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App Picker & Selection Pattern

A comprehensive implementation for listing, filtering, and selecting installed applications (system and user) with high performance and premium UI.

1. Data Models

The system uses two primary models: one for the UI representation (NotificationApp) and one for persistence (AppSelection).

data class NotificationApp(
    val packageName: String,
    val appName: String,
    val isEnabled: Boolean,
    val icon: ImageBitmap,
    val isSystemApp: Boolean,
    val lastUpdated: Long
)

data class AppSelection(
    val packageName: String,
    val isEnabled: Boolean
)

2. The App Utility (AppUtil)

The AppUtil object handles the heavy lifting of interacting with the PackageManager.

Key Features

  • Icon Caching & Scaling: App icons are scaled down (e.g., 64x64) and cached in memory to prevent IPC overhead and high memory usage when scrolling through hundreds of apps.
  • System App Detection: Accurate detection using ApplicationInfo.FLAG_SYSTEM.
  • Merge Logic: Merges the live installed apps list with user-saved preferences.
  • Brand Color Extraction: Uses the Palette API to extract vibrant colors from app icons for themed UI elements.
suspend fun getInstalledApps(context: Context): List<NotificationApp> = withContext(Dispatchers.IO) {
    val pm = context.packageManager
    pm.getInstalledApplications(0).map { appInfo ->
        NotificationApp(
            packageName = appInfo.packageName,
            appName = pm.getApplicationLabel(appInfo).toString(),
            icon = getLowQualityIcon(context, appInfo.packageName).asImageBitmap(),
            isSystemApp = (appInfo.flags and ApplicationInfo.FLAG_SYSTEM) != 0,
            // ...
        )
    }
}

3. UI Variants

Multi-Selection Sheet (AppSelectionSheet)

Used when the user needs to enable/disable multiple apps (e.g., for notification lighting).

Features:

  • Search: Real-time filtering by app name.
  • System Toggle: Ability to show/hide system apps.
  • Invert Selection: A quick action to flip all visible checkboxes.
  • Sorting: Enabled apps are pinned to the top, followed by alphabetical order.

Single Selection Sheet (SingleAppSelectionSheet)

Used when a single app needs to be picked for a specific action (e.g., "Open this app on click").

4. Performance Optimizations

1. IO Offloading

Always load apps inside a LaunchedEffect using Dispatchers.IO to keep the UI responsive.

LaunchedEffect(Unit) {
    withContext(Dispatchers.IO) {
        val allApps = AppUtil.getInstalledApps(context)
        selectedApps = AppUtil.mergeWithSavedApps(allApps, savedSelections)
    }
}

2. Lazy Loading

The LazyColumn uses the packageName as a key to ensure efficient list updates and animations.

LazyColumn {
    items(filteredApps, key = { it.packageName }) { app ->
        AppToggleItem(...)
    }
}

3. Icon Management

Scaling icons to a fixed ICON_SIZE (e.g., 64px) is critical. Large, unscaled Bitmaps will quickly lead to OutOfMemoryError or severe scroll stuttering.

5. Implementation Tips

  • Haptics: Apply virtual key haptics on every toggle and sheet action.
  • Visuals: Use a LoadingIndicator while the apps are being fetched from the system.
  • Edge-to-Edge: Ensure the sheet has a fillMaxHeight(0.9f) or similar to prevent it from covering the entire screen while allowing plenty of space for scrolling.