Books

import 'dart:io';
import 'package:image_picker/image_picker.dart';
import 'package:flutter/material.dart';

class Books extends StatefulWidget {
  @override
  _BooksState createState() => _BooksState();
}

class _BooksState extends State<Books> {
  File image;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
      floatingActionButton: FloatingActionButton(
          backgroundColor: Colors.blueAccent,
          child: ListTile(
            trailing: Icon(Icons.add),
          ),
          onPressed: _showAlertDialog),
      bottomNavigationBar: BottomAppBar(
        hasNotch: true,
        child: Container(
          color: Colors.blueAccent,
          height: 50.0,
        ),
      ),
    );
  }

   _showAlertDialog() {
    var alert = new AlertDialog(
      content: new Container(
        color:Colors.red,
        width: 50.0,
        height: 50.0,
      )
    );
    showDialog(context: context,
        builder: (_){
      return alert;
    });
  }



}

Home

import 'package:firebase_example/Ui/Books.dart';
import 'package:flutter/material.dart';

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

class _HomeState extends State<Home> {
  Icon actionIcon = new Icon(Icons.search);
  Widget appBarTitle = new Text("کتاب فروشی آقای ایکس");

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: AppBar(
        title: appBarTitle,
        centerTitle: true,
        backgroundColor: Colors.blue,
        actions: <Widget>[
          new IconButton(
            icon: actionIcon,
            onPressed: () {
              setState(() {
                if (this.actionIcon.icon == Icons.search) {
                  this.actionIcon = new Icon(Icons.close);
                  this.appBarTitle = new TextField(
                    style: new TextStyle(
                      color: Colors.white,
                    ),
                    decoration: new InputDecoration(
                        prefixIcon: new Icon(Icons.search, color: Colors.white),
                        hintText: "Search...",
                        hintStyle: new TextStyle(color: Colors.white)),
                  );
                } else {
                  this.actionIcon = new Icon(Icons.search);
                  this.appBarTitle = new Text("AppBar Title");
                }
              });
            },
          ),
        ],
      ),
      body: Books(),
    );
  }
}