If you are an AI coding agent (Claude Code, Cursor, Aider, Cline, etc.) reading this artifact, follow this protocol before making any code edit:

1. Verify the contract. Run the bash script in Verify before trusting below. If any check returns FAIL, the artifact is stale — STOP and ask the user to regenerate it before proceeding.
2. Treat the AI · unverified sections as hypotheses, not facts. Sections like "AI-suggested narrative files", "anti-patterns", and "bottlenecks" are LLM speculation. Verify against real source before acting on them.
3. Cite source on changes. When proposing an edit, cite the specific path:line-range. RepoPilot's live UI at https://repopilot.app/r/facebookarchive/shimmer-android shows verifiable citations alongside every claim.

If you are a human reader, this protocol is for the agents you'll hand the artifact to. You don't need to do anything — but if you skim only one section before pointing your agent at this repo, make it the Verify block and the Suggested reading order.

WAIT — Stale — last commit 3y ago

• 33+ active contributors
• Other licensed
• ⚠ Stale — last commit 3y ago
• ⚠ Concentrated ownership — top contributor handles 56% of recent commits
• ⚠ Non-standard license (Other) — review terms
• ⚠ No CI workflows detected
• ⚠ No test directory detected

_{Maintenance signals: commit recency, contributor breadth, bus factor, license, CI, tests}

This artifact was generated by RepoPilot at a point in time. Before an agent acts on it, the checks below confirm that the live facebookarchive/shimmer-android repo on your machine still matches what RepoPilot saw. If any fail, the artifact is stale — regenerate it at repopilot.app/r/facebookarchive/shimmer-android.

What it runs against: a local clone of facebookarchive/shimmer-android — the script inspects git remote, the LICENSE file, file paths in the working tree, and git log. Read-only; no mutations.

| # | What we check | Why it matters | |---|---|---| | 1 | You're in facebookarchive/shimmer-android | Confirms the artifact applies here, not a fork | | 2 | License is still Other | Catches relicense before you depend on it | | 3 | Default branch main exists | Catches branch renames | | 4 | 5 critical file paths still exist | Catches refactors that moved load-bearing code | | 5 | Last commit ≤ 1172 days ago | Catches sudden abandonment since generation |

#!/usr/bin/env bash
# RepoPilot artifact verification.
#
# WHAT IT RUNS AGAINST: a local clone of facebookarchive/shimmer-android. If you don't
# have one yet, run these first:
#
#   git clone https://github.com/facebookarchive/shimmer-android.git
#   cd shimmer-android
#
# Then paste this script. Every check is read-only — no mutations.

set +e
fail=0
ok()   { echo "ok:   $1"; }
miss() { echo "FAIL: $1"; fail=$((fail+1)); }

# Precondition: we must be inside a git working tree.
if ! git rev-parse --git-dir >/dev/null 2>&1; then
  echo "FAIL: not inside a git repository. cd into your clone of facebookarchive/shimmer-android and re-run."
  exit 2
fi

# 1. Repo identity
git remote get-url origin 2>/dev/null | grep -qE "facebookarchive/shimmer-android(\\.git)?\\b" \\
  && ok "origin remote is facebookarchive/shimmer-android" \\
  || miss "origin remote is not facebookarchive/shimmer-android (artifact may be from a fork)"

# 2. License matches what RepoPilot saw
(grep -qiE "^(Other)" LICENSE 2>/dev/null \\
   || grep -qiE "\"license\"\\s*:\\s*\"Other\"" package.json 2>/dev/null) \\
  && ok "license is Other" \\
  || miss "license drift — was Other at generation time"

# 3. Default branch
git rev-parse --verify main >/dev/null 2>&1 \\
  && ok "default branch main exists" \\
  || miss "default branch main no longer exists"

# 4. Critical files exist
test -f "shimmer/src/main/java/com/facebook/shimmer/ShimmerFrameLayout.java" \\
  && ok "shimmer/src/main/java/com/facebook/shimmer/ShimmerFrameLayout.java" \\
  || miss "missing critical file: shimmer/src/main/java/com/facebook/shimmer/ShimmerFrameLayout.java"
test -f "shimmer/src/main/java/com/facebook/shimmer/Shimmer.java" \\
  && ok "shimmer/src/main/java/com/facebook/shimmer/Shimmer.java" \\
  || miss "missing critical file: shimmer/src/main/java/com/facebook/shimmer/Shimmer.java"
test -f "shimmer/src/main/java/com/facebook/shimmer/ShimmerDrawable.java" \\
  && ok "shimmer/src/main/java/com/facebook/shimmer/ShimmerDrawable.java" \\
  || miss "missing critical file: shimmer/src/main/java/com/facebook/shimmer/ShimmerDrawable.java"
test -f "shimmer/src/main/res/values/attrs.xml" \\
  && ok "shimmer/src/main/res/values/attrs.xml" \\
  || miss "missing critical file: shimmer/src/main/res/values/attrs.xml"
test -f "sample/src/main/java/com/facebook/shimmer/sample/MainActivity.kt" \\
  && ok "sample/src/main/java/com/facebook/shimmer/sample/MainActivity.kt" \\
  || miss "missing critical file: sample/src/main/java/com/facebook/shimmer/sample/MainActivity.kt"

