Glance Appwidget Updates And Memory

This skill provides guidance for managing state updates and keeping Android AppWidgets that use Jetpack Glance (androidx.glance:glance-appwidget) or RemoteViews within the Android 17 widget bitmap memory limits. For widget UI layout templates, suggest the glance-canonical-layouts skill.

• When configuring a Glance widget, see Create an app widget with Glance.

• When targeting Android 17 (targetSdk = 37), see Android 17 widget memory limits.

• When maintaining a classic AppWidgetProvider, see Create an app widget.

Prerequisites

• Kotlin Android project (minSdk >= 26) with compileSdk = 37 (targetSdk = 37 when targeting Android 17) in build.gradle.kts.

• Jetpack Glance (1.2.0, minimum 1.1.1+) and the Compose compiler Gradle plugin enabled on the module.

Critical mandates

• Preserve existing package name and toolchain versions : Inspect build.gradle.kts, gradle/libs.versions.toml, and Kotlin files first. Keep existing namespace, applicationId, package, targetSdk (unless migrating to Android 17), Android Gradle Plugin (AGP), and Kotlin versions.

• Downsample images to widget dimensions and estimate the memory cap : Android system_server computes the RemoteViews bitmap memory cap (6 * width * height bytes, or 1.5 * 4 * width * height) once at boot from the real size of the default display and does not expose this cap in a public API. Because unfolding a foldable or switching display resolution to QHD+ after boot can make active window metrics report a larger value than the boot-time cap, always downsample each image first to the widget's target dimensions (maxWidthDp x maxHeightDp in RGB_565 or ALPHA_8), and enforce the per-image byte ceiling (calculateWidgetMemoryCapBytes(context) / distinctImageCount) estimated as 6 * width * height from WindowManager.currentWindowMetrics.bounds on API 30+ (falling back to resources.displayMetrics on API 26-29 or if WindowManager is unavailable).

• Decode shared bitmaps once outside provideContent : Both SizeMode.Exact (used by glance-canonical-layouts to compose the current span's portrait and landscape orientations) and SizeMode.Responsive (used to pre-bundle a set of DpSize breakpoints) invoke provideContent multiple times per update. Decode shared bitmaps once in provideGlance before provideContent and pass them to ImageProvider(bitmap) so RemoteViews deduplicates the shared Bitmap across all sizes in either mode. If a widget scales distinct bitmaps per LocalSize.current, divide calculateWidgetMemoryCapBytes(context) by the number of distinct bitmaps.

• Downsample content URIs and grant launcher read permissions : On Android 17 (targetSdk >= 37), bitmap-backed Icons count toward the cap alongside Bitmaps. content:// URIs passed to ImageProvider(uri) or RemoteViews.setImageViewUri don't count toward the inter-process communication (IPC) cap, but the launcher decodes them at full resolution. Downsample the file into context.cacheDir, expose it with FileProvider.getUriForFile, and grant Intent.FLAG_GRANT_READ_URI_PERMISSION to Intent.CATEGORY_HOME packages.

• Trigger explicit widget updates after state mutations : updateAppWidgetState writes preferences to DataStore without updating the widget UI. After you mutate state, call GlanceAppWidget.update(context, glanceId) or GlanceAppWidget.updateAll(context).

• Use full updateAppWidget calls when you replace images : In AppWidgetProvider classes, when you replace bitmaps or Icons, call AppWidgetManager.updateAppWidget instead of partiallyUpdateAppWidget.

