Firebase populateViewHolder永远不会被调用 [英] Firebase populateViewHolder is never called

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：[e-mail]
 -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: "[e-mail]"
     -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"
            />


                        
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