Flutter之页面布局二

1、列表布局

1.1、基础列表

dart 复制代码

import 'package:flutter/material.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    const title = 'Basic List';

    return MaterialApp(
      title: title,
      home: Scaffold(
        appBar: AppBar(title: const Text(title)),
        body: ListView(
          children: const <Widget>[
            ListTile(leading: Icon(Icons.map), title: Text('Map')),
            ListTile(leading: Icon(Icons.photo_album), title: Text('Album')),
            ListTile(leading: Icon(Icons.phone), title: Text('Phone')),
          ],
        ),
      ),
    );
  }
}

1.2、水平滑动的列表

dart 复制代码

import 'package:flutter/material.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    const title = 'Horizontal List';

    return MaterialApp(
      title: title,
      home: Scaffold(
        appBar: AppBar(title: const Text(title)),
        body: Container(
          margin: const EdgeInsets.symmetric(vertical: 20),
          height: 200,
          child: ListView(
            // This next line does the trick.
            scrollDirection: Axis.horizontal,
            children: <Widget>[
              Container(width: 160, color: Colors.red),
              Container(width: 160, color: Colors.blue),
              Container(width: 160, color: Colors.green),
              Container(width: 160, color: Colors.yellow),
              Container(width: 160, color: Colors.orange),
            ],
          ),
        ),
      ),
    );
  }
}

1.3、网格列表

dart 复制代码

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    const title = 'Grid List';

    return MaterialApp(
      title: title,
      home: Scaffold(
        appBar: AppBar(title: const Text(title)),
        body: GridView.count(
          // Create a grid with 2 columns.
          // If you change the scrollDirection to horizontal,
          // this produces 2 rows.
          crossAxisCount: 2,
          // Generate 100 widgets that display their index in the list.
          children: List.generate(100, (index) {
            return Center(
              child: Text(
                'Item $index',
                style: TextTheme.of(context).headlineSmall,
              ),
            );
          }),
        ),
      ),
    );
  }
}

1.3、不同列表项的列表

dart 复制代码

import 'package:flutter/material.dart';

void main() {
  runApp(
    MyApp(
      items: List<ListItem>.generate(
        1000,
        (i) =>
            i % 6 == 0
                ? HeadingItem('Heading $i')
                : MessageItem('Sender $i', 'Message body $i'),
      ),
    ),
  );
}

class MyApp extends StatelessWidget {
  final List<ListItem> items;

  const MyApp({super.key, required this.items});

  @override
  Widget build(BuildContext context) {
    const title = 'Mixed List';

    return MaterialApp(
      title: title,
      home: Scaffold(
        appBar: AppBar(title: const Text(title)),
        body: ListView.builder(
          // Let the ListView know how many items it needs to build.
          itemCount: items.length,
          // Provide a builder function. This is where the magic happens.
          // Convert each item into a widget based on the type of item it is.
          itemBuilder: (context, index) {
            final item = items[index];

            return ListTile(
              title: item.buildTitle(context),
              subtitle: item.buildSubtitle(context),
            );
          },
        ),
      ),
    );
  }
}

/// The base class for the different types of items the list can contain.
abstract class ListItem {
  /// The title line to show in a list item.
  Widget buildTitle(BuildContext context);

  /// The subtitle line, if any, to show in a list item.
  Widget buildSubtitle(BuildContext context);
}

/// A ListItem that contains data to display a heading.
class HeadingItem implements ListItem {
  final String heading;

  HeadingItem(this.heading);

  @override
  Widget buildTitle(BuildContext context) {
    return Text(heading, style: Theme.of(context).textTheme.headlineSmall);
  }

  @override
  Widget buildSubtitle(BuildContext context) => const SizedBox.shrink();
}

/// A ListItem that contains data to display a message.
class MessageItem implements ListItem {
  final String sender;
  final String body;

  MessageItem(this.sender, this.body);

  @override
  Widget buildTitle(BuildContext context) => Text(sender);

  @override
  Widget buildSubtitle(BuildContext context) => Text(body);
}

1.4、包含间隔的列表

dart 复制代码

import 'package:flutter/material.dart';

void main() => runApp(const SpacedItemsList());

class SpacedItemsList extends StatelessWidget {
  const SpacedItemsList({super.key});