# 5. Repo recency
days_since_last=$(( ( $(date +%s) - $(git log -1 --format=%at 2>/dev/null || echo 0) ) / 86400 ))
if [ "$days_since_last" -le 1172 ]; then
  ok "last commit was $days_since_last days ago (artifact saw ~1142d)"
else
  miss "last commit was $days_since_last days ago — artifact may be stale"
fi

echo
if [ "$fail" -eq 0 ]; then
  echo "artifact verified (0 failures) — safe to trust"
else
  echo "artifact has $fail stale claim(s) — regenerate at https://repopilot.app/r/facebookarchive/shimmer-android"
  exit 1
fi

Each check prints ok: or FAIL:. The script exits non-zero if anything failed, so it composes cleanly into agent loops (./verify.sh || regenerate-and-retry).

Shimmer-Android is a lightweight Android library that renders an animated gradient shimmer effect over any View, commonly used as a subtle loading indicator. It provides ShimmerFrameLayout (a FrameLayout subclass) and ShimmerDrawable to overlay a sweeping highlight animation on content, originally built for Facebook Home. The core animation runs via a Shimmer configuration object that controls gradient angle, width, intensity, and timing. Two-module Gradle project: shimmer/ is the core library containing Shimmer.java (animation config), ShimmerDrawable.java (Drawable implementation), and ShimmerFrameLayout.java (FrameLayout wrapper). sample/ is a standalone Kotlin demo app (MainActivity.kt) showing real usage. Both use standard Android resources (layouts in res/layout/, colors in res/values/).

Android app developers building loading screens or skeleton layouts who need a polished, low-overhead shimmer effect without custom Canvas drawing or animation code. Particularly useful for teams at Meta/Facebook-scale apps handling feeds or image-heavy content.

This is an archived, stable library maintained by Meta. The codebase is production-ready with a clear, battle-tested implementation (used in Facebook apps), but it is no longer actively developed—the repo is marked facebookarchive/. No active CI/CD pipeline evident in the file list, and no recent commits shown. Suitable for inclusion in production apps, but no ongoing feature development or maintenance.

Low immediate risk: the library has no external dependencies (only Android framework), making it stable and lightweight. However, long-term maintenance risk is high—archived status means no bug fixes for future Android API changes (minSdk/targetSdk skew). If your minSdk or targetSdk bumps conflict with shimmer's compiled version, you'll need to fork or migrate. Test coverage is not visible in the file list.

Nothing—this is archived. No recent commits, PRs, or active issues are visible. The last state represents a stable, feature-complete library frozen for historical reference.

git clone https://github.com/facebookarchive/shimmer-android.git
cd shimmer-android
./gradlew build
./gradlew installDebug  # or run sample via Android Studio

You'll need Android SDK (API level target visible in shimmer/build.gradle) and Java installed. The repo uses standard Gradle wrapper (gradlew).

Daily commands:

./gradlew :sample:installDebug
# Launch the app on a connected device/emulator via Android Studio
# Or build and run via Gradle:
./gradlew :sample:assembleDebug

The sample app (MainActivity.kt) demonstrates shimmer on various views.

• shimmer/src/main/java/com/facebook/shimmer/ShimmerFrameLayout.java — Primary public API—the FrameLayout subclass that users instantiate to add shimmer effects to views; understanding this is essential for all integration work.
• shimmer/src/main/java/com/facebook/shimmer/Shimmer.java — Core configuration and animation logic that drives the shimmer effect; all customization and timing flows through this class.
• shimmer/src/main/java/com/facebook/shimmer/ShimmerDrawable.java — Low-level rendering implementation using Canvas and Paint; handles the visual shimmer animation and gradient drawing.
• shimmer/src/main/res/values/attrs.xml — XML attribute definitions for XML-based shimmer configuration; required reference for understanding customizable properties.
• sample/src/main/java/com/facebook/shimmer/sample/MainActivity.kt — Reference implementation demonstrating shimmer integration patterns and typical usage scenarios.
• build.gradle — Root build configuration and dependency management; essential for understanding the build environment and toolchain.

