我试图在我的firebase回收站视图中实现无休止的滚动。我将查询限制为5个项目，然后用户滚动到列表的末尾，查询被更新，限制增加了我的另一个5.但是适配器仅在我离开并返回活动时更新。我尝试过notifydatasetchange（），但这并不起作用。我试过了recyclerview.setadapter（）。它有效，但它也重置了我的回收者视图的滚动位置。似乎没有其他工作。
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
View view=inflater.inflate(R.layout.card_view,container,false);
mDatabase= FirebaseDatabase.getInstance().getReference().child("Posts");
mDatabaseUpvote= FirebaseDatabase.getInstance().getReference().child("Upvote");
mAuth=FirebaseAuth.getInstance();
recyclerView = (RecyclerView) view.findViewById(R.id.recycleview_new);
recyclerView.setHasFixedSize(true);
mLayoutManager=(new LinearLayoutManager(getActivity()));
recyclerView.setLayoutManager(mLayoutManager);
mDatabaseUpvote.keepSynced(true);
mDatabase.keepSynced(true);
query=mDatabase.limitToFirst(count);
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
firstItem=mLayoutManager.findLastVisibleItemPosition();
ItemCount=recyclerView.getChildCount();
TotalItemCount=mLayoutManager.getItemCount();
if (loading){
if (TotalItemCount>prevTotal){
loading=false;
prevTotal=TotalItemCount;
}
}
if (!loading && (TotalItemCount-firstItem) <= (firstItem+visthresh)){
count=count+2;
query=mDatabase.limitToFirst(count);
Toast.makeText(getActivity(), "ThresholdReached", Toast.LENGTH_SHORT).show();
loading=true;
}
}
});
firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<Cards, Postviewholder>(
Cards.class,
R.layout.cards,
Postviewholder.class,
query
) {
@Override
protected void populateViewHolder(final Postviewholder viewHolder, Cards model, final int position) {
final String postKey=getRef(position).getKey();
viewHolder.setUsername(model.getUsername());
viewHolder.setImage(getActivity(),model.getImage());
viewHolder.setimage_icon(getActivity(),model.getImageicon());
viewHolder.setTitle(model.getTitle());
viewHolder.setTextColor(model.getTextColor());
viewHolder.setUpvote(postKey);
viewHolder.post_Image.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent2= new Intent(getActivity(),View_post.class);
intent2.putExtra("Userprofile",postKey);
startActivity(intent2);
}
});
viewHolder.imageicon.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent2= new Intent(getActivity(),UserActivity_2.class);
intent2.putExtra("Userprofile",postKey);
startActivity(intent2);
}
});
viewHolder.upvote.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
ProcessUpvote = true;
mDatabaseUpvote.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (ProcessUpvote) {
if (dataSnapshot.child(postKey).hasChild(mAuth.getCurrentUser().getUid())) {
mDatabaseUpvote.child(postKey).child(mAuth.getCurrentUser().getUid()).removeValue();
ProcessUpvote = false;
} else {
mDatabaseUpvote.child(postKey).child(mAuth.getCurrentUser().getUid()).setValue("RandomValue");
ProcessUpvote = false;
}
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
});
}
};
recyclerView.setAdapter(firebaseRecyclerAdapter);
if (sharedPreferences != null) {
SharedPreferences preferences=PreferenceManager.getDefaultSharedPreferences(getActivity());
Posit=(preferences.getInt(RV_POS_INDEX,0));
mRvTopView=(preferences.getInt(RV_TOP_VIEW,0));
Toast.makeText(getActivity(), "RestoreState", Toast.LENGTH_SHORT).show();
firebaseRecyclerAdapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() {
public void onItemRangeInserted(int positionStart, int itemCount) {
mLayoutManager.scrollToPositionWithOffset(Posit, mRvTopView);
}
});
}
return view;
}
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
super.onSaveInstanceState(savedInstanceState);
Posit = mLayoutManager.findFirstVisibleItemPosition();
View startView = recyclerView.getChildAt(0);
mRvTopView = (startView == null) ? 0 : (startView.getTop() - recyclerView.getPaddingTop());
Toast.makeText(getActivity(), "SaveState", Toast.LENGTH_SHORT).show();
sharedPreferences= PreferenceManager.getDefaultSharedPreferences(getActivity());
SharedPreferences.Editor editor=sharedPreferences.edit();
editor.putInt(RV_POS_INDEX,Posit);
editor.putInt(RV_TOP_VIEW,mRvTopView);
editor.apply();
}
public static class Postviewholder extends RecyclerView.ViewHolder {
View mView;
ImageView upvote;
ImageView imageicon;
ImageView post_Image;
private DatabaseReference mDatabaseUpvote;
private FirebaseAuth mAuth;
public Postviewholder(View itemView) {
super(itemView);
mView = itemView;
imageicon = (ImageView) mView.findViewById(R.id.Post_imiageicon);
post_Image = (ImageView) mView.findViewById(R.id.CardImage);
upvote = (ImageView) mView.findViewById(R.id.upvote);
mDatabaseUpvote = FirebaseDatabase.getInstance().getReference().child("Upvote");
mAuth = FirebaseAuth.getInstance();
}
public void setUpvote(final String postKey) {
mDatabaseUpvote.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.child(postKey).hasChild(mAuth.getCurrentUser().getUid())) {
upvote.setImageResource(R.drawable.ic_thumb_up_black_24dp2);
} else {
upvote.setImageResource(R.drawable.ic_thumb_up_black_24dp);
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
public void setImage(final Context ctx, final String image) {
final ImageView imageView = (ImageView) mView.findViewById(R.id.CardImage);
Glide.with(ctx)
.load(image)
.into(imageView);
}
public void setTitle(String title) {
TextView cardtitle = (TextView) mView.findViewById(R.id.cardTitle);
cardtitle.setText(title);
}
public void setUsername(String username) {
TextView post_username = (TextView) mView.findViewById(R.id.post_username);
post_username.setText(username);
}
public void setimage_icon(final Context ctx, final String imageicon) {
final ImageView image_icon = (ImageView) mView.findViewById(R.id.Post_imiageicon);
Glide.with(ctx)
.load(imageicon)
.into(image_icon);
}
public void setTextColor(int TextColor) {
CardView cardView= (CardView)mView.findViewById(R.id.Cardview_card);
TextView post_username = (TextView) mView.findViewById(R.id.post_username);
TextView cardtitle = (TextView) mView.findViewById(R.id.cardTitle);
int textcolr=getContrastColor(TextColor);
int white=Color.WHITE;
int resultColor = blendARGB(TextColor,white,0.1f);
cardView.setCardBackgroundColor(resultColor);
cardtitle.setTextColor(textcolr);
post_username.setTextColor(textcolr);
}
}
}