Skin2.java

import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.files.FileHandle;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.BitmapFont;
import com.badlogic.gdx.graphics.g2d.DistanceFieldFont;
import com.badlogic.gdx.graphics.g2d.TextureAtlas;
import com.badlogic.gdx.graphics.g2d.TextureRegion;
import com.badlogic.gdx.scenes.scene2d.ui.Skin;
import com.badlogic.gdx.utils.Array;
import com.badlogic.gdx.utils.Json;
import com.badlogic.gdx.utils.JsonValue;
import com.badlogic.gdx.utils.SerializationException;

public class Skin2 extends Skin {

    public Skin2(FileHandle skinFile) {
        super(skinFile);
    }

    public Skin2(FileHandle skinFile, TextureAtlas atlas) {
        super(skinFile, atlas);
    }

    public Skin2(TextureAtlas atlas) {
        super(atlas);
    }

    @Override
    protected Json getJsonLoader(final FileHandle skinFile) {
        final Skin2 skin = this;

        //first get default json with default BitmapFont.class Serializer
        final Json json = super.getJsonLoader(skinFile); 
        
        // set new serializer
        json.setSerializer(BitmapFont.class, new Json.ReadOnlySerializer<BitmapFont>() {
            public DistanceFieldFont read(Json json, JsonValue jsonData, Class type) {
                String path = json.readValue("file", String.class, jsonData);
                int scaledSize = json.readValue("scaledSize", int.class, -1, jsonData);
                Boolean flip = json.readValue("flip", Boolean.class, false, jsonData);
                Boolean markupEnabled = json.readValue("markupEnabled", Boolean.class, false, jsonData);
                float distanceFieldSmoothing = json.readValue("distanceFieldSmoothing", float.class, 0f, jsonData);

                if (distanceFieldSmoothing < 0f) throw new IllegalArgumentException("distanceFieldSmoothing cannot be < 0.");

                FileHandle fontFile = skinFile.parent().child(path);
                if (!fontFile.exists()) fontFile = Gdx.files.internal(path);
                if (!fontFile.exists()) throw new SerializationException("Font file not found: " + fontFile);

                // Use a region with the same name as the font, else use a PNG file in the same directory as the FNT file.
                String regionName = fontFile.nameWithoutExtension();
                try {
                    DistanceFieldFont font;
                    Array<TextureRegion> regions = skin.getRegions(regionName);
                    if (regions != null)
                        font = new DistanceFieldFont(new BitmapFont.BitmapFontData(fontFile, flip), regions, true);
                    else {
                        TextureRegion region = skin.optional(regionName, TextureRegion.class);
                        if (region != null)
                            font = new DistanceFieldFont(fontFile, region, flip);
                        else {
                            FileHandle imageFile = fontFile.parent().child(regionName + ".png");
                            if (imageFile.exists())
                                font = new DistanceFieldFont(fontFile, imageFile, flip);
                            else
                                font = new DistanceFieldFont(fontFile, flip);
                        }
                    }
                    font.getData().markupEnabled = markupEnabled;
                    // Scaled size is the desired cap height to scale the font to.
                    if (scaledSize != -1) font.getData().setScale(scaledSize / font.getCapHeight());

                    if (distanceFieldSmoothing == 0f) {
                        regions = font.getRegions();
                        for (TextureRegion region : regions.items)
                            region.getTexture().setFilter(Texture.TextureFilter.Nearest, Texture.TextureFilter.Nearest);
                    }
                    font.setDistanceFieldSmoothing(distanceFieldSmoothing);
                    return font;
                } catch (RuntimeException ex) {
                    throw new SerializationException("Error loading bitmap font: " + fontFile, ex);
                }
            }
        });
        return json;
    }

    public DistanceFieldFont getDistanceFieldFont (String name) {
        return (DistanceFieldFont) get(name, BitmapFont.class);
    }
}