custom_nav.dart

import 'package:flutter/material.dart';

class WidgetAppBar extends StatefulWidget implements PreferredSizeWidget {
  final double height;
  final bool automaticallyImplyLeading;
  final Widget leading;

  @override
  final Size preferredSize;

  WidgetAppBar({
    Key key,
    this.height,
    this.leading,
    this.automaticallyImplyLeading = true,
  })  : preferredSize = Size.fromHeight(height != null ? height : 85),
        assert(automaticallyImplyLeading != null);

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

class _WidgetAppBarState extends State<WidgetAppBar> {
  Widget backButton(canPop, leading, useCloseButton) {
    if (leading == null && widget.automaticallyImplyLeading) {
      if (canPop) {
        return Row(
          mainAxisSize: MainAxisSize.max,
          mainAxisAlignment: MainAxisAlignment.spaceAround,
          children: <Widget>[
            GestureDetector(
              child: Icon(
                Icons.arrow_back_ios,
                size: 30,
                color: Colors.white,
              ),
              onTap: () {
                Navigator.of(context).pop();
              },
            ),
            SizedBox(
              width: MediaQuery.of(context).size.width * 0.03,
            ),
            Image.asset(
              'assets/logoTransparantBox.png',
              height: 75.0,
              width: 75.0,
              fit: BoxFit.fill,
            ),
          ],
        );
      } else {
        return Image.asset(
          'assets/logoTransparantBox.png',
          height: 75.0,
          width: 75.0,
          fit: BoxFit.fill,
        );
      }
    } else {
      return Image.asset(
        'assets/logoTransparantBox.png',
        height: 75.0,
        width: 75.0,
        fit: BoxFit.fill,
      );
    }
  }

  @override
  Widget build(BuildContext context) {
    final ModalRoute<dynamic> parentRoute = ModalRoute.of(context);
    final bool canPop = parentRoute?.canPop ?? false;

    final bool useCloseButton =
        parentRoute is PageRoute<dynamic> && parentRoute.fullscreenDialog;

    Widget leading = widget.leading;

    return Container(
      margin: EdgeInsets.only(bottom: 4),
      decoration: BoxDecoration(
        boxShadow: [
          BoxShadow(
            color: Color(0xff60D6E4).withOpacity(0.40),
            blurRadius: 4.0, // has the effect of softening the shadow
            spreadRadius: 4.0, // has the effect of extending the shadow
            offset: Offset(
              0, // horizontal, move right 10
              2, // vertical, move down 10
            ),
          ),
        ],
      ),
      child: Container(
        padding: EdgeInsets.symmetric(vertical: 4),
        color: Color(0xff60D6E4),
        child: SafeArea(
          child: Row(
            mainAxisSize: MainAxisSize.max,
            mainAxisAlignment: MainAxisAlignment.spaceEvenly,
            children: <Widget>[
              backButton(canPop, leading, useCloseButton),
              Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                mainAxisSize: MainAxisSize.min,
                mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                children: <Widget>[
                  Text(
                    "ELECTRONIC SANTRI TRACKING",
                    style: new TextStyle(
                      fontSize: 15.0,
                      color: Colors.white,
                      fontWeight: FontWeight.bold,
                    ),
                    textAlign: TextAlign.left,
                  ),
                  Text(
                    "& MONITORING SYSTEM",
                    style: new TextStyle(
                      fontSize: 15.0,
                      color: Colors.white,
                      fontWeight: FontWeight.bold,
                    ),
                    textAlign: TextAlign.left,
                  ),
                  Text(
                    "Al Wafi Islamic Boarding School",
                    style: new TextStyle(
                      fontSize: 15.0,
                    ),
                    textAlign: TextAlign.left,
                  ),
                ],
              )
            ],
          ),
        ),
      ),
    );
  }
}