[android] Add a way to use a custom location source

[Guardiola31337]

Fixes #8668

👀 @tobrun

[tobrun]

Looking great, could we add a test around this? maybe adding a mock example in the test app (could be integrated in an existing activity)? Changelog entry would be appreciated

[zugaldia]

Let's call this setLocationEngine.

[zugaldia]

Similarly, let's call it setLocationEngine().

[zugaldia]

I'd rather call it locationEngine even if LocationSource is our default implementation.

[zugaldia]

Same: setLocationEngine().

[zugaldia]

Similarly, let's call the variable locationEngine.

[zugaldia]

@Guardiola31337 Do we need to set a location source every time the FAB is clicked? Wouldn't we need to set it just once if it hasn't been set before? Also, I don't see a getLocationSource() method to check that, or alternatively a isCustomLocationSourceSet().

[Guardiola31337]

@zugaldia you're right, setting it once would be enough.
I don't see the necessity of having getLocationSource or isCustomLocationSourceSet methods, because if it isn't set we use LocationSource (default). What would be the use case?

[zugaldia]

What would be the use case?

@Guardiola31337 Check if it's been set or not. For example, this activity could've been written like:

if (mapboxMap.getLocationSource() == null) {
  mapboxMap.setLocationSource(locationServices);
}

[Guardiola31337]

@zugaldia there is always a location source. It can't be null. So it doesn't make sense.

[zugaldia]

@Guardiola31337 Alternatively:

if (mapboxMap.getLocationSource() instanceof MyCustomLocationSource) {
  // Safe cast
}

[Ehekatl]

I manage to use this to fix issue #8639 #8848
However after I change location source to my own location engine in background service, the map view lost the ability to update user location gradually and start jumping to the new position immediately on location change.
Is there any way to solve it?

[zugaldia]

@Ehekatl thanks for the report. I'd like to explore the root cause for this misbehavior. Could you open a new ticket and, if possible, share the code for your custom location engine? For reference, we provide a sample implementation of a custom location engine on CustomLocationEngineActivity