feat: Implement initial Android launcher application with Compose, including app listing and launching capabilities.

app/build.gradle.kts

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+plugins {
+    alias(libs.plugins.android.application)
+    alias(libs.plugins.kotlin.android)
+    alias(libs.plugins.compose.compiler)
+}
+
+android {
+    namespace = "com.example.luncher"
+    compileSdk = 35
+
+    defaultConfig {
+        applicationId = "com.example.luncher"
+        minSdk = 26
+        targetSdk = 35
+        versionCode = 1
+        versionName = "1.0"
+
+        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
+    }
+
+    buildTypes {
+        release {
+            isMinifyEnabled = false
+            proguardFiles(
+                getDefaultProguardFile("proguard-android-optimize.txt"),
+                "proguard-rules.pro"
+            )
+        }
+    }
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_11
+        targetCompatibility = JavaVersion.VERSION_11
+    }
+    kotlinOptions {
+        jvmTarget = "11"
+    }
+    buildFeatures {
+        compose = true
+    }
+}
+
+dependencies {
+    implementation(libs.androidx.core.ktx)
+    implementation(libs.androidx.lifecycle.runtime.ktx)
+    implementation(libs.androidx.activity.compose)
+    implementation(platform(libs.androidx.compose.bom))
+    implementation(libs.androidx.ui)
+    implementation(libs.androidx.ui.graphics)
+    implementation(libs.androidx.ui.tooling.preview)
+    implementation(libs.androidx.material3)
+    implementation(libs.androidx.datastore.preferences)
+    
+    debugImplementation(libs.androidx.ui.tooling)
+}

app/src/main/AndroidManifest.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools">
+
+    <application
+        android:allowBackup="true"
+        android:dataExtractionRules="@xml/data_extraction_rules"
+        android:fullBackupContent="@xml/backup_rules"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:roundIcon="@mipmap/ic_launcher_round"
+        android:supportsRtl="true"
+        android:theme="@style/Theme.Luncher"
+        tools:targetApi="31">
+        
+        <activity
+            android:name=".MainActivity"
+            android:exported="true"
+            android:launchMode="singleInstance"
+            android:stateNotNeeded="true"
+            android:theme="@style/Theme.Luncher">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.HOME" />
+                <category android:name="android.intent.category.DEFAULT" />
+            </intent-filter>
+        </activity>
+
+        <activity
+            android:name=".SettingsActivity"
+            android:exported="false"
+            android:theme="@style/Theme.Luncher" />
+            
+    </application>
+
+</manifest>

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

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+package com.example.luncher
+
+import android.content.Intent
+import android.os.Bundle
+import androidx.activity.ComponentActivity
+import androidx.activity.compose.setContent
+import androidx.activity.enableEdgeToEdge
+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.unit.dp
+import androidx.lifecycle.lifecycleScope
+import com.example.luncher.data.PreferencesRepository
+import com.example.luncher.ui.theme.LuncherTheme
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.launch
+
+class MainActivity : ComponentActivity() {
+
+    private lateinit var preferencesRepository: PreferencesRepository
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        enableEdgeToEdge()
+        preferencesRepository = PreferencesRepository(this)
+
+        lifecycleScope.launch {
+            val selectedPackage = preferencesRepository.selectedAppPackage.first()
+            if (selectedPackage != null) {
+                launchApp(selectedPackage)
+            }
+        }
+
+        setContent {
+            LuncherTheme {
+                MainScreen(
+                    onOpenSettings = {
+                        startActivity(Intent(this, SettingsActivity::class.java))
+                    }
+                )
+            }
+        }
+    }
+
+    override fun onResume() {
+        super.onResume()
+        // Every time the user hits the Home button, this activity is resumed.
+        // We check if an app is selected and launch it.
+        lifecycleScope.launch {
+            val selectedPackage = preferencesRepository.selectedAppPackage.first()
+            if (selectedPackage != null) {
+                launchApp(selectedPackage)
+            }
+        }
+    }
+
+    private fun launchApp(packageName: String) {
+        val launchIntent = packageManager.getLaunchIntentForPackage(packageName)
+        if (launchIntent != null) {
+            // Use FLAG_ACTIVITY_REORDER_TO_FRONT to bring the existing task to the front
+            // instead of creating a new one or restarting the app.
+            launchIntent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT)
+            launchIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
+            startActivity(launchIntent)
+        }
+    }
+}
+
+@Composable
+fun MainScreen(onOpenSettings: () -> Unit) {
+    Surface(
+        modifier = Modifier.fillMaxSize(),
+        color = MaterialTheme.colorScheme.background
+    ) {
+        Column(
+            modifier = Modifier
+                .fillMaxSize()
+                .padding(32.dp),
+            verticalArrangement = Arrangement.Center,
+            horizontalAlignment = Alignment.CenterHorizontally
+        ) {
+            Text(
+                text = "Luncher",
+                style = MaterialTheme.typography.displayMedium,
+                color = MaterialTheme.colorScheme.primary
+            )
+            Spacer(modifier = Modifier.height(16.dp))
+            Text(
+                text = "No app selected yet.",
+                style = MaterialTheme.typography.bodyLarge
+            )
+            Spacer(modifier = Modifier.height(32.dp))
+            Button(onClick = onOpenSettings) {
+                Text("Open Settings")
+            }
+        }
+    }
+}

