Bottom Navigation Activity如何不重置fragment？

这个内置的demo用了navigation作为路由工具

navigation的出栈会让下个 fragment重新调用onVIewCreated

所以可以通过在fragment中持有一个实例 来复用view 从而做到防止页面重置

abstract class BaseFragment<VB : ViewBinding> : Fragment() {

    lateinit var viewBinding: VB
    private var initView: View? = null
    private var hasInit = false

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View {
        return if (initView != null) {
            hasInit = true
            initView!!
        } else {
            viewBinding = inflateViewBinding(inflater, container)
            initView = viewBinding.root
            initView!!
        }
    }

    @CallSuper
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        if (!hasInit) {
            // 以下代码块 只初始化一次
            hasInit = true
            initView()
            registerListener()
        }
        // 数据的回调无论何时都需监听
        // navigation 的出栈会让下个 fragment 重新调用 onViewCreated
        registerObserver()
    }

    abstract fun inflateViewBinding(inflater: LayoutInflater, container: ViewGroup?): VB

    abstract fun initView()

    abstract fun registerListener()

    abstract fun registerObserver()

}