Question

我正在尝试使GestureDetector缩放文本小部件，但它根本无法工作，甚至没有错误...

请注意，我尝试了很多事情，例如用GestureDetector包裹支架本身。

main.dart

import 'package:flutter/material.dart';
import 'package:testy/zoomable.dart';

void main() => runApp(
  MaterialApp(
    debugShowCheckedModeBanner: false,
    title: 'Testy',
    theme: ThemeData(
      primarySwatch: Colors.green,
      primaryColor: Colors.green
    ),
    home: Zoomable(),
  )
);

zoomable.dart

import 'package:flutter/material.dart';

class Zoomable extends StatefulWidget {
  @override
  _ZoomableState createState() => _ZoomableState();
}

class _ZoomableState extends State<Zoomable> {
  @override
  Widget build(BuildContext context) {
    double size = 70;
    return Scaffold(
      appBar: AppBar(
        title: Text('Zoomable'),
      ),
      body: GestureDetector(
        onScaleStart: (details) {},
        onScaleUpdate: (ScaleUpdateDetails details) {
          if (size < 150.0 && size > 50.0) {
            setState(() {
              size = size + details.scale;
            });
          }
        },
        onTap: () {
          if (size < 150.0 && size > 50.0) {
            setState(() {
              size = size + 1;
            });
          }
        },
        child: Text(
          'Zoomable',
          style: TextStyle(fontSize: size),
        ),
      ),
    );
  }
}

Answer 1

这是因为您正在NaN函数中调用double size = 70;。调用build()时，将调用setState()函数并将大小设置回70。只需将build()移动到size函数外部，它将起作用

Flutter GestureDetector根本不起作用

1 个答案: