如何在android Firestore上实现Paginate查询[重复] _android

历览千载书，时时见遗烈。这篇文章主要讲述如何在android Firestore上实现Paginate查询[重复]相关的知识，希望能为你提供帮助。
这个问题在这里已有答案：

How to paginate Firestore with Android? 2回答

在GitHub friendly eat app上学习firebase firestore的例子
我想实现分区节点10的分页

private static final int LIMIT = 10;

在firestore示例应用程序中，mAdapter加载数据/节点，如下所示

mFirestore = FirebaseFirestore.getInstance(); // Get ${LIMIT} restaurants mQuery = mFirestore.collection("restaurants") .orderBy("avgRating", Query.Direction.DESCENDING) .limit(LIMIT); // RecyclerView mAdapter = new RestaurantAdapter(mQuery, this) { @Override protected void onDataChanged() { // Show/hide content if the query returns empty. if (getItemCount() == 0) { mRestaurantsRecycler.setVisibility(View.GONE); mEmptyView.setVisibility(View.VISIBLE); } else { mRestaurantsRecycler.setVisibility(View.VISIBLE); mEmptyView.setVisibility(View.GONE); } }@Override protected void onError(FirebaseFirestoreException e) { // Show a snackbar on errors Snackbar.make(findViewById(android.R.id.content), "Error: check logs for info.", Snackbar.LENGTH_LONG).show(); } }; mRestaurantsRecycler.setLayoutManager(new LinearLayoutManager(this)); mRestaurantsRecycler.setAdapter(mAdapter); // Filter Dialog mFilterDialog = new FilterDialogFragment(); }

和

@Override public void onStart() { super.onStart(); // Start sign in if necessary if (shouldStartSignIn()) { startSignIn(); return; }// Apply filters onFilter(mViewModel.getFilters()); // Start listening for Firestore updates if (mAdapter != null) { mAdapter.startListening(); } }

在firestore文档上说要分页

// Construct query for first 25 cities, ordered by population Query first = db.collection("cities") .orderBy("population") .limit(25); first.get() .addOnSuccessListener(new OnSuccessListener< QuerySnapshot> () { @Override public void onSuccess(QuerySnapshot documentSnapshots) { // ...// Get the last visible document DocumentSnapshot lastVisible = documentSnapshots.getDocuments() .get(documentSnapshots.size() -1); // Construct a new query starting at this document, // get the next 25 cities. Query next = db.collection("cities") .orderBy("population") .startAfter(lastVisible) .limit(25); // Use the query for pagination // ... } });

结合上面的代码当我滚动到回收器视图的底部时，我应该如何实现paginate加载超过10个节点来加载

//使用查询进行分页
// ...

【如何在android Firestore上实现Paginate查询[重复]】更新：我正在基于关于Paginate query的firestore doc工作并且看看possible duplicate of another question我没有让它完成工作
谢谢
答案在这里我找到了解决方案但不是更好的一个，如果有更好的方法请发布
通过在加载更多节点之前保存RecyclerView状态并在增加限制后重新加载RecyclerView状态

private static final int LIMIT = 10;

变成

private int LIMIT = 10;

当recyclerView滚动到底部时

mRestaurantsRecycler.addOnScrollListener(new RecyclerView.OnScrollListener() {@Override public void onScrolled(RecyclerView recyclerView, int dx, int dy) { super.onScrolled(recyclerView, dx, dy); final int mLastVisibleItemPosition = mManager.findLastVisibleItemPosition(); if ( mLastVisibleItemPosition == (LIMIT-1)) { LIMIT = LIMIT*2; showSpotDialog(); // save RecyclerView state mBundleRecyclerViewState = new Bundle(); Parcelable listState = mRestaurantsRecycler.getLayoutManager().onSaveInstanceState(); mBundleRecyclerViewState.putParcelable(KEY_RECYCLER_STATE, listState); loadMore(query); new Handler().postDelayed(new Runnable() {@Override public void run() {// restore RecyclerView state if (mBundleRecyclerViewState != null) { Parcelable listState = mBundleRecyclerViewState.getParcelable(KEY_RECYCLER_STATE); mRestaurantsRecycler.getLayoutManager().onRestoreInstanceState(listState); }hideSpotDialog(); }}, 500); } } });

在限制之后加载节点时看起来很不寻常，但现在没办法...而且我正在寻找加载更多没有缺陷的节点
另一答案我已经扩展了FirestoreAdapter如下：

跟踪DocumentSnapshots标识符。

private Set< String> mIdentifier = new HashSet< > ();

为分页添加一个新的公共方法，因为我希望查询的其余部分保持不变，不需要更改给定的查询

/** * Extends the query to load even more data rows. This method will do nothing if the query has * not yet been set. * @param limit the new limit */ public void paginate(long limit) { if (mQuery != null) { if (mRegistration != null) { mRegistration.remove(); mRegistration = null; } // Expect the query to stay the same, only the limit will change mQuery = mQuery.limit(limit); startListening(); } }

通过调用setQuery(Query)清除mIdentifier.clear()方法中的标识符
采用onDocumentAdded(DocumentChange)和onDocumentRemoved(DocumentChange)如下

protected void onDocumentAdded(DocumentChange change) { if (!mIdentifier.contains(change.getDocument().getId())) { mSnapshots.add(change.getNewIndex(), change.getDocument()); mIdentifier.add(change.getDocument().getId()); notifyItemInserted(change.getNewIndex()); } } protected void onDocumentRemoved(DocumentChange change) { mSnapshots.remove(change.getOldIndex()); mIdentifier.remove(change.getDocument().getId()); notifyItemRemoved(change.getOldIndex()); }