如何在导航体系结构组件中实现条件导航

问题描述

在新的Navigation体系结构组件中，如何实现条件导航?

In the new Navigation architecture component, how to implement conditional navigation?

目前，我只有一个与LoginFragment和HomeFragment有关的活动.基于特定的login_flag，我曾经从MainActivity调用任一片段.由于LoginFragment仅被调用一次，因此我将startDestination设置为HomeFragment，并且Navigation加载了此HomeFragment.在导航加载HomeFragment之前，有什么方法可以检查login_flag.

Currently I have a single activity with LoginFragment and HomeFragment. Based on a certain login_flag, I used to call either fragment from the MainActivity. Since LoginFragment is called only once, I have set the startDestination to HomeFragment and the Navigation loads this HomeFragment. is there any way to check the login_flag before the Navigation loads the HomeFragment.

推荐答案

这就是我处理条件导航:

1. 将HomeFragment设置为开始目标

2. 创建全局操作用于LoginFragment

1. Set HomeFragment as the start destination

2. Create a global action for LoginFragment

<action
    android:id="@+id/action_global_loginFragment"
    app:destination="@id/loginFragment"
    app:launchSingleTop="false"
    app:popUpTo="@+id/nav_graph"
    app:popUpToInclusive="true" />

在onViewCreated内进行条件导航:

Perform conditional navigation inside onViewCreated :

// HomeFragment.kt
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)

    if(!appAuth.isAuthenticated()) {
        view.findNavController().navigate(R.id.action_global_loginFragment)
    }
}

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