Plexamp Lite 1.14: Android 4.1 build with ExoPlayer, lyrics, home-screen widget

- One build per Android level, as in Tenda: build/PlexampLite.apk (Android 2.2+, versionCode 1508) and
  build/PlexampLite-api16.apk (Android 4.1+, 1516), from shared src/ plus platform/api8 or platform/api16.
- Android 4.1 build: ExoPlayer 2.18.7 behind a small Engine interface (gapless hand-over to read-ahead and
  downloaded files, a longer buffer, MediaPlayer fallback for tracks it can't decode), a notification and
  lock screen with art and buttons, a resizable widget, Holo, a menu button without a Menu key, metered networks.
  R8 shrinks ExoPlayer and Guava (tools/fetch_exoplayer.sh, tools/r8-rules.pro).
- Both builds: lyrics in Now Playing as in the Mac app (timed lyrics follow and seek), a home-screen widget,
  media play/pause keys, the moon icon drawn without clipPath.
- PlexampLite-noreport on the SD card stops play reports, for tests against a real server.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -1,8 +1,9 @@
 # Plexamp Lite
 
 A small Plexamp-style music player for Plex, built for the Samsung Galaxy Mini (GT-S5570:
-Android 2.2/2.3, 240×320 ldpi screen, 600 MHz ARMv6, 384 MB RAM). Runs on any Android 2.2+ phone.
-Formerly Minamp (the package name, `com.minamp`, stays so updates install over it).
+Android 2.2/2.3, 240×320 ldpi screen, 600 MHz ARMv6, 384 MB RAM). Runs on any Android 2.2+ phone, and comes
+in a second build for Android 4.1 and later (Xperia J, Galaxy S II…) that uses what those phones can do: see
+*Android 4.1 build*. Formerly Minamp (the package name, `com.minamp`, stays so updates install over it).
 
 ## Language
 
@@ -14,7 +15,7 @@ log stays in English since it's meant for troubleshooting.
 ## Install
 
 1. On the phone: **Settings → Applications → Unknown sources** (tick it).
-2. Copy `PlexampLite.apk` to the SD card (USB cable, or download it in the browser) and open it
+2. Copy `PlexampLite.apk` (Android 4.1+: `PlexampLite-api16.apk`; Tenda picks the right one by itself) to the SD card (USB cable, or download it in the browser) and open it
    with a file manager, or from a computer: `adb install PlexampLite.apk`.
 3. Plexamp Lite installs to internal storage (about 1 MB): an app on the SD card is killed whenever the
    phone shares its SD card over USB, which stopped the music.
@@ -71,7 +72,9 @@ clock has been reset to before 2024 the certificate date check is skipped rather
 * A Bluetooth speaker that drops its link for a moment pauses Plexamp Lite, which resumes by itself if the
   speaker is back within 20 s. Why playback paused or stopped is written to the connection log,
   which also goes to logcat (tag `PlexampLite`, readable over USB with `adb logcat`).
-* Plays are reported to Plex (Now Playing in the Plex dashboard, play counts, resume position).
+* Plays are reported to Plex (Now Playing in the Plex dashboard, play counts, resume position). For testing
+  against a real server, an empty file named `PlexampLite-noreport` at the top of the SD card turns that off
+  (`adb shell touch /sdcard/PlexampLite-noreport`; delete it afterwards).
 
 ## Features
 
@@ -82,6 +85,12 @@ clock has been reset to before 2024 the certificate date check is skipped rather
 * Long-press anything: Play next, Add to queue, Go to album/artist, Love.
 * Now Playing: big art on a backdrop coloured from the cover, seek bar, shuffle, repeat
   (queue/track), love, sleep timer (15–90 min or end of track), where it's streaming from.
+* **Lyrics**: the microphone button in Now Playing shows the track's lyrics from Plex in place of the art (as in
+  the Mac app). It's a lasting setting: it stays on for the following tracks and after restarts. Timed (LRC)
+  lyrics follow the song with the current line lit (tap a line to jump there; scrolling by hand pauses the
+  follow for a few seconds); plain-text lyrics just scroll. With several versions, timed ones win, else the
+  longest text (a local `.txt` can be a broken copy).
+* **Home-screen widget** (4×1): art, title, artist, previous / play-pause / next; tap the art for Now Playing.
 * Up Next queue: jump, play next, remove, clear; the queue and position survive restarts.
 * Downloads for offline listening: long-press a track, album, artist or playlist -> *Download*;
   *Menu -> Downloads* shows progress, space used and free, play/shuffle, retry and remove. Files go to
@@ -92,15 +101,47 @@ clock has been reset to before 2024 the certificate date check is skipped rather
 * Wired headset button: 1 click play/pause, 2 next, 3 previous; Bluetooth media keys;
   pauses for calls and when headphones are unplugged.
 
