How to create an Observable of cursor - sqlite

Question

I have cursor returned by an SQLite query, I would like to know correct approach for creating an Observable the emits each row in the cursor.
I created cursor observable as follows, please check if this is the correct:
Observable<Cursor> cursorObservable = Observable.create(new ObservableOnSubscribe<Cursor>() {
#Override
public void subscribe(ObservableEmitter<Cursor> e) throws Exception {
SQLDbHelper dbHelper = SQLDbHelper.getInstance(ctx);
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cursor = db.rawQuery("select * from " + MoviesContract.MovieEntry.TABLE_NAME, null);
if (cursor != null) {
try {
while (cursor.moveToNext() && !e.isDisposed()) {
e.onNext(cursor);
}
} catch (Exception exception) {
e.onError(exception);
} finally {
cursor.close();
}
}
if (!e.isDisposed()) {
e.onComplete();
}
}
});

Answer 1

I thank that you will have better results wrapping the rows into a Map and passing it through the stream than passing cursor itself.
class SimpleTest {
#Test
fun testCursorStream() {
val cursor = fakeCursor()
val stream = getCursorStream(cursor)
stream.subscribe {
Log.d("Test", it.entries.toString())
}
}
private fun fakeCursor() : Cursor {
val columns = arrayOf("id", "name", "age")
val cursor = MatrixCursor(columns)
val row1 = arrayOf(1, "Rodrigo", 26L)
val row2 = arrayOf(2, "Lucas", 23L)
val row3 = arrayOf(3, "Alan", 26L)
cursor.addRow(row1)
cursor.addRow(row2)
cursor.addRow(row3)
return cursor
}
private fun getCursorStream(cursor: Cursor) : Observable<Map<String, Any?>> {
return Observable.create<Map<String, Any?>> {
try {
if (!cursor.moveToFirst()) {
it.onCompleted()
return#create
}
val row = HashMap<String, Any?>()
do {
val lastColumnIndex = cursor.columnCount - 1
for (index in 0..lastColumnIndex) {
val name = cursor.getColumnName(index)
val type = cursor.getType(index)
when (type) {
Cursor.FIELD_TYPE_STRING -> row.put(name, cursor.getString(index))
Cursor.FIELD_TYPE_BLOB -> row.put(name, cursor.getBlob(index))
Cursor.FIELD_TYPE_FLOAT -> row.put(name, cursor.getFloat(index))
Cursor.FIELD_TYPE_INTEGER -> row.put(name, cursor.getInt(index))
Cursor.FIELD_TYPE_NULL -> row.put(name, null)
}
}
it.onNext(row)
} while (cursor.moveToNext())
it.onCompleted()
} catch (e: Exception) {
it.onError(e)
}
}
}
}
Hope that it helps.