使用 LibGDX Gdx.files.internal 加载 .png 文件时遇到问题

Here's the code that's trying to load the .png file.

//Textures
private Texture tiles;
private TextureRegion grassImage;
private TextureRegion dirtImage;
private TextureRegion stoneImage;

//Entities
private Texture entities;
private TextureRegion playerImage;

public WorldRenderer(World world, boolean debug) {
    this.world = world;
    this.camera = new OrthographicCamera(CAMERA_WIDTH, CAMERA_HEIGHT);
    this.camera.position.set(CAMERA_WIDTH/2f, CAMERA_HEIGHT/2f, 0);
    this.camera.update();
    this.debug = debug;
    spriteBatch = new SpriteBatch();
    loadTextures();
}

public void loadTextures() {
    tiles = new Texture(Gdx.files.internal("tiles.png"));
    grassImage = new TextureRegion(tiles, 0, 0, 32, 32);
    dirtImage = new TextureRegion(tiles, 0, 64, 32, 32);
    stoneImage = new TextureRegion(tiles, 64, 0, 32, 32);

    entities = new Texture(Gdx.files.internal("entities.png"));
    playerImage = new TextureRegion(entities, 0, 0, 32, 32);
}

public void render() {
    spriteBatch.begin();
    drawGrass();
    drawDirt();
    drawStone();
    drawPlayer();
    spriteBatch.end();
    if (debug) {
        drawDebug();
    }
}

这是错误信息:

Exception in thread "LWJGL Application" com.badlogic.gdx.utils.GdxRuntimeException: Couldn't load file: tiles.png
    at com.badlogic.gdx.graphics.Pixmap.<init>(Pixmap.java:140)
    at com.badlogic.gdx.graphics.glutils.FileTextureData.prepare(FileTextureData.java:64)
    at com.badlogic.gdx.graphics.Texture.load(Texture.java:175)
    at com.badlogic.gdx.graphics.Texture.create(Texture.java:159)
    at com.badlogic.gdx.graphics.Texture.<init>(Texture.java:133)
    at com.badlogic.gdx.graphics.Texture.<init>(Texture.java:122)
    at com.mr.zen.level.WorldRenderer.loadTextures(WorldRenderer.java:62)
    at com.mr.zen.level.WorldRenderer.<init>(WorldRenderer.java:58)
    at com.mr.zen.screens.GameScreen.show(GameScreen.java:29)
    at com.badlogic.gdx.Game.setScreen(Game.java:62)
    at com.mr.zen.Zen.create(Zen.java:12)
    at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:136)
    at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:114)
Caused by: com.badlogic.gdx.utils.GdxRuntimeException: File not found: tiles.png (Internal)
    at com.badlogic.gdx.files.FileHandle.read(FileHandle.java:132)
    at com.badlogic.gdx.files.FileHandle.length(FileHandle.java:586)
    at com.badlogic.gdx.files.FileHandle.readBytes(FileHandle.java:220)
    at com.badlogic.gdx.graphics.Pixmap.<init>(Pixmap.java:137)
    ... 12 more

loadTextures() 方法中存在问题.找不到文件

 tiles = new Texture(Gdx.files.internal("tiles.png"));