flutter 问题整理

Published: · LastMod: December 11, 2022 · 717 words

Undefined name ‘OutlineButton’. 🔗

使用TextButton代替

Try adding either an explicit non-’null’ default value or the ‘required’ modifier. 🔗

空安全报错，一旦sdk升级到2.12以上之后，那么就会执行空安全检查

  1. 添加关键字 required
  2. 添加默认值

flutter 运行时 “Your session has expired. Please log in.” 🔗

image.png

Xcode ——>Preferences…——> accounts 重新登录 ——> fix

Failed assertion: line 4680 pos 14: ‘owner!._debugCurrentBuildTarget == this’: is not true. 🔗

出现在使用CustomScrollView的时候

Sliver名称说明
SliverAppBar对应 AppBar，主要是为了在 CustomScrollView 中使用。
SliverToBoxAdapter一个适配器，可以将 RenderBox 适配为 Sliver，后面介绍。
SliverPersistentHeader滑动到顶部时可以固定住，后面介绍。

常规组件需要使用SliverToBoxAdapter包裹一层

Error: The default value of an optional parameter must be constant 🔗

当在声明Color类型时， 使用Colors.grey.shade600会报错，查询后需要定义成常量，前面加const

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class CardPanelHeader extends StatelessWidget {
  final String leadingPanelText;
  final Color leadingPanelTextColor;
  final String trailingPanelText;
  final Color trailingPanelTextColor;

  const CardPanelHeader({
    Key key,
    this.leadingPanelText,
    this.leadingPanelTextColor = Colors.black87,
    this.trailingPanelText,
    this.trailingPanelTextColor = const Colors.grey.shade600,
  }) : super(key: key);

生成对应的应用图标 🔗

https://icon.wuruihong.com/

Column children中动态添加元素 🔗

在children中进行if判断

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Column(
     children: <Widget>[
     if(condition1)
      widget1,
     if(condition2)
     widget2,
_    ..._getWeatherDataWidgets(),
],)

The method ‘[]’ can’t be unconditionally invoked because the receiver can be ’null 🔗

简单判断

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var list = someList;
if (list != null) {
  int a = list[0]; // No error
}

使用**?** and ??:

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int a = someList?[0] ?? -1;

如果是数组中进行索引，加个!进行强制判断

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int a = someList![0];

背景色渐变 🔗

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Container(
  width: 60,
  height: 60,
  decoration: BoxDecoration(
      borderRadius: BorderRadius.all(Radius.circular(30)),
      boxShadow: [
        BoxShadow(
          color: Color.fromARGB(255, 111, 187, 249),
          blurRadius: 5,
          spreadRadius: 0.0,
        ),
      ],
      gradient: LinearGradient(
          begin: Alignment.topCenter,
          end: Alignment.bottomCenter,
          colors: [
            Color.fromARGB(255, 80, 174, 252),
            Color.fromARGB(255, 32, 131, 212),
          ])),
  child: Icon(
    Icons.edit_rounded,
    color: Colors.white,
    size: 30,
  ),
),

行平均4等份 🔗

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Row(
  children: [
    Expanded(
      flex: 1, // you can play with this value, by default it is 1
      child: Child1(),
    ),
    Expanded(
      flex: 1, 
      child: Child2(),
    ),
    Expanded(
      flex: 1, 
      child: Child3(),
    ),
    Expanded(
      flex: 1, 
      child: Child4(),
    ),
  ],
);

Unable to upgrade Flutter: no origin repository configured 🔗

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flutter channel stable
flutter upgrade --force