app/src/main/java/com/example/luncher/SettingsActivity.kt

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+package com.example.luncher
+
+import android.content.Context
+import android.content.Intent
+import android.os.Bundle
+import android.provider.Settings
+import androidx.activity.ComponentActivity
+import androidx.activity.compose.setContent
+import androidx.activity.enableEdgeToEdge
+import androidx.compose.foundation.Image
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.*
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.Settings
+import androidx.compose.material3.*
+import androidx.compose.runtime.*
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.asImageBitmap
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.unit.dp
+import androidx.core.graphics.drawable.toBitmap
+import com.example.luncher.data.AppInfo
+import com.example.luncher.data.AppRepository
+import com.example.luncher.data.PreferencesRepository
+import com.example.luncher.ui.theme.LuncherTheme
+import kotlinx.coroutines.launch
+
+class SettingsActivity : ComponentActivity() {
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        enableEdgeToEdge()
+        val appRepository = AppRepository(this)
+        val preferencesRepository = PreferencesRepository(this)
+
+        setContent {
+            LuncherTheme {
+                SettingsScreen(
+                    appRepository = appRepository,
+                    preferencesRepository = preferencesRepository,
+                    onBack = { finish() }
+                )
+            }
+        }
+    }
+}
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun SettingsScreen(
+    appRepository: AppRepository,
+    preferencesRepository: PreferencesRepository,
+    onBack: () -> Unit
+) {
+    val context = LocalContext.current
+    val scope = rememberCoroutineScope()
+    val apps = remember { appRepository.getInstalledApps() }
+    val selectedApp by preferencesRepository.selectedAppPackage.collectAsState(initial = null)
+
+    Scaffold(
+        topBar = {
+            TopAppBar(
+                title = { Text("Launcher Settings") },
+                actions = {
+                   Button(onClick = {
+                       val intent = Intent(Settings.ACTION_HOME_SETTINGS)
+                       context.startActivity(intent)
+                   }) {
+                       Text("Switch Launcher")
+                   }
+                }
+            )
+        }
+    ) { innerPadding ->
+        LazyColumn(
+            modifier = Modifier
+                .padding(innerPadding)
+                .fillMaxSize()
+        ) {
+            item {
+                Text(
+                    "Select the app you want to use as your main interface:",
+                    style = MaterialTheme.typography.bodyLarge,
+                    modifier = Modifier.padding(16.dp)
+                )
+            }
+            items(apps) { app ->
+                AppItem(
+                    app = app,
+                    isSelected = selectedApp == app.packageName,
+                    onClick = {
+                        scope.launch {
+                            preferencesRepository.setSelectedAppPackage(app.packageName)
+                            onBack()
+                        }
+                    }
+                )
+            }
+        }
+    }
+}
+
+@Composable
+fun AppItem(
+    app: AppInfo,
+    isSelected: Boolean,
+    onClick: () -> Unit
+) {
+    ListItem(
+        modifier = Modifier.clickable { onClick() },
+        headlineContent = { Text(app.name) },
+        supportingContent = { Text(app.packageName) },
+        leadingContent = {
+            app.icon?.let { icon ->
+                Image(
+                    bitmap = icon.toBitmap().asImageBitmap(),
+                    contentDescription = null,
+                    modifier = Modifier.size(40.dp)
+                )
+            }
+        },
+        trailingContent = {
+            if (isSelected) {
+                RadioButton(selected = true, onClick = null)
+            }
+        }
+    )
+}

