| // Copyright 2014 The Flutter Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| import 'package:flutter/rendering.dart'; |
| |
| import 'framework.dart'; |
| import 'layout_builder.dart'; |
| |
| /// The signature of the [SliverLayoutBuilder] builder function. |
| typedef SliverLayoutWidgetBuilder = Widget Function(BuildContext context, SliverConstraints constraints); |
| |
| /// Builds a sliver widget tree that can depend on its own [SliverConstraints]. |
| /// |
| /// Similar to the [LayoutBuilder] widget except its builder should return a sliver |
| /// widget, and [SliverLayoutBuilder] is itself a sliver. The framework calls the |
| /// [builder] function at layout time and provides the current [SliverConstraints]. |
| /// The [SliverLayoutBuilder]'s final [SliverGeometry] will match the [SliverGeometry] |
| /// of its child. |
| /// |
| /// {@macro flutter.widgets.ConstrainedLayoutBuilder} |
| /// |
| /// See also: |
| /// |
| /// * [LayoutBuilder], the non-sliver version of this widget. |
| class SliverLayoutBuilder extends ConstrainedLayoutBuilder<SliverConstraints> { |
| /// Creates a sliver widget that defers its building until layout. |
| /// |
| /// The [builder] argument must not be null. |
| const SliverLayoutBuilder({ |
| super.key, |
| required super.builder, |
| }); |
| |
| @override |
| RenderObject createRenderObject(BuildContext context) => _RenderSliverLayoutBuilder(); |
| } |
| |
| class _RenderSliverLayoutBuilder extends RenderSliver with RenderObjectWithChildMixin<RenderSliver>, RenderConstrainedLayoutBuilder<SliverConstraints, RenderSliver> { |
| @override |
| double childMainAxisPosition(RenderObject child) { |
| assert(child == this.child); |
| return 0; |
| } |
| |
| @override |
| void performLayout() { |
| rebuildIfNecessary(); |
| child?.layout(constraints, parentUsesSize: true); |
| geometry = child?.geometry ?? SliverGeometry.zero; |
| } |
| |
| @override |
| void applyPaintTransform(RenderObject child, Matrix4 transform) { |
| assert(child == this.child); |
| // child's offset is always (0, 0), transform.translate(0, 0) does not mutate the transform. |
| } |
| |
| @override |
| void paint(PaintingContext context, Offset offset) { |
| // This renderObject does not introduce additional offset to child's position. |
| if (child?.geometry?.visible ?? false) { |
| context.paintChild(child!, offset); |
| } |
| } |
| |
| @override |
| bool hitTestChildren(SliverHitTestResult result, {required double mainAxisPosition, required double crossAxisPosition}) { |
| return child != null |
| && child!.geometry!.hitTestExtent > 0 |
| && child!.hitTest(result, mainAxisPosition: mainAxisPosition, crossAxisPosition: crossAxisPosition); |
| } |
| } |