flutter/examples/widgets/pageable_list.dart

// Copyright 2015 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 'package:flutter/material.dart';
import 'package:flutter/painting.dart';

class CardModel {
  CardModel(this.value, this.size, this.color);
  int value;
  Size size;
  Color color;
  String get label => "Card $value";
  Key get key => new ObjectKey(this);
}

class PageableListApp extends StatefulComponent {
  PageableListAppState createState() => new PageableListAppState();
}

class PageableListAppState extends State<PageableListApp> {
  void initState() {
    super.initState();
    List<Size> cardSizes = [
      [100.0, 300.0], [300.0, 100.0], [200.0, 400.0], [400.0, 400.0], [300.0, 400.0]
    ]
    .map((args) => new Size(args[0], args[1]))
    .toList();

    cardModels = new List<CardModel>.generate(cardSizes.length, (int i) {
      Color color = Color.lerp(Colors.red[300], Colors.blue[900], i / cardSizes.length);
      return new CardModel(i, cardSizes[i], color);
    });
  }

  static const TextStyle cardLabelStyle =
    const TextStyle(color: Colors.white, fontSize: 18.0, fontWeight: bold);

  List<CardModel> cardModels;
  Size pageSize = new Size(200.0, 200.0);
  ScrollDirection scrollDirection = ScrollDirection.horizontal;
  bool itemsWrap = false;

  void updatePageSize(Size newSize) {
    setState(() {
      pageSize = newSize;
    });
  }

  Widget buildCard(BuildContext context, CardModel cardModel, int index) {
    Widget card = new Card(
      color: cardModel.color,
      child: new Container(
        width: cardModel.size.width,
        height: cardModel.size.height,
        padding: const EdgeDims.all(8.0),
        child: new Center(child: new Text(cardModel.label, style: cardLabelStyle))
      )
    );

    BoxConstraints constraints = (scrollDirection == ScrollDirection.vertical)
      ? new BoxConstraints.tightFor(height: pageSize.height)
      : new BoxConstraints.tightFor(width: pageSize.width);

    return new Container(
      key: cardModel.key,
      constraints: constraints,
      child: new Center(child: card)
    );
  }

  void switchScrollDirection() {
    setState(() {
      scrollDirection = (scrollDirection == ScrollDirection.vertical)
        ? ScrollDirection.horizontal
        : ScrollDirection.vertical;
    });
  }

  void toggleItemsWrap() {
    setState(() {
      itemsWrap = !itemsWrap;
    });
  }

  void _showDrawer() {
    showDrawer(
      context: context,
      child: new Block(<Widget>[
        new DrawerHeader(child: new Text('Options')),
        new DrawerItem(
          icon: 'navigation/more_horiz',
          selected: scrollDirection == ScrollDirection.horizontal,
          child: new Text('Horizontal Layout'),
          onPressed: switchScrollDirection
        ),
        new DrawerItem(
          icon: 'navigation/more_vert',
          selected: scrollDirection == ScrollDirection.vertical,
          child: new Text('Vertical Layout'),
          onPressed: switchScrollDirection
        ),
        new DrawerItem(
          onPressed: toggleItemsWrap,
          child: new Row(<Widget>[
            new Flexible(child: new Text('Scrolling wraps around')),
            new Checkbox(value: itemsWrap)
          ])
        )
      ])
    );
  }

  Widget buildToolBar() {
    return new ToolBar(
      left: new IconButton(icon: "navigation/menu", onPressed: _showDrawer),
      center: new Text('PageableList'),
      right: <Widget>[
        new Text(scrollDirection == ScrollDirection.horizontal ? "horizontal" : "vertical")
      ]
    );
  }

  Widget buildBody(BuildContext context) {
    Widget list = new PageableList<CardModel>(
      items: cardModels,
      itemsWrap: itemsWrap,
      itemBuilder: buildCard,
      scrollDirection: scrollDirection,
      itemExtent: (scrollDirection == ScrollDirection.vertical)
          ? pageSize.height
          : pageSize.width
    );
    return new SizeObserver(
      onSizeChanged: updatePageSize,
      child: list
    );
  }

  Widget build(BuildContext context) {
    return new IconTheme(
      data: const IconThemeData(color: IconThemeColor.white),
      child: new Scaffold(
        toolBar: buildToolBar(),
        body: buildBody(context)
      )
    );
  }
}

void main() {
  runApp(new MaterialApp(
    title: 'PageableList',
    theme: new ThemeData(
      brightness: ThemeBrightness.light,
      primarySwatch: Colors.blue,
      accentColor: Colors.redAccent[200]
    ),
    routes: <String, RouteBuilder>{
      '/': (RouteArguments args) => new PageableListApp(),
    }
  ));
}