app/src/main/java/com/example/luncher/data/AppRepository.kt

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+package com.example.luncher.data
+
+import android.content.Context
+import android.content.Intent
+import android.graphics.drawable.Drawable
+
+data class AppInfo(
+    val name: String,
+    val packageName: String,
+    val icon: Drawable?
+)
+
+class AppRepository(private val context: Context) {
+
+    fun getInstalledApps(): List<AppInfo> {
+        val pm = context.packageManager
+        val mainIntent = Intent(Intent.ACTION_MAIN, null)
+        mainIntent.addCategory(Intent.CATEGORY_LAUNCHER)
+        
+        val resolvedInfos = pm.queryIntentActivities(mainIntent, 0)
+        
+        return resolvedInfos
+            .filter { it.activityInfo.packageName != context.packageName } // Exclude our own app
+            .map {
+                AppInfo(
+                    name = it.loadLabel(pm).toString(),
+                    packageName = it.activityInfo.packageName,
+                    icon = it.loadIcon(pm)
+                )
+            }
+            .sortedBy { it.name }
+    }
+}

app/src/main/java/com/example/luncher/data/PreferencesRepository.kt

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+package com.example.luncher.data
+
+import android.content.Context
+import androidx.datastore.core.DataStore
+import androidx.datastore.preferences.core.Preferences
+import androidx.datastore.preferences.core.edit
+import androidx.datastore.preferences.core.stringPreferencesKey
+import androidx.datastore.preferences.preferencesDataStore
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.map
+
+private val Context.dataStore: DataStore<Preferences> by preferencesDataStore(name = "launcher_settings")
+
+class PreferencesRepository(private val context: Context) {
+
+    private object PreferencesKeys {
+        val SELECTED_APP_PACKAGE = stringPreferencesKey("selected_app_package")
+    }
+
+    val selectedAppPackage: Flow<String?> = context.dataStore.data
+        .map { preferences ->
+            preferences[PreferencesKeys.SELECTED_APP_PACKAGE]
+        }
+
+    suspend fun setSelectedAppPackage(packageName: String?) {
+        context.dataStore.edit { preferences ->
+            if (packageName == null) {
+                preferences.remove(PreferencesKeys.SELECTED_APP_PACKAGE)
+            } else {
+                preferences[PreferencesKeys.SELECTED_APP_PACKAGE] = packageName
+            }
+        }
+    }
+}

app/src/main/java/com/example/luncher/ui/theme/Theme.kt

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+package com.example.luncher.ui.theme
+
+import android.os.Build
+import androidx.compose.foundation.isSystemInDarkTheme
+import androidx.compose.material3.*
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.platform.LocalContext
+
+@Composable
+fun LuncherTheme(
+    darkTheme: Boolean = isSystemInDarkTheme(),
+    dynamicColor: Boolean = true,
+    content: @Composable () -> Unit
+) {
+    val colorScheme = when {
+        dynamicColor && Build.VERSION.SDK_INT >= Build.VERSION_31 -> {
+            val context = LocalContext.current
+            if (darkTheme) dynamicDarkColorScheme(context) else dynamicLightColorScheme(context)
+        }
+        darkTheme -> darkColorScheme()
+        else -> lightColorScheme()
+    }
+
+    MaterialTheme(
+        colorScheme = colorScheme,
+        content = content
+    )
+}