  @override
  Widget build(BuildContext context) {
    const items = 4;

    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        cardTheme: CardTheme(color: Colors.blue.shade50),
      ),
      home: Scaffold(
        body: LayoutBuilder(
          builder: (context, constraints) {
            return SingleChildScrollView(
              child: ConstrainedBox(
                constraints: BoxConstraints(minHeight: constraints.maxHeight),
                child: Column(
                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
                  crossAxisAlignment: CrossAxisAlignment.stretch,
                  children: List.generate(
                    items,
                    (index) => ItemWidget(text: 'Item $index'),
                  ),
                ),
              ),
            );
          },
        ),
      ),
    );
  }
}

class ItemWidget extends StatelessWidget {
  const ItemWidget({super.key, required this.text});

  final String text;

  @override
  Widget build(BuildContext context) {
    return Card(child: SizedBox(height: 100, child: Center(child: Text(text))));
  }
}

1.6、长列表

dart 复制代码

import 'package:flutter/material.dart';

void main() {
  runApp(
    MyApp(
      items: List<String>.generate(10000, (i) => 'Item $i'),
    ),
  );
}

class MyApp extends StatelessWidget {
  final List<String> items;

  const MyApp({super.key, required this.items});

  @override
  Widget build(BuildContext context) {
    const title = 'Long List';

    return MaterialApp(
      title: title,
      home: Scaffold(
        appBar: AppBar(title: const Text(title)),
        body: ListView.builder(
          itemCount: items.length,
          prototypeItem: ListTile(title: Text(items.first)),
          itemBuilder: (context, index) {
            return ListTile(title: Text(items[index]));
          },
        ),
      ),
    );
  }
}

2、滚动

2.1、浮动的顶栏

dart 复制代码

import 'package:flutter/material.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    const title = 'Floating App Bar';

    return MaterialApp(
      title: title,
      home: Scaffold(
        // No appbar provided to the Scaffold, only a body with a
        // CustomScrollView.
        body: CustomScrollView(
          slivers: [
            // Add the app bar to the CustomScrollView.
            const SliverAppBar(
              // Provide a standard title.
              title: Text(title),
              // Allows the user to reveal the app bar if they begin scrolling
              // back up the list of items.
              floating: true,
              // Display a placeholder widget to visualize the shrinking size.
              flexibleSpace: Placeholder(),
              // Make the initial height of the SliverAppBar larger than normal.
              expandedHeight: 200,
            ),
            // Next, create a SliverList
            SliverList(
              // Use a delegate to build items as they're scrolled on screen.
              delegate: SliverChildBuilderDelegate(
                // The builder function returns a ListTile with a title that
                // displays the index of the current item.
                (context, index) => ListTile(title: Text('Item #$index')),
                // Builds 1000 ListTiles
                childCount: 1000,
              ),
            ),
          ],
        ),
      ),
    );
  }
}

2.2、平衡错位滚动

dart 复制代码

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

const Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
      debugShowCheckedModeBanner: false,
      home: const Scaffold(body: Center(child: ExampleParallax())),
    );
  }
}

class ExampleParallax extends StatelessWidget {
  const ExampleParallax({super.key});

  @override
  Widget build(BuildContext context) {
    return SingleChildScrollView(
      child: Column(
        children: [
          for (final location in locations)
            LocationListItem(
              imageUrl: location.imageUrl,
              name: location.name,
              country: location.place,
            ),
        ],
      ),
    );
  }
}

class LocationListItem extends StatelessWidget {
  LocationListItem({
    super.key,
    required this.imageUrl,
    required this.name,
    required this.country,
  });

  final String imageUrl;
  final String name;
  final String country;
  final GlobalKey _backgroundImageKey = GlobalKey();

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 16),
      child: AspectRatio(
        aspectRatio: 16 / 9,
        child: ClipRRect(
          borderRadius: BorderRadius.circular(16),
          child: Stack(
            children: [
              _buildParallaxBackground(context),
              _buildGradient(),
              _buildTitleAndSubtitle(),
            ],
          ),
        ),
      ),
    );
  }