Reference implementation files

Read the companion reference files in references/ when implementing each step, and update the sample package declaration and class names to match your app:

• Bitmap Cap & FileProvider Helper : WidgetBitmapUtils.kt

• Responsive Widget, Receiver & Error Fallback : SampleGlanceWidget.kt

• LazyColumn Collection Widget & Revision Cache : FeedCollectionGlanceWidget.kt

• DataStore State Push, CoroutineWorker & ActionCallback : WidgetStateAndActions.kt

• Classic AppWidgetProvider WorkManager & Full Update : ClassicWidgetImageUpdater.kt

• Manifest, Widget Info, FileProvider Paths & R8 Rules : AndroidManifest.xml, sample_widget_info.xml, file_paths.xml, proguard-rules.pro

Detailed steps

Step 1: Configure SDK levels, dependencies, and manifest declarations

1. Read gradle/libs.versions.toml, app/build.gradle.kts, and app/src/main/AndroidManifest.xml first. If AGP, Kotlin, or library versions are already present, keep them; otherwise, add glance = "1.2.0" along with androidx.glance:glance-appwidget and androidx.glance:glance-material3 to gradle/libs.versions.toml.

2. In app/build.gradle.kts, keep namespace, applicationId, and any existing minSdk >= 26, targetSdk, or library versions. Set compileSdk = 37 (and targetSdk = 37 only when explicitly migrating the app to target Android 17), enable buildFeatures { compose = true }, and add implementation(libs.androidx.glance.appwidget) and implementation(libs.androidx.glance.material3).

3. In AndroidManifest.xml (see AndroidManifest.xml), declare <queries> with <action android:name="android.intent.action.MAIN" /> and <category android:name="android.intent.category.HOME" /> so queryIntentActivities discovers launcher packages on API 30+. Register your GlanceAppWidgetReceiver (pointing android.appwidget.provider to @xml/sample_widget_info, see sample_widget_info.xml) and register androidx.core.content.FileProvider with android:authorities="${applicationId}.fileprovider", android:exported="false", android:grantUriPermissions="true", and android.support.FILE_PROVIDER_PATHS pointing to @xml/file_paths (which declares <cache-path name="widget_cache" path="widget_images/" />, see file_paths.xml):

<br />

<receiver android:name=".glance.MyReceiver"
    android:exported="true">
    <intent-filter>
        <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
    </intent-filter>
    <meta-data
        android:name="android.appwidget.provider"
        android:resource="@xml/my_app_widget_info" />
</receiver>

<br />

Step 2: Estimate the widget memory cap and downsample images

Read WidgetBitmapUtils.kt and implement the memory cap and downsampling helpers:

1. Estimate the cap (calculateWidgetMemoryCapBytes) : On API 30+ (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R), read val bounds = context.getSystemService(WindowManager::class.java)?.currentWindowMetrics?.bounds and, when bounds != null && bounds.width() > 0 && bounds.height() > 0, return 6L * bounds.width().toLong() * bounds.height().toLong() (calling WindowManager from a non-UI widget or worker Context logs a nonfatal StrictMode violation on API 30+, which is expected for this estimate). On API 26-29 (or if WindowManager is unavailable), fall back to context.resources.displayMetrics (6L * dm.widthPixels.toLong() * dm.heightPixels.toLong()). Because system_server caches 6 * width * height once at boot, always size images to the widget's maxWidthDp x maxHeightDp first (Stage 1) rather than filling the full screen budget.

2. Downsample in two stages (decodeDownsampledWidgetBitmap) :

   • First, probe dimensions with BitmapFactory.Options().apply { inJustDecodeBounds = true; inPreferredConfig = config } and double sampleSize *= 2 while (bounds.outWidth / (sampleSize * 2) >= targetWidthPx && bounds.outHeight / (sampleSize * 2) >= targetHeightPx) || (bounds.outWidth / sampleSize > targetWidthPx * 2) || (bounds.outHeight / sampleSize > targetHeightPx * 2) (where targetWidthPx = max(1, (maxWidthDp * density).toInt())), so wide banners or tall screenshots do not bypass downsampling when one axis already fits.

   • Second, enforce the per-image byte ceiling (perImageCapBytes = calculateWidgetMemoryCapBytes(context) / max(1, distinctImageCount)) by doubling sampleSize *= 2 while (max(1, bounds.outWidth / sampleSize).toLong() * max(1, bounds.outHeight / sampleSize).toLong() * bytesPerPixel) > perImageCapBytes. Use 2L bytes per pixel for Bitmap.Config.RGB_565 (opaque photos), 1L for Bitmap.Config.ALPHA_8 masks, and 4L when bounds.outConfig != null && bounds.outConfig != config (because BitmapFactory upgrades translucent PNG or WebP files from RGB_565 to 4-byte ARGB_8888). Decode with inSampleSize = sampleSize and inPreferredConfig = config.

