blob: 89ca49725a818794fdc2f85d9469d682c47675f7 [file] [log] [blame]
// Copyright 2017 The Chromium 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 'dart:math' as math;
import 'package:flutter/foundation.dart';
import 'box.dart';
import 'sliver.dart';
import 'sliver_fixed_extent_list.dart';
import 'sliver_multi_box_adaptor.dart';
/// A sliver that contains multiple box children that each fill the viewport.
/// [RenderSliverFillViewport] places its children in a linear array along the
/// main axis. Each child is sized to fill the viewport, both in the main and
/// cross axis. A [viewportFraction] factor can be provided to size the children
/// to a multiple of the viewport's main axis dimension (typically a fraction
/// less than 1.0).
/// See also:
/// * [RenderSliverFillRemaining], which sizes the children based on the
/// remaining space rather than the viewport itself.
/// * [RenderSliverFixedExtentList], which has a configurable [itemExtent].
/// * [RenderSliverList], which does not require its children to have the same
/// extent in the main axis.
class RenderSliverFillViewport extends RenderSliverFixedExtentBoxAdaptor {
/// Creates a sliver that contains multiple box children that each fill the
/// viewport.
/// The [childManager] argument must not be null.
@required RenderSliverBoxChildManager childManager,
double viewportFraction = 1.0,
}) : assert(viewportFraction != null),
assert(viewportFraction > 0.0),
_viewportFraction = viewportFraction,
super(childManager: childManager);
double get itemExtent => constraints.viewportMainAxisExtent * viewportFraction;
/// The fraction of the viewport that each child should fill in the main axis.
/// If this fraction is less than 1.0, more than one child will be visible at
/// once. If this fraction is greater than 1.0, each child will be larger than
/// the viewport in the main axis.
double get viewportFraction => _viewportFraction;
double _viewportFraction;
set viewportFraction(double value) {
assert(value != null);
if (_viewportFraction == value)
_viewportFraction = value;
double get _padding => (1.0 - viewportFraction) * constraints.viewportMainAxisExtent * 0.5;
double indexToLayoutOffset(double itemExtent, int index) {
return _padding + super.indexToLayoutOffset(itemExtent, index);
int getMinChildIndexForScrollOffset(double scrollOffset, double itemExtent) {
return super.getMinChildIndexForScrollOffset(math.max(scrollOffset - _padding, 0.0), itemExtent);
int getMaxChildIndexForScrollOffset(double scrollOffset, double itemExtent) {
return super.getMaxChildIndexForScrollOffset(math.max(scrollOffset - _padding, 0.0), itemExtent);
double estimateMaxScrollOffset(
SliverConstraints constraints, {
int firstIndex,
int lastIndex,
double leadingScrollOffset,
double trailingScrollOffset,
}) {
final double padding = _padding;
return childManager.estimateMaxScrollOffset(
firstIndex: firstIndex,
lastIndex: lastIndex,
leadingScrollOffset: leadingScrollOffset - padding,
trailingScrollOffset: trailingScrollOffset - padding,
) + padding + padding;
/// A sliver that contains a single box child that fills the remaining space in
/// the viewport.
/// [RenderSliverFillRemaining] sizes its child to fill the viewport in the
/// cross axis and to fill the remaining space in the viewport in the main axis.
/// Typically this will be the last sliver in a viewport, since (by definition)
/// there is never any room for anything beyond this sliver.
/// See also:
/// * [RenderSliverFillViewport], which sizes its children based on the
/// size of the viewport, regardless of what else is in the scroll view.
/// * [RenderSliverList], which shows a list of variable-sized children in a
/// viewport.
class RenderSliverFillRemaining extends RenderSliverSingleBoxAdapter {
/// Creates a [RenderSliver] that wraps a [RenderBox] which is sized to fit
/// the remaining space in the viewport.
RenderBox child,
}) : super(child: child);
void performLayout() {
final double extent = constraints.remainingPaintExtent - math.min(constraints.overlap, 0.0);
if (child != null)
child.layout(constraints.asBoxConstraints(minExtent: extent, maxExtent: extent), parentUsesSize: true);
final double paintedChildSize = calculatePaintOffset(constraints, from: 0.0, to: extent);
assert(paintedChildSize >= 0.0);
geometry = SliverGeometry(
scrollExtent: constraints.viewportMainAxisExtent,
paintExtent: paintedChildSize,
maxPaintExtent: paintedChildSize,
hasVisualOverflow: extent > constraints.remainingPaintExtent || constraints.scrollOffset > 0.0,
if (child != null)
setChildParentData(child, constraints, geometry);