【发布时间】：2020-05-11 17:51:33
【问题描述】：
我希望我做对了，但我希望澄清以下代码被视为良好做法。
这是我的片段（请注意我放置setupObservers() 和initRecyclerView 的位置）。
private const val TAG = "DAS.SitesFragment"
class SitesFragment : Fragment() {
private lateinit var businessViewModel: BusinessViewModel
private var sitesList = ArrayList<SiteObject>()
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
// Inflate the layout for this fragment
val binding: SitesFragmentBinding = DataBindingUtil.inflate(
inflater, R.layout.sites_fragment, container, false
)
binding.apply {
sitesFloatingActionButtonAdd.setOnClickListener{
findNavController().navigate(R.id.action_sitesFragment_to_siteAddEditFragment)
Log.d(TAG,"sitesFloatingActionButtonAdd clicked, navigating to siteAddEditFragment")
}
sitesClearIconImageView.setOnClickListener{
findNavController().navigate(R.id.action_sitesFragment_to_siteFragment)
Log.d(TAG,"sitesClearIconImageView clicked, navigating to siteFragment")
}
}
return binding.root
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
activity?.let {
businessViewModel = ViewModelProvider(it).get(BusinessViewModel::class.java)
Log.d(TAG, "businessViewModel = ${businessViewModel.toString()}")
}
setupObservers()
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
initRecyclerView()
}
private fun initRecyclerView() {
Log.d(TAG, "initRecyclerView()")
sitesRecyclerView.apply {
adapter = SitesRecyclerViewAdapter(sitesList)
layoutManager = LinearLayoutManager(activity)
setHasFixedSize(true)
}
}
private fun setupObservers() {
Log.d(TAG, "setupObservers()")
businessViewModel.listenToSites().observe(viewLifecycleOwner, Observer { allSites ->
sitesList = allSites
sitesRecyclerView.adapter = SitesRecyclerViewAdapter(sitesList)
// sitesRecyclerView.adapter?.notifyDataSetChanged() - don't think I even need this..
Log.d(TAG,"siteAdapter updated, sitesList size = ${sitesList.size}")
})
}
}
这是我的适配器
private const val TAG = "DAS.SitesRViewAdapter"
class SitesRecyclerViewAdapter(private val sitesList: ArrayList<SiteObject>): RecyclerView.Adapter<SitesRecyclerViewAdapter.SiteViewHolder> (){
class SiteViewHolder (itemView: View): RecyclerView.ViewHolder (itemView) {
val siteItemTitle: TextView = itemView.sitesItemTitleText
val siteItemProjectText: TextView = itemView.sitesItemProjectsText
val siteItemMapImage: ImageView = itemView.sitesItemMapImageView
val siteItemPriorityImage: ImageView = itemView.sitesItemPriorityImageView
val siteItemRating1Image: ImageView = itemView.sitesItemRating1ImageView
val siteItemRating2Image: ImageView = itemView.sitesItemRating2ImageView
val siteItemRating3Image: ImageView = itemView.sitesItemRating3ImageView
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): SiteViewHolder {
Log.d(TAG, "onCreateViewHolder()")
val itemView = LayoutInflater.from(parent.context).inflate(R.layout.sites_list_item, parent, false)
return SiteViewHolder(itemView)
}
override fun onBindViewHolder(holder: SiteViewHolder, position: Int) {
val currentItem = sitesList[position]
Log.d(TAG, "onBindViewHolder(), currentItem = ${currentItem.siteReference}")
holder.siteItemTitle.text = currentItem.siteReference
holder.siteItemProjectText.text = currentItem.recentProjectsText
// Reset visibility
holder.siteItemPriorityImage.visibility = View.INVISIBLE
holder.siteItemMapImage.visibility = View.INVISIBLE
holder.siteItemRating1Image.visibility = View.INVISIBLE
holder.siteItemRating2Image.visibility = View.INVISIBLE
holder.siteItemRating3Image.visibility = View.INVISIBLE
// Make relevant icons visible
if (currentItem.plusCode.isNotEmpty()) holder.siteItemMapImage.visibility = View.VISIBLE
if (currentItem.sitePriority) holder.siteItemPriorityImage.visibility = View.VISIBLE
when (currentItem.siteRating) {
1 -> holder.siteItemRating1Image.visibility = View.VISIBLE
2 -> holder.siteItemRating2Image.visibility = View.VISIBLE
