Añadir pantalla login y conexion a mariadb

app/build.gradle.kts

@@ -42,6 +42,7 @@ dependencies {
     implementation(libs.androidx.compose.ui.tooling.preview)
     implementation(libs.androidx.core.ktx)
     implementation(libs.androidx.lifecycle.runtime.ktx)
+    implementation(libs.mariadb.java.client)
     testImplementation(libs.junit)
     androidTestImplementation(platform(libs.androidx.compose.bom))
     androidTestImplementation(libs.androidx.compose.ui.test.junit4)

app/src/main/AndroidManifest.xml

@@ -2,6 +2,8 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools">
 
+    <uses-permission android:name="android.permission.INTERNET" />
+
     <application
         android:allowBackup="true"
         android:dataExtractionRules="@xml/data_extraction_rules"

app/src/main/java/com/example/saludapp/MainActivity.kt

@@ -4,6 +4,16 @@ import android.os.Bundle
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.material3.Text
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import com.example.saludapp.ui.LoginScreen
 import com.example.saludapp.ui.StartScreen
 import com.example.saludapp.ui.theme.SaludappTheme
 
@@ -13,8 +23,24 @@ class MainActivity : ComponentActivity() {
         enableEdgeToEdge()
         setContent {
             SaludappTheme {
-                StartScreen {
-                    // Acción al presionar el botón
+                var currentScreen by remember { mutableStateOf("start") }
+
+                when (currentScreen) {
+                    "start" -> StartScreen {
+                        currentScreen = "login"
+                    }
+                    "login" -> LoginScreen {
+                        // Aquí iría la lógica tras login exitoso
+                        currentScreen = "home"
+                    }
+                    "home" -> {
+                        Box(
+                            modifier = Modifier.fillMaxSize(),
+                            contentAlignment = Alignment.Center
+                        ) {
+                            Text("Bienvenido a Saludapp")
+                        }
+                    }
                 }
             }
         }

app/src/main/java/com/example/saludapp/data/DatabaseHelper.kt

@@ -0,0 +1,43 @@
+package com.example.saludapp.data
+
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+import java.sql.Connection
+import java.sql.DriverManager
+import java.sql.SQLException
+
+object DatabaseHelper {
+    private const val URL = "jdbc:mariadb://mariadb.peta9.com:3306/saludapp_db"
+    private const val USER = "saludapp_dba"
+    private const val PASSWORD = "TU_CONTRASEÑA_AQUÍ" // TODO: Reemplazar con la contraseña real
+
+    suspend fun validateLogin(user: String, pass: String): Boolean = withContext(Dispatchers.IO) {
+        var connection: Connection? = null
+        try {
+            // Cargar el driver explícitamente si es necesario
+            Class.forName("org.mariadb.jdbc.Driver")
+            connection = DriverManager.getConnection(URL, USER, PASSWORD)
+            
+            val query = "SELECT COUNT(*) FROM usuarios WHERE (username = ? OR email = ?) AND password = ?"
+            connection.prepareStatement(query).use { statement ->
+                statement.setString(1, user)
+                statement.setString(2, user)
+                statement.setString(3, pass)
+                
+                val resultSet = statement.executeQuery()
+                if (resultSet.next()) {
+                    return@withContext resultSet.getInt(1) > 0
+                }
+            }
+        } catch (e: Exception) {
+            e.printStackTrace()
+        } finally {
+            try {
+                connection?.close()
+            } catch (e: SQLException) {
+                e.printStackTrace()
+            }
+        }
+        return@withContext false
+    }
+}

app/src/main/java/com/example/saludapp/ui/LoginScreen.kt

@@ -0,0 +1,102 @@
+package com.example.saludapp.ui
+
+import androidx.compose.foundation.layout.*
+import androidx.compose.material3.*
+import androidx.compose.runtime.*
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.input.PasswordVisualTransformation
+import androidx.compose.ui.unit.dp
+import com.example.saludapp.data.DatabaseHelper
+import kotlinx.coroutines.launch
+
+@Composable
+fun LoginScreen(onLoginSuccess: () -> Unit) {
+    var email by remember { mutableStateOf("") }
+    var password by remember { mutableStateOf("") }
+    var isLoading by remember { mutableStateOf(false) }
+    var errorMessage by remember { mutableStateOf<String?>(null) }
+    val scope = rememberCoroutineScope()
+
+    Surface(
+        modifier = Modifier.fillMaxSize(),
+        color = MaterialTheme.colorScheme.background
+    ) {
+        Column(
+            modifier = Modifier
+                .fillMaxSize()
+                .padding(24.dp),
+            horizontalAlignment = Alignment.CenterHorizontally,
+            verticalArrangement = Arrangement.Center
+        ) {
+            Text(
+                text = "Iniciar Sesión",
+                style = MaterialTheme.typography.headlineMedium,
+                color = MaterialTheme.colorScheme.primary
+            )
+
+            Spacer(modifier = Modifier.height(32.dp))
+
+            OutlinedTextField(
+                value = email,
+                onValueChange = { email = it },
+                label = { Text("Usuario o Email") },
+                modifier = Modifier.fillMaxWidth(),
+                singleLine = true,
+                enabled = !isLoading
+            )
+
+            Spacer(modifier = Modifier.height(16.dp))
+
+            OutlinedTextField(
+                value = password,
+                onValueChange = { password = it },
+                label = { Text("Contraseña") },
+                visualTransformation = PasswordVisualTransformation(),
+                modifier = Modifier.fillMaxWidth(),
+                singleLine = true,
+                enabled = !isLoading
+            )
+
+            if (errorMessage != null) {
+                Text(
+                    text = errorMessage!!,
+                    color = MaterialTheme.colorScheme.error,
+                    modifier = Modifier.padding(top = 16.dp)
+                )
+            }
+
+            Spacer(modifier = Modifier.height(32.dp))
+
+            Button(
+                onClick = { 
+                    scope.launch {
+                        isLoading = true
+                        errorMessage = null
+                        val success = DatabaseHelper.validateLogin(email, password)
+                        isLoading = false
+                        if (success) {
+                            onLoginSuccess()
+                        } else {
+                            errorMessage = "Usuario o contraseña incorrectos"
+                        }
+                    }
+                },
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .height(56.dp),
+                enabled = !isLoading && email.isNotEmpty() && password.isNotEmpty()
+            ) {
+                if (isLoading) {
+                    CircularProgressIndicator(
+                        modifier = Modifier.size(24.dp),
+                        color = MaterialTheme.colorScheme.onPrimary,
+                        strokeWidth = 2.dp
+                    )
+                } else {
+                    Text("Entrar")
+                }
+            }
+        }
+    }
+}