Flutter第六期 - ListView+GridView混合

    列表是APP的核心功能,目前這個庫不算完善,以後國外的大神應該會補全,現在的樣式就是很基礎的東西,解決一些常用的加載,至於後面的自定義tag需要一個過程,混合佈局可以參考flutter_staggered_grid_view,下面是基礎的寫法:

import 'package:flutter/material.dart';

void main() => runApp(new MyApp());

//Stateless widgets 是不可變的, 這意味着它們的屬性不能改變 - 所有的值都是最終的.
//Stateful widgets 持有的狀態可能在widget生命週期中發生變化. 實現一個 stateful widget 至少需要兩個類:

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
//    final wordPair = new WordPair.random();
    return new MaterialApp(
      title: 'ListView3+GridView33',
      debugShowCheckedModeBanner: false,
      theme: new ThemeData(
        primarySwatch: Colors.blue,
//        fontFamily: 'fontdemo1'
      ),
      home: new Scaffold(
        appBar: new AppBar(
          title: new Text('圖片加載'),
        ),
        body: new Center(
//          child: new ListView(
//            shrinkWrap: true,
//            padding: const EdgeInsets.all(20.0),
//            children: <Widget>[
//              const Text('I\'m dedicating every day to you'),
//              const Text('Domestic life was never quite my style'),
//              const Text('When you smile, you knock me out, I fall apart'),
//              const Text('And I thought I was so smart'),
//            ],
//          ),
//          child: new ListView3(),
//          child: new GridView3(),
//          child: new GridView33(),
          child: new InfiniteGridView(),
        ),
      ),
    );
  }
}

class ListView3 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    //下劃線widget預定義以供複用。
    Widget divider1 = Divider(
      color: Colors.blue,
    );
    Widget divider2 = Divider(color: Colors.green);
    return ListView.separated(
      itemCount: 100,
      //列表項構造器
      itemBuilder: (BuildContext context, int index) {
        return ListTile(title: Text("$index"));
      },
      //分割器構造器
      separatorBuilder: (BuildContext context, int index) {
        return index % 2 == 0 ? divider1 : divider2;
      },
    );
  }
}

class GridView3 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return GridView(
        gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
          crossAxisCount: 3, //橫軸三個子widget
          childAspectRatio: 1.0, //寬高比爲1時,子widget
        ),
        children: <Widget>[
          Icon(Icons.ac_unit),
          Icon(Icons.airport_shuttle),
          Icon(Icons.all_inclusive),
          Icon(Icons.beach_access),
          Icon(Icons.cake),
          Icon(Icons.free_breakfast)
        ]);
  }
}

class GridView33 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return GridView(
      padding: EdgeInsets.zero,
      gridDelegate: SliverGridDelegateWithMaxCrossAxisExtent(
        maxCrossAxisExtent: 120.0, childAspectRatio: 2.0, //寬高比爲2
      ),
      children: <Widget>[
        Icon(Icons.ac_unit),
        Icon(Icons.airport_shuttle),
        Icon(Icons.all_inclusive),
        Icon(Icons.beach_access),
        Icon(Icons.cake),
        Icon(Icons.free_breakfast),
      ],
    );
  }
}

class InfiniteGridView extends StatefulWidget {
  @override
  _InfiniteGridViewState createState() => new _InfiniteGridViewState();
}

class _InfiniteGridViewState extends State<InfiniteGridView> {

  List<IconData> _icons = []; //保存Icon數據

  @override
  void initState() {
    // 初始化數據
    _retrieveIcons();
  }

  @override
  Widget build(BuildContext context) {
    return GridView.builder(
        gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
            crossAxisCount: 3, //每行三列
            childAspectRatio: 1.0 //顯示區域寬高相等
        ),
        itemCount: _icons.length,
        itemBuilder: (context, index) {
          //如果顯示到最後一個並且Icon總數小於200時繼續獲取數據
          if (index == _icons.length - 1 && _icons.length < 200) {
            _retrieveIcons();
          }
          return Icon(_icons[index]);
        }
    );
  }

