我有一个类，其中有一个 slider.adaptive 以及它的整个布局。在我的主类中，我调用该滑块类并声明布局的值（标题等）。我遇到的问题是滑块本身的值无法访问并保存在调用滑块类的类中。 我仍然是 Flutter 的初学者，所以我喜欢尽可能简单的解释，这样我就能理解它们。
我目前拥有的代码：
class CustomSlider extends StatefulWidget {
final double value;
final String title;
final String good;
final String bad;
CustomSlider({
required this.value,
required this.title,
required this.good,
required this.bad,
});
@override
_CustomSlider createState() {
return _CustomSlider(value: value, title: title, good: good, bad: bad);
}
}
class _CustomSlider extends State<CustomSlider> {
double value;
String title = "";
double height = 15.0;
double width = 10.0;
String good;
String bad;
_CustomSlider({
required this.value,
required this.title,
required this.good,
required this.bad,
});
//double value = 0.0;
@override
Widget build(BuildContext context) {
return Container(
//more layout here in-between
Expanded(
child: Slider.adaptive(
value: value,
min: 0,
max: 10,
divisions: 10,
activeColor: Colors.cyanAccent,
onChanged: (double changedValue) {
setState((){
value = changedValue;
});
print(value);
},
// semanticFormatterCallback: (double endValue){
// return '$value';
// },
label: value.toString(),
),
),
调用 Customslider 的类：
class RecordSymptoms extends StatefulWidget {
@override
State createState() => new _RecordSymptoms();
}
class _RecordSymptoms extends State<RecordSymptoms> {
final double height = 20;
double symptomTotal = 0;
var generalWellbeing1;
double generalWellbeing = 0;
double cramps = 0;
double flatulence = 0;
double bowel = 0;
@override
Widget build(BuildContext context) => Scaffold(
backgroundColor: Colors.teal[100],
endDrawer: menu(),
appBar: AppBar(
title: Text(
'Symptome erfassen',
style: TextStyle(
color: Colors.black,
),
),
backgroundColor: Colors.cyanAccent,
),
body: Stack(
children: <Widget>[
Positioned.fill(
child: Image(
image: AssetImage('assets/Inner_Peace.png'),
fit: BoxFit.fill,
),
),
Column(
children: <Widget>[
CustomSlider(
value: generalWellbeing,
title: 'Allgemeines Wohlbefinden',
good: "Gut",
bad: "Schlecht"),
CustomSlider(
value: cramps,
title: 'Krämpfe',
good: "Keine",
bad: "Extrem"),
CustomSlider(
value: flatulence,
title: 'Blähungen',
good: "Keine",
bad: "Extrem"),
CustomSlider(
value: bowel,
title: 'Stuhlgang',
good: "Fest",
bad: "Flüssig"),
Spacer(),
Container(
child: Row(
children: <Widget>[
Flexible(
flex: 20,
child: CustomButton(
text: 'Keine Symptome',
onClick: () {
Navigator.of(context).push(
MaterialPageRoute(
builder: (context) => RecordedMeals(),
),
);
},
),
),
Flexible(
flex: 20,
child: CustomButton(
text: 'Symptome speichern',
onClick: () async {
Navigator.of(context).push(
MaterialPageRoute(
builder: (context) => RecordedMeals(),
),
);
print(generalWellbeing);
print(bowel.toString());
print(cramps.toString());
print(flatulence.toString());
},
),
),
],
),
),
SizedBox(height: height),
],
),
],
),
);
我尝试了
semanticFormatterCallbackprint(flatulence.toString());我不知道为什么当时没有人回答你的问题，但这是合法的方法......
1 - 在构造函数中创建回调，将其命名为“onChanged”，因为它只会从滑块自己的 onChanged 属性传递值。请注意，这与为您提供的任何滑块的默认 onChanged 属性不同。这将在默认的 onChanged 中用作您的 onChanged （您可以像我所说的那样将其命名为您喜欢的名称）。
class SliderWidget extends StatefulWidget {
final double sliderHeight;
final int min;
final int max;
final fullWidth;
final ValueChanged<int> onChanged; // HERE IS THE IMPORTANT PART -> DO THIS
// late final int value;
SliderWidget({
this.sliderHeight = 60,
this.max = 5,
this.min = 0,
this.fullWidth = false,
required this.onChanged, // HERE IS THE IMPORTANT PART -> DO THIS
// required this.value,
});
这个 sliderWidget 的效果介于两者之间：
Slider(
value: indexTop.toDouble(),
min: min,
max: max,
divisions: divisions,
// label: labels[indexTop],
onChanged: (value) => // THIS IS DEFAULT PROPERTY!
setState(() {
this.indexTop = value.toInt();
widget.onChanged.call(value.toInt()); // THIS IS YOUR CALLBACK!
// widget.value = value.toInt();
}),
),
2-现在只需在任何其他小部件类中创建此小部件的实例，每次对该实例进行更改时您的回调都会侦听...
new SliderWidget(onChanged: (int value) {
print(value.toInt();
}
,),
如果仍然难以执行，请写信给我，我会向您和任何想要实现相同结果的人解释......
这很好，但是如果我想在类之外控制滑块值怎么办？