Reset Android UI to simple Material 3 Kotlin template

android/app/src/main/java/com/programperfect/messagesexpressive/MainActivity.kt

@@ -1,20 +1,219 @@
+@file:OptIn(androidx.compose.material3.ExperimentalMaterial3Api::class)
+
 package com.programperfect.messagesexpressive
 
 import android.os.Bundle
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
-import com.programperfect.messagesexpressive.core.designsystem.MessagesExpressiveTheme
-import com.programperfect.messagesexpressive.ui.MessagesApp
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.rounded.Add
+import androidx.compose.material.icons.rounded.Chat
+import androidx.compose.material.icons.rounded.Home
+import androidx.compose.material.icons.rounded.Notifications
+import androidx.compose.material.icons.rounded.Person
+import androidx.compose.material.icons.rounded.Settings
+import androidx.compose.material3.Badge
+import androidx.compose.material3.BadgedBox
+import androidx.compose.material3.CenterAlignedTopAppBar
+import androidx.compose.material3.ElevatedCard
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.ExtendedFloatingActionButton
+import androidx.compose.material3.Icon
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.NavigationBar
+import androidx.compose.material3.NavigationBarItem
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Surface
+import androidx.compose.material3.Text
+import androidx.compose.material3.TopAppBarDefaults
+import androidx.compose.material3.lightColorScheme
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
 
 class MainActivity : ComponentActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         enableEdgeToEdge()
         setContent {
-            MessagesExpressiveTheme {
-                MessagesApp()
+            Material3TemplateTheme {
+                TemplateApp()
+            }
+        }
+    }
+}
+
+@Composable
+private fun Material3TemplateTheme(content: @Composable () -> Unit) {
+    MaterialTheme(
+        colorScheme = lightColorScheme(
+            primary = Color(0xFF6750A4),
+            secondary = Color(0xFF625B71),
+            tertiary = Color(0xFF7D5260),
+            background = Color(0xFFFFFBFE),
+            surface = Color(0xFFFFFBFE),
+            surfaceVariant = Color(0xFFE7E0EC)
+        ),
+        content = content
+    )
+}
+
+@Composable
+private fun TemplateApp() {
+    Scaffold(
+        topBar = { TemplateTopBar() },
+        bottomBar = { TemplateBottomBar() },
+        floatingActionButton = {
+            ExtendedFloatingActionButton(
+                onClick = {},
+                icon = { Icon(Icons.Rounded.Add, contentDescription = null) },
+                text = { Text("Create") }
+            )
+        }
+    ) { padding ->
+        TemplateContent(padding)
+    }
+}
+
+@Composable
+private fun TemplateTopBar() {
+    CenterAlignedTopAppBar(
+        title = { Text("M3 Kotlin Template") },
+        actions = {
+            BadgedBox(
+                badge = { Badge { Text("3") } },
+                modifier = Modifier.padding(end = 16.dp)
+            ) {
+                Icon(Icons.Rounded.Notifications, contentDescription = "Notifications")
+            }
+        },
+        colors = TopAppBarDefaults.centerAlignedTopAppBarColors(
+            containerColor = MaterialTheme.colorScheme.surface,
+            titleContentColor = MaterialTheme.colorScheme.onSurface
+        )
+    )
+}
+
+@Composable
+private fun TemplateContent(padding: PaddingValues) {
+    val items = listOf(
+        TemplateItem("Native Kotlin", "Single Activity, Jetpack Compose, Material 3"),
+        TemplateItem("Design System", "MaterialTheme, colorScheme, typography, shapes"),
+        TemplateItem("Ready Layout", "Top app bar, cards, navigation bar, FAB")
+    )
+
+    LazyColumn(
+        modifier = Modifier
+            .fillMaxSize()
+            .padding(padding),
+        contentPadding = PaddingValues(20.dp),
+        verticalArrangement = Arrangement.spacedBy(16.dp)
+    ) {
+        item { HeroCard() }
+        items(items) { item -> TemplateCard(item) }
+        item { Spacer(Modifier.height(80.dp)) }
+    }
+}
+
+@Composable
+private fun HeroCard() {
+    Surface(
+        modifier = Modifier.fillMaxWidth(),
+        shape = RoundedCornerShape(28.dp),
+        color = MaterialTheme.colorScheme.primaryContainer,
+        contentColor = MaterialTheme.colorScheme.onPrimaryContainer,
+        tonalElevation = 4.dp
+    ) {
+        Column(
+            modifier = Modifier.padding(24.dp),
+            verticalArrangement = Arrangement.spacedBy(10.dp)
+        ) {
+            Text(
+                text = "Material 3 App",
+                style = MaterialTheme.typography.headlineMedium,
+                fontWeight = FontWeight.Bold
+            )
+            Text(
+                text = "Clean native Android starter on Kotlin and Jetpack Compose.",
+                style = MaterialTheme.typography.bodyLarge
+            )
+        }
+    }
+}
+
+@Composable
+private fun TemplateCard(item: TemplateItem) {
+    ElevatedCard(
+        modifier = Modifier.fillMaxWidth(),
+        shape = RoundedCornerShape(24.dp)
+    ) {
+        Row(
+            modifier = Modifier.padding(20.dp),
+            verticalAlignment = Alignment.CenterVertically,
+            horizontalArrangement = Arrangement.spacedBy(16.dp)
+        ) {
+            Surface(
+                modifier = Modifier.size(48.dp),
+                shape = RoundedCornerShape(16.dp),
+                color = MaterialTheme.colorScheme.secondaryContainer,
+                contentColor = MaterialTheme.colorScheme.onSecondaryContainer
+            ) {
+                Icon(
+                    imageVector = Icons.Rounded.Chat,
+                    contentDescription = null,
+                    modifier = Modifier.padding(12.dp)
+                )
+            }
+            Column(verticalArrangement = Arrangement.spacedBy(4.dp)) {
+                Text(item.title, style = MaterialTheme.typography.titleMedium, fontWeight = FontWeight.SemiBold)
+                Text(item.subtitle, style = MaterialTheme.typography.bodyMedium, color = MaterialTheme.colorScheme.onSurfaceVariant)
             }
         }
     }
 }
+
+@Composable
+private fun TemplateBottomBar() {
+    NavigationBar {
+        NavigationBarItem(
+            selected = true,
+            onClick = {},
+            icon = { Icon(Icons.Rounded.Home, contentDescription = null) },
+            label = { Text("Home") }
+        )
+        NavigationBarItem(
+            selected = false,
+            onClick = {},
+            icon = { Icon(Icons.Rounded.Person, contentDescription = null) },
+            label = { Text("Profile") }
+        )
+        NavigationBarItem(
+            selected = false,
+            onClick = {},
+            icon = { Icon(Icons.Rounded.Settings, contentDescription = null) },
+            label = { Text("Settings") }
+        )
+    }
+}
+
+private data class TemplateItem(
+    val title: String,
+    val subtitle: String
+)