颤动底部导航栏样式问题

Question

这是我正在尝试做的底部导航。

如何实现这个底部导航栏？我尝试了弯曲的底部导航，但它没有给我解决方案，我尝试使用 fab 中心停靠的颤动底部导航栏，但这也没有用。

Answer 1

Flutter 对这种 UI 有一个特定的形状，称为 CircularNotchedRectangle。您可以获取该类的代码来查看形状是如何绘制的，从中构建您的自定义形状，并对其进行调整以获得您想要的样式，因为它与CircularNotchedRectangle 非常相似。我写了一个小sn-p，您可以在DartPad 中运行，以便您了解如何在BottomNavigationBar 中实现它。它可能不是完全相同的形状，但我想我已经很接近了。如果没有该曲线的参数，我不可能得到确切的形状。使用s1、s2 和addedRadius 参数来获得您想要的结果：

import 'dart:math' as math;

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class CustomNotchedRectangle extends NotchedShape {
  const CustomNotchedRectangle();

  @override
  Path getOuterPath(Rect host, Rect guest) {
    if (guest == null || !host.overlaps(guest)) return Path()..addRect(host);

    const double s1 = 10.0;
    const double s2 = 8.0;
    const double addedRadius = 3;

    final double notchRadius = guest.width / 2.0 + addedRadius;
    final double r = notchRadius;
    final double a = -1.0 * r - s2;
    final double b = host.top - guest.center.dy;

    final double n2 = math.sqrt(b * b * r * r * (a * a + b * b - r * r));
    final double p2xA = ((a * r * r) - n2) / (a * a + b * b);
    final double p2xB = ((a * r * r) + n2) / (a * a + b * b);
    final double p2yA = math.sqrt(r * r - p2xA * p2xA);
    final double p2yB = math.sqrt(r * r - p2xB * p2xB);

    final List<Offset> p = List<Offset>(6);

    p[0] = Offset(a - s1, b);
    p[1] = Offset(a, b);
    final double cmp = b < 0 ? -1.0 : 1.0;
    p[2] =
        cmp * p2yA > cmp * p2yB ? Offset(p2xA, p2yA) : Offset(p2xB, p2yB);

    p[3] = Offset(-1.0 * p[2].dx, p[2].dy);
    p[4] = Offset(-1.0 * p[1].dx, p[1].dy);
    p[5] = Offset(-1.0 * p[0].dx, p[0].dy);

    for (int i = 0; i < p.length; i += 1) p[i] += guest.center;

    return Path()
      ..moveTo(host.left, host.top)
      ..lineTo(p[0].dx, p[0].dy)
      ..quadraticBezierTo(p[1].dx, p[1].dy, p[2].dx, p[2].dy)
      ..arcToPoint(
        p[3],
        radius: Radius.circular(notchRadius),
        clockwise: false,
      )
      ..quadraticBezierTo(p[4].dx, p[4].dy, p[5].dx, p[5].dy)
      ..lineTo(host.right, host.top)
      ..lineTo(host.right, host.bottom)
      ..lineTo(host.left, host.bottom)
      ..close();
  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

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

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Sample Code'),
      ),
      body: Center(
        child: Text('You have pressed the button $_counter times.'),
      ),
      bottomNavigationBar: BottomAppBar(
        shape: const CustomNotchedRectangle(),
        child: Container(height: 50.0, color: Theme.of(context).primaryColor),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment Counter',
        child: Icon(Icons.add),
      ),
      floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
    );
  }
}

结果如下：