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fix: remove need for an extra pull #42

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merged 2 commits into from
Oct 14, 2022
Merged

fix: remove need for an extra pull #42

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ba13b15
fix: remove need for an extra pull
Oct 13, 2022
e245471
change refetch logc
Oct 13, 2022
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3 changes: 0 additions & 3 deletions lib/src/defaults.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -20,8 +20,5 @@ Widget defaultInfiniteListErrorBuilder(BuildContext buildContext) {
);
}

/// Default value to [InfiniteList.scrollExtentThreshold].
const defaultScrollExtentThreshold = 400.0;

/// Default value to [InfiniteList.debounceDuration].
const defaultDebounceDuration = Duration(milliseconds: 100);
33 changes: 9 additions & 24 deletions lib/src/infinite_list.dart
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
import 'package:very_good_infinite_list/src/defaults.dart';
import 'package:very_good_infinite_list/src/sliver_infinite_list.dart';

Expand Down Expand Up @@ -28,7 +29,7 @@ class InfiniteList extends StatelessWidget {
this.scrollController,
this.scrollDirection = Axis.vertical,
this.physics,
this.scrollExtentThreshold = defaultScrollExtentThreshold,
this.cacheExtent,
this.debounceDuration = defaultDebounceDuration,
this.reverse = false,
this.isLoading = false,
Expand All @@ -39,10 +40,7 @@ class InfiniteList extends StatelessWidget {
this.loadingBuilder,
this.errorBuilder,
this.separatorBuilder,
}) : assert(
scrollExtentThreshold >= 0.0,
'scrollExtentThreshold must be greater than or equal to 0.0',
);
});

/// {@template scroll_controller}
/// An optional [ScrollController] to be used by the internal [ScrollView].
Expand All @@ -60,22 +58,6 @@ class InfiniteList extends StatelessWidget {
/// {@endtemplate}
final ScrollPhysics? physics;

/// {@template scroll_extent_threshold}
/// The offset, in pixels, that the [scrollController] must be scrolled over
/// to trigger [onFetchData].
///
/// This is useful for fetching data _before_ the user has scrolled all the
/// way to the end of the list, so the fetching mechanism is more well hidden.
///
/// For example, if this is set to `400.0` (the default), [onFetchData] will
/// be called when the list is scrolled `400.0` pixels away from the bottom
/// (or the top if [reverse] is `true`).
///
/// This value must be `0.0` or greater, is set to
/// [defaultScrollExtentThreshold] by default and cannot be `null`.
/// {@endtemplate}
final double scrollExtentThreshold;

/// {@template debounce_duration}
/// The duration with which calls to [onFetchData] will be debounced.
///
Expand Down Expand Up @@ -135,14 +117,17 @@ class InfiniteList extends StatelessWidget {
/// In normal operation, this method should trigger new data to be fetched and
/// [isLoading] to be set to `true`.
///
/// Exactly when this is called depends on the [scrollExtentThreshold].
/// Exactly when this is called depends on the [cacheExtent].
/// Additionally, every call to this will be debounced by the provided
/// [debounceDuration].
///
/// Is required and cannot be `null`.
/// {@endtemplate}
final VoidCallback onFetchData;

/// See [RenderViewportBase.cacheExtent]
final double? cacheExtent;

