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>

platform/api16/com/minamp/ExoEngine.java

@@ -0,0 +1,141 @@
+package com.minamp;
+
+import java.io.File;
+
+import android.content.Context;
+import android.net.Uri;
+import android.os.Handler;
+import android.os.Looper;
+
+import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.DefaultLoadControl;
+import com.google.android.exoplayer2.ExoPlayer;
+import com.google.android.exoplayer2.MediaItem;
+import com.google.android.exoplayer2.PlaybackException;
+import com.google.android.exoplayer2.Player;
+import com.google.android.exoplayer2.Renderer;
+import com.google.android.exoplayer2.RenderersFactory;
+import com.google.android.exoplayer2.Tracks;
+import com.google.android.exoplayer2.audio.AudioAttributes;
+import com.google.android.exoplayer2.audio.AudioRendererEventListener;
+import com.google.android.exoplayer2.audio.MediaCodecAudioRenderer;
+import com.google.android.exoplayer2.extractor.DefaultExtractorsFactory;
+import com.google.android.exoplayer2.mediacodec.MediaCodecSelector;
+import com.google.android.exoplayer2.metadata.MetadataOutput;
+import com.google.android.exoplayer2.source.ProgressiveMediaSource;
+import com.google.android.exoplayer2.text.TextOutput;
+import com.google.android.exoplayer2.upstream.DefaultDataSource;
+import com.google.android.exoplayer2.upstream.DefaultHttpDataSource;
+import com.google.android.exoplayer2.video.VideoRendererEventListener;
+
+/**
+ * ExoPlayer 2.18 (Android 4.1+ build): audio only, decoded with Android's MediaCodec. Over MediaPlayer it brings
+ * gapless hand-over to a queued file, a buffer of minutes instead of seconds, and errors that say what failed.
+ * Audio focus, headphone unplugging and the wake/Wi-Fi locks stay with PlayerService, as for MediaPlayer.
+ */
+final class ExoEngine implements Engine {
+
+    private final ExoPlayer player;
+    private Listener listener;
+    private boolean preparedSent;
+    private boolean failed;
+
+    ExoEngine(final Context c) {
+        RenderersFactory audioOnly = new RenderersFactory() {
+            public Renderer[] createRenderers(Handler h, VideoRendererEventListener v, AudioRendererEventListener a,
+                                              TextOutput t, MetadataOutput m) {
+                return new Renderer[] {new MediaCodecAudioRenderer(c, MediaCodecSelector.DEFAULT, h, a)};
+            }
+        };
+        // the loopback StreamProxy: it never takes long to answer, but may wait on the server for data
+        DefaultHttpDataSource.Factory http = new DefaultHttpDataSource.Factory()
+                .setUserAgent("PlexampLite").setConnectTimeoutMs(8000).setReadTimeoutMs(30000);
+        ProgressiveMediaSource.Factory sources = new ProgressiveMediaSource.Factory(new DefaultDataSource.Factory(c, http),
+                new DefaultExtractorsFactory().setConstantBitrateSeekingEnabled(true));
+        player = new ExoPlayer.Builder(c, audioOnly, sources)
+                // up to 3 minutes ahead in memory (a few MB of compressed audio): rides out Wi-Fi gaps that
+                // MediaPlayer's few seconds of buffer couldn't
+                .setLoadControl(new DefaultLoadControl.Builder()
+                        .setBufferDurationsMs(60000, 180000, 1500, 3000)
+                        .setPrioritizeTimeOverSizeThresholds(true)
+                        .build())
+                .setAudioAttributes(new AudioAttributes.Builder()
+                        .setUsage(C.USAGE_MEDIA).setContentType(C.AUDIO_CONTENT_TYPE_MUSIC).build(), false)
+                .setHandleAudioBecomingNoisy(false)
+                .setWakeMode(C.WAKE_MODE_LOCAL)
+                .setLooper(Looper.getMainLooper())
+                .build();
+        player.addListener(new Player.Listener() {
+            public void onPlaybackStateChanged(int state) {
+                if (listener == null || failed) return;
+                if (state == Player.STATE_READY && !preparedSent) {
+                    preparedSent = true;
+                    listener.onPrepared(ExoEngine.this);
+                } else if (state == Player.STATE_ENDED) {
+                    listener.onCompletion(ExoEngine.this);
+                }
+            }
+
+            public void onPlayerError(PlaybackException e) {
+                if (listener == null || failed) return;
+                failed = true;
+                int code = e.errorCode;
+                // 4xxx: decoding; 3003: a container this player can't read. Android's MediaPlayer may manage.
+                boolean decoder = (code >= 4000 && code < 5000) || code == PlaybackException.ERROR_CODE_PARSING_CONTAINER_UNSUPPORTED;
+                Throwable cause = e.getCause();
+                String why = cause != null && cause.getMessage() != null ? cause.getMessage() : e.getMessage();
+                listener.onError(ExoEngine.this, e.getErrorCodeName() + (why != null ? ": " + why : ""), decoder);
+            }
+
+            public void onTracksChanged(Tracks tracks) {
+                // ExoPlayer plays silence through a track it can't decode instead of failing: fail, so another try can
+                if (listener == null || failed || tracks.isEmpty() || tracks.isTypeSupported(C.TRACK_TYPE_AUDIO, true)) return;
+                failed = true;
+                listener.onError(ExoEngine.this, "no decoder on this phone for this audio", true);
+            }
+
+            public void onMediaItemTransition(MediaItem item, int reason) {
+                if (reason != Player.MEDIA_ITEM_TRANSITION_REASON_AUTO || listener == null) return;
+                // the queued file took over: forget the finished one
+                int i = player.getCurrentMediaItemIndex();
+                if (i > 0) player.removeMediaItems(0, i);
+                listener.onGaplessNext(ExoEngine.this);
+            }
+        });
+    }
+
+    public void setListener(Listener l) { listener = l; }
+
+    public void setSource(File file, String url) {
+        player.setMediaItem(MediaItem.fromUri(file != null ? Uri.fromFile(file) : Uri.parse(url)));
+    }
+
+    public void prepare() { player.prepare(); }
+
+    public void start() { player.setPlayWhenReady(true); }
+
+    public void pause() { player.setPlayWhenReady(false); }
+
+    public void seekTo(long ms) { player.seekTo(ms); }
+
+    public long position() { return player.getCurrentPosition(); }
+
+    public void setVolume(float v) { player.setVolume(v); }
+
+    public boolean canSeek() { return player.isCurrentMediaItemSeekable(); }
+
+    public boolean supportsNext() { return true; }
+
+    public void setNext(File file) {
+        int after = player.getCurrentMediaItemIndex() + 1;
+        if (player.getMediaItemCount() > after) player.removeMediaItems(after, player.getMediaItemCount());
+        if (file != null) player.addMediaItem(MediaItem.fromUri(Uri.fromFile(file)));
+    }
+
+    public void release() {
+        listener = null;
+        player.release();
+    }
+
+    public String name() { return "ExoPlayer"; }
+}