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Add convenience constructors for SliverList (#116605)
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* init

* lint

* add the other two slivers

* fix lint

* add test for sliverlist.separated

* add3 more

* fix lint and tests

* remove trailing spaces

* remove trailing spaces 2

* fix lint

* fix lint again
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@thkim1011
thkim1011 committed Jan 3, 2023
1 parent bd69ef7 commit a7942e8
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289 changes: 289 additions & 0 deletions packages/flutter/lib/src/widgets/sliver.dart
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Expand Up @@ -3,6 +3,7 @@
// found in the LICENSE file.

import 'dart:collection' show HashMap, SplayTreeMap;
import 'dart:math' as math;

import 'package:flutter/foundation.dart';
import 'package:flutter/rendering.dart';
Expand Down Expand Up @@ -1035,6 +1036,184 @@ class SliverList extends SliverMultiBoxAdaptorWidget {
required super.delegate,
});

/// A sliver that places multiple box children in a linear array along the main
/// axis.
///
/// This constructor is appropriate for sliver lists with a large (or
/// infinite) number of children because the builder is called only for those
/// children that are actually visible.
///
/// Providing a non-null `itemCount` improves the ability of the [SliverGrid]
/// to estimate the maximum scroll extent.
///
/// `itemBuilder` will be called only with indices greater than or equal to
/// zero and less than `itemCount`.
///
/// {@macro flutter.widgets.ListView.builder.itemBuilder}
///
/// {@macro flutter.widgets.PageView.findChildIndexCallback}
///
/// The `addAutomaticKeepAlives` argument corresponds to the
/// [SliverChildBuilderDelegate.addAutomaticKeepAlives] property. The
/// `addRepaintBoundaries` argument corresponds to the
/// [SliverChildBuilderDelegate.addRepaintBoundaries] property. The
/// `addSemanticIndexes` argument corresponds to the
/// [SliverChildBuilderDelegate.addSemanticIndexes] property.
///
/// {@tool snippet}
/// This example, which would be inserted into a [CustomScrollView.slivers]
/// list, shows an infinite number of items in varying shades of blue:
///
/// ```dart
/// SliverList.builder(
/// itemBuilder: (BuildContext context, int index) {
/// return Container(
/// alignment: Alignment.center,
/// color: Colors.lightBlue[100 * (index % 9)],
/// child: Text('list item $index'),
/// );
/// },
/// )
/// ```
/// {@end-tool}
SliverList.builder({
super.key,
required NullableIndexedWidgetBuilder itemBuilder,
ChildIndexGetter? findChildIndexCallback,
int? itemCount,
bool addAutomaticKeepAlives = true,
bool addRepaintBoundaries = true,
bool addSemanticIndexes = true,
}) : super(delegate: SliverChildBuilderDelegate(
itemBuilder,
findChildIndexCallback: findChildIndexCallback,
childCount: itemCount,
addAutomaticKeepAlives: addAutomaticKeepAlives,
addRepaintBoundaries: addRepaintBoundaries,
addSemanticIndexes: addSemanticIndexes,
));

