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在Flutter开发中有一个使用非常广泛的组件，它的作用是：

有效容纳一个子组件并且可以自定义样式的容器。

这篇博客主要分享容器组件的Container的使用，希望对看文章的小伙伴有所帮助。

主要使用的场景：

• 设置宽高：Flutter中大部分组件不能设置宽高，需要依赖容器;
• 添加背景颜色;
• 添加背影图像;
• 添加内外边距：padding和margin属性；
• 添加边框；
• 设置圆角；
• 设置child对齐：居中、居左、居右、居上、居下或偏移；
• 设置变换：旋转或变形。

简单示例代码

Container(
        height: 300,
        color: Colors.red,
        padding: const EdgeInsets.all(10),
        margin: const EdgeInsets.all(10),
        alignment: Alignment.center,
        child: const Text(
          '使用Container组件',
          style: TextStyle(color: Colors.white),
        ),
      ),

效果如下：

image.png

源码

Container({
    Key? key,
    this.alignment,
    this.padding,
    this.color,
    this.decoration,
    this.foregroundDecoration,
    double? width,
    double? height,
    BoxConstraints? constraints,
    this.margin,
    this.transform,
    this.transformAlignment,
    this.child,
    this.clipBehavior = Clip.none,
  }) : assert(margin == null || margin.isNonNegative),
       assert(padding == null || padding.isNonNegative),
       assert(decoration == null || decoration.debugAssertIsValid()),
       assert(constraints == null || constraints.debugAssertIsValid()),
       assert(clipBehavior != null),
       assert(decoration != null || clipBehavior == Clip.none),
       assert(color == null || decoration == null,
         'Cannot provide both a color and a decoration\n'
         'To provide both, use "decoration: BoxDecoration(color: color)".',
       ),
       constraints =
        (width != null || height != null)
          ? constraints?.tighten(width: width, height: height)
            ?? BoxConstraints.tightFor(width: width, height: height)
          : constraints,
       super(key: key);

属性说明

这里针对源码做出相应的属性说明，熟悉控件的属性方便大家的使用。

完整的示例代码

以下的代码，可以直接复制到编译器去运行，方便小伙伴查看运行结果或者直接使用：

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Container(
        height: 300,
        color: Colors.red,
        padding: const EdgeInsets.all(10),
        margin: const EdgeInsets.all(10),
        alignment: Alignment.center,
        child: const Text(
          '使用Container组件',
          style: TextStyle(color: Colors.white),
        ),
      ),
    );
  }
}