How to make members of an Array into an actor and add them to stage?

Question

I have an animation (enemies) that I would like to add multiple times on the screen. From what I know, I can save memory and framerate-per-second by using one animating image and make an arraylist of it wherein each member is turned to an actor and added multiple times to the stage. I have searched similar problems like this but the answers were really not that helpful. Any help will be appreciated. Here's my code:

EnemyAnimation class:

    public class EnemyAnimation extends Actor{

    Ninja app;
    LevelOneScreen levelOneScreen;

    private Animation animation;
    private static final int  FRAME_COLS_WALK = 10;
    private static final int  FRAME_ROWS_WALK= 1;
    public TextureRegion   currentFrame;
    private float stateTime = 0f;

    public float Xpos;
    public float Ypos;
    public static final int fallSpeed = 250;
    public boolean remove = false;
    final float delta = Gdx.graphics.getDeltaTime();



    public animation(final Ninja app){
        this.app = app;
        Texture ninSprite = new Texture(Gdx.files.internal("ninSprite.jpg"), true);
        ninSprite.setFilter(Texture.TextureFilter.MipMapLinearNearest,Texture.TextureFilter.MipMapLinearNearest);



        TextureRegion[][] tmp = TextureRegion.split(ninSprite, (int) ninSprite.getWidth() / FRAME_COLS_WALK, (int) ninSprite.getHeight() / FRAME_ROWS_WALK);
        TextureRegion[] ninTexRegion = new TextureRegion[FRAME_COLS_WALK * FRAME_ROWS_WALK];
        int index = 0 ;
        for (int i = 0; i < FRAME_ROWS_WALK; i++) {
            for (int j = 0; j < FRAME_COLS_WALK; j++) {
                ninTexRegion[index++] = tmp[i][j];
            }
        }

        animation = new Animation(0.044f,ninTexRegion);
        currentFrame = animation.getKeyFrame(stateTime, true);

    }

    public void draw(Batch batch, float parentAlpha) {

        super.draw(batch, parentAlpha);

        final float delta = Gdx.graphics.getDeltaTime();

        stateTime += delta;

        TextureRegion currentFrame = animation.getKeyFrame(stateTime, true);


        batch.draw(currentFrame,Xpos,Ypos,getWidth(),getHeight());

    }
}

LevelOneScreen class:

public class LevelOneScreen implements Screen {

    public Ninja app;
    private Stage stage;
    private Stage stageNinja;
    public EnemyAnimation enemyAnimation;
    private Image ninImage;
    private Image levelOneImage;
    private float deltaTime = Gdx.graphics.getDeltaTime();

    public ArrayList<EnemyAnimation> enemyAnimate;


    public LevelOneScreen(final Ninja app){
        this.app = app;
        this.stage = new Stage(new StretchViewport(app.screenWidth, app.screenHeight, app.camera));
        this.stageNinja = new Stage(new StretchViewport(app.screenWidth, app.screenHeight, app.camera));
        enemyAnimate = new ArrayList<EnemyAnimation>();
        enemyAnimation = new EnemyAnimation(app);
    }


    @Override
    public void show() {

        InputMultiplexer inputMultiplexer = new InputMultiplexer();
        inputMultiplexer.addProcessor(stage);
        inputMultiplexer.addProcessor(stageNinja);
        Gdx.input.setInputProcessor(inputMultiplexer);




        levelOneBackground();
        enemy();
    }


    public void enemy(){


        stageNinja.addActor(enemyAnimate);


       /* 

         From here I cannot add the Arraylist enemyAnimate to the 
         stage and I received some errors. I would like to add elements to
         enemyAnimate and make each added elements into actors with 
         different positions to be added to the stage.

        */


    }





    @Override
    public void render(float delta) {


        Gdx.gl.glClearColor(0, 0, 0, 1);
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

        update(delta);

    }



    public void update(float deltaTime){

        stage.draw();
        stageNinja.draw();

        stage.act(deltaTime);
        stageNinja.act(deltaTime);

    }

Update to my code:

I now use Array of libgdx but it still won't show the enemies on stage without an indexOutOfBounds error. Here's the code:

public class LevelOneScreen implements Screen {

    public Ninja app;
    private Stage stage;
    private Stage stageNinja;
    public EnemyAnimation enemyAnimation;
    private Image ninImage;
    private Image levelOneImage;
    private float deltaTime = Gdx.graphics.getDeltaTime();

    public Array<EnemyAnimation> enemyAnimate;


    public LevelOneScreen(final Ninja app){
        this.app = app;
        this.stage = new Stage(new StretchViewport(app.screenWidth, app.screenHeight, app.camera));
        this.stageNinja = new Stage(new StretchViewport(app.screenWidth, app.screenHeight, app.camera));
        enemyAnimate = new Array<EnemyAnimation>();
        enemyAnimate.add(new EnemyAnimation(app));
        enemyAnimation = new EnemyAnimation(app);
    }