  //模擬異步獲取數據
  void _retrieveIcons() {
    Future.delayed(Duration(milliseconds: 200)).then((e) {
      setState(() {
        _icons.addAll([
          Icons.ac_unit,
          Icons.airport_shuttle,
          Icons.all_inclusive,
          Icons.beach_access, Icons.cake,
          Icons.free_breakfast
        ]);
      });
    });
  }
}


    blob.png blob.png

    ListView+GridView圖文混合:

import 'package:flutter/material.dart';

void main() => runApp(new MyApp());

//Stateless widgets 是不可變的, 這意味着它們的屬性不能改變 - 所有的值都是最終的.
//Stateful widgets 持有的狀態可能在widget生命週期中發生變化. 實現一個 stateful widget 至少需要兩個類:

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
//    final wordPair = new WordPair.random();
    return new MaterialApp(
      title: 'ListView+GridView綜合佈局',
      debugShowCheckedModeBanner: false,
      theme: new ThemeData(
        primarySwatch: Colors.blue,
//        fontFamily: 'fontdemo1'
      ),
      home: new Scaffold(
//        appBar: new AppBar(
////          title: new Text('圖片加載'),
////        ),
        body: new Center(
//          child: new ListView(
//            shrinkWrap: true,
//            padding: const EdgeInsets.all(20.0),
//            children: <Widget>[
//              const Text('I\'m dedicating every day to you'),
//              const Text('Domestic life was never quite my style'),
//              const Text('When you smile, you knock me out, I fall apart'),
//              const Text('And I thought I was so smart'),
//            ],
//          ),
//          child: new ListView3(),
//          child: new GridView3(),
//          child: new GridView33(),
          child: new CustomScrollViewTestRoute(),
        ),
      ),
    );
  }
}

class CustomScrollViewTestRoute extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    //因爲本路由沒有使用Scaffold,爲了讓子級Widget(如Text)使用
    //Material Design 默認的樣式風格,我們使用Material作爲本路由的根。
    return Material(
      child: CustomScrollView(
        slivers: <Widget>[
          //AppBar,包含一個導航欄
          SliverAppBar(
            //標題居中
            centerTitle: true,
            leading: Builder(builder: (context) {
              return IconButton(
                icon: Icon(Icons.arrow_back, color: Colors.white), //自定義圖標
                onPressed: () {
                  //
                },
              );
            }),
//            leading: Icon(
//              Icons.arrow_back,
//            ),
            //展開高度250
            expandedHeight: 250.0,
            //不隨着滑動隱藏標題
            floating: false,
            //固定在頂部
            pinned: true,
            flexibleSpace: FlexibleSpaceBar(
              title: const Text('YUN'),
              background: Image.asset(
                "assets/images/food04.jpeg",
                fit: BoxFit.cover,
              ),
            ),
          ),

          SliverPadding(
            padding: const EdgeInsets.all(8.0),
            sliver: new SliverGrid(
              //Grid
              gridDelegate: new SliverGridDelegateWithFixedCrossAxisCount(
                crossAxisCount: 2, //Grid按兩列顯示
                mainAxisSpacing: 10.0,
                crossAxisSpacing: 10.0,
                childAspectRatio: 4.0,
              ),
              delegate: new SliverChildBuilderDelegate(
                (BuildContext context, int index) {
                  //創建子widget
                  return new Container(
                    alignment: Alignment.center,
                    color: Colors.cyan[100 * (index % 9)],
                    child: new Text('grid item $index'),
                  );
                },
                childCount: 20,
              ),
            ),
          ),
          //List
          new SliverFixedExtentList(
            itemExtent: 50.0,
            delegate: new SliverChildBuilderDelegate(
                (BuildContext context, int index) {
              //創建列表項
              return new Container(
                alignment: Alignment.center,
                color: Colors.lightBlue[100 * (index % 9)],
                child: new Text('list item $index'),
              );
            }, childCount: 50 //50個列表項
                ),
          ),
        ],
      ),
    );
  }
}

    blob.png

    

    blob.png

    滾動監聽及控制:

import 'package:flutter/material.dart';

void main() => runApp(new MyApp());

//Stateless widgets 是不可變的, 這意味着它們的屬性不能改變 - 所有的值都是最終的.
//Stateful widgets 持有的狀態可能在widget生命週期中發生變化. 實現一個 stateful widget 至少需要兩個類:

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
//    final wordPair = new WordPair.random();
    return new MaterialApp(
      title: '滾動監聽及控制',
      debugShowCheckedModeBanner: false,
      theme: new ThemeData(
        primarySwatch: Colors.blue,
//        fontFamily: 'fontdemo1'
      ),
      home: new Scaffold(
        appBar: new AppBar(
          title: new Text('滾動監聽及控制'),
        ),
        body: new Center(
//          child: new ListView(
//            shrinkWrap: true,
//            padding: const EdgeInsets.all(20.0),
//            children: <Widget>[
//              const Text('I\'m dedicating every day to you'),
//              const Text('Domestic life was never quite my style'),
//              const Text('When you smile, you knock me out, I fall apart'),
//              const Text('And I thought I was so smart'),
//            ],
//          ),
//          child: new ListView3(),
//          child: new GridView3(),
//          child: new GridView33(),
          child: new ScrollControllerTestRoute(),
//          child: new ScrollNotificationTestRoute(),
        ),
      ),
    );
  }
}

class ScrollControllerTestRoute extends StatefulWidget {
  @override
  ScrollControllerTestRouteState createState() {
    return new ScrollControllerTestRouteState();
  }
}

class ScrollControllerTestRouteState extends State<ScrollControllerTestRoute> {
  ScrollController _controller = new ScrollController();
  bool showToTopBtn = false; //是否顯示“返回到頂部”按鈕

  @override
  void initState() {
    //監聽滾動事件,打印滾動位置
    _controller.addListener(() {
      print(_controller.offset); //打印滾動位置
      if (_controller.offset < 1000 && showToTopBtn) {
        setState(() {
          showToTopBtn = false;
        });
      } else if (_controller.offset >= 1000 && showToTopBtn == false) {
        setState(() {
          showToTopBtn = true;
        });
      }
    });
  }

  @override
  void dispose() {
    //爲了避免內存泄露,需要調用_controller.dispose
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
//      appBar: AppBar(title: Text("滾動控制")),
      body: Scrollbar(
        child: ListView.builder(
            itemCount: 100,
            itemExtent: 50.0, //列表項高度固定時,顯式指定高度是一個好習慣(性能消耗小)
            controller: _controller,
            itemBuilder: (context, index) {
              return ListTile(
                title: Text("$index"),
              );
            }),
      ),
      floatingActionButton: !showToTopBtn
          ? null
          : FloatingActionButton(
              child: Icon(Icons.arrow_upward),
              onPressed: () {
                //返回到頂部時執行動畫
                _controller.animateTo(.0,
                    duration: Duration(milliseconds: 200), curve: Curves.ease);
              }),
    );
  }
}

class ScrollNotificationTestRoute extends StatefulWidget {
  @override
  _ScrollNotificationTestRouteState createState() =>
      new _ScrollNotificationTestRouteState();
}

class _ScrollNotificationTestRouteState
    extends State<ScrollNotificationTestRoute> {
  String _progress = "0%"; //保存進度百分比

  @override
  Widget build(BuildContext context) {
    return Scrollbar(
      //進度條
      // 監聽滾動通知
      child: NotificationListener<ScrollNotification>(
        onNotification: (ScrollNotification notification) {
          double progress = notification.metrics.pixels /
              notification.metrics.maxScrollExtent;
          //重新構建
          setState(() {
            _progress = "${(progress * 100).toInt()}%";
          });
          print("BottomEdge: ${notification.metrics.extentAfter == 0}");
          //return true; //放開此行註釋後,進度條將失效
        },
        child: Stack(
          alignment: Alignment.center,
          children: <Widget>[
            ListView.builder(
                itemCount: 100,
                itemExtent: 50.0,
                itemBuilder: (context, index) {
                  return ListTile(title: Text("$index"));
                }),
            CircleAvatar(
              //顯示進度百分比
              radius: 30.0,
              child: Text(_progress),
              backgroundColor: Colors.black54,
            )
          ],
        ),
      ),
    );
  }
}

    blob.png

    總結:學完網絡請求,大家把tolist裏面改寫就可以獨立出來不同的樣式去加載數據,還是挺方便的,代碼精簡不少~加油~

    scc.jpg



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