app/src/main/res/drawable/ic_launcher_foreground.xml

@@ -0,0 +1,12 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="108dp"
+    android:height="108dp"
+    android:viewportWidth="108"
+    android:viewportHeight="108">
+    <path
+        android:fillColor="#FF6200EE"
+        android:pathData="M54,54m-40,0a40,40 0,1 1,80 0a40,40 0,1 1,-80 0" />
+    <path
+        android:fillColor="#FFFFFFFF"
+        android:pathData="M65,40L43,40C41.34,40 40,41.34 40,43L40,65C40,66.66 41.34,68 43,68L65,68C66.66,68 68,66.66 68,65L68,43C68,41.34 66.66,40 65,40ZM64,64L44,64L44,44L64,44L64,64Z" />
+</vector>

app/src/main/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@color/white"/>
+    <foreground android:drawable="@drawable/ic_launcher_foreground"/>
+</adaptive-icon>

app/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@color/white"/>
+    <foreground android:drawable="@drawable/ic_launcher_foreground"/>
+</adaptive-icon>

app/src/main/res/values/colors.xml

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+<resources>
+    <color name="white">#FFFFFFFF</color>
+</resources>

app/src/main/res/values/strings.xml

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+<resources>
+    <string name="app_name">Luncher</string>
+</resources>

app/src/main/res/values/themes.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <style name="Theme.Luncher" parent="android:Theme.Material.Light.NoActionBar" />
+</resources>

app/src/main/res/xml/backup_rules.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<full-backup-content>
+    <include domain="file" path="." />
+</full-backup-content>

app/src/main/res/xml/data_extraction_rules.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<data-extraction-rules>
+    <cloud-backup>
+        <include domain="file" path="." />
+    </cloud-backup>
+    <device-transfer>
+        <include domain="file" path="." />
+    </device-transfer>
+</data-extraction-rules>

build.gradle.kts

@@ -0,0 +1,5 @@
+plugins {
+    alias(libs.plugins.android.application) apply false
+    alias(libs.plugins.kotlin.android) apply false
+    alias(libs.plugins.compose.compiler) apply false
+}

gradle/libs.versions.toml

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+[versions]
+agp = "8.7.3"
+kotlin = "2.0.0"
+coreKtx = "1.15.0"
+lifecycleRuntimeKtx = "2.8.7"
+activityCompose = "1.9.3"
+composeBom = "2024.12.01"
+datastore = "1.1.1"
+
+[libraries]
+androidx-core-ktx = { group = "androidx.core", name = "core-ktx", version.ref = "coreKtx" }
+androidx-lifecycle-runtime-ktx = { group = "androidx.lifecycle", name = "lifecycle-runtime-ktx", version.ref = "lifecycleRuntimeKtx" }
+androidx-activity-compose = { group = "androidx.activity", name = "activity-compose", version.ref = "activityCompose" }
+androidx-compose-bom = { group = "androidx.compose", name = "compose-bom", version.ref = "composeBom" }
+androidx-ui = { group = "androidx.compose.ui", name = "ui" }
+androidx-ui-graphics = { group = "androidx.compose.ui", name = "ui-graphics" }
+androidx-ui-tooling = { group = "androidx.compose.ui", name = "ui-tooling" }
+androidx-ui-tooling-preview = { group = "androidx.compose.ui", name = "ui-tooling-preview" }
+androidx-material3 = { group = "androidx.compose.material3", name = "material3" }
+androidx-datastore-preferences = { group = "androidx.datastore", name = "datastore-preferences", version.ref = "datastore" }
+
+[plugins]
+android-application = { id = "com.android.application", version.ref = "agp" }
+kotlin-android = { id = "org.jetbrains.kotlin.android", version.ref = "kotlin" }
+compose-compiler = { id = "org.jetbrains.kotlin.plugin.compose", version.ref = "kotlin" }

settings.gradle.kts

@@ -0,0 +1,16 @@
+pluginManagement {
+    repositories {
+        google()
+        mavenCentral()
+        gradlePluginPortal()
+    }
+}
+dependencyResolutionManagement {
+    repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
+    repositories {
+        google()
+        mavenCentral()
+    }
+}
+rootProject.name = "Luncher"
+include(":app")