creacion de tres paginas login, home, articles

lib/login.dart

-import 'package:flutter/material.dart';
-
-class PantallaInicioSesion extends StatefulWidget {
-  @override
-  _PantallaInicioSesionState createState() => _PantallaInicioSesionState();
-}
-
-class _PantallaInicioSesionState extends State<PantallaInicioSesion> {
-  final _formKey = GlobalKey<FormState>();
-  final TextEditingController _usuarioController = TextEditingController();
-  final TextEditingController _contrasenaController = TextEditingController();
-
-  void _iniciarSesion() {
-    if (_formKey.currentState!.validate()) {
-      Navigator.pushReplacementNamed(context, '/categorias');
-    }
-  }
-
-  @override
-  Widget build(BuildContext context) {
-    return Scaffold(
-      appBar: AppBar(
-        title: Text('Inicio de Sesión'),
-      ),
-      body: Padding(
-        padding: EdgeInsets.all(16.0),
-        child: Form(
-          key: _formKey,
-          child: Column(
-            mainAxisAlignment: MainAxisAlignment.center,
-            children: [
-              TextFormField(
-                controller: _usuarioController,
-                decoration: InputDecoration(labelText: 'Usuario'),
-                validator: (value) {
-                  if (value!.isEmpty) {
-                    return 'Por favor ingrese su usuario';
-                  }
-                  return null;
-                },
-              ),
-              TextFormField(
-                controller: _contrasenaController,
-                decoration: InputDecoration(labelText: 'Contraseña'),
-                obscureText: true,
-                validator: (value) {
-                  if (value!.isEmpty) {
-                    return 'Por favor ingrese su contraseña';
-                  }
-                  return null;
-                },
-              ),
-              SizedBox(height: 20),
-              ElevatedButton(
-                onPressed: _iniciarSesion,
-                child: Text('Iniciar Sesión'),
-              ),
-            ],
-          ),
-        ),
-      ),
-    );
-  }
-}

lib/main.dart

 import 'package:flutter/material.dart';
 
-import 'login.dart';
-
-
 void main() {
   runApp(const MyApp());
 }
@@ -10,37 +7,119 @@ void main() {
 class MyApp extends StatelessWidget {
   const MyApp({super.key});
 
+  // This widget is the root of your application.
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
       title: 'Flutter Demo',
       theme: ThemeData(
+        // This is the theme of your application.
+        //
+        // TRY THIS: Try running your application with "flutter run". You'll see
+        // the application has a purple toolbar. Then, without quitting the app,
+        // try changing the seedColor in the colorScheme below to Colors.green
+        // and then invoke "hot reload" (save your changes or press the "hot
+        // reload" button in a Flutter-supported IDE, or press "r" if you used
+        // the command line to start the app).
+        //
+        // Notice that the counter didn't reset back to zero; the application
+        // state is not lost during the reload. To reset the state, use hot
+        // restart instead.
+        //
+        // This works for code too, not just values: Most code changes can be
+        // tested with just a hot reload.
         colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
         useMaterial3: true,
       ),
-      initialRoute: '/',
-      routes: {
-        '/': (context) => PantallaInicioSesion(),
-        '/categorias': (context) => CategoriasListScreen(),
-      },
+      home: const MyHomePage(title: 'Flutter Demo Home Page'),
     );
   }
 }
 
-// Aquí va tu CategoriasListScreen para la pantalla de categorías.
-// Crea un archivo llamado categorias_list_screen.dart en la carpeta lib/screens
-// y define la pantalla de categorías. Aquí tienes un ejemplo básico:
+class MyHomePage extends StatefulWidget {
+  const MyHomePage({super.key, required this.title});
+
+  // This widget is the home page of your application. It is stateful, meaning
+  // that it has a State object (defined below) that contains fields that affect
+  // how it looks.
+
+  // This class is the configuration for the state. It holds the values (in this
+  // case the title) provided by the parent (in this case the App widget) and
+  // used by the build method of the State. Fields in a Widget subclass are
+  // always marked "final".
+
+  final String title;
+
+  @override
+  State<MyHomePage> createState() => _MyHomePageState();
+}
+
+class _MyHomePageState extends State<MyHomePage> {
+  int _counter = 0;
+
+  void _incrementCounter() {
+    setState(() {
+      // This call to setState tells the Flutter framework that something has
+      // changed in this State, which causes it to rerun the build method below
+      // so that the display can reflect the updated values. If we changed
+      // _counter without calling setState(), then the build method would not be
+      // called again, and so nothing would appear to happen.
+      _counter++;
+    });
+  }
 
-class CategoriasListScreen extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
+    // This method is rerun every time setState is called, for instance as done
+    // by the _incrementCounter method above.
+    //
+    // The Flutter framework has been optimized to make rerunning build methods
+    // fast, so that you can just rebuild anything that needs updating rather
+    // than having to individually change instances of widgets.
     return Scaffold(
       appBar: AppBar(
-        title: Text('Categorias'),
+        // TRY THIS: Try changing the color here to a specific color (to
+        // Colors.amber, perhaps?) and trigger a hot reload to see the AppBar
+        // change color while the other colors stay the same.
+        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
+        // Here we take the value from the MyHomePage object that was created by
+        // the App.build method, and use it to set our appbar title.
+        title: Text(widget.title),
       ),
       body: Center(
-        child: Text('Lista de Categorías'),
+        // Center is a layout widget. It takes a single child and positions it
+        // in the middle of the parent.
+        child: Column(
+          // Column is also a layout widget. It takes a list of children and
+          // arranges them vertically. By default, it sizes itself to fit its
+          // children horizontally, and tries to be as tall as its parent.
+          //
+          // Column has various properties to control how it sizes itself and
+          // how it positions its children. Here we use mainAxisAlignment to
+          // center the children vertically; the main axis here is the vertical
+          // axis because Columns are vertical (the cross axis would be
+          // horizontal).
+          //
+          // TRY THIS: Invoke "debug painting" (choose the "Toggle Debug Paint"
+          // action in the IDE, or press "p" in the console), to see the
+          // wireframe for each widget.
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: <Widget>[
+            const Text(
+              'You have pushed the button this many times:',
+            ),
+            Text(
+              '$_counter',
+              style: Theme.of(context).textTheme.headlineMedium,
+            ),
+          ],
+        ),
       ),
+      floatingActionButton: FloatingActionButton(
+        onPressed: _incrementCounter,
+        tooltip: 'Increment',
+        child: const Icon(Icons.add),
+      ), // This trailing comma makes auto-formatting nicer for build methods.
     );
   }
 }