Brightness toggle Quick Settings

• requires Nougat (Android 7)
• add a brightness toggle tile to quick settings
• useful when the quick settings is in compact mode (without the brightness sliders)

TODOs

• toggle through brightness steps basics:
  • use predefined / hardcoded steps
  • UI to configure the steps
    • UI prototype
    • Implement persistence
• Use percentage consistent with system default brightness slider UI
  • standalone conversion with unit test
  • unit test refactor: https://github.com/junit-team/junit4/wiki/Parameterized-tests , https://github.com/junit-team/junit4/wiki/Exception-testing
  • integrate with TileService
• Improve responsiveness by implementing background service to monitor brightness
  • change Tile service to Active Tile
  • barebone service
  • auto start on boot
  • start service upon re-installation as well.
• Use a linear Percentage Converter for now (Motorola devices)
  • show percentage on tile UI
• Different devices have differing brightness slider implementation. Consider adapt percentage to differing devices. E.g.,
  • a slider as perceived brightness, which has a non-linear relationship with underlying system brightness value, found in ASUS tables
  • a slider that has a simple linear relationship to underlying system brightness, found in Motorola phones.
• Misc. UI Polish
  • settings error reporting (for invalid level string)
  • show current percentage at MainActivity UI
• UI to request WRITE_SETTINGS permission
• Misc. code cleanup refactoring changes
  • review context usage for memory leak (no-op)
• Experiment to try to increase snappiness of brightness change upon click
  • v0.1.9: base (try to update icon if applicable)
  • v0.1.10 : do not update tile at all
  • v0.1.11 : update only state (no UI changes)
  • v0.1.12 : update tile icon, but not state
  • v0.1.14 : update icon with AsyncTask (that only update UI)
  • v0.1.15 : an empty tile (still calling tile.updateTile())
  • Conclusion:
    • any tile update, even an empty one, could stall UI intermittently
    • using AsyncTask brings no noticeable change
    • Reasons
      • by stalling, it means that after clicking the tile, occasionally it does not accept further clicks for a few seconds, making cycling through brightness a tad unpleasant.
      • the reason seems to be when there is a tile update, Android would occasionally stop listening to tile (calling #onStopListening()). A few seconds later, it would start listening again (calling #onStartListening()).
      • In the interval between stop and start, clicking on tile would be fruitless
      • For now, either live will the intermittent stalling, or do not update UI at all
        • One possible enhancement is to use META_DATA_ACTIVE_TILE
• Debug build use a different name. See https://stackoverflow.com/a/41301021
• Get a release build (requires a certificate)
• Refactor some codes with closures, which requires using Java 8 (jack toolchain)
• (probably not desirable) drawing percentage over the tile icon?
• (Not possible) NoUse SVG for launch icon