限制可拖动区域

限制可拖动区域

不，那不是

Draggable

小部件的目标。而是使用a

GestureDetector

来检测阻力。然后将其与类似

Align

内容移动的内容结合起来

这是一个基于您当前代码的完全可用的滑块。

import 'package:flutter/material.dart';void main() => runApp(MyApp());class MyApp extends StatelessWidget {  @override  Widget build(BuildContext context) {    return MaterialApp(      home: Scaffold(        body: Center(          child: Slider(),        ),      ),    );  }}class Slider extends StatefulWidget {  final ValueChanged<double> valueChanged;  Slider({this.valueChanged});  @override  SliderState createState() {    return new SliderState();  }}class SliderState extends State<Slider> {  ValueNotifier<double> valueListener = ValueNotifier(.0);  @override  void initState() {    valueListener.addListener(notifyParent);    super.initState();  }  void notifyParent() {    if (widget.valueChanged != null) {      widget.valueChanged(valueListener.value);    }  }  @override  Widget build(BuildContext context) {    return Container(      color: Colors.green,      height: 50.0,      padding: EdgeInsets.symmetric(horizontal: 40.0),      child: Builder(        builder: (context) {          final handle = GestureDetector( onHorizontalDragUpdate: (details) {   valueListener.value = (valueListener.value +details.delta.dx / context.size.width)       .clamp(.0, 1.0); }, child: FlutterLogo(size: 50.0),          );          return AnimatedBuilder( animation: valueListener, builder: (context, child) {   return Align(     alignment: Alignment(valueListener.value * 2 - 1, .5),     child: child,   ); }, child: handle,          );        },      ),    );  }}