Firebase populateViewHolder永遠不會被調用

Question

我的Firebase控制檯中有以下結構。我正在嘗試讀取值並顯示所有用戶，但populateViewHolder永遠不會被調用。

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

而在下面的代碼我收到的項目數爲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); 
      } 
     } 
    }); 

這裏是我的代碼

@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); 
} 

佔位符：

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"); 
} 
} 

Answer 1

問題是RecyclerView有一個WrapConte的高度nt，所以請確保您的回收站高度設置爲Match_Parent。這將解決這個問題。

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