/// {@template padding}
/// The amount of space by which to inset the list of items.
///
Expand Down Expand Up @@ -193,9 +178,10 @@ class InfiniteList extends StatelessWidget {
Widget build(BuildContext context) {
return CustomScrollView(
scrollDirection: scrollDirection,
reverse: reverse,
controller: scrollController,
physics: physics,
reverse: reverse,
cacheExtent: cacheExtent,
slivers: [
_ContextualSliverPadding(
padding: padding,
Expand All @@ -204,7 +190,6 @@ class InfiniteList extends StatelessWidget {
itemCount: itemCount,
onFetchData: onFetchData,
itemBuilder: itemBuilder,
scrollExtentThreshold: scrollExtentThreshold,
debounceDuration: debounceDuration,
isLoading: isLoading,
hasError: hasError,
Expand Down
151 changes: 20 additions & 131 deletions lib/src/sliver_infinite_list.dart
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Original file line number Diff line number Diff line change
@@ -1,4 +1,3 @@
import 'package:flutter/rendering.dart';
import 'package:flutter/widgets.dart';
import 'package:very_good_infinite_list/src/callback_debouncer.dart';
import 'package:very_good_infinite_list/src/defaults.dart';
Expand All @@ -10,14 +9,13 @@ import 'package:very_good_infinite_list/src/infinite_list.dart';
///
/// As a infinite list, it is supposed to be the last sliver in the current
/// [ScrollView]. Otherwise, re-fetching data will have an unintuitive behavior.
class SliverInfiniteList extends StatelessWidget {
class SliverInfiniteList extends StatefulWidget {
/// Constructs a [SliverInfiniteList].
const SliverInfiniteList({
super.key,
required this.itemCount,
required this.onFetchData,
required this.itemBuilder,
this.scrollExtentThreshold = defaultScrollExtentThreshold,
this.debounceDuration = defaultDebounceDuration,
this.isLoading = false,
this.hasError = false,
Expand All @@ -26,13 +24,7 @@ class SliverInfiniteList extends StatelessWidget {
this.errorBuilder,
this.separatorBuilder,
this.emptyBuilder,
}) : assert(
scrollExtentThreshold >= 0.0,
'scrollExtentThreshold must be greater than or equal to 0.0',
);

/// {@macro scroll_extent_threshold}
final double scrollExtentThreshold;
});

/// {@macro debounce_duration}
final Duration debounceDuration;
Expand Down Expand Up @@ -68,154 +60,48 @@ class SliverInfiniteList extends StatelessWidget {
final ItemBuilder itemBuilder;

@override
Widget build(BuildContext context) {
return SliverLayoutBuilder(
builder: (context, constraints) {
return _SliverInfiniteListInternal(
itemCount: itemCount,
onFetchData: onFetchData,
itemBuilder: itemBuilder,
scrollExtentThreshold: scrollExtentThreshold,
debounceDuration: debounceDuration,
isLoading: isLoading,
hasError: hasError,
hasReachedMax: hasReachedMax,
precedingScrollExtent: constraints.precedingScrollExtent,
loadingBuilder: loadingBuilder,
errorBuilder: errorBuilder,
separatorBuilder: separatorBuilder,
emptyBuilder: emptyBuilder,
);
},
);
}
State<SliverInfiniteList> createState() => _SliverInfiniteListState();
}

class _SliverInfiniteListInternal extends StatefulWidget {
const _SliverInfiniteListInternal({
required this.itemCount,
required this.onFetchData,
required this.itemBuilder,
required this.scrollExtentThreshold,
required this.debounceDuration,
required this.isLoading,
required this.hasError,
required this.hasReachedMax,
required this.precedingScrollExtent,
this.loadingBuilder,
this.errorBuilder,
this.separatorBuilder,
this.emptyBuilder,
});

final double scrollExtentThreshold;

final Duration debounceDuration;

final int itemCount;

final bool isLoading;

final bool hasError;

final bool hasReachedMax;

final VoidCallback onFetchData;

/// See [SliverConstraints.precedingScrollExtent]
final double precedingScrollExtent;

final WidgetBuilder? loadingBuilder;

final WidgetBuilder? errorBuilder;

final WidgetBuilder? separatorBuilder;

final ItemBuilder itemBuilder;

final WidgetBuilder? emptyBuilder;

@override
State<_SliverInfiniteListInternal> createState() =>
_SliverInfiniteListInternalState();
}

class _SliverInfiniteListInternalState
extends State<_SliverInfiniteListInternal> {
class _SliverInfiniteListState extends State<SliverInfiniteList> {
late final CallbackDebouncer debounce;

ScrollPosition? scrollPosition;
int? _lastFetchedIndex;

@override
void initState() {
super.initState();
debounce = CallbackDebouncer(widget.debounceDuration);
WidgetsBinding.instance.addPostFrameCallback((_) {
attemptFetch();
});
}

@override
void didChangeDependencies() {
super.didChangeDependencies();

detachFromPosition();
scrollPosition = Scrollable.of(context)?.position;
attachToPosition();
attemptFetch();
}

