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96 lines
3.1 KiB
96 lines
3.1 KiB
// Copyright 2018-present the Flutter authors. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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import 'package:flutter/material.dart';
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import '../model/product.dart';
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import 'product_columns.dart';
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class AsymmetricView extends StatelessWidget {
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final List<Product> products;
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const AsymmetricView({Key key, this.products});
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List<Container> _buildColumns(BuildContext context) {
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if (products == null || products.isEmpty) {
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return const <Container>[];
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}
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/// This will return a list of columns. It will oscillate between the two
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/// kinds of columns. Even cases of the index (0, 2, 4, etc) will be
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/// TwoProductCardColumn and the odd cases will be OneProductCardColumn.
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///
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/// Each pair of columns will advance us 3 products forward (2 + 1). That's
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/// some kinda awkward math so we use _evenCasesIndex and _oddCasesIndex as
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/// helpers for creating the index of the product list that will correspond
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/// to the index of the list of columns.
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return List.generate(_listItemCount(products.length), (int index) {
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double width = .59 * MediaQuery.of(context).size.width;
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Widget column;
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if (index % 2 == 0) {
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/// Even cases
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int bottom = _evenCasesIndex(index);
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column = TwoProductCardColumn(
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bottom: products[bottom],
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top: products.length - 1 >= bottom + 1
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? products[bottom + 1]
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: null);
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width += 32.0;
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} else {
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/// Odd cases
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column = OneProductCardColumn(
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product: products[_oddCasesIndex(index)],
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);
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}
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return Container(
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width: width,
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child: Padding(
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padding: EdgeInsets.symmetric(horizontal: 16.0),
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child: column,
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),
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);
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}).toList();
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}
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int _evenCasesIndex(int input) {
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/// The operator ~/ is a cool one. It's the truncating division operator. It
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/// divides the number and if there's a remainder / decimal, it cuts it off.
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/// This is like dividing and then casting the result to int. Also, it's
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/// functionally equivalent to floor() in this case.
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return input ~/ 2 * 3;
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}
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int _oddCasesIndex(int input) {
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assert(input > 0);
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return (input / 2).ceil() * 3 - 1;
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}
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int _listItemCount(int totalItems) {
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if (totalItems % 3 == 0) {
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return totalItems ~/ 3 * 2;
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} else {
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return (totalItems / 3).ceil() * 2 - 1;
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}
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}
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@override
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Widget build(BuildContext context) {
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return ListView(
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scrollDirection: Axis.horizontal,
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padding: EdgeInsets.fromLTRB(0.0, 34.0, 16.0, 44.0),
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children: _buildColumns(context),
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);
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}
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}
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