如何使用导航架构组件查找子片段 [英] How to find a child Fragment with Navigation Architecture components

问题描述

在学习了有关新架构组件的基础知识之后，我决定应用这些知识并进行一个演示项目.在这个项目中，我一直在使用Google Map.

After learning basics about new architecture components, I decided to apply this knowledge and work a demo project. In this project I have been working with google map.

在我的navHost片段中，其中一个片段以这种方式显示了Google地图

In my navHost fragment, one of the fragment shows google map this way

<fragment android:layout_width="match_parent" android:layout_height="match_parent"
          android:id="@+id/map"
          android:name="com.google.android.gms.maps.SupportMapFragment"></fragment>

从我一直试图获取该片段类的代码中，相关代码如下所示:

from the code I have been trying to get this fragment class, the related code looks like this

private val host: NavHostFragment? by lazyFast {
    activity?.supportFragmentManager
        ?.findFragmentById(R.id.my_nav_host_fragment) as NavHostFragment?
}

在onCreateView中，我尝试了

and in onCreateView I tried this

val mapFragment = host?.childFragmentManager?.findFragmentById(R.id.map) as SupportMapFragment
    mapFragment.getMapAsync(this)

它给了我这个错误

运行时异常:非null不能强制转换为null

Runtime Exception: non-null can not be casted to null

有人知道我在做什么错吗?

Anyone has any idea what I am doing wrong?

推荐答案

此错误与导航组件无关.例如，host?.childFragmentManager?.findFragmentById(R.id.map) as SupportMapFragment实际上找到了嵌套的导航图.

this error has nothing to do with Navigation Components. for example, host?.childFragmentManager?.findFragmentById(R.id.map) as SupportMapFragment actually find a nested navigation graph.

如果您只想访问自己的子片段，则可以通过这种方式重构代码来完成

If you just want to get access to your child fragment, it can be done just refactoring your code this way

val mapFragment = this.childFragmentManager.findFragmentById(R.id.map) as SupportMapFragment

希望有帮助

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