如何在 Flutter 應用程式的底部導覽列中切出浮動操作按鈕

在本指南中，我們將向您展示如何在底部導覽應用程式列中設定凹口浮動操作按鈕。底部欄中的凹口浮動操作按鈕使您的應用程式使用者介面美觀。請參閱下面的程式碼以了解更多詳細資訊：

1.底部導覽列左側有凹口的FloatingActionButton：

Scaffold(
  floatingActionButton:FloatingActionButton( //Floating action button on Scaffold
      onPressed: (){
          //code to execute on button press
      },
      child: Icon(Icons.send), //icon inside button
  ),

  floatingActionButtonLocation: FloatingActionButtonLocation.startDocked,
  //floating action button location to left

  bottomNavigationBar: BottomAppBar( //bottom navigation bar on scaffold
    color:Colors.redAccent,
    shape: CircularNotchedRectangle(), //shape of notch
    notchMargin: 5, //notche margin between floating button and bottom appbar
    child: Row( //children inside bottom appbar
      mainAxisSize: MainAxisSize.max,
      mainAxisAlignment: MainAxisAlignment.spaceBetween,
      children: <Widget>[
        Padding(
          padding: EdgeInsets.only(left:90),
          child:IconButton(icon: Icon(Icons.menu, color: Colors.white,), onPressed: () {},),
        ),
        IconButton(icon: Icon(Icons.search, color: Colors.white,), onPressed: () {},),
        IconButton(icon: Icon(Icons.print, color: Colors.white,), onPressed: () {},),
        IconButton(icon: Icon(Icons.people, color: Colors.white,), onPressed: () {},),
      ],
    ),
  ),
)

2.底部導覽列中心的凹口FloatingActionButton：

Scaffold(
  floatingActionButton:FloatingActionButton( //Floating action button on Scaffold
      onPressed: (){
          //code to execute on button press
      },
      child: Icon(Icons.send), //icon inside button
  ),

  floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
  //floating action button position to center

  bottomNavigationBar: BottomAppBar( //bottom navigation bar on scaffold
    color:Colors.redAccent,
    shape: CircularNotchedRectangle(), //shape of notch
    notchMargin: 5, //notche margin between floating button and bottom appbar
    child: Row( //children inside bottom appbar
      mainAxisSize: MainAxisSize.max,
      mainAxisAlignment: MainAxisAlignment.spaceBetween,
      children: <Widget>[
        IconButton(icon: Icon(Icons.menu, color: Colors.white,), onPressed: () {},),
        IconButton(icon: Icon(Icons.search, color: Colors.white,), onPressed: () {},),
        IconButton(icon: Icon(Icons.print, color: Colors.white,), onPressed: () {},),
        IconButton(icon: Icon(Icons.people, color: Colors.white,), onPressed: () {},),
      ],
    ),
  ),
)

2.底部導覽列右側有凹口的FloatingActionButton：

Scaffold(
  floatingActionButton:FloatingActionButton( //Floating action button on Scaffold
      onPressed: (){
          //code to execute on button press
      },
      child: Icon(Icons.send), //icon inside button
  ),

  floatingActionButtonLocation: FloatingActionButtonLocation.endDocked,
  //floating action button position to right

  bottomNavigationBar: BottomAppBar( //bottom navigation bar on scaffold
    color:Colors.redAccent,
    shape: CircularNotchedRectangle(), //shape of notch
    notchMargin: 5, //notche margin between floating button and bottom appbar
    child: Row( //children inside bottom appbar
      mainAxisSize: MainAxisSize.max,
      mainAxisAlignment: MainAxisAlignment.spaceBetween,
      children: <Widget>[
        IconButton(icon: Icon(Icons.menu, color: Colors.white,), onPressed: () {},),
        IconButton(icon: Icon(Icons.search, color: Colors.white,), onPressed: () {},),
        IconButton(icon: Icon(Icons.print, color: Colors.white,), onPressed: () {},),
        Padding(
          padding: EdgeInsets.only(right:90),
          child:IconButton(icon: Icon(Icons.people, color: Colors.white,), onPressed: () {},),
        )
      ],
    ),
  ),
)

完整的 Dart 程式碼範例： 

import 'package:flutter/material.dart';
void main(){
  runApp(MyApp());
}

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

class Home extends StatefulWidget{
  @override
  _HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> {
  @override
  Widget build(BuildContext context) {
    return  Scaffold(
      floatingActionButton:FloatingActionButton( //Floating action button on Scaffold
          onPressed: (){
              //code to execute on button press
          },
          child: Icon(Icons.send), //icon inside button
      ),

      floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
      //floating action button position to center

      bottomNavigationBar: BottomAppBar( //bottom navigation bar on scaffold
        color:Colors.redAccent,
        shape: CircularNotchedRectangle(), //shape of notch
        notchMargin: 5, //notche margin between floating button and bottom appbar
        child: Row( //children inside bottom appbar
          mainAxisSize: MainAxisSize.max,
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          children: <Widget>[
            IconButton(icon: Icon(Icons.menu, color: Colors.white,), onPressed: () {},),
            IconButton(icon: Icon(Icons.search, color: Colors.white,), onPressed: () {},),
            IconButton(icon: Icon(Icons.print, color: Colors.white,), onPressed: () {},),
            IconButton(icon: Icon(Icons.people, color: Colors.white,), onPressed: () {},),
          ],
        ),
      ),
    );
  }
}