Version 3 Goals

1. Simplify.
2. De-couple. TileView itself should be a single View; ZoomPanLayout should be super for several subclasses, including MultiAxisScrollView and TileViewStack.
3. Tests.
4. Tile instances should manage their own threading and state.
5. Plugin architecture. Opt-in for markers, paths, hotspots, etc.
6. Allow reuse of Bitmap instances.
7. Allow null Bitmaps (or bitmaps not found); accommodate previous tile sets (consider null as fully opaque, or fully transparent).
8. DetailLevel or Manager should only return start/end column/row - TileView should figure out what tiles are "active" from that.
9. Implemented a limited cache of Tiles; when retired, a Tile should be light (no bitmap); the cache should be FIFO and capped to a reasonable (configurable?) number, so that multi-million pixel stacks won't impose massive caches.
10. More framework-centric api - e.g., addMarker(R.layout.whatever) and android attributes for things like anchorX and anchorY.
11. Instead of setting a padding (with setViewportPadding(int) to have more tiles loaded, add the ability to opt-in for a more intelligent way of loading tiles, based on the direction of a scroll. Combined to the tile cache, a "predictive" tile loading could be implemented.

Feature Requests: https://github.com/moagrius/TileView/pull/358