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Deferred ListView.separator cleanups (#18720)

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Hans Muller 2018-07-06 15:21:29 -07:00 committed by GitHub
parent e5d9feb59d
commit 7ac183794b
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1 changed files with 12 additions and 7 deletions
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19
packages/flutter/lib/src/widgets/scroll_view.dart
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@ -452,7 +452,7 @@ abstract class BoxScrollView extends ScrollView {
/// machinery can make use of the foreknowledge of the children's extent to save
/// work, for example when the scroll position changes drastically.
///
/// There are three options for constructing a [ListView]:
/// There are four options for constructing a [ListView]:
///
/// 1. The default constructor takes an explicit [List<Widget>] of children. This
/// constructor is appropriate for list views with a small number of
@ -460,13 +460,18 @@ abstract class BoxScrollView extends ScrollView {
/// child that could possibly be displayed in the list view instead of just
/// those children that are actually visible.
///
/// 2. The [ListView.builder] takes an [IndexedWidgetBuilder], which builds the
/// children on demand. This constructor is appropriate for list views with
/// a large (or infinite) number of children because the builder is called
/// 2. The [ListView.builder] constructor takes an [IndexedWidgetBuilder], which
/// builds the children on demand. This constructor is appropriate for list views
/// with a large (or infinite) number of children because the builder is called
/// only for those children that are actually visible.
///
/// 3. The [ListView.custom] takes a [SliverChildDelegate], which provides the
/// ability to customize additional aspects of the child model. For example,
/// 3. The [ListView.separated] constructor takes two [IndexedWidgetBuilder]s:
/// `itemBuilder` builds child items on demand, and `separatorBuilder`
/// similarly builds separator children which appear in between the child items.
/// This constructor is appropriate for list views with a fixed number of children.
///
/// 4. The [ListView.custom] constructor takes a [SliverChildDelegate], which provides
/// the ability to customize additional aspects of the child model. For example,
/// a [SliverChildDelegate] can control the algorithm used to estimate the
/// size of children that are not actually visible.
///
@ -749,7 +754,7 @@ class ListView extends BoxScrollView {
childrenDelegate = new SliverChildBuilderDelegate(
(BuildContext context, int index) {
final int itemIndex = index ~/ 2;
return (index == 0 || index.isEven)
return index.isEven
? itemBuilder(context, itemIndex)
: separatorBuilder(context, itemIndex);
},