我正在使用NavigationDrawer
并尝试MVVM体系结构,所有布局都很好,然后我实现了一个RecyclerView,它在其中一个片段中显示了firebase
中的数据,代码都很好,但是RecyclerView却不填充数据,然后我登录了该应用程序,发现适配器返回了大小data != null
,然后有趣的是recyclerView仅在设备配置更改时填充数据:设备方向
在片段之间切换并返回到recyclerView片段;同样的问题,直到我旋转设备
**我尝试过:**
将过程从参考转移到onCreateView
将数据源更改为虚拟集并起作用
在terminal
上显示数据并打印数据
HomeFragment
...
class HomeFragment : Fragment() {
private lateinit var homeViewModel: HomeViewModel
lateinit var recyclerView: RecyclerView
lateinit var swipeRefresh: SwipeRefreshLayout
lateinit var postAdapter: PostAdapter
val viewModelFactory = HomeViewModelFactory()
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?
): View? {
val view = inflater.inflate(R.layout.fragment_home, container, false)
homeViewModel = ViewModelProviders.of(this, viewModelFactory).get(HomeViewModel::class.java)
recyclerView = view.findViewById(R.id.post_recycler_view)
recyclerView.setHasFixedSize(true)
val linearLayoutManager = LinearLayoutManager(context, RecyclerView.VERTICAL, true)
linearLayoutManager.stackFromEnd = true
recyclerView.layoutManager = linearLayoutManager
// Observe the model
homeViewModel.postList.observe(this@HomeFragment, Observer { posts ->
postAdapter = PostAdapter(context!!, posts)
recyclerView.adapter = postAdapter
postAdapter.notifyDataSetChanged()
homeViewModel.myRef.keepSynced(true)
})
swipeRefresh = view.findViewById(R.id.swiperefresh)
swipeRefresh.setOnRefreshListener {
Toast.makeText(context, " Adapter size: ${postAdapter.itemCount}", Toast.LENGTH_LONG).show() // works : returns 12
println("list:${homeViewmodel.postList.value} ") works : prints data
swipeRefresh.isRefreshing = false
}
return view
}
viewModel
class HomeViewModel() : ViewModel() {
var postList = loadPosts()
fun loadPosts(): MutableLiveData<MutableList<Post>> {
val postList = mutableListOf<Post>()
val l_postList = MutableLiveData<MutableList<Post>>()
firebaseRepo.retrievePosts(postList)
l_postList.value = postList
return l_postList
}
}
firebaseRepo
fun retrievePosts(postList: MutableList<Post>) {
val postsRef = ref.child("Posts")
postsRef.addValueEventListener(object : ValueEventListener{
override fun onCancelled(p0: DatabaseError) {}
override fun onDataChange(p0: DataSnapshot) {
postList.clear()
for(snapshot in p0.children){
val post = snapshot.getValue(Post::class.java)
postList.add(post!!)
}
}
})
}
请帮助...?
您的retrievePosts
方法仅更改MutableList<Post>
中的postList
,而不更改MutableLiveData<MutableList<Post>>
中的l_postList
,因此从不将更改通知RecyclerView
。
您应该更新retrievePosts
方法以引用MutableLiveData
,并在更改时设置value
的MutableLiveData
。