git-touch-android-ios-app/lib/scaffolds/list.dart

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import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/widgets.dart';
import '../providers/settings.dart';
import '../widgets/error_reload.dart';
import '../widgets/loading.dart';
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import '../widgets/empty.dart';
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class ListPayload<T, K> {
K cursor;
List<T> items;
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bool hasMore;
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ListPayload({this.items, this.cursor, this.hasMore});
}
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// This is a scaffold for infinite scroll screens
class ListScaffold<T, K> extends StatefulWidget {
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final Widget title;
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final Widget Function({Function({bool force}) refresh}) trailingBuiler;
final Widget Function(T payload) itemBuilder;
final Future<ListPayload<T, K>> Function() onRefresh;
final Future<ListPayload<T, K>> Function(K cursor) onLoadMore;
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ListScaffold({
@required this.title,
@required this.itemBuilder,
@required this.onRefresh,
@required this.onLoadMore,
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this.trailingBuiler,
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});
@override
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_ListScaffoldState<T, K> createState() => _ListScaffoldState();
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}
class _ListScaffoldState<T, K> extends State<ListScaffold<T, K>> {
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bool loading = false;
bool loadingMore = false;
String error = '';
List<T> items = [];
K cursor;
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bool hasMore;
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ScrollController _controller = ScrollController();
@override
void initState() {
super.initState();
_refresh();
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_controller.addListener(onScroll);
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}
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@override
void dispose() {
_controller.dispose();
super.dispose();
}
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void onScroll() {
// print(_controller.position.maxScrollExtent - _controller.offset);
if (_controller.position.maxScrollExtent - _controller.offset < 100 &&
!_controller.position.outOfRange &&
!loading &&
!loadingMore &&
hasMore) {
_loadMore();
}
}
// FIXME: if items not enough, fetch next page
// This should be triggered after build
void _makeSureItemsFill() {
Future.delayed(Duration(milliseconds: 300)).then((_) {
onScroll();
});
}
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Future<void> _refresh({bool force = false}) async {
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// print('list scaffold refresh');
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setState(() {
error = '';
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loading = true;
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if (force) {
items = [];
}
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});
try {
var _payload = await widget.onRefresh();
items = _payload.items;
cursor = _payload.cursor;
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hasMore = _payload.hasMore;
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} catch (err) {
error = err.toString();
throw err;
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} finally {
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if (mounted) {
setState(() {
loading = false;
});
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_makeSureItemsFill();
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}
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}
}
Future<void> _loadMore() async {
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// print('list scaffold load more');
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setState(() {
loadingMore = true;
});
try {
var _payload = await widget.onLoadMore(cursor);
items.addAll(_payload.items);
cursor = _payload.cursor;
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hasMore = _payload.hasMore;
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} catch (err) {
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error = err.toString();
throw err;
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} finally {
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if (mounted) {
setState(() {
loadingMore = false;
});
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_makeSureItemsFill();
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}
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}
}
Widget _buildItem(BuildContext context, int index) {
if (index == 2 * items.length) {
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if (hasMore) {
return Loading(more: true);
} else {
return Container();
}
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}
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if (index % 2 == 1) {
return Container(
decoration: BoxDecoration(
border: Border(bottom: BorderSide(color: Colors.black12)),
),
);
}
return widget.itemBuilder(items[index ~/ 2]);
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}
Widget _buildSliver(BuildContext context) {
if (error.isNotEmpty) {
return SliverToBoxAdapter(
child: ErrorReload(text: error, onTap: _refresh),
);
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} else if (loading && items.isEmpty) {
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return SliverToBoxAdapter(child: Loading(more: false));
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} else if (items.isEmpty) {
return SliverToBoxAdapter(child: EmptyWidget());
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} else {
return SliverList(
delegate: SliverChildBuilderDelegate(
_buildItem,
childCount: 2 * items.length + 1,
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),
);
}
}
Widget _buildBody(BuildContext context) {
if (error.isNotEmpty) {
return ErrorReload(text: error, onTap: _refresh);
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} else if (loading && items.isEmpty) {
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return Loading(more: false);
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} else if (items.isEmpty) {
return EmptyWidget();
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} else {
return ListView.builder(
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// shrinkWrap: true,
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controller: _controller,
itemCount: 2 * items.length + 1,
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itemBuilder: _buildItem,
);
}
}
@override
Widget build(BuildContext context) {
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switch (SettingsProvider.of(context).theme) {
case ThemeMap.cupertino:
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List<Widget> slivers = [
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CupertinoSliverRefreshControl(onRefresh: _refresh)
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];
// if (widget.header != null) {
// slivers.add(SliverToBoxAdapter(child: widget.header));
// }
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slivers.add(_buildSliver(context));
return CupertinoPageScaffold(
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navigationBar: CupertinoNavigationBar(
middle: widget.title,
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trailing: widget.trailingBuiler == null
? null
: widget.trailingBuiler(refresh: _refresh),
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),
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child: SafeArea(
child: CustomScrollView(
controller: _controller,
slivers: slivers,
),
),
);
default:
return Scaffold(
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appBar: AppBar(
title: widget.title,
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actions: widget.trailingBuiler == null
? null
: [widget.trailingBuiler(refresh: _refresh)],
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),
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body: RefreshIndicator(
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onRefresh: _refresh,
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child: _buildBody(context),
),
);
}
}
}