  Widget _buildParallaxBackground(BuildContext context) {
    return Flow(
      delegate: ParallaxFlowDelegate(
        scrollable: Scrollable.of(context),
        listItemContext: context,
        backgroundImageKey: _backgroundImageKey,
      ),
      children: [
        Image.network(imageUrl, key: _backgroundImageKey, fit: BoxFit.cover),
      ],
    );
  }

  Widget _buildGradient() {
    return Positioned.fill(
      child: DecoratedBox(
        decoration: BoxDecoration(
          gradient: LinearGradient(
            colors: [Colors.transparent, Colors.black.withValues(alpha: 0.7)],
            begin: Alignment.topCenter,
            end: Alignment.bottomCenter,
            stops: const [0.6, 0.95],
          ),
        ),
      ),
    );
  }

  Widget _buildTitleAndSubtitle() {
    return Positioned(
      left: 20,
      bottom: 20,
      child: Column(
        mainAxisSize: MainAxisSize.min,
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Text(
            name,
            style: const TextStyle(
              color: Colors.white,
              fontSize: 20,
              fontWeight: FontWeight.bold,
            ),
          ),
          Text(
            country,
            style: const TextStyle(color: Colors.white, fontSize: 14),
          ),
        ],
      ),
    );
  }
}

class ParallaxFlowDelegate extends FlowDelegate {
  ParallaxFlowDelegate({
    required this.scrollable,
    required this.listItemContext,
    required this.backgroundImageKey,
  }) : super(repaint: scrollable.position);


  final ScrollableState scrollable;
  final BuildContext listItemContext;
  final GlobalKey backgroundImageKey;

  @override
  BoxConstraints getConstraintsForChild(int i, BoxConstraints constraints) {
    return BoxConstraints.tightFor(width: constraints.maxWidth);
  }

  @override
  void paintChildren(FlowPaintingContext context) {
    // Calculate the position of this list item within the viewport.
    final scrollableBox = scrollable.context.findRenderObject() as RenderBox;
    final listItemBox = listItemContext.findRenderObject() as RenderBox;
    final listItemOffset = listItemBox.localToGlobal(
      listItemBox.size.centerLeft(Offset.zero),
      ancestor: scrollableBox,
    );

    // Determine the percent position of this list item within the
    // scrollable area.
    final viewportDimension = scrollable.position.viewportDimension;
    final scrollFraction = (listItemOffset.dy / viewportDimension).clamp(
      0.0,
      1.0,
    );

    // Calculate the vertical alignment of the background
    // based on the scroll percent.
    final verticalAlignment = Alignment(0.0, scrollFraction * 2 - 1);

    // Convert the background alignment into a pixel offset for
    // painting purposes.
    final backgroundSize =
        (backgroundImageKey.currentContext!.findRenderObject() as RenderBox)
            .size;
    final listItemSize = context.size;
    final childRect = verticalAlignment.inscribe(
      backgroundSize,
      Offset.zero & listItemSize,
    );

    // Paint the background.
    context.paintChild(
      0,
      transform:
          Transform.translate(offset: Offset(0.0, childRect.top)).transform,
    );
  }

  @override
  bool shouldRepaint(ParallaxFlowDelegate oldDelegate) {
    return scrollable != oldDelegate.scrollable ||
        listItemContext != oldDelegate.listItemContext ||
        backgroundImageKey != oldDelegate.backgroundImageKey;
  }

}

class Parallax extends SingleChildRenderObjectWidget {
  const Parallax({super.key, required Widget background})
    : super(child: background);

  @override
  RenderObject createRenderObject(BuildContext context) {
    return RenderParallax(scrollable: Scrollable.of(context));
  }

  @override
  void updateRenderObject(
    BuildContext context,
    covariant RenderParallax renderObject,
  ) {
    renderObject.scrollable = Scrollable.of(context);
  }
}

class ParallaxParentData extends ContainerBoxParentData<RenderBox> {}

class RenderParallax extends RenderBox
    with RenderObjectWithChildMixin<RenderBox>, RenderProxyBoxMixin {
  RenderParallax({required ScrollableState scrollable})
    : _scrollable = scrollable;

