Flutter之Padding

心已赠人 2021-09-24 15:50 372阅读 0赞

## 1 、Padding介绍 ##

Padding用来为子元素添加填充，也就是指定子元素与容器边界的距离，作用基本上与Android中ViewGroup的padding属性差不多

const Padding({
        Key key,
        @required this.padding,
        Widget child,
      }) : assert(padding != null),
           super(key: key, child: child);

EdgeInsets提供了一些方法

*  fromLTRB(double left, double top, double right, double bottom)：分别指定四个方向的填充。
 *  all(double value) : 所有方向均使用相同数值的填充。
 *  only(\{left, top, right ,bottom \})：可以设置具体某个方向的填充(可以同时指定多个方向)。
 *  symmetric(\{ vertical, horizontal \})：用于设置对称方向的填充，vertical指top和bottom，horizontal指left和right。

## 2 、代码测试 ##

@override
      Widget build(BuildContext context) {
          return MaterialApp(
              title: 'open url',
              home: 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('hello flutter'),
                ),
                body: Padding(
    //              padding: EdgeInsets.all(16),
    //            padding: EdgeInsets.fromLTRB(10, 20, 30, 40),
    //            padding: EdgeInsets.only(left: 10, right: 30),
                padding: EdgeInsets.symmetric(vertical: 20),
                  child: Container(
                     color: Colors.blue,
                  ),
                ),
              ),
          );
      }
    }

## 3、运行效果 ##

分别用上面注释的4个padding效果如下

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTEwNjg3MDI_size_16_color_FFFFFF_t_70][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTEwNjg3MDI_size_16_color_FFFFFF_t_70 1][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTEwNjg3MDI_size_16_color_FFFFFF_t_70 2][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTEwNjg3MDI_size_16_color_FFFFFF_t_70 3][]

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTEwNjg3MDI_size_16_color_FFFFFF_t_70 1]: /images/20210923/efab7fbfa3f0403cb30a544a3719d0a2.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTEwNjg3MDI_size_16_color_FFFFFF_t_70 2]: /images/20210923/07ca972d59a1489dbb27166975f229d0.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTEwNjg3MDI_size_16_color_FFFFFF_t_70 3]: /images/20210923/76da278ed2e048919bc6fe07c687ffa6.png