AnnotationOptions.alpha Needs To Return SuperType

[bleege]

Currently AnnotationOptions.alpha() returns an AnnotationsOptions object. While this is functional, it requires casting to be applied in common Builder patterns which isn't good. For example:

MapView map = ...;

// works
map.addPolygon(new PolygonOptions().add(latLngs));

// currently doesn't work due to typing, but is ideal
map.addPolygon(new PolygonOptions().add(latLngs).alpha(0.5f));

// casting needed to make work, but not something that should be used 
map.addPolygon((PolygonOptions) new PolygonOptions().add(latLngs).alpha(0.5f));

/cc @tobrun @ljbade

[ljbade]

Interesting, the other options support this. Also core GL marker don't support alpha, so only needed for lines and polygons.

[tobrun]

@bleege didn't the generic builder pattern solve this?

[bleege]

@tobrun I didn't have time to finish yesterday afternoon so I just created this issue to make sure this was known. Hoping to get it to today.

[bleege]

Looking at Google's implementation they avoided this problem all together by keeping PolygonOptions, PolyLineOptions, and MarkerOptions all independent. In other words, they don't use DRY and each one of these Option classes extends from java.lang.Object and implements android.os.Parcelable.

[bleege]

Doing some R&D on this shows that the AnnotationsOptions abstract class came as part of clean up / refactoring in #1716. In other words this was introduced in Mapbox and not needed as part of the Google API (confirms previous statement on API).

[ljbade]

@bleege Does the same apply to the Marker, Polyline, Polygon classes? If we split these up we will need to do a bit of re-factoring in MapView.

Also should point out this was an easy fix in my large PR, I just pushed .alpha to the concrete classes.

[bleege]

I decided to remove AnnotationsOptions and MultiPointOptions as they were for abstract classes that are not part of the Google Maps API. I moved their features to concrete implementations which mirrors Google and also solves this issue. Tests (see below) look good. I also added an explicit usage of .alpha() to the Polygon Annotation. Was able to confirm that the builder pattern worked code wise and more importantly the polygon actually was rendered using the proper alpha.

Test, Test, Test

Original Polygon, No Alpha

Original Polygon, 0.5 Alpha

[bleege]

Rebased and merged.