有没有更好的方法来检查#flutter中的左/右拖动？

Question

有没有更好的方法来检查#flutter中的左/右拖动.我已经完成了它,但是有时它不工作.

  new GestureDetector(
  onHorizontalDragEnd: (DragEndDetails details) {
      print("Drag Left - AddValue");

    setState((){
      _value++;
    });
    if (details.velocity.pixelsPerSecond.dx > -1000.0) {
      print("Drag Right - SubValue");

      setState((){
        _value--;
      });
    }
  },
  child: new Container(
    child:new Text("$_value"),
  ),
);

Answer 1

我会Dismissible为此使用一个小部件.它非常易于配置.

注意:如果您不想在滑动上提供视觉反馈,则可以使用a Stack将透明Dismissible放在另一个小部件的顶部.

import 'package:flutter/material.dart';

void main() {
  runApp(new MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  State createState() => new MyHomePageState();
}

class MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      body: new Dismissible(
        resizeDuration: null,
        onDismissed: (DismissDirection direction) {
          setState(() {
            _counter += direction == DismissDirection.endToStart ? 1 : -1;
          });
        },
        key: new ValueKey(_counter),
        child: new Center(
          child: new Text(
            '$_counter',
            style: Theme.of(context).textTheme.display4,
          ),
        ),
      ),
    );
  }
}

Answer 2

您可以使用onHorizontalDragUpdate：

onHorizontalDragUpdate: (details){
    print(details.primaryDelta);
},

如果details.primaryDelta为正，则从左到右拖动。如果details.primaryDelta是负数，则从右到左拖动

Answer 3

使用GestureDetector小部件及其panUpdate方法，计算移动的距离。

    GestureDetector(
     onPanStart: (DragStartDetails details) {
      initial = details.globalPosition.dx;
     },
     onPanUpdate: (DragUpdateDetails details) {
      distance= details.globalPosition.dx - initial;  
     },
     onPanEnd: (DragEndDetails details) {
      initial = 0.0; 
     print(distance);
     //+ve distance signifies a drag from left to right(start to end)
     //-ve distance signifies a drag from right to left(end to start)
});