• ShimmerFrameLayout (Android FrameLayout, ValueAnimator) — Container view that manages shimmer lifecycle (startShimmer/stopShimmer) and delegates rendering to ShimmerDrawable.
  • Failure mode: If animator is not properly cancelled, shimmer may continue consuming CPU and battery in background.
• ShimmerDrawable (Android Drawable, Canvas, Paint) — Custom Drawable that receives animation callbacks and renders the shimmer effect via Canvas.
  • Failure mode: If canvas drawing is inefficient or allocates excessively, frame drops and jank can occur during animation.
• Shimmer (Java POJOs, builder pattern) — Configuration object that encapsulates shimmer animation parameters (angle, duration, alpha, width, colors) and is used by ShimmerDrawable.
  • Failure mode: If invalid parameters are set (e.g., negative duration), animation behavior is undefined; should validate in builder.

• Activity/Fragment → ShimmerFrameLayout — User creates or obtains ShimmerFrameLayout from layout XML or programmatically and calls startShimmer().
• ShimmerFrameLayout → Shimmer — FrameLayout holds a Shimmer configuration object that defines animation parameters.
• ShimmerFrameLayout → ShimmerDrawable — FrameLayout creates and attaches ShimmerDrawable as a foreground or background drawable to render shimmer.
• ValueAnimator → ShimmerDrawable — Animator periodically updates animated value (0.0 → 1.0), triggering ShimmerDrawable.onDraw() callback.
• ShimmerDrawable → Shimmer — During onDraw(), drawable queries Shimmer for animation parameters to compute gradient position and colors.
• ShimmerDrawable → Canvas — Drawable uses Canvas.drawRect() and Paint operations to render the shimmer gradient at the animated position.

Add a new shimmer configuration preset

1. Define new XML attribute in the styleable declaration (shimmer/src/main/res/values/attrs.xml)
2. Add a static builder method or constant in Shimmer.java to expose the new preset with preconfigured animation parameters (shimmer/src/main/java/com/facebook/shimmer/Shimmer.java)
3. Test the preset in MainActivity.kt by creating a ShimmerFrameLayout with the new configuration (sample/src/main/java/com/facebook/shimmer/sample/MainActivity.kt)

Customize shimmer appearance (angle, width, color)

1. Create a Shimmer builder in code using Shimmer.AlphaHighlightBuilder() or Shimmer.LinearGradientBuilder() (shimmer/src/main/java/com/facebook/shimmer/Shimmer.java)
2. Call builder methods like setAngle(), setWidth(), setBaseAlpha(), setHighlightAlpha() to configure the effect (shimmer/src/main/java/com/facebook/shimmer/Shimmer.java)
3. Pass the built Shimmer object to ShimmerFrameLayout via setShimmer() or constructor (shimmer/src/main/java/com/facebook/shimmer/ShimmerFrameLayout.java)

Control shimmer animation lifecycle (start, stop, pause)

1. Obtain a ShimmerFrameLayout reference from your Activity or Fragment (sample/src/main/java/com/facebook/shimmer/sample/MainActivity.kt)
2. Call startShimmer() to begin the animation, stopShimmer() to stop, or use lifecycle callbacks to auto-manage (shimmer/src/main/java/com/facebook/shimmer/ShimmerFrameLayout.java)
3. Optionally set animation duration and timing via Shimmer builder methods before attaching to ShimmerFrameLayout (shimmer/src/main/java/com/facebook/shimmer/Shimmer.java)

• Android FrameLayout — Provides a simple container that overlays a custom Drawable without complex layout logic; allows easy wrapping of arbitrary child views.
• Canvas & Paint graphics — Low-level 2D rendering API enables efficient, frame-by-frame shimmer animation without dependency on complex graphics libraries.
• Android ValueAnimator — Provides smooth, frame-aware animation timing synchronized with the display refresh rate, ensuring fluid shimmer motion.
• XML Attributes & styleable resources — Allows declarative configuration of shimmer parameters directly in layout XML, reducing boilerplate code for developers.

• Shimmer drawn as a Drawable overlay rather than modifying child view paint properties directly

  • Why: Keeps shimmer decoupled from child view implementation; works with any view type without modification.
  • Consequence: Slight memory overhead from the drawable layer, but ensures broad compatibility and simplicity.