3. Choose between in-memory Bitmap and FileProvider Uri (cacheWidgetImageUri) : Use decodeDownsampledWidgetBitmap with androidx.glance.ImageProvider(bitmap) when passing bitmaps directly in memory. Use cacheWidgetImageUri when the widget passes a content:// Uri to ImageProvider(uri) or RemoteViews.setImageViewUri: it writes the downsampled bitmap into File(context.cacheDir, "widget_images"), obtains a content:// URI with FileProvider.getUriForFile(context, "${context.packageName}.fileprovider", outFile), queries Intent(Intent.ACTION_MAIN).addCategory(Intent.CATEGORY_HOME), and calls context.grantUriPermission(pkg, uri, Intent.FLAG_GRANT_READ_URI_PERMISSION).

Step 3: Deduplicate multi-size bitmaps and handle composition errors

Read SampleGlanceWidget.kt to configure multi-size bitmap deduplication and composition error recovery:

1. Choose SizeMode for your layout : Use SizeMode.Exact (recommended when using glance-canonical-layouts to render exact LocalSize.current dimensions for the current grid span's portrait and landscape orientations), SizeMode.Responsive(RESPONSIVE_BUCKETS) (using import androidx.compose.ui.unit.DpSize and import androidx.compose.ui.unit.dp to pre-bundle fixed DpSize breakpoints such as setOf(DpSize(120.dp, 120.dp), DpSize(240.dp, 120.dp), DpSize(240.dp, 240.dp)) so resize transitions don't wake the app process), or SizeMode.Single (for a single layout).

2. Hoist shared bitmap decodes before provideContent : Because both SizeMode.Exact (2-4 orientation sizes) and SizeMode.Responsive (N buckets) run provideContent multiple times per update, decode shared bitmaps once in provideGlance before provideContent with decodeDownsampledWidgetBitmap and Bitmap.Config.RGB_565 for opaque images (distinctImageCount = 1). Pass the resulting Bitmap to androidx.glance.ImageProvider(sharedBitmap) so RemoteViews deduplicates the shared Bitmap across all sizes.

3. Provide a zero-bitmap error fallback : Override onCompositionError(context, glanceId, appWidgetId, throwable) and call AppWidgetManager.getInstance(context).updateAppWidget(appWidgetId, fallback) with a text-only RemoteViews layout (0 bitmaps).

Step 4: Pre-decode LazyColumn collection images and assign stable itemIds

Read FeedCollectionGlanceWidget.kt when rendering collection widgets with LazyColumn:

1. Replace import androidx.glance.appwidget.ImageProvider (which accepts Uri) with import androidx.glance.ImageProvider (which accepts Bitmap). Remove Uri.fromFile and Icon.createWithContentUri calls.

2. While a Glance session is active (~45 seconds after an update), .update() and .updateAll() do not restart provideGlance. Declare var cachedRevision = -1 and var cachedThumbnails = emptyMap<String, Bitmap>() in provideGlance before provideContent. Inside provideContent, read val revision = currentState<Preferences>()[KEY_REVISION] ?: 0, and only when revision != cachedRevision, update cachedRevision = revision and decode the feedItems thumbnails with cachedThumbnails = feedItems.mapNotNull { item -> decodeDownsampledWidgetBitmap(..., distinctImageCount = max(1, feedItems.size), config = Bitmap.Config.RGB_565)?.let { item.id to it } }.toMap() (use mapNotNull rather than associate so the map stays Map<String, Bitmap> instead of Map<String, Bitmap?>). This re-decodes when DataStore state updates during an active session while sharing one decoded Map<String, Bitmap> across all SizeMode.Responsive buckets.

