view_demo.dart

import 'package:flutter/material.dart';
import 'package:pro_flutter/demo/model/post.dart';

class ViewDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return GridViewBuildDemo();
  }
}

class GridViewBuildDemo extends StatelessWidget {
  Widget _gridItemBuilder(BuildContext context, int index) {
    return Container(
      child: Image.network(
        posts[index].imageUrl,
        fit: BoxFit.cover,
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return GridView.builder(
      padding: EdgeInsets.all(8.0),
      itemCount: posts.length,
      itemBuilder: _gridItemBuilder,
      gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
        crossAxisCount: 3,
        crossAxisSpacing: 8.0,
        mainAxisSpacing: 8.0,
      ),
    );
  }
}

class GridViewExtentDemo extends StatelessWidget {
  List<Widget> _buildTiles(int length) {
    return List.generate(length, (int index) {
      return Container(
        color: Colors.grey,
        alignment: Alignment(0.0, 0.0),
        child: Text(
          'item ${index + 1}',
          style: TextStyle(fontSize: 20.0, color: Colors.grey[100]),
        ),
      );
    });
  }

  @override
  Widget build(BuildContext context) {
    return GridView.extent(
      maxCrossAxisExtent: 160.0,
      crossAxisSpacing: 8.0,
      mainAxisSpacing: 8.0,
      children: _buildTiles(50),
    );
  }
}

class GridViewCountDemo extends StatelessWidget {
  List<Widget> _buildTiles(int length) {
    return List.generate(length, (int index) {
      return Container(
        color: Colors.grey,
        alignment: Alignment(0.0, 0.0),
        child: Text(
          'item ${index + 1}',
          style: TextStyle(fontSize: 20.0, color: Colors.grey[100]),
        ),
      );
    });
  }

  @override
  Widget build(BuildContext context) {
    return GridView.count(
      crossAxisCount: 3,
      crossAxisSpacing: 8.0,
      mainAxisSpacing: 8.0,
      children: _buildTiles(50),
    );
  }
}

class PageBuildViewDemo extends StatelessWidget {
  Widget _pageItemBuilder(BuildContext context, int index) {
    return Stack(
      children: <Widget>[
        SizedBox.expand(
          child: Image.network(
            posts[index].imageUrl,
            fit: BoxFit.cover,
          ),
        ),
        Positioned(
          bottom: 20.0,
          left: 20.0,
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.start,
            children: <Widget>[
              Text(
                posts[index].title,
                style: TextStyle(fontWeight: FontWeight.bold),
              ),
              Text(
                posts[index].author,
                style: TextStyle(fontWeight: FontWeight.w100),
              ),
            ],
          ),
        ),
      ],
    );
  }

  @override
  Widget build(BuildContext context) {
    return PageView.builder(
      itemCount: posts.length,
      itemBuilder: _pageItemBuilder,
    );
  }
}

class PageViewDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return PageView(
      // pageSnapping: false,
      // scrollDirection: Axis.vertical,
      onPageChanged: (currentPage) => debugPrint('$currentPage'),
      controller: PageController(
        initialPage: 1,
        keepPage: false,
        viewportFraction: 0.85,
      ),
      children: <Widget>[
        Container(
          color: Colors.amberAccent[100],
          alignment: Alignment(0.0, 0.0),
          child: Text(
            'One',
            style: TextStyle(fontSize: 23.0, color: Colors.black),
          ),
        ),
        Container(
          color: Colors.blueAccent[100],
          alignment: Alignment(0.0, 0.0),
          child: Text(
            'Two',
            style: TextStyle(fontSize: 23.0, color: Colors.black),
          ),
        ),
        Container(
          color: Colors.blueGrey[100],
          alignment: Alignment(0.0, 0.0),
          child: Text(
            'Three',
            style: TextStyle(fontSize: 23.0, color: Colors.black),
          ),
        ),
      ],
    );
  }
}