Published: October 16, 2022
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LastMod: December 11, 2022
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717 words
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
添加关键字 required 添加默认值 flutter 运行时 “Your session has expired. Please log in.” 🔗
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
背景色渐变 🔗 1
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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 🔗 1
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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 (),
),
],
);
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flutter channel stable
flutter upgrade -- force
