination?.id)
}

@Test
fun gameToLandingFragmentTest() {

    init(launchFragmentInContainer<GameFragment>(themeResId = THEME, fragmentArgs = Bundle()))

    onView(withId(R.id.button_end_game))
        .perform(click())

    assertEquals("Navigation to LandingFragment failed",
        R.id.landingFragment,
        navController.currentDestination?.id)
}

我為其引數設定了一個默認值，但我仍然得到一個空引數例外，直到我傳遞一個空包。現在片段將啟動，但似乎無法導航到任何其他片段！

我在 SO 上找不到類似的問題，堆疊輸出超出了我的范圍。

在這init(launchFragmentInContainer())行之后，我逐步瀏覽了代碼，發現這拋出了一個illegalArgumentException：

public static int parseInt(@RecentlyNonNull String s, int radix) throws NumberFormatException {
    throw new RuntimeException("Stub!");
}

Which then leads to getNavigator(), which passes the name "fragment". However the only navigators are "navigation" and "test", of which I believe it should be test. The illegalStateException is then thrown:

/**
 * Retrieves a registered [Navigator] by name.
 *
 * @param name name of the navigator to return
 * @return the registered navigator with the given name
 *
 * @throws IllegalStateException if the Navigator has not been added
 *
 * @see NavigatorProvider.addNavigator
 */
@Suppress("UNCHECKED_CAST")
@CallSuper
public open fun <T : Navigator<*>> getNavigator(name: String): T {
    require(validateName(name)) { "navigator name cannot be an empty string" }
    val navigator = _navigators[name]
        ?: throw IllegalStateException(
            "Could not find Navigator with name \"$name\". You must call "  
                "NavController.addNavigator() for each navigation type."
        )
    return navigator as T
}

Finally navigate() is called on onView(withId(R.id.button_end_game)) generating:

I likely don't have to keep this test in this specific instance. However, I certainly will need to know how to launch a Fragment in isolation (that depends on safe args) in the future.

Thank you for your consideration!!

uj5u.com熱心網友回復：

您在這里有兩個完全不同的問題：

您的 Fragment 需要將引數傳遞給它。

引數通過Fragment testing guide中解釋的fragmentArgs引數傳遞給您的片段。launchFragmentInContainer

每個 Args 類（例如您的LandingFragmentArgs）都有一個建構式，可讓您Args直接構造該類。然后，您可以使用該toBundle()方法制作Bundle您傳遞給的launchFragmentInContainer：

val args = GameFragmentArgs(/* pass in your required args here */)
val bundle = args.toBundle()
init(launchFragmentInContainer<GameFragment>(fragmentArgs = bundle, themeResId = THEME))

您的 NavController 需要將其狀態設定為 GameFragment 目的地

您TestNavHostController不知道您的測驗需要從與關聯的目的地開始GameFragment- 默認情況下，它只會在startDestination您的圖表上（您嘗試觸發的任何操作都不存在）。

根據測驗導航檔案：

TestNavHostController提供了一種setCurrentDestination方法，允許您設定當前目的地，以便在測驗開始之前 NavController 處于正確狀態。

因此，您需要確保在通話setCurrentDestination后init撥打電話：

val args = GameFragmentArgs(/* pass in your required args here */)
val bundle = args.toBundle()
val scenario = launchFragmentInContainer<GameFragment>(fragmentArgs = bundle, themeResId = THEME)
init(scenario)

// Ensure that the NavController is set to the expected destination
// using the ID from your navigation graph associated with GameFragment
scenario.onFragment {
  // Just like setGraph(), this needs to be called on the main thread
  navController.setCurrentDestination(R.id.game_fragment, bundle)
}

標籤：android-fragments androidx android-navigation android-safe-args

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