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android - 错误：BottomNavigationView 支持的最大项目数为 5，删除项目并添加新项目后

问题描述

目前，我需要bottomnavigation#menu在用户注销或登录时动态更改我的。这样，bottomnavigation#menu 是R.menu.user_logged_inor R.menu.user_logged_out。我的第一种方法是这样的：

private fun setUpBottomNav(newMenu: Int) {
    with(binding.bottomNavigationView) {
        menu.clear()
        inflateMenu(newMenu)
        setupWithNavController(findNavController(R.id.fragment_container))
        // fix blinking when re selecting bottom nav item
        setOnItemReselectedListener {}
    }
}

这种方法的主要问题是，当重新创建活动时（例如，当进程被终止或当您通过 Intent 从应用程序打开 Web 浏览器然后单击后退按钮时），菜单将被清除并再次膨胀通过menu#clearand inflateMenu，导致当前底部导航状态丢失（例如，当配置文件选项卡被选中并被menu#clear调用时activity#oncreate，所选状态将丢失，主页选项卡将被选中）。

我的下一个想法是将我的 item_amount 减少R.menu_user_logged_out到四个项目，而是在运行时通过检查用户是否登录到我们的已注销来添加第五个菜单项。这将是我的第二种方法：

// NO CLUE WHAT Menu.NONE, ..., Menu.NONE means!!!!
private fun inflateFifthMenuItem() {
   if(user.isLoggedIn) {
       binding.bottomNavigationView.menu.add(Menu.NONE, R.id.userLoggedInFragment, Menu.NONE, "Profil").setIcon(R.drawable.child_selector_profil)
   } else {
       binding.bottomNavigationView.menu.add(Menu.NONE, R.id.userLoggedOutFragment, Menu.NONE, "Profil").setIcon(R.drawable.child_selector_profil)
   }
}

现在即使上述解决方案听起来合乎逻辑，android也有另一种看法：

   java.lang.IllegalArgumentException: Maximum number of items supported by BottomNavigationView is 5. Limit can be checked with BottomNavigationView#getMaxItemCount()
        at com.google.android.material.navigation.NavigationBarMenu.addInternal(NavigationBarMenu.java:67)
        at androidx.appcompat.view.menu.MenuBuilder.add(MenuBuilder.java:476)
        at com.example.app.presentation.main.MainActivity.signInUserBottomNav(MainActivity.kt:94)
        at com.example.app.presentation.main.MainActivity.observeLoginState$lambda-2(MainActivity.kt:75)
        at com.example.app.presentation.main.MainActivity.$r8$lambda$-vuA_npkMdEgJfGZeCrh_HfU3LQ(Unknown Source:0)
        at com.example.app.presentation.main.MainActivity$$ExternalSyntheticLambda0.onChanged(Unknown Source:4)
        at androidx.lifecycle.LiveData.considerNotify(LiveData.java:133)
        at androidx.lifecycle.LiveData.dispatchingValue(LiveData.java:151)
        at androidx.lifecycle.LiveData.setValue(LiveData.java:309)
        at androidx.lifecycle.MutableLiveData.setValue(MutableLiveData.java:50)
        at androidx.lifecycle.LiveDataScopeImpl$emit$2.invokeSuspend(CoroutineLiveData.kt:99)
        at androidx.lifecycle.LiveDataScopeImpl$emit$2.invoke(Unknown Source:10)
        at kotlinx.coroutines.intrinsics.UndispatchedKt.startUndispatchedOrReturn(Undispatched.kt:89)
        at kotlinx.coroutines.BuildersKt__Builders_commonKt.withContext(Builders.common.kt:165)
        at kotlinx.coroutines.BuildersKt.withContext(Unknown Source:1)
        at androidx.lifecycle.LiveDataScopeImpl.emit(CoroutineLiveData.kt:97)
        at com.example.app.presentation.main.ActivityViewModel$loginState$1.invokeSuspend(ActivityViewModel.kt:26)
        at com.example.app.presentation.main.ActivityViewModel$loginState$1.invoke(Unknown Source:8)
        at com.example.app.presentation.main.ActivityViewModel$loginState$1.invoke(Unknown Source:4)
        at androidx.lifecycle.BlockRunner$maybeRun$1.invokeSuspend(CoroutineLiveData.kt:176)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
        at kotlinx.coroutines.internal.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:367)
        at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:30)
        at kotlinx.coroutines.BuildersKt__Builders_commonKt.startCoroutineImpl(Builders.common.kt:192)
        at kotlinx.coroutines.BuildersKt.startCoroutineImpl(Unknown Source:1)
        at kotlinx.coroutines.AbstractCoroutine.start(AbstractCoroutine.kt:134)
        at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch(Builders.common.kt:56)
        at kotlinx.coroutines.BuildersKt.launch(Unknown Source:1)
        at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch$default(Builders.common.kt:47)
        at kotlinx.coroutines.BuildersKt.launch$default(Unknown Source:1)
        at androidx.lifecycle.BlockRunner.maybeRun(CoroutineLiveData.kt:174)
        at androidx.lifecycle.CoroutineLiveData.onActive(CoroutineLiveData.kt:240)
        at androidx.lifecycle.LiveData.changeActiveCounter(LiveData.java:390)
        at androidx.lifecycle.LiveData$ObserverWrapper.activeStateChanged(LiveData.java:466)
        at androidx.lifecycle.LiveData$LifecycleBoundObserver.onStateChanged(LiveData.java:425)
        at androidx.lifecycle.LifecycleRegistry$ObserverWithState.dispatchEvent(LifecycleRegistry.java:354)
        at androidx.lifecycle.LifecycleRegistry.forwardPass(LifecycleRegistry.java:265)
        at androidx.lifecycle.LifecycleRegistry.sync(LifecycleRegistry.java:307)
        at androidx.lifecycle.LifecycleRegistry.moveToState(LifecycleRegistry.java:148)
        at androidx.lifecycle.LifecycleRegistry.handleLifecycleEvent(LifecycleRegistry.java:134)
        at androidx.lifecycle.ReportFragment.dispatch(ReportFragment.java:68)
        at androidx.lifecycle.ReportFragment$LifecycleCallbacks.onActivityPostStarted(ReportFragment.java:187)
        at android.app.Activity.dispatchActivityPostStarted(Activity.java:1248)
        at android.app.Activity.performStart(Activity.java:7865)
        at android.app.ActivityThread.handleStartActivity(ActivityThread.java:3294)
        at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:221)
        at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:201)
        at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:173)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        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)

所以我的问题是：

  1. 如何根据某些条件动态添加第五个项目或
  2. 如何根据某些条件动态更改菜单（例如，当用户登录时，按下配置文件按钮应该将您导航到 userLoggedInFragment 而不是 userLoggedOutFragment

标签： androidkotlinbottomnavigationviewandroid-architecture-navigationandroid-navigation

解决方案

在开始时，BottomNavigationView 默认以空菜单开头。之后根据这样的条件设置菜单

  when (condition) {
    one -> bottomNavigationView.inflateMenu(R.menu.menu_bottom_navigation_one)
    two -> bottomNavigationView.inflateMenu(R.menu.menu_bottom_navigation_two)
    three ->bottomNavigationView.inflateMenu(R.menu.menu_bottom_navigation_three)
    else -> bottomNavigationView.inflateMenu(R.menu.menu_bottom_navigation_defaults)
}

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