我在使用childFragmentManager的片段内或使用supportFragmentManager的活动内显示一个对话框，在这个过程中，我想设置目标片段，如下所示:
val textSearchDialog = TextSearchDialogFragment.newInstance()
textSearchDialog.setTargetFragment(PlaceSearchFragment@this, 0)
But when running that code I get the error:
JAVAlang.IllegalStateException:片段
我不知道如何访问导航组件用来管理片段显示的FragmentManager，有什么解决方案吗？
Update: as part of Navigation 2.3.0, Navigation adds explicit support for returning a result with a specific section on returning a result from a Dialog destination as an alternative to using a shared ViewModel.
Previous answer:
The recommended pattern for communicating between Fragments with the Navigation Architecture Components is via a shared ViewModel - a ViewModel that lives at the Activity level achieved by retrieving the ViewModel using ViewModelProvider(getActivity())
As per the documentation, this offers a number of benefits:
- The activity does not need to do anything, or know anything about this communication.
- Fragments don't need to know about each other besides the
SharedViewModelcontract. If one of the fragments disappears, the other one keeps working as usual.- 每个片段都有自己的生命周期，不受另一个片段生命周期的影响.如果一个片段替换了另一个片段，UI将继续工作，没有任何问题.
您还可以使用navigation graph scoped ViewModel在比整个活动更小的范围内共享ViewModel.