3. In LazyColumn, pass a stable Long itemId to items(items = feedItems, itemId = { item -> item.id.hashCode().toLong() }) (preferring a persistent numeric ID when available) and render Image(provider = ImageProvider(bitmap), contentDescription = item.title) only when bitmap != null (never fall back to Uri.fromFile in an else branch).

Step 5: Push state updates, configure ActionCallbacks, and use WorkManager

Read WidgetStateAndActions.kt, proguard-rules.pro, and ClassicWidgetImageUpdater.kt to implement these patterns:

1. Push DataStore updates (requires androidx.datastore:datastore-preferences-core:1.2.1 and import androidx.glance.appwidget.GlanceAppWidgetManager, import androidx.glance.appwidget.state.updateAppWidgetState, and import androidx.glance.appwidget.updateAll): In pushWidgetRevisionUpdate(context) (see WidgetStateAndActions.kt), iterate over for (glanceId in GlanceAppWidgetManager(context).getGlanceIds(Widget::class.java)), mutate state inside updateAppWidgetState(context, glanceId) { prefs -> ... } (passing both context and glanceId), and immediately call widget.update(context, glanceId) (or widget.updateAll(context)).

2. Use zero-argument ActionCallback classes with ActionParameters.Key and keep <init>() under R8 (requires androidx.work:work-runtime-ktx:2.12.0 when scheduling background work): RunCallbackAction instantiates ActionCallback classes with Class.getDeclaredConstructor().newInstance(), so a constructor parameter fails in every build. Remove constructor parameters from ActionCallback implementations, pass values with ActionParameters.Key and actionParametersOf (see RefreshWidgetAction in WidgetStateAndActions.kt), and add -keep class * implements androidx.glance.appwidget.action.ActionCallback { public <init>(); } to proguard-rules.pro (see proguard-rules.pro). Inside SyncWidgetWorker.doWork(), call pushWidgetRevisionUpdate(applicationContext) so background work updates DataStore and refreshes the widget.

3. Avoid unconditional one-time WorkManager enqueues in AppWidgetProvider.onUpdate and use full updateAppWidget for images (see ClassicWidgetImageUpdater.kt): Never call context.startForegroundService from AppWidgetProvider.onReceive or onUpdate (which throws ForegroundServiceStartNotAllowedException). GlanceAppWidgetReceiver already keeps a 10-year delayed session worker queued internally so WorkManager's RescheduleReceiver never toggles. In a classic AppWidgetProvider, avoid enqueuing a OneTimeWorkRequest directly inside onUpdate: even with ExistingWorkPolicy.KEEP, once the one-time worker finishes (SUCCEEDED), UnfinishedWorkListener disables RescheduleReceiver, which broadcasts ACTION_PACKAGE_CHANGED and re-triggers onUpdate in a loop. Instead, schedule repeating syncs in onUpdate with enqueueUniquePeriodicWork(..., ExistingPeriodicWorkPolicy.KEEP, ...) (which stays ENQUEUED across runs), use goAsync() for short < 10s updates, or enqueue one-time work (enqueueUniqueWork(..., ExistingWorkPolicy.KEEP, ...)) only from specific action broadcasts in onReceive. When you update a Bitmap or Icon on a classic RemoteViews widget, call appWidgetManager.updateAppWidget rather than partiallyUpdateAppWidget.

Common errors and fixes

Antipatterns

• NEVER decode or scale a Bitmap inside provideContent per size bucket with SizeMode.Responsive or SizeMode.Exact.

• NEVER size widget bitmaps to fill the full screen memory cap (6 * width * height); always downsample to the widget's target maxWidthDp x maxHeightDp first so unfolding a foldable or switching display resolution after boot does not exceed the boot-time cap.

• NEVER pass an unscaled content:// Uri or Uri.fromFile to ImageProvider(uri) or RemoteViews.setImageViewUri, or omit context.grantUriPermission for Intent.CATEGORY_HOME.

• NEVER call updateAppWidgetState without calling GlanceAppWidget.update(context, glanceId) or GlanceAppWidget.updateAll(context).

• NEVER call partiallyUpdateAppWidget when you replace widget images.