    @Override
    public void show() {

        InputMultiplexer inputMultiplexer = new InputMultiplexer();
        inputMultiplexer.addProcessor(stage);
        inputMultiplexer.addProcessor(stageNinja);
        Gdx.input.setInputProcessor(inputMultiplexer);




        levelOneBackground();
        enemyAct1();
        //  ......
        enemyAct4();
    }


        public void enemyAct1(){

      for(int i = 0; i < 6; i++){enemyAnimate.add(new EnemyAnimation(app));}

    enemyAnimate.get(1).setPosition(app.screenWidth*0.1f,app.screenHeight);
    stageEnemy.addActor(enemyAnimate.get(1));
    float enemyTimeDrop1 = (app.screenHeight/app.screenHeight)*4.85f ;
    enemyAnimate.get(1).addAction(moveTo(app.screenWidth*0.1f,enemyDestination,enemyTimeDrop1));


    enemyAnimate.get(2).setPosition(app.screenWidth*0.1f+enemyAnimation.enemyWidth,app.screenHeight+enemyAnimation.enemyHeight);
       stageEnemy.addActor(enemyAnimate.get(2));
    float enemyHeight2 = app.screenHeight+enemyAnimation.enemyHeight;
    float enemyTimeDrop2 = (enemyHeight2/app.screenHeight)*4.85f ;
    enemyAnimate.get(2).addAction(moveTo(app.screenWidth*0.1f+enemyAnimation.enemyWidth,enemyDestination,enemyTimeDrop2));


    enemyAnimate.get(3).setPosition(app.screenWidth*0.1f+enemyAnimation.enemyWidth*2f,app.screenHeight+enemyAnimation.enemyHeight*2f);
        stageEnemy.addActor(enemyAnimate.get(3));
    float enemyHeight3 = app.screenHeight+enemyAnimation.enemyHeight*2f;
    float enemyTimeDrop3 = (enemyHeight3/app.screenHeight)*4.85f ;
    enemyAnimate.get(3).addAction(moveTo(app.screenWidth*0.1f+enemyAnimation.enemyWidth*2f,enemyDestination,enemyTimeDrop3));


    enemyAnimate.get(4).setPosition(app.screenWidth*0.1f+enemyAnimation.enemyWidth*3f,app.screenHeight+enemyAnimation.enemyHeight*3f);
        stageEnemy.addActor(enemyAnimate.get(4));
    float enemyHeight4 = app.screenHeight+enemyAnimation.enemyHeight*3f;
    float enemyTimeDrop4 = (enemyHeight4/app.screenHeight)*4.85f ;
    enemyAnimate.get(4).addAction(moveTo(app.screenWidth*0.1f+enemyAnimation.enemyWidth*3f,enemyDestination,enemyTimeDrop4));


    enemyAnimate.get(5).setPosition(app.screenWidth*0.1f+enemyAnimation.enemyWidth*4f,app.screenHeight+enemyAnimation.enemyHeight*4f);
        stageEnemy.addActor(enemyAnimate.get(5));
    float enemyHeight5 = app.screenHeight+(enemyAnimation.enemyHeight*4f);
    float enemyTimeDrop5 = (enemyHeight5/app.screenHeight)*4.85f ;
    enemyAnimate.get(5).addAction(moveTo(app.screenWidth*0.1f+enemyAnimation.enemyWidth*4f,enemyDestination,enemyTimeDrop5));


}

enemyAct1() is drawn but enemyAct4() is not and returns an indexOutOfBoundsError : index can't be >= size: 21 >= 17. Here's enemyAct4():

public void enemyAct4(){
    for(int i = 20; i < 30; i++){
        enemyAnimate.add(new EnemyAnimation(app));
    }


    enemyAnimate.get(21).setPosition(app.screenWidth/2-enemyAnimation.enemyWidth/2,app.screenHeight);
        stageEnemy.addActor(enemyAnimate.get(21));
    float enemyTimeDrop1 = 4.85f ;
    enemyAnimate.get(21).addAction(moveTo(app.screenWidth/2-enemyAnimation.enemyWidth/2,enemyDestination,enemyTimeDrop1));



