SL Post Stamps — Android WebView wrapper

An Android wrapper around the Sri Lanka Philatelic Bureau storefront. The site is rendered in a WebView; the app supplies native chrome (toolbar, bottom navigation, drawer) and injects CSS and JavaScript to adapt the desktop site for mobile.

Features

• Native chrome around the site — toolbar, bottom navigation bar with a live cart badge, and a drawer for account and information pages.
• Page-aware UI — page-detector.js classifies each page (home, listing, product, cart, checkout, login, register, account) and reports the result to the app over a JavaScript bridge, which drives the toolbar subtitle, the cart badge and the signed-in/signed-out menu state.
• Injected styling — inject.css and inject.js restyle the site for mobile: Material-styled auth forms, quantity steppers, image zoom, password visibility toggles, and hiding the site's own header and footer so the native toolbar can take over.
• Session persistence — cookies are flushed on pause, so a sign-in survives an app restart, and the last on-site page is restored on cold start.
• Downloads and uploads — downloads are handed to DownloadManager with the session cookie attached; <input type="file"> opens the system picker.
• Pull to refresh, offline error state, and web-history back navigation.

Architecture

MainActivity.kt        WebViewClient/WebChromeClient overrides, navigation,
                       drawer and bottom nav, downloads, file chooser,
                       lifecycle and asset injection
WebContentBridge.kt    @JavascriptInterface bridge exposed to the page as
                       `SLPBridge` — page type, auth state, cart count, product
PageType.kt            The page classification enum

assets/page-detector.js   Classifies the page, extracts cart/auth/product
                          context, calls the bridge
assets/inject.js          UX enhancements, gated by page type
assets/inject.css         Mobile restyling of the site

res/layout/activity_main.xml   CoordinatorLayout + DrawerLayout + Toolbar +
                               WebView + bottom nav + error and splash states

The JavaScript bridge

page-detector.js and inject.js are injected into a third-party site that this project does not control. Two consequences worth keeping in mind when editing them:

• Selectors are assumptions. If the site's markup changes they stop matching, usually silently.
• SLPBridge is reachable from page JavaScript, so anything it accepts is untrusted input. URLs coming across the bridge are validated against the storefront host before being stored or loaded.

Build requirements

• Android SDK 36
• JDK 17 or newer (CI uses 21). Gradle 9.3.1 with AGP 9.1 will not run on JDK 11.

Building

./gradlew assembleDebug          # debug APK
./gradlew testDebugUnitTest      # unit tests
./gradlew lintDebug              # Android Lint

CI and releases

.github/workflows/build-apk.yml runs tests, lint and a debug build on every push and pull request. Pushing a v* tag additionally builds and publishes a signed release APK to GitHub Releases.

Debug APKs are CI artifacts only and are never published — they are debuggable and signed with a throwaway key. See docs/RELEASING.md for keystore setup and the required repository secrets.