flutter - 异常类型 Future(void) 不是 Future 的子类型
问题描述
下面的代码在颤动中执行布局的创建,要创建布局,我必须首先确保执行 set 函数以使其使用未来的构建器,但是当我运行代码时出现以下错误。它告诉我存在以下错误,future 不是 future 的子类型,理论上两者都是从 object 派生的,所以 dart 上不应该存在继承问题,这是因为什么?
错误:
在不是 Future 的子类型中键入 Future(void)
颤振代码:
import ...
double latitudine=0;
Future<void> setValori() async {
latitudine=await Gps.getLatitudine();
print("Latitudine: "+latitudine.toString());
print("\n \n Sono dentro set valori \n \n");
}
class MediterranesnDietView extends StatelessWidget {
final AnimationController animationController;
final Animation animation;
const MediterranesnDietView(
{Key key, this.animationController, this.animation})
: super(key: key);
@override
Widget build(BuildContext context) {
return FutureBuilder<AnimatedBuilder>(
future: setValori(),
builder: (BuildContext context, AsyncSnapshot<AnimatedBuilder> snapshot) {
return AnimatedBuilder(
animation: animationController,
builder: (BuildContext context, Widget child) {
return FadeTransition(
opacity: animation,
child: new Transform(
transform: new Matrix4.translationValues(
0.0, 30 * (1.0 - animation.value), 0.0),
child: Padding(
padding: const EdgeInsets.only(
left: 24, right: 24, top: 16, bottom: 18),
child: Container(
decoration: BoxDecoration(
color: FintnessAppTheme.white,
borderRadius: BorderRadius.only(
topLeft: Radius.circular(8.0),
bottomLeft: Radius.circular(8.0),
bottomRight: Radius.circular(8.0),
topRight: Radius.circular(68.0)),
boxShadow: <BoxShadow>[
BoxShadow(
color: FintnessAppTheme.grey.withOpacity(0.2),
offset: Offset(1.1, 1.1),
blurRadius: 10.0),
],
),
child: Column(
children: <Widget>[
Padding(
padding:
const EdgeInsets.only(top: 16, left: 16, right: 16),
child: Row(
children: <Widget>[
Expanded(
child: Padding(
padding: const EdgeInsets.only(
left: 8, right: 8, top: 4),
child: Column(
children: <Widget>[
Row(
children: <Widget>[
Container(
height: 48,
width: 2,
decoration: BoxDecoration(
color: HexColor('#87A0E5')
.withOpacity(0.5),
borderRadius: BorderRadius.all(
Radius.circular(4.0)),
),
),
Padding(
padding: const EdgeInsets.all(8.0),
child: Column(
mainAxisAlignment:
MainAxisAlignment.center,
crossAxisAlignment:
CrossAxisAlignment.start,
children: <Widget>[
Padding(
padding: const EdgeInsets.only(
left: 4, bottom: 2),
child: Text(
'Latitudine',
textAlign: TextAlign.center,
style: TextStyle(
fontFamily:
FintnessAppTheme.fontName,
fontWeight: FontWeight.w500,
fontSize: 16,
letterSpacing: -0.1,
color: FintnessAppTheme.grey
.withOpacity(0.5),
),
),
),
Row(
mainAxisAlignment:
MainAxisAlignment.center,
crossAxisAlignment:
CrossAxisAlignment.end,
children: <Widget>[
SizedBox(
width: 28,
height: 28,
child: Image.asset(
"assets/Home/eaten.png"),
),
Padding(
padding:
const EdgeInsets.only(
left: 4, bottom: 3),
child: Text(
'${(latitudine * animation.value).toInt()}',
textAlign: TextAlign.center,
style: TextStyle(
fontFamily:
FintnessAppTheme
.fontName,
fontWeight:
FontWeight.w600,
fontSize: 16,
color: FintnessAppTheme
.darkerText,
),
),
),
Padding(
padding:
const EdgeInsets.only(
left: 4, bottom: 3),
child: Text(
'',
textAlign: TextAlign.center,
style: TextStyle(
fontFamily:
FintnessAppTheme
.fontName,
fontWeight:
FontWeight.w600,
fontSize: 12,
letterSpacing: -0.2,
color: FintnessAppTheme
.grey
.withOpacity(0.5),
),
),
),
],
)
],
),
)
],
),
SizedBox(
height: 8,
),
Row(
children: <Widget>[
Container(
height: 48,
width: 2,
decoration: BoxDecoration(
color: HexColor('#F56E98')
.withOpacity(0.5),
borderRadius: BorderRadius.all(
Radius.circular(4.0)),
),
),
Padding(
padding: const EdgeInsets.all(8.0),
child: Column(
mainAxisAlignment:
MainAxisAlignment.center,
crossAxisAlignment:
CrossAxisAlignment.start,
children: <Widget>[
Padding(
padding: const EdgeInsets.only(
left: 4, bottom: 2),
child: Text(
'Longitudine',
textAlign: TextAlign.center,
style: TextStyle(
fontFamily:
FintnessAppTheme.fontName,
fontWeight: FontWeight.w500,
fontSize: 16,
letterSpacing: -0.1,
color: FintnessAppTheme.grey