  ScrollableState _scrollable;

  ScrollableState get scrollable => _scrollable;

  set scrollable(ScrollableState value) {
    if (value != _scrollable) {
      if (attached) {
        _scrollable.position.removeListener(markNeedsLayout);
      }
      _scrollable = value;
      if (attached) {
        _scrollable.position.addListener(markNeedsLayout);
      }
    }
  }

  @override
  void attach(covariant PipelineOwner owner) {
    super.attach(owner);
    _scrollable.position.addListener(markNeedsLayout);
  }

  @override
  void detach() {
    _scrollable.position.removeListener(markNeedsLayout);
    super.detach();
  }

  @override
  void setupParentData(covariant RenderObject child) {
    if (child.parentData is! ParallaxParentData) {
      child.parentData = ParallaxParentData();
    }
  }

  @override
  void performLayout() {
    size = constraints.biggest;

    // Force the background to take up all available width
    // and then scale its height based on the image's aspect ratio.
    final background = child!;
    final backgroundImageConstraints = BoxConstraints.tightFor(
      width: size.width,
    );
    background.layout(backgroundImageConstraints, parentUsesSize: true);

    // Set the background's local offset, which is zero.
    (background.parentData as ParallaxParentData).offset = Offset.zero;
  }

  @override
  void paint(PaintingContext context, Offset offset) {
    // Get the size of the scrollable area.
    final viewportDimension = scrollable.position.viewportDimension;

    // Calculate the global position of this list item.
    final scrollableBox = scrollable.context.findRenderObject() as RenderBox;
    final backgroundOffset = localToGlobal(
      size.centerLeft(Offset.zero),
      ancestor: scrollableBox,
    );

    // Determine the percent position of this list item within the
    // scrollable area.
    final scrollFraction = (backgroundOffset.dy / viewportDimension).clamp(
      0.0,
      1.0,
    );

    // Calculate the vertical alignment of the background
    // based on the scroll percent.
    final verticalAlignment = Alignment(0.0, scrollFraction * 2 - 1);

    // Convert the background alignment into a pixel offset for
    // painting purposes.
    final background = child!;
    final backgroundSize = background.size;
    final listItemSize = size;
    final childRect = verticalAlignment.inscribe(
      backgroundSize,
      Offset.zero & listItemSize,
    );

    // Paint the background.
    context.paintChild(
      background,
      (background.parentData as ParallaxParentData).offset +
          offset +
          Offset(0.0, childRect.top),
    );
  }
}

class Location {
  const Location({
    required this.name,
    required this.place,
    required this.imageUrl,
  });

  final String name;
  final String place;
  final String imageUrl;
}

const urlPrefix =
    'https://docs.flutter.dev/cookbook/img-files/effects/parallax';
const locations = [
  Location(
    name: 'Mount Rushmore',
    place: 'U.S.A',
    imageUrl: '$urlPrefix/01-mount-rushmore.jpg',
  ),
  Location(
    name: 'Gardens By The Bay',
    place: 'Singapore',
    imageUrl: '$urlPrefix/02-singapore.jpg',
  ),
  Location(
    name: 'Machu Picchu',
    place: 'Peru',
    imageUrl: '$urlPrefix/03-machu-picchu.jpg',
  ),
  Location(
    name: 'Vitznau',
    place: 'Switzerland',
    imageUrl: '$urlPrefix/04-vitznau.jpg',
  ),
  Location(
    name: 'Bali',
    place: 'Indonesia',
    imageUrl: '$urlPrefix/05-bali.jpg',
  ),
  Location(
    name: 'Mexico City',
    place: 'Mexico',
    imageUrl: '$urlPrefix/06-mexico-city.jpg',
  ),
  Location(name: 'Cairo', place: 'Egypt', imageUrl: '$urlPrefix/07-cairo.jpg'),
];

Flutter之页面布局二

目录：

1、列表布局

1.1、基础列表

1.2、水平滑动的列表

1.3、网格列表

1.3、不同列表项的列表

1.4、包含间隔的列表

1.6、长列表

2、滚动

2.1、浮动的顶栏

2.2、平衡错位滚动