+## Android 4.1 build
+
+One build per **Android level**, never per phone (the same pattern as Tenda): `build/PlexampLite.apk` for
+Android 2.2+ and `build/PlexampLite-api16.apk` for 4.1+, from the same source, package and key.
+`versionCode` is the manifest's × 100 + the level (15 → 1508 and 1516), so a phone that moves up a level
+gets the newer build as an ordinary update, and Tenda gives each phone the build for its Android. Everything is
+shared in `src/`; what only one level can do is in `platform/api8/…/Platform.java` and
+`platform/api16/…/Platform.java` (the same methods; keep them in step), plus `platform/api16/res`, which
+overrides a few resources. The Android 4.1 build adds:
+
+* **ExoPlayer 2.18** (`platform/api16/…/ExoEngine.java`) instead of Android's MediaPlayer, behind the small
+  `Engine` interface the player service uses (`MediaPlayerEngine` on Android 2.x):
+  * **gapless playback**: when the next track's file is already here (read ahead or downloaded), it's queued
+    in the player and starts with no gap;
+  * a buffer of up to 3 minutes instead of seconds, so Wi-Fi gaps don't silence it;
+  * errors that say what failed. A track ExoPlayer can't decode is retried with Android's MediaPlayer.
+  Read-ahead, the stream proxy, the transcodes and the recovery steps are the same in both builds.
+* A **notification** with the art and ⏮ ⏯ ⏭ × (pull it down for a larger one); swiping it away while paused stops.
+* **Lock-screen controls** with the art (RemoteControlClient).
+* The **widget** can be resized; two rows or taller shows a larger layout.
+* Android 4's **Holo** dialogs and text fields; a ⋮ button on phones without a Menu key.
+* **Metered networks**: a phone's Wi-Fi hotspot counts as away, like mobile data.
+
+The Galaxy Mini's build is unchanged in how it plays, and also got the widget and the lyrics.
+
 ## Building (no Android SDK needed)
 
 ```
 tools/setup_toolchain.sh      # once: fetches aapt2, the API 8 android.jar, builds dx, renames Bouncy Castle
-./build.sh                    # -> build/PlexampLite.apk
+tools/fetch_exoplayer.sh      # once: ExoPlayer 2.18.7 + Guava (checksums pinned) into ~/android-toolchain
+./build.sh                    # -> build/PlexampLite.apk (Android 2.2+) and build/PlexampLite-api16.apk (4.1+)
+./build.sh 16                 # one level only
 ```
 
-`build.sh` runs `aapt2` (resources), `javac` (Java 8 bytecode checked against the API 8
-`android.jar`), `dx` (dex 035) and `tools/signapk.py`, which writes the v1 signature in the
+Also needed for the Android 4.1 build: the API 16 `android.jar` in `~/android-toolchain/platforms/android-16/`,
+R8 (`d8.jar` from build-tools 34, in `~/android-toolchain/calendar-tools/`) and a JDK 11+ (`build.sh` finds
+Homebrew's openjdk@17). ExoPlayer 2.18.7 is the newest that needs only Guava; R8 (`tools/r8-rules.pro`) keeps
+the app whole and shrinks ExoPlayer and Guava to what it uses, in one dex.
+
+Per level `build.sh` runs `aapt2` (resources), `javac` (Java 8 bytecode checked against that level's
+`android.jar`), then for Android 2.x the Dalvik 2.x link check and `dx` (dex 035), for 4.1 R8; then `tools/signapk.py`, which writes the v1 signature in the
 classic Android SignApk format and aligns the APK. (Modern `jarsigner` output does *not* install on
 Android 4.2 and older: it names digests `SHA-1-Digest` and labels the PKCS#7 signer algorithm in a
 way old `JarUtils` can't read, so the phone treats the APK as unsigned.) The debug key in `signing/` (password `minamp123`) is what this APK is
@@ -113,6 +154,8 @@ Tests (desktop JVM, no device):
   untrusted-root rejection, browsing, search, artwork, and the stream proxy (Range requests over
   TLS, de-chunking transcodes, aborting).
 * `test/QueueTest.java`: shuffle/unshuffle, repeat modes, play next, remove, move, clear.
+* `test/LyricsTest.java`: LRC (several stamps a line, offsets, word stamps) and plain-text lyrics
+  (`javac -d /tmp/lt src/com/minamp/util/Lrc.java test/LyricsTest.java && java -cp /tmp/lt LyricsTest`).
 * `test/PreferHomeTest.java` + `test/identity_server.py`: after being away, the home address wins
   again as soon as it answers.
 * `test/NetTest.java`: the bundled TLS + HTTP client against real servers; `test/HandshakeProfile.java`
@@ -120,5 +163,7 @@ Tests (desktop JVM, no device):
 
 ## Limits
 
-* No gapless playback (Android 2.2/2.3 have no API for it).
-* Notification has no playback buttons (pre-Android 3 can't); tap it to open Now Playing.
+* Android 2.x build: no gapless playback (no API for it), and the notification has no playback buttons
+  (pre-Android 3 can't): tap it to open Now Playing, or use the widget.
+* Android 4.1 build: gapless only into a track whose file is already on the phone; FLAC is still transcoded
+  (ExoPlayer has no FLAC decoder on Android 4.1).