Firebase populateViewHolder永远不会被调用

本文介绍了Firebase populateViewHolder永远不会被调用的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 我的firebase控制台中有以下结构。我试图读取值，并显示所有的用户，但populateViewHolder永远不会被调用。

用户 + OW5BYennVRXvfzOjfKpup9rZEYv2 -email：abc@gmail -username：abc

在下面的代码中，我收到的物品计数为1 / b pre $ m $ c $ mAdapter.registerAdapterDataObserver（new RecyclerView.AdapterDataObserver（）{ @Override public void onItemRangeInserted（int positionStart，int itemCount）{ super.onItemRangeInserted（positionStart，itemCount）; int friendlyMessageCount = mAdapter.getItemCount（）; int lastVisiblePosition = mManager.findLastCompletelyVisibleItemPosition（）; //如果回收者视图最初被加载或者 //用户在列表底部，滚动到底部 //列表显示新添加的消息智者。 if（lastVisiblePosition == -1 || （positionStart> =（friendlyMessageCount - 1）&& lastVisiblePosition ==（positionStart - 1）））{ recyclerView.scrollToPosition（positionStart）; } } }）;

这里是我的代码

@Override public view onCreateView（LayoutInflater inflater，ViewGroup container， Bundle savedInstanceState）{ super.onCreateView（inflater，container，savedInstanceState）; 查看rootView = inflater.inflate（R.layout.fragment_home_page，container，false）; mDatabase = FirebaseDatabase.getInstance（）。getReference（）; recyclerView =（RecyclerView）rootView.findViewById（R.id.recycler_view）; recyclerView.setHasFixedSize（true）; return rootView; } @Override public void onActivityCreated（Bundle savedInstanceState）{ super.onActivityCreated（savedInstanceState）; mManager = new LinearLayoutManager（getActivity（））; mManager.setReverseLayout（true）; mManager.setStackFromEnd（true）; Query postsQuery = mDatabase.child（users）; mAdapter = new FirebaseRecyclerAdapter< User，PostViewHolder>（User.class，R.layout.post， PostViewHolder.class，postsQuery）{ @Override 保护void populateViewHolder（PostViewHolder viewHolder，User model，int position）{ final DatabaseReference postRef = getRef（position）; final String postKey = postRef.getKey（）; viewHolder.bindToPost（model）; } }; mAdapter.registerAdapterDataObserver（new RecyclerView.AdapterDataObserver（）{ @Override $ b $ public void onItemRangeInserted（int positionStart，int itemCount）{ super.onItemRangeInserted（positionStart， itemCount）; int friendlyMessageCount = mAdapter.getItemCount（）; int lastVisiblePosition = mManager.findLastCompletelyVisibleItemPosition（）; //如果回收者视图最初被加载或 //用户位于列表的底部，滚动到列表的底部 //显示新添加的消息 if（lastVisiblePosition == -1 || （positionStart> =（friendlyMessageCount - 1）& lastVisiblePosition ==（positionStart - 1）））{ recyclerView.scrollToPosition（positionStart）; } } }）; recyclerView.setAdapter（mAdapter）; $ / code>

PlaceHolder：

public class PostViewHolder extends RecyclerView.ViewHolder { public TextView title，emailt; public PostViewHolder（View view）{ super（view）; title =（TextView）view.findViewById（R.id.title）; emailt =（TextView）view.findViewById（R.id.count）; $ b public void bindToPost（User post，View.OnClickListener starClickListener）{ title.setText（post.username）; emailt.setText（post.email +Likes）; $ b public void bindToPost（User post）{ title.setText（post.username）; emailt.setText（post.email +Likes）; $ / code $ / pre

解决方案

问题是RecyclerView有一个WrapContent的高度，所以请确保您的回收站高度设置为Match_Parent。

< android.support.v7.widget.RecyclerView android：id = android：layout_width =match_parent android：layout_height =match_parent android：scrollbars =vertical />

I have below structure in my firebase console . I am trying to read the values and display all the users but populateViewHolder never gets called.

users +OW5BYennVRXvfzOjfKpup9rZEYv2 -email: "abc@gmail" -username: "abc"

While in the below code I receive the item count as 1

mAdapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() { @Override public void onItemRangeInserted(int positionStart, int itemCount) { super.onItemRangeInserted(positionStart, itemCount); int friendlyMessageCount = mAdapter.getItemCount(); int lastVisiblePosition = mManager.findLastCompletelyVisibleItemPosition(); // If the recycler view is initially being loaded or the // user is at the bottom of the list, scroll to the bottom // of the list to show the newly added message. if (lastVisiblePosition == -1 || (positionStart >= (friendlyMessageCount - 1) && lastVisiblePosition == (positionStart - 1))) { recyclerView.scrollToPosition(positionStart); } } });

Here is my code

@Override public View onCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { super.onCreateView(inflater, container, savedInstanceState); View rootView = inflater.inflate(R.layout.fragment_home_page, container, false); mDatabase = FirebaseDatabase.getInstance().getReference(); recyclerView = (RecyclerView) rootView.findViewById(R.id.recycler_view); recyclerView.setHasFixedSize(true); return rootView; } @Override public void onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); mManager = new LinearLayoutManager(getActivity()); mManager.setReverseLayout(true); mManager.setStackFromEnd(true); Query postsQuery = mDatabase.child("users"); mAdapter = new FirebaseRecyclerAdapter<User, PostViewHolder>(User.class, R.layout.post, PostViewHolder.class, postsQuery) { @Override protected void populateViewHolder(PostViewHolder viewHolder, User model, int position) { final DatabaseReference postRef = getRef(position); final String postKey = postRef.getKey(); viewHolder.bindToPost(model); } }; mAdapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() { @Override public void onItemRangeInserted(int positionStart, int itemCount) { super.onItemRangeInserted(positionStart, itemCount); int friendlyMessageCount = mAdapter.getItemCount(); int lastVisiblePosition = mManager.findLastCompletelyVisibleItemPosition(); // If the recycler view is initially being loaded or the // user is at the bottom of the list, scroll to the bottom // of the list to show the newly added message. if (lastVisiblePosition == -1 || (positionStart >= (friendlyMessageCount - 1) && lastVisiblePosition == (positionStart - 1))) { recyclerView.scrollToPosition(positionStart); } } }); recyclerView.setAdapter(mAdapter); }

PlaceHolder :

public class PostViewHolder extends RecyclerView.ViewHolder { public TextView title, emailt; public PostViewHolder(View view) { super(view); title = (TextView) view.findViewById(R.id.title); emailt = (TextView) view.findViewById(R.id.count); } public void bindToPost(User post, View.OnClickListener starClickListener) { title.setText(post.username); emailt.setText(post.email + "Likes"); } public void bindToPost(User post) { title.setText(post.username); emailt.setText(post.email + "Likes"); } }

解决方案

The Problem is RecyclerView had a height of WrapContent , So Please Make Sure your recycler Height is set to Match_Parent. This will fix this issue.

<android.support.v7.widget.RecyclerView android:id="@+id/recycler_view" android:layout_width="match_parent" android:layout_height="match_parent" android:scrollbars="vertical" />