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Refactor the DatabasePagingSource to deal with orderbyChild queries #2165

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Refactor the DatabasePagingSource to deal with orderbyChild queries #2165

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2 changes: 1 addition & 1 deletion database/src/main/java/com/firebase/ui/database/paging/DatabasePagingOptions.java
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Original file line number Diff line number Diff line change
Expand Up @@ -94,7 +94,7 @@ public Builder<T> setQuery(@NonNull Query query,
public Builder<T> setQuery(@NonNull Query query,
@NonNull PagingConfig config,
@NotNull SnapshotParser<T> parser) {
final Pager<String, DataSnapshot> pager = new Pager<>(config,
final Pager<Object, DataSnapshot> pager = new Pager<>(config,
() -> new DatabasePagingSource(query));
mData = PagingLiveData.cachedIn(PagingLiveData.getLiveData(pager),
mOwner.getLifecycle());
Expand Down
70 changes: 62 additions & 8 deletions database/src/main/java/com/firebase/ui/database/paging/DatabasePagingSource.java
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Original file line number Diff line number Diff line change
@@ -1,12 +1,14 @@
package com.firebase.ui.database.paging;

import android.annotation.SuppressLint;
import android.util.Pair;

import com.google.android.gms.tasks.Task;
import com.google.android.gms.tasks.Tasks;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.Query;
import com.google.firebase.database.snapshot.Index;

import org.jetbrains.annotations.Nullable;

Expand All @@ -21,7 +23,7 @@
import io.reactivex.rxjava3.core.Single;
import io.reactivex.rxjava3.schedulers.Schedulers;

public class DatabasePagingSource extends RxPagingSource<String, DataSnapshot> {
public class DatabasePagingSource extends RxPagingSource<Object, DataSnapshot> {
private final Query mQuery;

private static final String STATUS_DATABASE_NOT_FOUND = "DATA_NOT_FOUND";
Expand All @@ -32,18 +34,45 @@ public DatabasePagingSource(Query query) {
this.mQuery = query;
}

public Query startAt_childvalue(Object startvalue, String keyvalue) {
if (startvalue instanceof String)
return mQuery.startAt((String) startvalue, keyvalue);
else if (startvalue instanceof Boolean)
return mQuery.startAt((Boolean) startvalue, keyvalue);
else if (startvalue instanceof Double)
return mQuery.startAt((Double) startvalue, keyvalue);
else if (startvalue instanceof Long)
return mQuery.startAt(((Long) startvalue).doubleValue(), keyvalue);
else
return mQuery;
}

/**
* DatabaseError.fromStatus() is not meant to be public.
*/
@SuppressLint("RestrictedApi")
@NonNull
@Override
public Single<LoadResult<String, DataSnapshot>> loadSingle(@NonNull LoadParams<String> params) {
public Single<LoadResult<Object, DataSnapshot>> loadSingle(@NonNull LoadParams<Object> params) {
Task<DataSnapshot> task;

Index queryChildPathIndex = mQuery.getSpec().getIndex();
Pair<Object, String> pKey = (Pair<Object, String>) params.getKey();

if (params.getKey() == null) {
task = mQuery.limitToFirst(params.getLoadSize()).get();
} else {
task = mQuery.startAt(null, params.getKey()).limitToFirst(params.getLoadSize() + 1).get();
//change mQuery.startAt at value if child index
//if not null then what we have here is orderByChild query
if (queryChildPathIndex != null) {//orderByChild query mode
task = startAt_childvalue(pKey.first, pKey.second)
.limitToFirst(params.getLoadSize() + 1)
.get();
} else {
task = mQuery.startAt(null, pKey.second)
.limitToFirst(params.getLoadSize() + 1)
.get();
}
}

return Single.fromCallable(() -> {
Expand All @@ -54,7 +83,7 @@ public Single<LoadResult<String, DataSnapshot>> loadSingle(@NonNull LoadParams<S

//Make List of DataSnapshot
List<DataSnapshot> data = new ArrayList<>();
String lastKey = null;
Pair<Object, String> lastKey = null;

if (params.getKey() == null) {
for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
Expand All @@ -77,7 +106,14 @@ public Single<LoadResult<String, DataSnapshot>> loadSingle(@NonNull LoadParams<S
//Detect End of Data
if (!data.isEmpty()) {
//Get Last Key
lastKey = getLastPageKey(data);
Object lastkey_c = getLastPageChildKey(data, queryChildPathIndex);
String lastkey_k = getLastPageKey(data);
lastKey = (lastkey_c == null && lastkey_k == null)
? null
: (lastkey_k == null) ? new Pair<>(lastkey_c, "") : new Pair<>(
lastkey_c,
lastkey_k);

}
return toLoadResult(data, lastKey);
} else {
Expand All @@ -99,9 +135,9 @@ public Single<LoadResult<String, DataSnapshot>> loadSingle(@NonNull LoadParams<S
}).subscribeOn(Schedulers.io()).onErrorReturn(LoadResult.Error::new);
}

private LoadResult<String, DataSnapshot> toLoadResult(
private LoadResult<Object, DataSnapshot> toLoadResult(
@NonNull List<DataSnapshot> snapshots,
String nextPage
Pair<Object, String> nextPage
) {
return new LoadResult.Page<>(
snapshots,
Expand All @@ -111,6 +147,24 @@ private LoadResult<String, DataSnapshot> toLoadResult(
LoadResult.Page.COUNT_UNDEFINED);
}

@SuppressLint("RestrictedApi")
private Object getLastPageChildKey(@NonNull List<DataSnapshot> data, Index index) {
if (index == null) return null;
if (data.isEmpty()) {
return null;
} else {
return getChildValue(data.get(data.size() - 1), index);
}
}

@SuppressLint("RestrictedApi")
private Object getChildValue(DataSnapshot snapshot, Index index) {
String keypath = index.getQueryDefinition();
DataSnapshot data = snapshot.child(keypath);
if (!data.exists()) return null;
return data.getValue();
}

@Nullable
private String getLastPageKey(@NonNull List<DataSnapshot> data) {
if (data.isEmpty()) {
Expand All @@ -122,7 +176,7 @@ private String getLastPageKey(@NonNull List<DataSnapshot> data) {

@Nullable
@Override
public String getRefreshKey(@NonNull PagingState<String, DataSnapshot> state) {
public String getRefreshKey(@NonNull PagingState<Object, DataSnapshot> state) {
return null;
}
}