How do their APIs compare?

These two libraries operate at completely different layers and their "APIs" aren't really comparable in scope — one is a small UI widget library, the other is a full media-playback framework — but here's a concrete breakdown of how each exposes its functionality.

bingoogolapple/bgarefreshlayout-android: a single ViewGroup + delegate callback

The whole API surface centers on BGARefreshLayout, a custom ViewGroup you drop into XML:

• Delegate pattern: You implement BGARefreshLayout.BGARefreshLayoutDelegate with two callback methods — onBGARefreshLayoutBeginRefreshing(...) (void) and onBGARefreshLayoutBeginLoadingMore(...) (returns boolean to indicate whether loading-more should actually start) [library/src/main/java/cn/bingoogolapple/refreshlayout/BGARefreshLayout.java:L883-L890]. You register it via setDelegate(delegate) [library/src/main/java/cn/bingoogolapple/refreshlayout/BGARefreshLayout.java:L843-L849], or declaratively via a Data Binding @BindingAdapter("bga_refresh_delegate") in BGARefreshLayoutAdapter [library/src/main/java/cn/bingoogolapple/refreshlayout/adapters/BGARefreshLayoutAdapter.java:L27-L34].
• Imperative control methods: beginLoadingMore(), endRefreshing(), endLoadingMore(), isLoadingMore(), getCurrentRefreshStatus() [library/src/main/java/cn/bingoogolapple/refreshlayout/BGARefreshLayout.java:L774-L782, L862-L874]. A separate BGARefreshScaleDelegate.onRefreshScaleChanged(scale, moveYDistance) lets you hook into the pull progress directly [library/src/main/java/cn/bingoogolapple/refreshlayout/BGARefreshLayout.java:L892-L899].
• State model: a simple enum RefreshStatus { IDLE, PULL_DOWN, RELEASE_REFRESH, REFRESHING } [library/src/main/java/cn/bingoogolapple/refreshlayout/BGARefreshLayout.java:L901-L903].
• Extensibility via abstract class: to build a custom refresh visual, you extend BGARefreshViewHolder and implement lifecycle hooks like handleScale, changeToIdle/PullDown/ReleaseRefresh/Refreshing, onEndRefreshing, as seen in concrete implementations like BGAStickinessRefreshViewHolder [library/src/main/java/cn/bingoogolapple/refreshlayout/BGAStickinessRefreshViewHolder.java:L29-L118] and the corresponding low-level animated view BGAMeiTuanRefreshView (changeToIdle, changeToRefreshing, handleScale, etc.) [library/src/main/java/cn/bingoogolapple/refreshlayout/BGAMeiTuanRefreshView.java:L31-L125].
• Internally it also patches AbsListView's scroll listener via reflection to detect "scrolled to bottom" for auto-loading-more, without requiring users to subclass ListView [library/src/main/java/cn/bingoogolapple/refreshlayout/BGARefreshLayout.java:L290-L316].

This is a small, synchronous, callback-based UI API — a handful of classes, no async task graph, no lifecycle beyond the Android View lifecycle.

google/exoplayer: layered, component-based media framework

ExoPlayer's public API is vastly larger and organized very differently — the retrieved chunks here happen to be from extensions (ffmpeg, av1, cast, media2) rather than the core Player/ExoPlayer interfaces, but they illustrate the pattern well:

• Extension modules as pluggable components: e.g. FfmpegLibrary.getCodecName(mimeType) maps MIME types to native FFmpeg decoder names (aac, mp3, ac3, opus, etc.) [extensions/ffmpeg/src/main/java/com/google/android/exoplayer2/