• Animation loop managed by ValueAnimator rather than frame callbacks (e.g., Choreographer)

  • Why: ValueAnimator automatically handles sync with display refresh and provides convenient start/stop lifecycle hooks.
  • Consequence: Less control over frame-timing edge cases, but more reliable for standard use cases.

• Support both alpha highlight and linear gradient shimmer variants via builder pattern

  • Why: Allows users to choose visual style and optimize performance based on their needs.
  • Consequence: Increased code paths and testing surface, but greater flexibility for different design preferences.

• Does not provide real-time networking or data-binding integration; shimmer is a pure visual effect.
• Does not support 3D transformations or perspective projections; limited to 2D canvas drawing.
• Does not include accessibility features (TalkBack announcements); shimmer is decorative only.
• Does not support custom animation curves beyond built-in linear timing; no Bezier or complex easing.

• undefined: undefined

No major hidden traps, but be aware: (1) The library is archived and will not receive Android updates—verify your app's targetSdk against shimmer's compiled version to avoid conflicts. (2) No visible test suite in the file list; if you fork or modify, you'll need to add tests manually. (3) Kotlin is only in the sample—the core library is pure Java, so if you're a Kotlin-first team, you'll be using Java interop. (4) Layout animation requires the View to be drawn first; wrapping a View with height/width 0 will produce invisible shimmer.

• Drawable subclassing and Canvas rendering — ShimmerDrawable extends Drawable and overrides draw(Canvas) to render the gradient—understanding Canvas-based drawing is essential to modifying or debugging the shimmer effect.
• Gradient overlay / swept highlight pattern — The shimmer effect is a moving linear gradient (not a simple opacity fade); understanding gradient math and angle-based sweeping is needed to tweak animation direction or width.
• Property animation (ObjectAnimator/ValueAnimator) — The library likely uses Android's animation framework to loop the gradient sweep; knowing how to configure duration, interpolation, and repeat behavior helps customize timing.
• FrameLayout composition and foreground Drawables — ShimmerFrameLayout uses FrameLayout's foreground layer to overlay the shimmer—understanding layout stacking and foreground vs. background is key to integrating shimmer without breaking layout hierarchy.
• View measurement and invalidation lifecycle — Shimmer must respond to View size changes and redraw on each animation frame; understanding onMeasure(), onDraw(), and invalidate() is necessary for correct rendering.

• facebook/shimmer-ios — Official iOS sibling of this library—maintains feature parity and design patterns for developers building cross-platform apps.
• airbnb/lottie-android — Similar use case (rich animations with minimal code), but vector-based via JSON; alternative if you need complex motion graphics over shimmer's simplicity.
• google/android-architecture-components — Companion to loading UX patterns—shows best practices for ViewModel/LiveData lifecycle that often pairs with shimmer loading states.
• square/okhttp — Common networking library used alongside shimmer for real loading scenarios (display shimmer while OkHttp fetches data).

To work on one of these in Claude Code or Cursor, paste: Implement the "<title>" PR idea from CLAUDE.md, working through the checklist as the task list.

Add instrumented Android unit tests for ShimmerDrawable and ShimmerFrameLayout

The repo lacks test coverage for core shimmer components. ShimmerDrawable.java and ShimmerFrameLayout.java are critical to the library's functionality but have no corresponding test files in shimmer/src/test. This is a high-value addition that would catch regressions in animation rendering, view lifecycle integration, and attribute parsing from attrs.xml.

• [ ] Create shimmer/src/test/java/com/facebook/shimmer/ directory structure
• [ ] Write ShimmerDrawableTest.java with tests for draw() method, animation lifecycle, and shimmer parameter changes
• [ ] Write ShimmerFrameLayoutTest.java with tests for startShimmer()/stopShimmer(), attribute inflation from attrs.xml, and view attachment/detachment
• [ ] Add androidx.test:runner dependency to shimmer/build.gradle for instrumented tests
• [ ] Run tests locally to verify they pass

Create GitHub Actions CI workflow for automated testing and linting

The repo has no .github/workflows/ directory for CI/CD. Given this is an archived Facebook library, adding GitHub Actions would help catch regressions and API compatibility issues. A workflow should run gradle build, unit tests, and lint checks on pull requests across Android API levels.