/// A sliver that places multiple box children, separated by box widgets, in a linear array along the main
/// axis.
///
/// This constructor is appropriate for sliver lists with a large (or
/// infinite) number of children because the builder is called only for those
/// children that are actually visible.
///
/// Providing a non-null `itemCount` improves the ability of the [SliverGrid]
/// to estimate the maximum scroll extent.
///
/// `itemBuilder` will be called only with indices greater than or equal to
/// zero and less than `itemCount`.
///
/// {@macro flutter.widgets.ListView.builder.itemBuilder}
///
/// {@macro flutter.widgets.PageView.findChildIndexCallback}
///
///
/// The `separatorBuilder` is similar to `itemBuilder`, except it is the widget
/// that gets placed between itemBuilder(context, index) and itemBuilder(context, index + 1).
///
/// The `addAutomaticKeepAlives` argument corresponds to the
/// [SliverChildBuilderDelegate.addAutomaticKeepAlives] property. The
/// `addRepaintBoundaries` argument corresponds to the
/// [SliverChildBuilderDelegate.addRepaintBoundaries] property. The
/// `addSemanticIndexes` argument corresponds to the
/// [SliverChildBuilderDelegate.addSemanticIndexes] property.
/// {@tool snippet}
///
/// This example shows how to create a [SliverList] whose [Container] items
/// are separated by [Divider]s.
///
/// ```dart
/// SliverList.separated(
/// itemBuilder: (BuildContext context, int index) {
/// return Container(
/// alignment: Alignment.center,
/// color: Colors.lightBlue[100 * (index % 9)],
/// child: Text('list item $index'),
/// );
/// },
/// separatorBuilder: (BuildContext context, int index) => const Divider(),
/// )
/// ```
/// {@end-tool}
SliverList.separated({
super.key,
required NullableIndexedWidgetBuilder itemBuilder,
ChildIndexGetter? findChildIndexCallback,
required NullableIndexedWidgetBuilder separatorBuilder,
int? itemCount,
bool addAutomaticKeepAlives = true,
bool addRepaintBoundaries = true,
bool addSemanticIndexes = true,
}) : assert(itemBuilder != null),
assert(separatorBuilder != null),
super(delegate: SliverChildBuilderDelegate(
(BuildContext context, int index) {
final int itemIndex = index ~/ 2;
final Widget? widget;
if (index.isEven) {
widget = itemBuilder(context, itemIndex);
} else {
widget = separatorBuilder(context, itemIndex);
assert(() {
if (widget == null) {
throw FlutterError('separatorBuilder cannot return null.');
}
return true;
}());
}
return widget;
},
findChildIndexCallback: findChildIndexCallback,
childCount: itemCount == null ? null : math.max(0, itemCount * 2 - 1),
addAutomaticKeepAlives: addAutomaticKeepAlives,
addRepaintBoundaries: addRepaintBoundaries,
addSemanticIndexes: addSemanticIndexes,
semanticIndexCallback: (Widget _, int index) {
return index.isEven ? index ~/ 2 : null;
},
));

/// A sliver that places multiple box children in a linear array along the main
/// axis.
///
/// This constructor uses a list of [Widget]s to build the sliver.
///
/// The `addAutomaticKeepAlives` argument corresponds to the
/// [SliverChildBuilderDelegate.addAutomaticKeepAlives] property. The
/// `addRepaintBoundaries` argument corresponds to the
/// [SliverChildBuilderDelegate.addRepaintBoundaries] property. The
/// `addSemanticIndexes` argument corresponds to the
/// [SliverChildBuilderDelegate.addSemanticIndexes] property.
///
/// {@tool snippet}
/// This example, which would be inserted into a [CustomScrollView.slivers]
/// list, shows an infinite number of items in varying shades of blue:
///
/// ```dart
/// SliverList.list(
/// children: const <Widget>[
/// Text('Hello'),
/// Text('World!'),
/// ],
/// );
/// ```
/// {@end-tool}
SliverList.list({
super.key,
required List<Widget> children,
bool addAutomaticKeepAlives = true,
bool addRepaintBoundaries = true,
bool addSemanticIndexes = true,
}) : super(delegate: SliverChildListDelegate(
children,
addAutomaticKeepAlives: addAutomaticKeepAlives,
addRepaintBoundaries: addRepaintBoundaries,
addSemanticIndexes: addSemanticIndexes,
));

@override
SliverMultiBoxAdaptorElement createElement() => SliverMultiBoxAdaptorElement(this, replaceMovedChildren: true);

Expand Down Expand Up @@ -1098,6 +1277,116 @@ class SliverFixedExtentList extends SliverMultiBoxAdaptorWidget {
required this.itemExtent,
});

