add pagination
This commit is contained in:
Sai Naw Wun
163
lib/pagination/paginator_listener.dart
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163
lib/pagination/paginator_listener.dart
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@@ -0,0 +1,163 @@
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import 'dart:async';
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import 'package:cloud_firestore/cloud_firestore.dart';
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import 'package:fcs/pages/widgets/callbacks.dart';
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import 'package:logging/logging.dart';
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typedef ToObj = Function(Map<String, dynamic> data, String id);
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/*
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* PaginatorListener load data in page
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* and listen to document change based on 'update_time' and 'delete_time' fields
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* of the document
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*/
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class PaginatorListener<T> {
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final log = Logger('PaginatorListener');
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List<String> ids = [];
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List<T> data = [];
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DocumentSnapshot prev;
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int rowPerLoad = 10;
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bool ended = false;
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bool isLoading = false;
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bool insertNewByListener = false;
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ToObj toObj;
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CallBack onChange;
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StreamSubscription<QuerySnapshot> listener;
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Query listeningQuery;
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Query pageQuery;
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PaginatorListener(this.toObj,
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{this.onChange, this.rowPerLoad = 10, this.insertNewByListener = false});
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Future<bool> refresh({Query listeningQuery, Query pageQuery}) {
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this.listeningQuery = listeningQuery ?? this.listeningQuery;
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this.pageQuery = pageQuery ?? this.pageQuery;
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_clearState();
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_initListener();
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return _load();
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}
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void _clearState() {
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prev = null;
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ids = [];
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data = [];
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ended = false;
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isLoading = false;
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if (listener != null) listener.cancel();
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listener = null;
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}
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void close() {
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_clearState();
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}
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final String updateTimeField = 'update_time';
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final String deleteTimeField = 'delete_time';
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final String isDeletedField = 'is_deleted';
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void _initListener() {
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Query _query =
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listeningQuery.orderBy(updateTimeField, descending: true).limit(1);
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_query.getDocuments(source: Source.server).then((QuerySnapshot snapshot) {
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int count = snapshot.documents.length;
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int updateTime = 0;
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if (count == 1) {
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updateTime = snapshot.documents[0].data[updateTimeField];
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}
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Query _queryListener = listeningQuery
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.where(updateTimeField, isGreaterThan: updateTime)
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.orderBy(updateTimeField, descending: true);
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if (listener != null) listener.cancel();
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listener =
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_queryListener.snapshots(includeMetadataChanges: true).listen((qs) {
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qs.documentChanges.forEach((c) {
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switch (c.type) {
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case DocumentChangeType.added:
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_update(c.document.documentID, c.document.data);
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break;
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case DocumentChangeType.modified:
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_update(c.document.documentID, c.document.data);
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break;
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case DocumentChangeType.removed:
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_remove(c.document.documentID, c.document.data);
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break;
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default:
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}
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if (onChange != null) onChange();
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});
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});
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});
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}
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void _update(String id, Map<String, dynamic> map) {
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T t = toObj(map, id);
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if (ids.contains(id)) {
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var deleted = map[deleteTimeField];
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var isDeleted = map[isDeletedField];
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if ((deleted ?? 0) > 0 || (isDeleted ?? false)) {
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data.removeAt(ids.indexOf(id));
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ids.remove(id);
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} else {
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data.removeAt(ids.indexOf(id));
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data.insert(ids.indexOf(id), t);
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}
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} else if (insertNewByListener) {
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data.insert(0, t);
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ids.insert(0, id);
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}
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}
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void _add(String id, Map<String, dynamic> map) {
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T t = toObj(map, id);
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if (!ids.contains(id)) {
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data.add(t);
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ids.add(id);
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}
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}
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void _remove(String id, Map<String, dynamic> map) {
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if (ids.contains(id)) {
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data.removeAt(ids.indexOf(id));
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ids.remove(id);
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}
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}
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Future<bool> loadMore() {
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return this._load();
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}
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Future<bool> _load({CallBack onStarted, CallBack onFinished}) async {
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if (ended) return ended;
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Query _query =
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prev != null ? pageQuery.startAfterDocument(prev) : pageQuery;
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try {
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isLoading = true;
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if (onStarted != null) {
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onStarted();
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}
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if (onChange != null) onChange();
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await _query
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.where(isDeletedField, isEqualTo: false)
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.limit(rowPerLoad)
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.getDocuments(source: Source.server)
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.then((QuerySnapshot snapshot) {
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int count = snapshot.documents.length;
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ended = count < rowPerLoad;
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prev = count > 0 ? snapshot.documents[count - 1] : prev;
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snapshot.documents.forEach((e) {
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_add(e.documentID, e.data);
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});
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});
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} catch (e) {
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log.warning("Error!! $e");
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} finally {
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isLoading = false;
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if (onFinished != null) onFinished();
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if (onChange != null) onChange();
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}
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return ended;
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}
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}
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99
lib/pagination/paginator_listview.dart
Normal file
99
lib/pagination/paginator_listview.dart
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@@ -0,0 +1,99 @@
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import 'package:flutter/cupertino.dart';
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import 'package:flutter/material.dart';
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import 'package:flutter/rendering.dart';
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import 'paginator_listener.dart';
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typedef RowBuilder = Widget Function(dynamic);
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typedef OnScroll = void Function(bool down);
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class PaginatorListView<T> extends StatelessWidget {
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final PaginatorListener<T> paginatorListener;
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final RowBuilder rowBuilder;
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final OnScroll onScroll;
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final ScrollController _scrollController;
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final Color color;
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PaginatorListView(
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{Key key,
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this.paginatorListener,
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this.rowBuilder,
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this.onScroll,
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this.color = Colors.blueAccent})
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: _scrollController = ScrollController(),
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assert(paginatorListener != null),
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assert(rowBuilder != null),
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super(key: key) {
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_scrollController.addListener(() async {
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if (_scrollController.position.pixels ==
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_scrollController.position.maxScrollExtent) {
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paginatorListener.loadMore();
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}
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if (onScroll != null) {
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var down = _scrollController.position.userScrollDirection ==
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ScrollDirection.forward;
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onScroll(down);
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}
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});
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}
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@override
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Widget build(BuildContext context) {
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bool ended = paginatorListener.ended;
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int count = paginatorListener.data.length;
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if (ended) count++;
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return Column(
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children: [
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Expanded(
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child: RefreshIndicator(
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onRefresh: () {
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return paginatorListener.refresh();
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},
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child: ListView.separated(
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separatorBuilder: (context, index) =>
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Divider(height: 1, color: Colors.black),
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controller: _scrollController,
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scrollDirection: Axis.vertical,
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physics: const AlwaysScrollableScrollPhysics(),
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shrinkWrap: true,
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itemCount: count,
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itemBuilder: (BuildContext context, int index) {
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if (ended && index == count - 1) {
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return Padding(
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padding: const EdgeInsets.all(8.0),
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child: Center(child: Text("No more data")),
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);
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}
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T t = paginatorListener.data[index];
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return rowBuilder(t);
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}),
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),
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),
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paginatorListener.isLoading ? _loadingRow() : Container()
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],
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);
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}
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Widget _loadingRow() {
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return Container(
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padding: EdgeInsets.all(8),
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color: Colors.transparent,
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child: Row(
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mainAxisAlignment: MainAxisAlignment.center,
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children: [
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Column(
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children: [
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CircularProgressIndicator(
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valueColor: new AlwaysStoppedAnimation<Color>(color)),
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Text(
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"Loading...",
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style: TextStyle(color: color),
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)
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],
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),
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],
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),
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);
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}
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}
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