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Question

我正在尝试使用asink任务从后台firebase下载数据并使用它们来创建非专有的firebase recyclerview。然而，postexecute之后的滞后仍然相同。 我不知道我做的是对的。

我做错了什么？

公共类FriendFragmentFollow扩展了Fragment {

FriendHoldAdapter3 adapter;
RecyclerView recyclerView;
ArrayList<FriendItem> username;
ArrayList<String> uid, url;
DatabaseReference mDatabase;

@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
                         @Nullable Bundle savedInstanceState) {


    return inflater.inflate(R.layout.friend_fragment_follow, container, false);

}

@Override
public void onViewCreated(final View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    SearchView search = (SearchView) view.findViewById(R.id.ciao);

    mDatabase = FirebaseDatabase.getInstance().getReference();


    recyclerView = (RecyclerView) view.findViewById(R.id.friend_list2);
    //recyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext()));
    recyclerView.setLayoutManager(new GridLayoutManager(view.getContext(), 2));


    new LongOperation().execute("");


    search.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
        @Override
        public boolean onQueryTextSubmit(String query) {

            return true;
        }

        @Override
        public boolean onQueryTextChange(String newText) {
            if (newText.equals("")){
                newText = "             ";
            }
            if (newText.equals("View All")){
                newText = "";
            }
            final List<FriendItem> filteredModelList = filter(username, newText);
            adapter.setFilter(filteredModelList);
            return true;
        }

    });


}


public String getUid() {
    return FirebaseAuth.getInstance().getCurrentUser().getUid();
}

private class LongOperation extends AsyncTask<String, Void, String> {

    @Override
    protected String doInBackground(String... params) {

        final DatabaseReference mPostReference = FirebaseDatabase.getInstance().getReference().child("user-profile");
        mPostReference.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {



                username = new ArrayList<>();
                uid = new ArrayList<String>();
                url = new ArrayList<String>();

                for (DataSnapshot data : dataSnapshot.getChildren()){
                    final FriendItem friendItem = data.getValue(FriendItem.class);
                    //final String friendItem2 = data.getKey();



                    username.add(friendItem);
                    //uid.add(friendItem2);
                    adapter = new FriendHoldAdapter3(getContext(), username, uid, url);
                    //adapter.setClickListener(FriendActivity3.this);
                    recyclerView.setAdapter(adapter);

                    /**
                     adapter = new FriendHoldAdapter2(FriendActivity2.this, username, uid);
                     adapter.setClickListener(FriendActivity2.this);
                     recyclerView.setAdapter(adapter);
                     **/
                    final List<FriendItem> filteredModelList = filter(username, "        ");
                    adapter.setFilter(filteredModelList);



                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
            }});

        return "Executed";
    }

    @Override
    protected void onPostExecute(String result) {
        Toast.makeText(getContext(), "Post execute", Toast.LENGTH_SHORT).show();


    }

    @Override
    protected void onPreExecute() {}

    @Override
    protected void onProgressUpdate(Void... values) {}
}

Answer 1

您应该在onDataChange（）方法中使用AyncTask。从onDataChanged获取数据后，您只需要在后台线程中执行处理部分。尝试

final DatabaseReference mPostReference = FirebaseDatabase.getInstance()
               .getReference().child("user-profile");
mPostReference.addListenerForSingleValueEvent(new ValueEventListener() 
{
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
             new LongOperation().execute(dataSnapshot);
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
});

private class LongOperation extends AsyncTask<DataSnapshot, Void, String> {

@Override
protected String doInBackground(DataSnapshot... params) {

            for (DataSnapshot data : params[0].getChildren()){
                final FriendItem friendItem = data.getValue(FriendItem.class);
                //final String friendItem2 = data.getKey();



                username.add(friendItem);
                //uid.add(friendItem2);



            }
    return "Executed";
}

@Override
protected void onPostExecute(String result) {
                 adapter = new FriendHoldAdapter3(getContext(), username, uid, url);
                //adapter.setClickListener(FriendActivity3.this);
                recyclerView.setAdapter(adapter);

                /**
                 adapter = new FriendHoldAdapter2(FriendActivity2.this, username, uid);
                 adapter.setClickListener(FriendActivity2.this);
                 recyclerView.setAdapter(adapter);
                 **/
                final List<FriendItem> filteredModelList = filter(username, "        ");
                adapter.setFilter(filteredModelList);

    Toast.makeText(getContext(), "Post execute", Toast.LENGTH_SHORT).show();


}

@Override
protected void onPreExecute() {
      username = new ArrayList<>();
      uid = new ArrayList<String>();
      url = new ArrayList<String>();
}

@Override
protected void onProgressUpdate(Void... values) {}
}