Animations with Java2D

Newbie & Debugging Questions
#1

Hey there, I’m currently working on a concept for animations for sprites.
At the moment I want to initialize my Player-Object which inherits following Attribute from Sprite:

ArrayList<Animation> animations;

It’s a Container for animations (accessing them via STATE Constants)
My Animation-Class is built like this:

package Graphics;

import java.awt.Image;
import java.util.ArrayList;

/**
 *
 * @author Nils
 */
public class Animation
{

  private ArrayList<Frame> frames;
  private long totalTime, currentTime;
  private int frameIndex;
  private boolean looping;
  private Animation nextAnimation;
  private Image img;

  /**
   * Default constructor.
   */
  public Animation(Image img, boolean looping)
  {
    this.img = img;
    frames = new ArrayList<Frame>();
    this.looping = looping;
  }

  public void restart()
  {
    currentTime = frameIndex = 0;
  }

  /**
   * Adds an image to the animation.
   *
   * @param i The image to be added.
   * @param time The amount of time in milliseconds this image is displayed.
   */
  public void addFrame(Image i, long time)
  {
    totalTime += time;
    frames.add(new Frame(i, totalTime));
  }

  /**
   * Returns the current image displayed.
   *
   * @return The current image displayed.
   */
  public Image getFrame()
  {
    return frames.size() == 0 || isDone() ? null : frames.get(frameIndex).i;
  }

  public boolean isDone()
  {
    return looping ? false : frameIndex >= frames.size();
  }

  /**
   * Must be called to update the animation
   *
   * @param deltaTime The time passed since the last call to it.
   */
  public void update(long deltaTime)
  {
    if (frames.size() > 1)
    {
      currentTime += deltaTime;

      if (currentTime > totalTime)
      {
        if (looping)
        {
          frameIndex = 0;
          currentTime %= totalTime;
        }
        else
        {
          frameIndex++;
        }
      }

      if (!isDone())
      {
        while (currentTime > frames.get(frameIndex).time)
        {
          frameIndex++;
        }
      }
    }

  }

  public void setNextAnim(Animation anim)
  {
    this.nextAnimation = anim;
  }

  private static class Frame
  {

    private Image i;
    private long time;

    public Frame(Image i, long time)
    {
      this.i = i;
      this.time = time;
    }
  }
}

but how do I render my animations without a thread?
I somehow have to send the graphics-Object from Player, to the actual Animation and exchange the Player-Graphic with the one from the animation.
How do I do this?

#2

In your update method just leave out the while-loop


  /**
   * Must be called to update the animation
   *
   * @param deltaTime The time passed since the last call to it.
   */
  public void update(long deltaTime)
  {
    if (frames.size() > 1)
    {

      if (isDone())
        return;

      currentTime += deltaTime;

      if (currentTime > totalTime)
      {
        if (looping)
        {
          frameIndex = 0;
          currentTime = 0;
        }
        else
        {
          frameIndex++;
        }
      }
    }
  }

Now whenever you call your game’s render/update method and you just feed the delta to the animation there.

#3

As nhydock said, you call update() each time you go through your game loop. No need for a separate thread.

Wouldn’t you just use the current x/y position of the player object to determine where to render the Image returned by getFrame()? The actual player class could contain a “current state” variable (i.e. running, idle, jumping) and a “state start time” variable that’s used to retrieve the correct animation and the correct frame respectively. To get the delta to pass to the animation’s update() method each iteration of your game loop, subtract the “state start time” from the current system time. There’s really no need to store an actual Image/graphic in the player object.

@nhydock: The for loop is needed for cases where update() may be called at an inconsistent rate. If your delay between updates is too long, then it’s possible that you may have to skip a frame or more of the current animation. The for loop will keep going forward through the animation frames until it finds the one that’s supposed to be shown at the “currentTime” interval.

#4

I’m quite confused now ???
In my initializing method at the start I have this (testwise):

objectsToDraw.add(new Player(newImage));

(objectsToDraw is a ArrayList,Renderable is an interface)

my Player-Class looks like this now(testwise)

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package Core;

import Graphics.Animation;
import Graphics.Renderable;
import Graphics.Sprite;
import World.Actor;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.image.BufferedImage;

public class Player extends Sprite implements Renderable, Actor
{

  public static int health;
  public static final int maxHealth = 2000;

  /**
   * creates a Player-Object.
   *
   * @param img is the Spritesheet of the sprite representing the player.
   */
  public Player(BufferedImage img)
  {
    super(img);
    screenLocation = new Point(50, 50);
    initPlayer();
  }

  /**
   * Initiates the player for the Level. Means Animations will be added.
   */
  private void initPlayer()
  {
    BufferedImage tempImage = (BufferedImage) sheet;
    Animation temp = new Animation(sheet, true);
    tempImage.getSubimage(0, 0, 10, 5);
    temp.addFrame(tempImage, 5);
    tempImage.getSubimage(0, 5, 10, 5);
    temp.addFrame(tempImage, 5);
    animations.add(temp);
    System.out.println("initEnde");
  }

  /**
   * renders the current Player-Frame
   *
   * @param g
   */
  @Override
  public void render(Graphics g)
  {
  }

  /**
   * Disables the Render
   */
  @Override
  public void disableRender()
  {
  }

  @Override
  public void update()
  {
  }

  @Override
  public void calcBehav()
  {
  }

  @Override
  public void killThis()
  {
  }
}

my Animation Class looks like above(first post)

my Gameloop call these methods:

private void update()
  {
    for (int j = 0; j < actorList.size(); j++)
    {
      actorList.get(j).calcBehav();
      actorList.get(j).update();
    }
  }

  public void render()
  {
    Graphics2D g = (Graphics2D) getGraphics();
    g.setBackground(new Color(0, 0, 0));
    for (int i = 0; i < layer1.size(); i++)
    {
      layer1.get(i).render(g);
    }
    for (int i = 0; i < layer2.size(); i++)
    {
      layer2.get(i).render(g);
    }
    for (int i = 0; i < screensToDraw.size(); i++)
    {
      screensToDraw.get(i).render(g);
    }
    for (int i = 0; i < objectsToDraw.size(); i++)
    {
      objectsToDraw.get(i).render(g);
    }
    for (int i = 0; i < layer3.size(); i++)
    {
      layer3.get(i).render(g);
    }
    for (int i = 0; i < userInterface.size(); i++)
    {
      userInterface.get(i).render(g);
    }

  }

I don’t know how to play an animation.
It was just an idea.

#5

Well, for you player you probably only want one active animation playing, and you only need to update it during the update method


public class Player extends Sprite implements Renderable, Actor
{
   ...
   private Animation activeAnimation;
   ...

   public void update(long deltaTime)
   {
       activeAnimation.update(deltaTime);
   }

   public void render(Graphics g)
   {
        Image i = activeAnimation.getFrame();
        if (i != null)
            g.drawImage(i, transform);
   }
}

Also make sure your sprite class has a protected AffineTransform in Sprite that you’re operating on when you do things like set position and scaling of the sprite.

In your game loop, you just need to alter it like so


private void update()
{
    world.update() //or whatever you do to set the current delta time
    for (int j = 0; j < actorList.size(); j++)
    {
      actorList.get(j).calcBehav();
      actorList.get(j).update(world.deltaTime);
    }  
}
#6

Thanks for your help.
But Somehow it doesn’t want to draw the image.
Testwise I printed the (currentAnimation.getFrame())
it prints the 2 frames I inserted testwise (different sizes of the subimages)
but g.drawImage doesn’t seem to work…

Works now, had a wrong BufferedImage file.
Thanks to you guys. Dunno what I’d do without ya ;D