@override
void didUpdateWidget(_SliverInfiniteListInternal oldWidget) {
void didUpdateWidget(SliverInfiniteList oldWidget) {
super.didUpdateWidget(oldWidget);
if (widget.itemCount != oldWidget.itemCount ||
widget.hasReachedMax != oldWidget.hasReachedMax) {
WidgetsBinding.instance.addPostFrameCallback((_) {
attemptFetch();
});
if (!widget.hasReachedMax && oldWidget.hasReachedMax) {
attemptFetch();
}
}

@override
void dispose() {
super.dispose();
debounce.dispose();
detachFromPosition();
}

void attachToPosition() {
scrollPosition?.addListener(attemptFetch);
}

void detachFromPosition() {
scrollPosition?.removeListener(attemptFetch);
}

void attemptFetch() {
if (isAtEnd &&
!widget.hasReachedMax &&
!widget.isLoading &&
!widget.hasError) {
debounce(widget.onFetchData);
if (!widget.hasReachedMax && !widget.isLoading && !widget.hasError) {
WidgetsBinding.instance.addPostFrameCallback((_) {
debounce(widget.onFetchData);
});
}
}

bool get isAtEnd {
if (widget.itemCount == 0) {
return true;
}

final scrollPosition = this.scrollPosition;
if (scrollPosition == null) {
return false;
void onBuiltLast(int lastItemIndex) {
if (_lastFetchedIndex != lastItemIndex) {
_lastFetchedIndex = lastItemIndex;
attemptFetch();
}

// This considers the end of the scrollable content as the
// position to trigger a data fetch. It may cause unintuitive behaviors
// when there is any sliver after this one.
final maxScroll = scrollPosition.maxScrollExtent;

final currentScroll = scrollPosition.pixels - widget.precedingScrollExtent;
return currentScroll >= (maxScroll - widget.scrollExtentThreshold);
}

WidgetBuilder get loadingBuilder =>
Expand Down Expand Up @@ -244,6 +130,9 @@ class _SliverInfiniteListInternalState
delegate: SliverChildBuilderDelegate(
childCount: effectiveItemCount,
(context, index) {
if (index == lastItemIndex) {
onBuiltLast(lastItemIndex);
}
if (index == lastItemIndex && showBottomWidget) {
if (widget.hasError) {
return errorBuilder(context);
Expand Down
17 changes: 10 additions & 7 deletions test/sliver_infinite_list_test.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -3,13 +3,17 @@ import 'package:flutter_test/flutter_test.dart';
import 'package:very_good_infinite_list/src/sliver_infinite_list.dart';

extension on WidgetTester {
Future<void> pumpSlivers(List<Widget> slivers) async {
Future<void> pumpSlivers(
List<Widget> slivers, {
double? cacheExtent,
}) async {
await pumpWidget(
MaterialApp(
home: Scaffold(
body: SizedBox(
height: 500,
child: CustomScrollView(
cacheExtent: cacheExtent,
slivers: slivers,
),
),
Expand All @@ -28,16 +32,16 @@ void main() {
var onFetchDataCalls = 0;

await tester.pumpSlivers(
cacheExtent: 0,
[
StatefulBuilder(
builder: (context, setState) {
return SliverInfiniteList(
itemCount: itemCount,
debounceDuration: Duration.zero,
hasReachedMax: itemCount == 12,
onFetchData: () {
setState(() {
itemCount += 3;
itemCount += 8;
onFetchDataCalls++;
});
},
Expand All @@ -51,15 +55,15 @@ void main() {
);
await tester.pumpAndSettle();

expect(onFetchDataCalls, equals(4));
expect(onFetchDataCalls, equals(5));
});
});
group('consider preceding slivers', () {
testWidgets('on mount', (tester) async {
var itemCount = 0;
var onFetchDataCalls = 0;

await tester.pumpSlivers(
cacheExtent: 0,
[
const SliverAppBar(
expandedHeight: 500,
Expand All @@ -73,10 +77,9 @@ void main() {
return SliverInfiniteList(
itemCount: itemCount,
debounceDuration: Duration.zero,
hasReachedMax: itemCount == 12,
onFetchData: () {
setState(() {
itemCount += 3;
itemCount += 8;
onFetchDataCalls++;
});
},
Expand Down