Code

code.dart

import 'package:flutter/material.dart';
import 'package:iMooDSSP/util/box_decoration.dart';

class Marcas extends StatefulWidget {
  @override
  _MarcasState createState() => _MarcasState();
}

class _MarcasState extends State<Marcas> {
  Color colorMagenta = Color(0xFFD60B52);
  var colorDimGray = Color(0XFF666666);
  Future<bool> _onWillPop() async {
    return Navigator.of(context).pop(false);
  }

  @override
  Widget build(BuildContext context) {
    double mediaHeight = MediaQuery.of(context).size.height;
    double mediaWidth = MediaQuery.of(context).size.width;

    final customBorder = OutlineInputBorder(
        borderSide: BorderSide(color: colorDimGray, width: 1),
        borderRadius: BorderRadius.all(Radius.circular(70)));

    

    return WillPopScope(
      onWillPop: _onWillPop,
      child: Stack(
        children: <Widget>[
          Container(
            height: double.infinity,
            width: double.infinity,
            decoration: decorationFormat,
          ),
          Scaffold(
              appBar: AppBar(
                centerTitle: true,
                title: Text(
                  'Marcas',
                  style: TextStyle(fontFamily: 'Roboto'),
                ),
                backgroundColor: Colors.transparent,
                elevation: 0.0,
              ),
              backgroundColor: Colors.transparent,
              body: Center(
                child: Container(
                    child: ListView(
                  children: <Widget>[
                    
                    Container(
                      //height: 100,
                      child: Center(
                        child: Row(
                          children: <Widget>[
                            TextField(
                              style: TextStyle(
                                fontFamily: 'Roboto',
                                fontSize: 20,
                              ),
                              cursorColor: Colors.red,
                              decoration: InputDecoration(
                                contentPadding: EdgeInsets.only(
                                    left: 20, bottom: 40, top: 55),
                                enabledBorder: customBorder,
                                focusedBorder: customBorder,
                                border: customBorder,
                              ),
                            ),
                            IconButton(
                              icon: Icon(Icons.search,
                                  color: Colors.black, size: 40),
                              onPressed: () {},
                            ),
                          ],
                        ),
                      ),
                    ),
                    
                  ],
                )),
              )),
        ],
      ),
    );
  }
}