Android FireBase和LiveData在cardviews中显示文本；不显示并且内容不'；t更新（我可以看到卡片，但没有内容）

我使用Firebase实时数据库。我有RecycleViewAdapter类，一个显示recycleview的片段，一个向片段提供数据的ViewHolder类（我使用LiveData），还有一个与firebase数据库通信的Repository类

class Post(
var title: String = "",
var dateStr: String = "",
var desc: String = "",
var id: String = "")

类PostsFireBaseRepository（val bucketListViewModel:bucketListViewModel）{

BucketlisterRecycleServiceAdapter

class BucketListRecyclerViewAdapter() : RecyclerView.Adapter<BucketListRecyclerViewAdapter.ViewHolder>() {

interface PostItemClickListener {
    fun onItemLongClick(position: Int, view: View, post: Post?): Boolean
    fun onItemClick(position: Int, view: View, post: Post?): Boolean
}

private var postList = mutableListOf<Post>()

private var lastDeleted: Post? = null
private var lastDeletedPos: Int? = null

var postClickListener: PostItemClickListener? = null

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
    val view = LayoutInflater.from(parent.context).inflate(R.layout.bucketlist_post_row, parent, false)
    return ViewHolder(view)
}

override fun onBindViewHolder(holder: ViewHolder, position: Int) {
    val post = postList[holder.adapterPosition]

    holder.post = post

    holder.tvTitle.text = post.title
    holder.tvDesc.text = post.desc
    holder.tvRowDate.text = post.dateStr
}

override fun getItemCount() = postList.size

fun addItem(post: Post) {
    postList.add(post)
    notifyItemInserted(postList.size-1)
}

fun addAll(posts: List<Post>) {
    postList.clear()
    postList.addAll(posts)
    notifyDataSetChanged()
}

类BucketListRecycleServiceAdapter（）：RecyclerView.Adapter（）{
界面PostItemClickListener{
单击鼠标右键（位置：Int，视图：view，post:post？）：布尔值
单击（位置：Int，视图：view，post:post？）：布尔值
}
private var postList=mutableListOf（）
私有变量lastDeleted:Post？=null
私有变量lastDeletedPos:Int？=null
var postClickListener:PostItemClickListener？=null
override onCreateViewHolder（父级：ViewGroup，viewType:Int）：ViewHolder{
val view=LayoutInflater.from（parent.context）.充气（R.layout.bucketlist_post_行，parent，false）
返回视图保持器（视图）
}
覆盖BindViewHolder（holder:ViewHolder，位置：Int）{
val post=postList[持有者适配器位置]
holder.post=post
holder.tvTitle.text=post.title
holder.tvDesc.text=post.desc
holder.tvRowDate.text=post.dateStr
}
重写getItemCount（）=postList.size
趣味附加项（post:post）{
postList.add（post）
notifyItemInserted（postList.size-1）
}
fun addAll（帖子：列表）{
postList.clear（）
postList.addAll（posts）
notifyDataSetChanged（）
}

---

在您的

onDataChange

方法中，您需要通知该适配器其数据已更改，否则它将不会重新绘制UI元素。为此，请在更新该适配器的数据源后，在适配器上调用

notifyDataSetChanged（）

比如：

override fun onDataChange(dataSnapshot: DataSnapshot) {
    for (ds in dataSnapshot.children) {
        val newPost = dataSnapshot.getValue<Post>(Post::class.java)
        if (newPost != null) {
            data.add(newPost)
        }
    }
    bucketListViewModel.allPosts.value = data
    adapter.notifyDataSetChanged();        
}

覆盖数据更改（dataSnapshot:dataSnapshot）{
for（dataSnapshot.children中的ds）{
val newPost=dataSnapshot.getValue（Post:：class.java）
if（newPost！=null）{
data.add（newPost）
}
}
bucketListViewModel.allPosts.value=数据
adapter.notifyDataSetChanged（）；
}

---

具体如何到达适配器取决于您的代码。例如，在您的情况下，您可能需要向

BucketListViewModel

添加一个方法，从

onDataChange

调用该方法，然后调用适配器。

请同时添加

Post

clas的内容。我编辑了该帖子。谢谢您的回答。我尝试了这个但不幸的是，它对我不起作用。也许我的代码有其他问题。我用更改编辑了代码。我在帖子中添加了recycleview适配器类，在这里我还调用了notifyDataSetChanged函数。

class BucketListFragment : Fragment(), DatePickerDialogFragment.OnDateSelectedListener,
BucketListRecyclerViewAdapter.PostItemClickListener {

private lateinit var bucketListViewModel: BucketListViewModel

private lateinit var recyclerViewAdapter: BucketListRecyclerViewAdapter

override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
): View? {
    return inflater.inflate(R.layout.fragment_bucketlist, container, false)
}

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)

    setupRecyclerView()

    bucketListViewModel = ViewModelProvider(requireActivity()).get(BucketListViewModel::class.java)
    bucketListViewModel.allPosts.observe(viewLifecycleOwner) { posts ->
        recyclerViewAdapter.addAll(posts)
    }

}

class BucketListRecyclerViewAdapter() : RecyclerView.Adapter<BucketListRecyclerViewAdapter.ViewHolder>() {

interface PostItemClickListener {
    fun onItemLongClick(position: Int, view: View, post: Post?): Boolean
    fun onItemClick(position: Int, view: View, post: Post?): Boolean
}

private var postList = mutableListOf<Post>()

private var lastDeleted: Post? = null
private var lastDeletedPos: Int? = null

var postClickListener: PostItemClickListener? = null

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
    val view = LayoutInflater.from(parent.context).inflate(R.layout.bucketlist_post_row, parent, false)
    return ViewHolder(view)
}

override fun onBindViewHolder(holder: ViewHolder, position: Int) {
    val post = postList[holder.adapterPosition]

    holder.post = post

    holder.tvTitle.text = post.title
    holder.tvDesc.text = post.desc
    holder.tvRowDate.text = post.dateStr
}

override fun getItemCount() = postList.size

fun addItem(post: Post) {
    postList.add(post)
    notifyItemInserted(postList.size-1)
}

fun addAll(posts: List<Post>) {
    postList.clear()
    postList.addAll(posts)
    notifyDataSetChanged()
}

override fun onDataChange(dataSnapshot: DataSnapshot) {
    for (ds in dataSnapshot.children) {
        val newPost = dataSnapshot.getValue<Post>(Post::class.java)
        if (newPost != null) {
            data.add(newPost)
        }
    }
    bucketListViewModel.allPosts.value = data
    adapter.notifyDataSetChanged();        
}