Flutter学习(7)Stack组件

一.Stack组件

• demo

  class LayoutDemo extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return Stack(children: <Widget>[
        Container(
          height: 400,
          width: 300,
          color: Colors.red,
        ),
        Text("如果不是Stack组件,那么这行文本应该显示在Container的下面")
      ]);
    }
  }
  

  • 效果

    

  • 再往上堆叠一些东西

    比如文本

    import 'package:flutter/material.dart';
    
    void main() => runApp(MyApp());
    
    class MyApp extends StatelessWidget {
      const MyApp({Key? key}) : super(key: key);
    
      @override
      Widget build(BuildContext context) {
        return MaterialApp(
            home: Scaffold(
          appBar: AppBar(title: Text('FlutterDemo')),
          body: LayoutDemo(),
        ));
      }
    }
    
    class LayoutDemo extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        return Stack(children: <Widget>[
          Container(
            height: 400,
            width: 300,
            color: Colors.red,
          ),
          Text("如果不是Stack组件,那么这行文本应该显示在Container的下面"),
          Text("文本堆在文本上面")
        ]);
      }
    }
    
    

    

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
      appBar: AppBar(title: Text('FlutterDemo')),
      body: LayoutDemo(),
    ));
  }
}

class LayoutDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
      child: Stack(
        alignment: Alignment.center,
        children: <Widget>[
          Container(
            height: 400,
            width: 300,
            color: Colors.red,
          ),
          Text('我是一个文本', style: TextStyle(fontSize: 40, color: Colors.white))
        ],
      ),
    );
  }
}

• 如果把Text和Container的顺序换一下，Text就被盖住了

  class LayoutDemo extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return Center(
        child: Stack(
          alignment: Alignment.center,
          children: <Widget>[
            Text('我是一个文本', style: TextStyle(fontSize: 40, color: Colors.white)),
            Container(
              height: 400,
              width: 300,
              color: Colors.red,
            ),
          ],
        ),
      );
    }
  }
  

  

• Text恢复回去

  修改Alignment为alignment: Alignment.bottomLeft,效果如下

  

Alignment指定参数

• 使用Alignment的构造函数

  class LayoutDemo extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return Center(
        child: Stack(
          alignment: Alignment(0, 0),
          children: <Widget>[
            Container(
              height: 400,
              width: 300,
              color: Colors.red,
            ),
            Text('我是一个文本', style: TextStyle(fontSize: 10, color: Colors.white))
          ],
        ),
      );
    }
  }
  
  

  

  

  (0,0)是居中

二.Flutter Stack Align

• 当里面有多个组件仍然用Stack组件的Alignment属性来控制的话，所有的组件都会到同一个方位，仍然会重叠

  class LayoutDemo extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return Center(
          child: Container(
        height: 400,
        width: 300,
        color: Colors.red,
        child: Stack(
          alignment: Alignment.center,
          children: <Widget>[
            Icon(Icons.home, size: 40, color: Colors.white),
            Icon(Icons.search_off, size: 30, color: Colors.cyanAccent),
            Icon(Icons.send, size: 50, color: Colors.black)
          ],
        ),
      ));
    }
  }
  

  

• 此时可以用Align组件控制每一个组件的位置

  
  class LayoutDemo extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return Center(
          child: Container(
        height: 400,
        width: 300,
        color: Colors.red,
        child: Stack(
          children: <Widget>[
            Align(
              alignment: Alignment.center,
              child: Icon(Icons.home, size: 40, color: Colors.white),
            ),
            Align(
              alignment: Alignment.topLeft,
              child: Icon(Icons.search_off, size: 30, color: Colors.cyanAccent),
            ),
            Align(
                alignment: Alignment.bottomLeft,
                child: Icon(Icons.send, size: 50, color: Colors.black))
          ],
        ),
      ));
    }
  }
  
  

  

三、Flutter Stack Positioned

没写的属性值默认为0

class LayoutDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
        child: Container(
      height: 400,
      width: 300,
      color: Colors.red,
      child: Stack(
        children: <Widget>[
          Positioned(
            left: 100,
            child: Icon(Icons.home, size: 40, color: Colors.white),
          ),
          Positioned(
            bottom: 10,
            child: Icon(Icons.search_off, size: 30, color: Colors.cyanAccent),
          ),
          Positioned(
              top: 304,
              right: 10,
              child: Icon(Icons.send, size: 50, color: Colors.black))
        ],
      ),
    ));
  }
}