Exercise 2.1.08 alternative using "createSprite". Notice that using the Sprite's draw method does a better job than SpriteBatch's draw with scaling.

TextureAtlasExercise.java

package com.udacity.gamedev.textureatlas;

import com.badlogic.gdx.ApplicationAdapter;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.assets.AssetDescriptor;
import com.badlogic.gdx.assets.AssetErrorListener;
import com.badlogic.gdx.assets.AssetManager;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.g2d.Animation;
import com.badlogic.gdx.graphics.g2d.Sprite;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.graphics.g2d.TextureAtlas;
import com.badlogic.gdx.utils.Array;

public class TextureAtlasExercise extends ApplicationAdapter implements AssetErrorListener {

    public static final String TAG = TextureAtlasExercise.class.getName();

    private static final String ATLAS = "images/gigagal.pack.atlas";
    private static final String STANDING_RIGHT = "standing-right";

    // TODO: Add an AssetManager
    private AssetManager assetManager;

    SpriteBatch batch;

    // TODO: Add a Sprite to hold the standing right sprite
    Sprite standingRight;

    Array<Sprite> walkRight;

    int animTime = 0;
    Animation animation;

    @Override
    public void create() {
        batch = new SpriteBatch();

        // TODO: Initialize your AssetManager
        assetManager = new AssetManager();

        // TODO: Set this as the AssetManager's error listener
        assetManager.setErrorListener(this);

        // TODO: tell the AssetManager to load the TextureAtlas with name ATLAS
        assetManager.load(ATLAS, TextureAtlas.class);

        // TODO: Call finishLoading() on your AssetManager
        assetManager.finishLoading();

        // TODO: Get the TextureAtlas from the asset manager
        TextureAtlas atlas = assetManager.get(ATLAS);

        // TODO: Populate your ~ using your Atlas
        standingRight = atlas.createSprite(STANDING_RIGHT);

        walkRight = new Array<Sprite>(3);

        for (int i=1; i<4; i++) {
            walkRight.add(atlas.createSprite("walk-" + i + "-right"));
        }

        for (Sprite sprite: walkRight) {
            sprite.setScale(3f);
            sprite.setX(100f);
            sprite.setOrigin(sprite.getOriginX(), 0f);
        }

        animation = new Animation(1, walkRight, Animation.PlayMode.LOOP_PINGPONG);
    }

    @Override
    public void render() {
        Gdx.gl.glClearColor(1, 1, 1, 1);
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
        batch.begin();

        // TODO: Draw the standing right AtlasRegion
        standingRight.draw(batch);

        // Drawing with the Sprite.draw method. Uses the preset scaling, origin, etc.
        walkRight.get(animTime / 10).draw(batch);

        // Drawing the Sprite's Texture. This ignores Sprite scaling, origin, etc.
        float scale = 3f;
        batch.draw(animation.getKeyFrame(animTime / 10), 200, 0,
                scale*standingRight.getWidth(), scale*standingRight.getHeight());

        batch.end();

        animTime++;
        if (animTime >= 30) animTime = 0;
    }

    @Override
    public void error(AssetDescriptor asset, Throwable throwable) {
        Gdx.app.error(TAG, "Couldn't load asset: " + asset.fileName, throwable);
    }

    @Override
    public void dispose() {
        batch.dispose();
        // TODO: Dispose of the AssetManager
        assetManager.dispose();
    }
}