3 -> holder.siteItemRating3Image.visibility = View.VISIBLE
}
}
override fun getItemCount(): Int {
return sitesList.size
}
}
我在 logcat 中看到的内容如下：
2020-05-11 18:09:02.221 30982-30982/com.xxx.acorn D/DAS.SplashActivity: firebaseAuth = com.google.firebase.auth.internal.zzl@cb43e66, firebaseUser = com.google.firebase.auth.internal.zzn@ca5d5a7
2020-05-11 18:09:02.737 30982-30982/com.xxx.acorn D/DAS.SitesFragment: initRecyclerView()
2020-05-11 18:09:02.785 30982-30982/com.xxx.acorn D/DAS.SitesFragment: businessViewModel = com.locators.acorn.business.BusinessViewModel@f994bce
2020-05-11 18:09:02.785 30982-30982/com.xxx.acorn D/DAS.SitesFragment: setupObservers()
2020-05-11 18:09:02.785 30982-30982/com.xxx.acorn D/DAS.BusinessViewModel: listenToSites()
2020-05-11 18:09:03.414 30982-30982/com.xxx.acorn D/DAS.SitesFragment: siteAdapter updated, sitesList size = 12
2020-05-11 18:09:03.418 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onCreateViewHolder()
2020-05-11 18:09:03.440 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onBindViewHolder(), currentItem = Company 88383
2020-05-11 18:09:03.454 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onCreateViewHolder()
2020-05-11 18:09:03.464 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onBindViewHolder(), currentItem = Company HEY1
2020-05-11 18:09:03.476 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onCreateViewHolder()
2020-05-11 18:09:03.484 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onBindViewHolder(), currentItem = Company 9677
2020-05-11 18:09:03.490 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onCreateViewHolder()
2020-05-11 18:09:03.501 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onBindViewHolder(), currentItem = Company 313
2020-05-11 18:09:03.513 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onCreateViewHolder()
2020-05-11 18:09:03.522 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onBindViewHolder(), currentItem = Company 123
2020-05-11 18:09:03.528 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onCreateViewHolder()
2020-05-11 18:09:03.537 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onBindViewHolder(), currentItem = Company UTY
2020-05-11 18:09:03.546 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onCreateViewHolder()
2020-05-11 18:09:03.566 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onBindViewHolder(), currentItem = Company TJJF
2020-05-11 18:19:22.769 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onCreateViewHolder()
2020-05-11 18:19:22.775 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onBindViewHolder(), currentItem = Company ZHHPE
2020-05-11 18:19:22.852 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onCreateViewHolder()
2020-05-11 18:19:22.861 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onBindViewHolder(), currentItem = Company ZZZZ
2020-05-11 18:19:23.963 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onCreateViewHolder()
2020-05-11 18:19:23.970 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onBindViewHolder(), currentItem = Company XYZ
2020-05-11 18:19:24.047 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onBindViewHolder(), currentItem = Company ABC
2020-05-11 18:19:25.096 30982-30982/com.xxx.acorn D/DAS.SitesRViewAdapter: onBindViewHolder(), currentItem = Company ABCCC
所以它似乎正确触发，后面的条目仅在您向下滚动时显示（重要的是 OnCreateViewHolder 在回收 ViewHolder 时停止触发，但我担心这是不正确的，因为我正在使用空列表创建 RecyclerView ，然后在设置观察者后填充它..
有趣的是，我注意到的一件事是，当我添加一个新站点时，观察者会触发两次，所以我在 logcat 中得到如下内容：
2020-05-11 18:09:03.414 30982-30982/com.xxx.acorn D/DAS.SitesFragment: siteAdapter updated, sitesList size = 13
2020-05-11 18:09:03.414 30982-30982/com.xxx.acorn D/DAS.SitesFragment: siteAdapter updated, sitesList size = 13
它似乎也填充了 RecyclerView 两次（包括复制上述内容），但我认为这是观察者的怪癖，超出了这个问题的范围。..
【问题讨论】：
标签： android kotlin android-recyclerview