    enemyAnimate.get(22).setPosition((app.screenWidth/2-enemyAnimation.enemyWidth/2)+enemyAnimation.enemyWidth,(app.screenHeight+enemyAnimation.enemyHeight));
    stageEnemy.addActor(enemyAnimate.get(22));
    float enemyHeight22 = (app.screenHeight+enemyAnimation.enemyHeight);
    float enemyTimeDrop22 = (enemyHeight22/app.screenHeight)*4.85f ;
    enemyAnimate.get(22).addAction(moveTo((app.screenWidth/2-enemyAnimation.enemyWidth/2)+enemyAnimation.enemyWidth,enemyDestination,enemyTimeDrop22));


    enemyAnimate.get(23).setPosition((app.screenWidth/2-enemyAnimation.enemyWidth/2)-enemyAnimation.enemyWidth,app.screenHeight+(enemyAnimation.enemyHeight));
    stageEnemy.addActor(enemyAnimate.get(23));
    float enemyHeight23 = app.screenHeight+(enemyAnimation.enemyHeight);
    float enemyTimeDrop23 = (enemyHeight23 /app.screenHeight)*4.85f ;
    enemyAnimate.get(23).addAction(moveTo((app.screenWidth/2-enemyAnimation.enemyWidth/2)-enemyAnimation.enemyWidth,enemyDestination,enemyTimeDrop23));


    enemyAnimate.get(24).setPosition((app.screenWidth/2-enemyAnimation.enemyWidth/2)+(enemyAnimation.enemyWidth*2f),app.screenHeight+(enemyAnimation.enemyHeight*2f));
       stageEnemy.addActor(enemyAnimate.get(24));
    float enemyHeight24 = app.screenHeight+(enemyAnimation.enemyHeight*2f);
    float enemyTimeDrop24 = (enemyHeight24/app.screenHeight)*4.85f ;
    enemyAnimate.get(24).addAction(moveTo((app.screenWidth/2-enemyAnimation.enemyWidth/2)+(enemyAnimation.enemyWidth*2f),enemyDestination,enemyTimeDrop24));


    enemyAnimate.get(25).setPosition((app.screenWidth/2-enemyAnimation.enemyWidth/2)-(enemyAnimation.enemyWidth*2f),app.screenHeight+(enemyAnimation.enemyHeight*2f));
        stageEnemy.addActor(enemyAnimate.get(25));
    float enemyHeight25 = app.screenHeight+(enemyAnimation.enemyHeight*2f);
    float enemyTimeDrop25 = (enemyHeight25/app.screenHeight)*4.85f ;
    enemyAnimate.get(25).addAction(moveTo((app.screenWidth/2-enemyAnimation.enemyWidth/2)-(enemyAnimation.enemyWidth*2f),enemyDestination,enemyTimeDrop25));

}






    @Override
    public void render(float delta) {


        Gdx.gl.glClearColor(0, 0, 0, 1);
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

        update(delta);

    }



    public void update(float deltaTime){

        stage.draw();
        stageNinja.draw();

        stage.act(deltaTime);
        stageNinja.act(deltaTime);

    }

Answer 1

You load a new Texture in each EnemyAnimation which loads alot of memory.

For example if it's a 500x500 image, it has 250,000 pixels. One pixel has 3 bytes so it's 750000 bytes -> 0.71 MB. One enemy takes 1MB of RAM. Remember that I've mentioned 500x500 image, your is probably bigger.

It's unacceptable, you should reuse the image on all enemies.

Use AssetLoader/AssetManager as written here: https://github.com/libgdx/libgdx/wiki/Managing-your-assets

You should load your ninSprite.jpg with AssetManager and then in your NinjaAnimate class call

Texture tex = manager.get("data/mytexture.png", Texture.class);

Remember to use only one instance of your AssetManager and load them only once.

Answer 2

An EnemyAnimation is an actor in itself, you do not need to create an actor from the list of EnemyAnimation as the title of your post suggests.

EnemyAnimate is NOT an actor, it is a List of actors, so the line

stageNinja.addActor(enemyAnimate);

should be replaced by

stageNinja.addActor(enemyAnimate.get(i)); // where i is an iterator you need to set to get the actor you want to get.

In the LevelOneScreen constructor you initialize an EnemyAnimation object but you never add it to the List.

You can change the line

enemyAnimation = new EnemyAnimation(app);

to

enemyAnimate.add(new EnemyAnimation(app));

and you can get rid of the enemyAnimation variable as it will not be used anymore.