.withOpacity(0.5),
),
),
),
Row(
mainAxisAlignment:
MainAxisAlignment.center,
crossAxisAlignment:
CrossAxisAlignment.end,
children: <Widget>[
SizedBox(
width: 28,
height: 28,
child: Image.asset(
"assets/Home/burned.png"),
),
Padding(
padding:
const EdgeInsets.only(
left: 4, bottom: 3),
child: Text(
'${(102 * animation.value).toInt()}',
textAlign: TextAlign.center,
style: TextStyle(
fontFamily:
FintnessAppTheme
.fontName,
fontWeight:
FontWeight.w600,
fontSize: 16,
color: FintnessAppTheme
.darkerText,
),
),
),
Padding(
padding:
const EdgeInsets.only(
left: 8, bottom: 3),
child: Text(
'Kcal',
textAlign: TextAlign.center,
style: TextStyle(
fontFamily:
FintnessAppTheme
.fontName,
fontWeight:
FontWeight.w600,
fontSize: 12,
letterSpacing: -0.2,
color: FintnessAppTheme
.grey
.withOpacity(0.5),
),
),
),
],
)
],
),
)
],
)
],
),
),
),
Padding(
padding: const EdgeInsets.only(right: 16),
child: Center(
child: Stack(
overflow: Overflow.visible,
children: <Widget>[
Padding(
padding: const EdgeInsets.all(8.0),
child: Container(
width: 100,
height: 100,
decoration: BoxDecoration(
color: FintnessAppTheme.white,
borderRadius: BorderRadius.all(
Radius.circular(100.0),
),
border: new Border.all(
width: 4,
color: FintnessAppTheme
.nearlyDarkBlue
.withOpacity(0.2)),
),
child: Column(
mainAxisAlignment:
MainAxisAlignment.center,
crossAxisAlignment:
CrossAxisAlignment.center,
children: <Widget>[
Text(
'${(1503 * animation.value).toInt()}',
textAlign: TextAlign.center,
style: TextStyle(
fontFamily:
FintnessAppTheme.fontName,
fontWeight: FontWeight.normal,
fontSize: 24,
letterSpacing: 0.0,
color: FintnessAppTheme
.nearlyDarkBlue,
),
),
Text(
'Kcal left',
textAlign: TextAlign.center,
style: TextStyle(
fontFamily:
FintnessAppTheme.fontName,
fontWeight: FontWeight.bold,
fontSize: 12,
letterSpacing: 0.0,
color: FintnessAppTheme.grey
.withOpacity(0.5),
),
),
],
),
),
),
Padding(
padding: const EdgeInsets.all(4.0),
child: CustomPaint(
painter: CurvePainter(
colors: [
FintnessAppTheme.nearlyDarkBlue,
HexColor("#8A98E8"),
HexColor("#8A98E8")
],
angle: 140 +
(360 - 140) *
(1.0 - animation.value)),
child: SizedBox(
width: 108,
height: 108,
),
),
)
],
),
),
)
],
),
),
Padding(
padding: const EdgeInsets.only(
left: 24, right: 24, top: 8, bottom: 8),
child: Container(
height: 2,
decoration: BoxDecoration(
color: FintnessAppTheme.background,
borderRadius: BorderRadius.all(Radius.circular(4.0)),
),
),
),
Padding(
padding: const EdgeInsets.only(
left: 24, right: 24, top: 8, bottom: 16),
child: Row(
children: <Widget>[
Expanded(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text(
'Carbs',
textAlign: TextAlign.center,
style: TextStyle(
fontFamily: FintnessAppTheme.fontName,
fontWeight: FontWeight.w500,
fontSize: 16,
letterSpacing: -0.2,
color: FintnessAppTheme.darkText,
),
),
Padding(
padding: const EdgeInsets.only(top: 4),
child: Container(
height: 4,
width: 70,
decoration: BoxDecoration(
color:
HexColor('#87A0E5').withOpacity(0.2),
borderRadius: BorderRadius.all(
Radius.circular(4.0)),
),
child: Row(
children: <Widget>[
Container(
width: ((70 / 1.2) * animation.value),
height: 4,
decoration: BoxDecoration(
gradient: LinearGradient(colors: [
HexColor('#87A0E5'),
HexColor('#87A0E5')
.withOpacity(0.5),
]),
borderRadius: BorderRadius.all(
Radius.circular(4.0)),
),
)
],
),
),
),
Padding(
padding: const EdgeInsets.only(top: 6),
child: Text(
'12g left',
textAlign: TextAlign.center,
style: TextStyle(
fontFamily: FintnessAppTheme.fontName,
fontWeight: FontWeight.w600,
fontSize: 12,
color: FintnessAppTheme.grey
.withOpacity(0.5),
),
),
),
],
),
),
...
),
),
),
);
},
);
});
}
}
解决方案
该错误表明,您提供的 FutureFutureBuilder
与 Builders 泛型类型不匹配。
您FutureBuilder<AnimatedBuilder>
使用泛型参数定义AnimatedBuilder
,它需要一个Future<AnimatedBuilder>
. 该函数setValori()
返回一个Future<void>
.
如果您更改您的FutureBuilder<AnimatedBuilder>
toFutureBuilder<void>
并更改AsyncSnapshot<AnimatedBuilder>
为AsyncSnapshot<void>
,您解决了问题。
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