Untitled

import 'package:flutter/material.dart';

class JarakPage extends StatefulWidget {
  const JarakPage({Key? key}) : super(key: key);

  @override
  State<JarakPage> createState() => _JarakPageState();
}

class _JarakPageState extends State<JarakPage> {

  double? kecepatan;
  double? waktu;
  
  double hasil() {

    double tmpHasil = 0;

    if (kecepatan != null && waktu != null) {
      tmpHasil = kecepatan! * waktu!;
    }

    return tmpHasil;
  }


  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("Menghitung Jarak"),
      ),
      body: SingleChildScrollView(
        child: Padding(
          padding: const EdgeInsets.symmetric(horizontal: 30),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: [
              const Padding(
                padding: EdgeInsets.symmetric(vertical: 8.0),
                child: Center(
                  child: Text(
                    "s = v x t",
                    style: TextStyle(
                      fontSize: 20,
                      fontWeight: FontWeight.bold,
                    ),
                  ),
                ),
              ),
              Padding(
                padding: const EdgeInsets.symmetric(vertical: 10.0),
                child: TextFormField(
                  // controller: gayaController,
                  autofocus: true,
                  onChanged: (val) {
                    setState(() {
                      kecepatan = double.parse(val);
                    });
                  },
                  keyboardType: TextInputType.number,
                  decoration: const InputDecoration(
                    hintText: "Masukkan nilai kecepatan",
                  ),
                ),
              ),
              Padding(
                padding: const EdgeInsets.symmetric(vertical: 10.0),
                child: TextFormField(
                  // controller: percepatanController,
                  autofocus: true,
                  onChanged: (val) {
                    setState(() {
                      waktu = double.parse(val);
                    });
                  },
                  keyboardType: TextInputType.number,
                  decoration: const InputDecoration(
                    hintText: "Masukkan nilai kecepatan",
                  ),
                ),
              ),
              const Text(
                "Hasil: ",
                style: TextStyle(
                  fontSize: 18,
                ),
              ),
              Padding(
                padding: const EdgeInsets.symmetric(vertical: 10),
                child: Text(
                  hasil().toString(),
                  style: const TextStyle(
                    fontSize: 18,
                    fontWeight: FontWeight.bold,
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}