Variable label placement example

[osana]

This PR adds an example of variable label placement using PropertyFactory.textVariableAnchor().

The renderer attempts placing the label at the positions in this list in the provided order of the array at collision detection time. If the symbol was successfully placed in a previous round, the renderer attempts that anchor position first before moving on to the rest of the list.

In this example the following values were used:

textVariableAnchor: ["top", "bottom", "left", "right"],
textRadialOffse: 0.5
textJustify: auto

[tobrun]

We are currently trying to load a local geojson file and aren't manipulating its contet. We can remove a lot of this boilerplate code if we rely on the loading map resources through assets. Us asset://poi_places.geojson as url for the second parameter of the geojsonsource constructor.

The json loader can be removed and the whole asynctask setup

[langsmith]

Got rid of the AsyncTask and onDataLoaded().

Doing this didn't work for me (lol):

So, I used the loadJsonFromAsset() method that's used in some other examples:

mapbox-android-demo/MapboxAndroidDemo/src/main/java/com/mapbox/mapboxandroiddemo/examples/styles/VariableLabelPlacementActivity.java

Line 71 in fff1abe

loadJsonFromAsset("poi_places.geojson")))

mapbox-android-demo/MapboxAndroidDemo/src/main/java/com/mapbox/mapboxandroiddemo/examples/styles/VariableLabelPlacementActivity.java

Lines 95 to 109 in fff1abe

	private String loadJsonFromAsset(String filename) {
	// Using this method to load in GeoJSON files from the assets folder.
	try {
	InputStream is = getAssets().open(filename);
	int size = is.available();
	byte[] buffer = new byte[size];
	is.read(buffer);
	is.close();
	return new String(buffer, "UTF-8");
	} catch (IOException ex) {
	ex.printStackTrace();
	return null;
	}
	}

Example's working the same as seen in the GIF in OP.

Did I misinterpret your instructions? Is there some even smoother way to pull from the assets folder?

[tobrun]

My bad, didn't double check the constructors. The issue with this setup is that you are trying to load that URI as an geojson string.
I tried using the URL constructor but that failed as that URI is not a valid URL.
-> mapbox/mapbox-gl-native#14743

Was able to make it work as:

    source = new GeoJsonSource(MARKER_SOURCE);
    source.setUrl("asset://something.geojson");

[tobrun]

nit to remove an unused class, looks good otherwise

[tobrun]

class can be removed

[langsmith]

Gah, keep forgetting to delete that damn unused class. Still seeing weird behavior, so it's still WIP

[tobrun]

that issue is mapbox/mapbox-gl-native#14715, feel free to ignore this bug

[langsmith]

Awesome 🚀