使用Navigation Graph+底部导航栏时Home Fragment卡顿，求解决方案

问题描述 #

使用Navigation组件的Navigation Graph搭配底部导航栏时，切换到Home Fragment会出现轻微卡顿，但切换到其他空白Fragment则无卡顿。尝试用Fragment Transaction切换时非常流畅，但不知道如何将其与Navigation Graph结合——因为使用Navigation组件必须保留app:defaultNavHost="true"和app:navGraph="@navigation/mobile_navigation"，移除后使用Nav Graph导航会导致应用崩溃，求解决方案及建议。

相关截图 #

Main Activity截图 #

导航栏系统追踪截图 #

点击Home Fragment时的系统追踪截图 #

详细系统追踪截图 #

Home Fragment代码（唯一卡顿的Fragment） #

package com.example.ecom.ui.home

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.lifecycle.Observer
import androidx.lifecycle.ViewModelProvider
import androidx.navigation.fragment.findNavController
import com.example.ecom.databinding.FragmentHomeBinding

class HomeFragment : Fragment() {

private var _binding: FragmentHomeBinding? = null

// This property is only valid between onCreateView and onDestroyView.
private val binding get() = _binding!!

override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View {
val homeViewModel =
ViewModelProvider(this)[HomeViewModel::class.java]

_binding = FragmentHomeBinding.inflate(inflater, container, false)

binding.viewModel = homeViewModel

binding.lifecycleOwner = viewLifecycleOwner

val popularProductsAdapter = PopularProductsAdapter()

val allProductAdapter = PopularProductsAdapter()

val categoryAdapter = CategoryAdapter()

binding.saleProductsRecycler.adapter = allProductAdapter

binding.popularProductsRecycler.adapter = popularProductsAdapter

binding.categoryRecycler.adapter = categoryAdapter

categoryAdapter.selectedCategory = {
homeViewModel.getProductsFromRemote(it)
}

homeViewModel.categories.observe(viewLifecycleOwner, Observer {
categoryAdapter.submitList(it)
})

allProductAdapter.selectedProduct = {
homeViewModel.displayProductDetails(it)
}

popularProductsAdapter.selectedProduct = {
homeViewModel.displayProductDetails(it)
}

homeViewModel.navigateSelectedProduct.observe(viewLifecycleOwner, Observer {
if (it!=null) {
this.findNavController().navigate(HomeFragmentDirections.actionNavigationHomeToProductDetailsFragment(it))
homeViewModel.displayProductDetailsComplete()
}
})

return binding.root
}

override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
}

Home ViewModel代码 #

package com.example.ecom.ui.home

import android.util.Log
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.ViewModel
import com.example.ecom.network.ApiService
import com.example.ecom.network.Product
import kotlinx.coroutines.*

class HomeViewModel : ViewModel() {

private val _products = MutableLiveData<List<Product>>()
val products: LiveData<List<Product>> get() = _products

private val _popularProducts = MutableLiveData<List<Product>>()
val popularProducts: LiveData<List<Product>> get() = _popularProducts

private val _categories = MutableLiveData<List<String>>()
val categories: LiveData<List<String>> get() = _categories

private val _status = MutableLiveData<String>()
val status: LiveData<String> get() = _status

private val _navigateSelectedProduct = MutableLiveData<Product?>()
val navigateSelectedProduct: LiveData<Product?> get() = _navigateSelectedProduct

private val job = Job()

private val coroutineScope = CoroutineScope(job + Dispatchers.Main)

init {
getCategoryFromRemote()
getProductsFromRemote("All")
}

private fun getCategoryFromRemote() {
coroutineScope.launch {
val getCategoriesDeferred = ApiService.retrofitService.getCategoriesAsync()
try {
val listResult = getCategoriesDeferred.await()
if(listResult.isNotEmpty()) {
val list = mutableListOf<String>()
list.add("All")
list.addAll(listResult)
_categories.value = list
}
} catch (e: java.lang.Exception) {
_status.value = "Failure: ${e.message}"
}
}
}

fun getProductsFromRemote(string: String) {
coroutineScope.launch {
var getProductsDeferred: Deferred<List<Product>>? = null
getProductsDeferred = if (string == "All") {
ApiService.retrofitService.getProductsAsync()
} else {
ApiService.retrofitService.getProductsOfCategoryAsync(string)
}
try {
val listResult = getProductsDeferred.await()
Log.i("problem", listResult.toString())
if (listResult.isNotEmpty()) {
_products.value = listResult
val popularProductsList = mutableListOf<Product>()
for (i in listResult) {
if (i.rating.rate >= 4.0) {
popularProductsList.add(i)
}
}
_popularProducts.value = popularProductsList

}
} catch (e: java.lang.Exception) {
_status.value = "Failure: ${e.message}"
}
}
}

fun displayProductDetails(product: Product) {
_navigateSelectedProduct.value = product
}

fun displayProductDetailsComplete() {
_navigateSelectedProduct.value = null
}

override fun onCleared() {
super.onCleared()
job.cancel()
}

}

内容的提问来源于stack exchange，提问作者Mickey