renderer-design.md

Renderer Design

Core Components

• Renderer: The central orchestrator. It will be responsible for managing Layer objects and drawing them onto the GoogleMap.

  • Key methods: addLayer(layer), removeLayer(layer), getLayers()
  • It will hold a reference to the GoogleMap instance.

• Layer: A container for a collection of MapObjects. A layer represents a single, logical set of data, such as the contents of one KML file.

• MapObject: A common interface or base class for all renderable items. We'll have concrete implementations for each primitive type:

  • MarkerObject
  • PolylineObject
  • PolygonObject
  • CircleObject
  • These will encapsulate the Google Maps SDK's objects and associated styling.

• DataParser: An interface for parsing data files. We'll start with two implementations:

  • KmlParser
  • GeoJsonParser
  • The output of a parser will be a structured, in-memory representation of the data, specific to its format.

• Mapper: A component that translates the format-specific object model from a DataParser into a Layer of generic MapObjects that the Renderer can work with.

  • KmlMapper
  • GeoJsonMapper

High-Level Workflow

1. Instantiation: A developer creates an instance of the Renderer, associating it with a GoogleMap object.
2. Parsing: The developer provides a data source (e.g., an InputStream of a GeoJSON file) to the appropriate DataParser (e.g., GeoJsonParser). The parser returns a structured representation of the GeoJSON data.
3. Mapping: The developer passes the parsed data object to the corresponding Mapper (e.g., GeoJsonMapper). The mapper converts the data into a Layer instance, which contains a list of MapObjects (like PolygonObject, MarkerObject, etc.).
4. Rendering: The developer adds the Layer to the Renderer using renderer.addLayer(layer).
5. Drawing: The Renderer iterates through the MapObjects in the Layer and uses the Google Maps SDK to draw the corresponding shapes and markers on the map.