/// A sliver that places multiple box children in a linear array along the main
/// axis.
///
/// [SliverFixedExtentList] places its children in a linear array along the main
/// axis starting at offset zero and without gaps. Each child is forced to have
/// the [itemExtent] in the main axis and the
/// [SliverConstraints.crossAxisExtent] in the cross axis.
///
/// This constructor is appropriate for sliver lists with a large (or
/// infinite) number of children whose extent is already determined.
///
/// Providing a non-null `itemCount` improves the ability of the [SliverGrid]
/// to estimate the maximum scroll extent.
///
/// `itemBuilder` will be called only with indices greater than or equal to
/// zero and less than `itemCount`.
///
/// {@macro flutter.widgets.ListView.builder.itemBuilder}
///
/// The `itemExtent` argument is the extent of each item.
///
/// {@macro flutter.widgets.PageView.findChildIndexCallback}
///
/// The `addAutomaticKeepAlives` argument corresponds to the
/// [SliverChildBuilderDelegate.addAutomaticKeepAlives] property. The
/// `addRepaintBoundaries` argument corresponds to the
/// [SliverChildBuilderDelegate.addRepaintBoundaries] property. The
/// `addSemanticIndexes` argument corresponds to the
/// [SliverChildBuilderDelegate.addSemanticIndexes] property.
/// {@tool snippet}
///
/// This example, which would be inserted into a [CustomScrollView.slivers]
/// list, shows an infinite number of items in varying shades of blue:
///
/// ```dart
/// SliverFixedExtentList.builder(
/// itemExtent: 50.0,
/// itemBuilder: (BuildContext context, int index) {
/// return Container(
/// alignment: Alignment.center,
/// color: Colors.lightBlue[100 * (index % 9)],
/// child: Text('list item $index'),
/// );
/// },
/// )
/// ```
/// {@end-tool}
SliverFixedExtentList.builder({
super.key,
required NullableIndexedWidgetBuilder itemBuilder,
required this.itemExtent,
ChildIndexGetter? findChildIndexCallback,
int? itemCount,
bool addAutomaticKeepAlives = true,
bool addRepaintBoundaries = true,
bool addSemanticIndexes = true,
}) : super(delegate: SliverChildBuilderDelegate(
itemBuilder,
findChildIndexCallback: findChildIndexCallback,
childCount: itemCount,
addAutomaticKeepAlives: addAutomaticKeepAlives,
addRepaintBoundaries: addRepaintBoundaries,
addSemanticIndexes: addSemanticIndexes,
));

/// A sliver that places multiple box children in a linear array along the main
/// axis.
///
/// [SliverFixedExtentList] places its children in a linear array along the main
/// axis starting at offset zero and without gaps. Each child is forced to have
/// the [itemExtent] in the main axis and the
/// [SliverConstraints.crossAxisExtent] in the cross axis.
///
/// This constructor uses a list of [Widget]s to build the sliver.
///
/// The `addAutomaticKeepAlives` argument corresponds to the
/// [SliverChildBuilderDelegate.addAutomaticKeepAlives] property. The
/// `addRepaintBoundaries` argument corresponds to the
/// [SliverChildBuilderDelegate.addRepaintBoundaries] property. The
/// `addSemanticIndexes` argument corresponds to the
/// [SliverChildBuilderDelegate.addSemanticIndexes] property.
///
/// {@tool snippet}
/// This example, which would be inserted into a [CustomScrollView.slivers]
/// list, shows an infinite number of items in varying shades of blue:
///
/// ```dart
/// SliverFixedExtentList.list(
/// itemExtent: 50.0,
/// children: const <Widget>[
/// Text('Hello'),
/// Text('World!'),
/// ],
/// );
/// ```
/// {@end-tool}
SliverFixedExtentList.list({
super.key,
required List<Widget> children,
required this.itemExtent,
bool addAutomaticKeepAlives = true,
bool addRepaintBoundaries = true,
bool addSemanticIndexes = true,
}) : super(delegate: SliverChildListDelegate(
children,
addAutomaticKeepAlives: addAutomaticKeepAlives,
addRepaintBoundaries: addRepaintBoundaries,
addSemanticIndexes: addSemanticIndexes,
));

/// The extent the children are forced to have in the main axis.
final double itemExtent;

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