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| 1 // Copyright 2015 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 import 'dart:math' as math; | |
| 6 | |
| 7 import 'package:vector_math/vector_math.dart'; | |
| 8 | |
| 9 import '../animation/scroll_behavior.dart'; | |
| 10 import 'scrollable.dart'; | |
| 11 import 'basic.dart'; | |
| 12 | |
| 13 abstract class FixedHeightScrollable extends Scrollable { | |
| 14 | |
| 15 FixedHeightScrollable({ this.itemHeight, Object key }) : super(key: key) { | |
| 16 assert(itemHeight != null); | |
| 17 } | |
| 18 | |
| 19 double itemHeight; | |
| 20 | |
| 21 void syncFields(FixedHeightScrollable source) { | |
| 22 itemHeight = source.itemHeight; | |
| 23 super.syncFields(source); | |
| 24 } | |
| 25 | |
| 26 ScrollBehavior createScrollBehavior() => new OverscrollBehavior(); | |
| 27 OverscrollBehavior get scrollBehavior => super.scrollBehavior as OverscrollBeh
avior; | |
| 28 | |
| 29 int _itemCount = 0; | |
| 30 int get itemCount => _itemCount; | |
| 31 void set itemCount (int value) { | |
| 32 if (_itemCount != value) { | |
| 33 _itemCount = value; | |
| 34 scrollBehavior.contentsHeight = itemHeight * _itemCount; | |
| 35 } | |
| 36 } | |
| 37 | |
| 38 double _height; | |
| 39 void _handleSizeChanged(Size newSize) { | |
| 40 setState(() { | |
| 41 _height = newSize.height; | |
| 42 scrollBehavior.containerHeight = _height; | |
| 43 }); | |
| 44 } | |
| 45 | |
| 46 UINode buildContent() { | |
| 47 var itemShowIndex = 0; | |
| 48 var itemShowCount = 0; | |
| 49 | |
| 50 Matrix4 transform = new Matrix4.identity(); | |
| 51 | |
| 52 if (_height != null && _height > 0.0) { | |
| 53 if (scrollOffset < 0.0) { | |
| 54 double visibleHeight = _height + scrollOffset; | |
| 55 itemShowCount = (visibleHeight / itemHeight).round() + 1; | |
| 56 transform.translate(0.0, -scrollOffset); | |
| 57 } else { | |
| 58 itemShowCount = (_height / itemHeight).ceil() + 1; | |
| 59 double alignmentDelta = -scrollOffset % itemHeight; | |
| 60 if (alignmentDelta != 0.0) | |
| 61 alignmentDelta -= itemHeight; | |
| 62 | |
| 63 double drawStart = scrollOffset + alignmentDelta; | |
| 64 itemShowIndex = math.max(0, (drawStart / itemHeight).floor()); | |
| 65 | |
| 66 transform.translate(0.0, alignmentDelta); | |
| 67 } | |
| 68 } | |
| 69 | |
| 70 return new SizeObserver( | |
| 71 callback: _handleSizeChanged, | |
| 72 child: new ClipRect( | |
| 73 child: new Transform( | |
| 74 transform: transform, | |
| 75 child: new Block(buildItems(itemShowIndex, itemShowCount)) | |
| 76 ) | |
| 77 ) | |
| 78 ); | |
| 79 } | |
| 80 | |
| 81 List<UINode> buildItems(int start, int count); | |
| 82 | |
| 83 } | |
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