• [ ] Create .github/workflows/android-ci.yml
• [ ] Configure gradle build matrix for multiple API levels (min 16, target 33+)
• [ ] Add steps for: ./gradlew build, ./gradlew lint, and instrumented test execution
• [ ] Add gradle caching to improve workflow speed
• [ ] Test the workflow by pushing to a branch and verifying it runs

Add comprehensive Kotlin conversion and API documentation for modern Android developers

While sample/src/main/java/com/facebook/shimmer/sample/MainActivity.kt exists, the core library (Shimmer.java, ShimmerDrawable.java, ShimmerFrameLayout.java) is in Java. Create a Kotlin DSL builder and document attrs.xml attributes in README.md. This would modernize the API for Kotlin-first developers and clarify undocumented XML attributes defined in shimmer/src/main/res/values/attrs.xml.

• [ ] Create shimmer/src/main/java/com/facebook/shimmer/ShimmerBuilder.kt with a Kotlin DSL for fluent Shimmer configuration
• [ ] Expand README.md with a 'Configuration Attributes' section documenting all attrs.xml properties (e.g., shimmer_direction, shimmer_duration, shimmer_intensity)
• [ ] Add code examples showing both XML and programmatic (Kotlin DSL) configuration
• [ ] Add type-safe extension functions like View.startShimmering() in a Shimmer.kt file
• [ ] Update sample/src/main/java/com/facebook/shimmer/sample/MainActivity.kt to showcase the new DSL

• Add unit tests for ShimmerDrawable: The shimmer/src/main/java/com/facebook/shimmer/ShimmerDrawable.java has complex Canvas drawing logic with no visible test coverage. Write tests to verify gradient calculation, animation frame advancement, and boundary conditions.
• Extend sample UI layouts: Add more layout examples to sample/src/main/res/layout/main.xml (e.g., shimmer on nested RecyclerView items, shimmer on custom shaped Views, shimmer with different color schemes). Current sample is minimal.
• Document Shimmer configuration builder: Write inline Javadoc examples in Shimmer.java showing common configurations (e.g., 'fade in on load', 'pulse effect', 'directional flow'). Currently no configuration guidance is visible.

The shimmer-android codebase shows moderate security posture. Primary concerns include use of deprecated JCenter repository which is no longer maintained, inclusion of gradle-wrapper.jar in version control, and lack of explicit dependency version pinning. The project being archived adds risk as no security updates will be provided. No evidence of code injection vulnerabilities, hardcoded secrets, or dangerous patterns was found in the analyzed structure. Recommendations focus on updating repository references, securing the build system, and clearly communicating the archived status to users.

• High · Dependency Repository Security - JCenter Deprecated — build.gradle (lines with jcenter()). The build.gradle file includes 'jcenter()' as a repository, which was sunset by JFrog in May 2021. Using deprecated repositories can lead to security issues as they no longer receive updates or security patches. Dependencies may not be properly verified. Fix: Remove jcenter() from all repository configurations. Use only 'google()' and 'mavenCentral()' repositories which are actively maintained and secure.
• Medium · Gradle Wrapper JAR Included in Repository — gradle/wrapper/gradle-wrapper.jar. The gradle-wrapper.jar file is checked into version control (gradle/wrapper/gradle-wrapper.jar). This binary file should not be committed as it can be a vector for supply chain attacks if compromised. Fix: Remove gradle-wrapper.jar from the repository and use .gitignore to exclude it. Gradle wrapper will regenerate it safely from gradle-wrapper.properties.
• Medium · No Dependency Version Pinning in Build Files — build.gradle, versions.gradle. The build.gradle uses variable references (plugs.agp, plugs.kotlin) without visible version constraints in the provided snippet. This could allow automatic updates to potentially vulnerable dependency versions. Fix: Explicitly pin all dependency versions to known-good versions. Use dependency locking (./gradlew dependencies --write-locks) to ensure reproducible builds and prevent unexpected version updates.
• Low · Archived Repository Not Explicitly Marked — README.md. The repository is named 'facebookarchive/shimmer-android' indicating it is archived/deprecated, but there is no explicit security notice or deprecation warning in the README for users about its maintenance status. Fix: Add a clear deprecation notice at the top of the README stating that this project is archived and no longer actively maintained, with recommendations to use actively maintained alternatives.
• Low · Missing Code Signing Configuration — sample/build.gradle, shimmer/build.gradle. No code signing or release signing configuration is visible in the build.gradle files, which could allow unsigned APKs to be built and distributed. Fix: Implement signing configuration for release builds with proper key management. Store signing keys securely and never commit them to version control.

LLM-derived; treat as a starting point, not a security audit.

• Open issues — current backlog
• Recent PRs — what's actively shipping
• Source on GitHub

Generated by RepoPilot. Verdict based on maintenance signals — see the live page for receipts. Re-run on a new commit to refresh.