android - 使用 firebase 在无尽的回收器 View 中分页

Question

我正在开发问答应用程序。我已成功从 firebase 加载问题。但我无法像数据库一样从 Firebase 应用分页。以及如何识别我们已经到达回收站 View 的末尾，以便可以加载接下来的几个问题。

Answer 1

要识别我们已经到达 RecyclerView 的末尾，您可以使用此类 EndlessRecyclerOnScrollListener.java

要加载更多下一个问题，您应该在 Question class 中再定义一个字段，例如 number

public class Question {
    private int number; // it must unique and auto increase when you add new question
    ...
}

然后，当您从 FireBase 加载问题时，您可以这样做

public class MainActivity extends AppCompatActivity {
    private static final int TOTAL_ITEM_EACH_LOAD = 10;
    private DatabaseReference mDatabase;
    final List<Question> questionList = new ArrayList<>();

    private int currentPage = 0;

    private RecyclerView recyclerView;
    private RecyclerViewAdapter mAdapter; 

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ...
        // init and set layout manager for your RecyclerView
        ...
        mAdapter = new RecyclerViewAdapter(questionList);
        recyclerView.setAdapter(mAdapter);
        recyclerView.setOnScrollListener(new EndlessRecyclerOnScrollListener(mLayoutManager) {
            @Override
            public void onLoadMore(int current_page) { // when we have reached end of RecyclerView this event fired
                loadMoreData();
            }
        });
        loadData(); // load data here for first time launch app
    }

    private void loadData() {
        // example
        // at first load : currentPage = 0 -> we startAt(0 * 10 = 0)
        // at second load (first loadmore) : currentPage = 1 -> we startAt(1 * 10 = 10)
        mDatabase.child("questions")
                .limitToFirst(TOTAL_ITEM_EACH_LOAD)
                .startAt(currentPage*TOTAL_ITEM_EACH_LOAD)
                .orderByChild("number")
                .addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {
                        if(!dataSnapshot.hasChildren()){
                            Toast.makeText(MainActivity.this, "No more questions", Toast.LENGTH_SHORT).show();
                            currentPage--;
                        }
                        for (DataSnapshot data : dataSnapshot.getChildren()) {
                            Question question = data.getValue(Question.class);
                            questionList.add(question);
                            mAdapter.notifyDataSetChanged();
                        }
                    }

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

    private void loadMoreData(){
        currentPage++;
        loadData();
    }
}

Here is my DEMO project