我检索使用FirestoreRecyclerAdapter
数据,并在完成后,我需要检查是否有物品已经被检索与否。我无法弄清楚如何做到这一点。
我是从一个叫FragmentChartsList
类,如下所示调用它。这应该设置适配器开始,以“名”为mOrder
值。以后,它包含该片段的活动可以调用setOrderField()
用不同的值mOrder
的,其中用户已经从一个微调选择。
每次setOrderField()
被调用时,将创建一个新的适配器实例,并连接到recyclerView。在这一点上我需要检查适配器的新版本中是否包含任何数据,要么显示“没有图表发现”的消息,或显示其被检索到的图表(显然,如果名单只是进行排序,然后将数项目仍然是相同的,但我将要扩大这允许用户通过筛选不同的标准图表,所以图表的数量返回会改变)。
目前,setOrderField()
调用refreshViewOnNewData()
,这应该找出正在显示多少图表;如果是0,它应该显示“没有找到图表”消息,如果是> 0它应该显示含有图表的RecyclerView。
目前,我总是得到一个0值,当我尝试计数图表。我怀疑这是因为该适配器还没有完成从数据库中检索他们,但我无法找到任何东西,让我补充某种“onComplete
”监听,让我知道它的完成。
任何人都可以建议我如何才能做到这一点?
public abstract class FragmentChartsList extends Fragment {
private FirebaseFirestore mDatabaseRef;
private ChartListAdapter mAdapter;
private Query mChartsQuery;
private RecyclerView mRecycler;
private String mOrder = "name";
private TextView mLoadingList, mEmptyList;
public FragmentChartsList() {}
@Override
public View onCreateView(@NonNull LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
super.onCreateView(inflater, container, savedInstanceState);
View rootView = inflater.inflate(
R.layout.fragment_charts_list, container, false);
mRecycler = rootView.findViewById(R.id.charts_list);
mRecycler.setHasFixedSize(true);
mLoadingList = rootView.findViewById(R.id.loading_list);
mEmptyList = rootView.findViewById(R.id.empty_list);
// Set up Layout Manager, and set Recycler View to use it
LinearLayoutManager mManager = new LinearLayoutManager(getActivity());
mManager.setReverseLayout(true);
mManager.setStackFromEnd(true);
mRecycler.setLayoutManager(mManager);
// Connect to the database
mDatabaseRef = FirebaseFirestore.getInstance();
setOrderField(mOrder); // Initialised to "name"
return rootView;
}
@Override
public void onStart() {
super.onStart();
mAdapter.startListening();
}
@Override
public void onStop() {
super.onStop();
mAdapter.stopListening();
}
@Override
public void onDestroy() {
super.onDestroy();
mAdapter.stopListening();
}
// HELPER FUNCTIONS
public void setOrderField(String order) {
mOrder = order;
mChartsQuery = getQuery(mDatabaseRef, mOrder);
// Update recycler options
FirestoreRecyclerOptions<Chart> recyclerOptions = new FirestoreRecyclerOptions.Builder<Chart>()
.setQuery(mChartsQuery, Chart.class)
.build();
mAdapter = new ChartListAdapter(recyclerOptions, getActivity());
mAdapter.startListening();
mRecycler.swapAdapter(mAdapter, true);
refreshViewOnNewData();
}
private void refreshViewOnNewData() {
// Hide "loading" text
mLoadingList.setVisibility(View.GONE);
// Check number of charts being shown
//if (mAdapter != null && (mAdapter.getCount() > 0)) {
// If > 0, show Charts
mEmptyList.setVisibility(View.GONE);
mRecycler.setVisibility(View.VISIBLE);
} else {
// If number of Charts = 0
// show "no charts"
mEmptyList.setVisibility(View.VISIBLE);
mRecycler.setVisibility(View.GONE);
}
}
}
该适配器类看起来是这样的:
public class ChartListAdapter extends FirestoreRecyclerAdapter<Chart, ChartViewHolder> {
private Activity mActivity;
private int mCount;
public ChartListAdapter(FirestoreRecyclerOptions<Chart> recyclerOptions, Activity activity) {
super(recyclerOptions);
mActivity = activity;
}
@Override
protected void onBindViewHolder(@NonNull ChartViewHolder holder, int position, @NonNull Chart model) {
final String chartKey = this.getSnapshots().getSnapshot(position).getId();
model.setKey(chartKey);
// Set click listener for the chart
// On click, the user can view the chart
holder.itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(mActivity, ActivityViewChart.class);
intent.putExtra("ChartKey", chartKey);
mActivity.startActivity(intent);
}
});
// Implement long-click menu
mActivity.registerForContextMenu(holder.itemView);
// Bind Chart to ViewHolder
holder.bindToChart(model);
}
@NonNull
@Override
public ChartViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.item_chart, parent, false);
return new ChartViewHolder(view);
}
@Override
public void onDataChanged() {
super.onDataChanged();
mCount = getItemCount();
}
public int getCount() {
return mCount;
}
}
想通了这一点......我需要设置一个监听器上的查询,而不是。
因此,而不必调用从上面refreshViewOnNewData
到setOrder
,我现在有:
mChartsQuery.addSnapshotListener(new EventListener<QuerySnapshot>() {
@Override
public void onEvent(@Nullable QuerySnapshot queryDocumentSnapshots, @Nullable FirebaseFirestoreException e) {
if (queryDocumentSnapshots != null) {
mLoadingList.setVisibility(View.GONE);
if(queryDocumentSnapshots.size() > 0) {
mEmptyList.setVisibility(View.GONE);
mRecycler.setVisibility(View.VISIBLE);
}else {
mEmptyList.setVisibility(View.VISIBLE);
mRecycler.setVisibility(View.GONE);
}
}
}
});
}
也从适配器类中删除mCount
,与getCount
和onDataChanged
沿