Flutter学习（四）

手势处理
GestureDetector Class

void main() => runApp(MaterialApp(
      title: "手势处理示例",
      home: MyApp(),
    ));

class MyButton extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return new GestureDetector(
      onTap: () {
        final snackBar = new SnackBar(content: new Text("按钮被按下"));
        Scaffold.of(context).showSnackBar(snackBar);
      },
      child: new Container(
        decoration: new BoxDecoration(
            color: Theme.of(context).buttonColor,
            borderRadius: new BorderRadius.circular(10)),
        child: new Text("测试按钮"),
      ),
    );
  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("手势处理示例"),
        ),
        body: new Center(child: new MyButton()));
  }
}

运行效果：

滑动删除手势
DIsmissible class

void main() => runApp(MaterialApp(
      title: "滑动删除手势处理示例",
      home: MyApp(),
    ));

class MyApp extends StatelessWidget {
  final List<String> items =
      new List<String>.generate(30, (i) => "列表项${i + 1}");

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("滑动删除手势处理示例"),
        ),
        body: new ListView.builder(
            itemCount: items.length,
            itemBuilder: (context, index) {
              final item = items[index];
              return new Dismissible(
                  key: new Key(item),
                  onDismissed: (direction) {
                    items.removeAt(index);
                    Scaffold.of(context).showSnackBar(
                        new SnackBar(content: new Text("$item 被删除了")));
                  },
                  child: new ListTile(
                    title: new Text('$item'),
                  ));
            }));
  }
}

运行效果：

图片资源和字体资源

  child: Image.asset(
                  "images/2.jpg",
                  scale: 1,
                ),

自定义字体

void main() => runApp(MaterialApp(
      title: "自定义字体",
      home: MyApp(),
    ));

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("自定义字体"),
        ),
        body: new Center(
          child: new Text(
            "自定义字体",
            style: new TextStyle(fontFamily: 'myfont', fontSize: 20),
          ),
        ));
  }
}

运行效果：

工程的资源配置文件，要注意格式，在放开某项资源注释后，注意删除资源类别前的空格，否则会包如下错误：

页面跳转
MaterialPageRoute < T > class
压栈方法 Navigator.push
出栈方法 Navigator.pop
构建目标页面 MaterialPageRoute

void main() => runApp(MaterialApp(
      title: "导航页面示例",
      home: FirstScreen(),
    ));

class FirstScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("导航页面示例"),
        ),
        body: new Center(
            child: new RaisedButton(
                child: new Text("打开商品详情页面"),
                onPressed: () {
                  Navigator.push(
                      context,
                      new MaterialPageRoute(
                          builder: (context) => new SecondScreen()));
                })));
  }
}

class SecondScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return new Scaffold(
      appBar: new AppBar(title: new Text("宝宝尿不湿")),
      body: new Center(
        child: new RaisedButton(
          onPressed: () {
            Navigator.pop(context);
          },
          child: new Text("返回页面"),
        ),
      ),
    );
  }
}

运行效果：

页面跳转发送数据

class Product {
  final String title;
  final String description;

  Product(this.title, this.description);
}

void main() => runApp(MaterialApp(
    title: "页面跳转发送数据示例",
    home: new ProductList(
        products: new List.generate(
            20, (i) => new Product('商品 $i', '这是一个商品详情 $i')))));

class ProductList extends StatelessWidget {
  final List<Product> products;

  ProductList({Key key, @required this.products}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('商品列表'),
      ),
      body: new ListView.builder(
          itemCount: products.length,
          itemBuilder: (context, index) {
            return new ListTile(
              title: new Text(products[index].title),
              onTap: () {
                Navigator.push(
                    context,
                    new MaterialPageRoute(
                        builder: (context) =>
                            new ProductDetail(product: products[index])));
              },
            );
          }),
    );
  }
}

class ProductDetail extends StatelessWidget {
  final Product product;

  ProductDetail({Key key, @required this.product}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return new Scaffold(
      appBar: AppBar(
        title: new Text("${product.title}"),
      ),
      body: new Padding(
        padding: new EdgeInsets.all(10),
        child: new Text('${product.description}'),
      ),
    );
  }
}

运行效果：

页面跳转返回数据

void main() => runApp(MaterialApp(title: "页面跳转返回数据示例", home: FirstPage()));

class FirstPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return new Scaffold(
        appBar: new AppBar(
          title: new Text('页面跳转返回数据示例'),
        ),
        body: new Center(
          child: new RouteButton(),
        ));
  }
}

class RouteButton extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return new RaisedButton(
      onPressed: () {
        _navigateToScreenPage(context);
      },
      child: new Text('选择一个选项，任意选项'),
    );
  }

  _navigateToScreenPage(BuildContext context) async {
    final result = await Navigator.push(
        context, new MaterialPageRoute(builder: (context) => new SecondPage()));
    Scaffold.of(context)
        .showSnackBar(new SnackBar(content: new Text('$result')));
  }
}

class SecondPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return new Scaffold(
        appBar: new AppBar(
          title: new Text('选择一条数据'),
        ),
        body: new Center(
            child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            new Padding(
              padding: const EdgeInsets.all(8.0),
              child: new RaisedButton(
                onPressed: () {
                  Navigator.pop(context, 'ooooo');
                },
                child: new Text('ooooo'),
              ),
            ),
            new Padding(
              padding: const EdgeInsets.all(8.0),
              child: new RaisedButton(
                onPressed: () {
                  Navigator.pop(context, 'fffff');
                },
                child: new Text('fffff'),
              ),
            ),
          ],
        )));
  }
}

运行效果：

页面跳转动画
hero class

void main() => runApp(MaterialApp(title: "页面切换动画", home: FirstPage()));

class FirstPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: new AppBar(
          title: new Text('页面切换动画'),
        ),
        body: new GestureDetector(
          child: new Center(
            child: new Hero(
                tag: '第一张图片',
                child: new Image.asset(
                  "images/2.jpg",
                  scale: 1,
                )),
          ),
          onTap: () {
            Navigator.push(context, new MaterialPageRoute(builder: (_) {
              return new SecondPage();
            }));
          },
        ));
  }
}

class SecondPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: new AppBar(
          title: new Text('第二张图片'),
        ),
        body: new GestureDetector(
          child: new Center(
            child: new Hero(
                tag: "第二张图片",
                child: new Image.asset(
                  'images/7.jpg',
                  scale: 1,
                )),
          ),
          onTap: () {
            Navigator.pop(context);
          },
        ));
  }
}

运行效果：

动画

AnimatedOpacity class

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final appTitle = "flutter 动画详解";
    return new MaterialApp(
      title: appTitle,
      home: new MyHomePage(title: appTitle),
    );
  }
}

class MyHomePage extends StatefulWidget {
  final String title;

  MyHomePage({Key key, this.title}) : super(key: key);

  @override
  State<StatefulWidget> createState() {
    return new _MyHomePageState();
  }
}

class _MyHomePageState extends State<MyHomePage> {
  bool _visible = true;

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return new Scaffold(
      appBar: new AppBar(
        title: new Text(widget.title),
      ),
      body: new Center(
        child: new AnimatedOpacity(
          opacity: _visible ? 1.0 : 0.0,
          duration: new Duration(milliseconds: 500),
          child: new Container(
            width: 300,
            height: 300,
            color: Colors.deepOrange,
          ),
        ),
      ),
      floatingActionButton: new FloatingActionButton(
        onPressed: () {
          setState(() {
            _visible = !_visible;
          });
        },
        tooltip: '显示隐藏',
        child: new Icon(Icons.adb),
      ),
    );
  }
}

运行效果：