Develop Reference

LibGDX using Animations with a skin (for drag n' drop)

I have set up a game where Actor fireflies randomly fly across the screen, while glowing on and off — and a user can drag them into a mason jar. Pretty happy I've got this working, but I'd like to add a bit more detail. I'd like to add a two-step animation so that it looks like their wings are flapping.
I know how to do this with the Animation class, making use of TextureAtlas and TextureRegion. But that was prior to me heading in this Drag n Drop direction.
My issue, I think, is that I'm using skins, and they might not play nice with Animations.
///////////////////
Portions of my code.
///////////////////
Some of the items I declare up top:
private TextureAtlas textureAtlas;
private Texture texture;
private TextureRegion[] regions = new TextureRegion[3];
private Animation ffFlapping;
Setting up my TextureAtlas:
textureAtlas = new TextureAtlas(Gdx.files.internal("Player Animation/player_animation.png.atlas"));
texture = new Texture(Gdx.files.internal("Player Animation/player_animation.png.png"));
Setting up the skin:
final Skin skin = new Skin();
skin.addRegions(textureAtlas);
Doing the animation:
TextureRegion[] ffAnimation = new TextureRegion[2];
ffAnimation[0] = (textureAtlas.findRegion("firefly-0"));
ffAnimation[1] = (textureAtlas.findRegion("firefly-1"));
ffFlapping = new Animation(0.01f, ffAnimation);
For loop to create all my fireflies:
// ********************************************
// iterate through the number of fireflies
// we want to draw out using fireflyCount
// ********************************************
for (int fireflyIndex = 0; fireflyIndex < fireflyCount; fireflyIndex++) {
// YELLOW FIREFLY HERE
String fireflyName = "firefly" + fireflyIndex;
// if I replace ffFlapping below with object, I get no errors,
// but also no animation
skin.add(fireflyName, ffFlapping);
final Firefly ff = new Firefly(skin, fireflyName);
System.out.println("Fireflies objects:" + fireflyIndex);
// Not sure this affected the color, but it starts the alpha at 0
ff.setColor(150, 150, 150, 0);
ff.setOrigin(ff.getWidth()/2, ff.getHeight()/2);
stage.addActor(ff);
// This was set up in the attempt to continue movement if user misses target
final MoveToAction actionRight = new MoveToAction();
final MoveToAction actionLeft = new MoveToAction();
// setting up right and left targets, with a random Y position
float toRight = Gdx.graphics.getWidth() + 60;
float toLeft = (Gdx.graphics.getWidth() -Gdx.graphics.getWidth())-60f;
// sets up speed of glow, and the random time firefly is off, and also on
float glow = MathUtils.random(.5f, 1f);
float delayRandomOff = MathUtils.random(2.3f, 4.5f);
float delayRandomOn = MathUtils.random(.5f, .9f);
// sets up first variable to randomly choose between toRight and toLeft
// assigns direction to that value
float randomDirection = MathUtils.random.nextBoolean() ? toRight : toLeft;
float direction = randomDirection;
SequenceAction sequence = new SequenceAction();
AlphaAction aa = new AlphaAction();
Action alphaStartOn = Actions.delay(delayRandomOn, Actions.fadeOut(glow));
Action alphaStartOff = Actions.delay(delayRandomOff, Actions.fadeIn(glow));
// toRight is the x value ... it goes (x, y, duration)
Action startRight = Actions.moveTo(toRight, MathUtils.random(50, Gdx.graphics.getHeight() - 40), MathUtils.random(10f, 45f));
// toLeft is the x value ... it goes (x, y, duration)
// 170 makes sure they don't fly on top of mason jar
Action startLeft = Actions.moveTo(toLeft, MathUtils.random(170, Gdx.graphics.getHeight() - 40), MathUtils.random(10f, 45f));
Action faceOpposite = Actions.rotateBy(180f);
Action faceOpposite2 = Actions.rotateBy(180f);
// THIS ENDLESSLY LOOPS THEM ON THE SCREEN
Action loopRight = Actions.forever(Actions.sequence(faceOpposite, startRight, faceOpposite2, startLeft));
Action loopLeft = Actions.forever(Actions.sequence(startLeft, faceOpposite, startRight, faceOpposite2));
Action loopGlow1 = Actions.forever(Actions.sequence(alphaStartOn, alphaStartOff));
Action loopGlow2 = Actions.forever(Actions.sequence(alphaStartOff, alphaStartOn));
// THIS IS DEFINITELY TRIGGERING THE MOVEMENT
if(direction == toRight) {
ff.addAction(loopRight);
ff.addAction(loopGlow1);
} else {
ff.addAction(loopLeft);
ff.addAction(loopGlow2);
}
// MAKE EACH FIREFLY DRAGGABLE, and SET LARGER SIZE as you drag
dragAndDrop.addSource(new DragAndDrop.Source(ff) {
public DragAndDrop.Payload dragStart (InputEvent event, float x, float y, int pointer) {
DragAndDrop.Payload payload = new DragAndDrop.Payload();
payload.setObject("Firefly captured");
payload.setDragActor(ff);
ff.clearActions();
getActor().setSize(80, 80);
// Firefly freezes on drag, and enlarges ... disappears if dropped in jar
// Does not visually drag with cursor since it was part of animation.
return payload;
}
// IF YOU DON'T DROP FIREFLY ON TARGET, MAKE SURE IT STAYS ON STAGE
// AND GOES BACK TO THE NORMAL SIZE
#Override
public void dragStop(InputEvent event, float x, float y, int pointer, DragAndDrop.Payload payload, DragAndDrop.Target target) {
if(target == null)
stage.addActor(ff);
ff.addAction(actionLeft);
getActor().setSize(50, 50);
}
});
// MAKE EACH FIREFLY DRAGGABLE, and SET LARGER SIZE as you drag
dragAndDrop.addSource(new DragAndDrop.Source(ff) {
public DragAndDrop.Payload dragStart (InputEvent event, float x, float y, int pointer) {
DragAndDrop.Payload payload = new DragAndDrop.Payload();
payload.setObject("Firefly captured");
payload.setDragActor(ff);
ff.clearActions();
getActor().setSize(80, 80);
// Firefly freezes on drag, and enlarges ... disappears if dropped in jar
// Does not visually drag with cursor since it was part of animation.
return payload;
}
// IF YOU DON'T DROP FIREFLY ON TARGET, MAKE SURE IT STAYS ON STAGE
// AND GOES BACK TO THE NORMAL SIZE
#Override
public void dragStop(InputEvent event, float x, float y, int pointer, DragAndDrop.Payload payload, DragAndDrop.Target target) {
if(target == null)
stage.addActor(ff);
ff.addAction(actionLeft);
getActor().setSize(50, 50);
}
});
} // ***** END OF FOR LOOP ***********
And here's my Firefly code:
public class Firefly extends Image {
private float x = MathUtils.random(20, Gdx.graphics.getWidth() -40);
private float y = MathUtils.random(200, Gdx.graphics.getHeight() - 40);
private float width = 70;
private float height = 70;
public Firefly(Skin skin, String drawableName) {
super(skin, drawableName);
this.setBounds(x, y, width, height);
}
} // firefly
The error I'm getting is:
com.badlogic.gdx.utils.GdxRuntimeException: No Drawable, NinePatch, TextureRegion, Texture, or Sprite registered with name: firefly-2
///////////////////////////////
Any tips are very much appreciated.
In the meantime, I'm creating a new feature branch and keeping at it.
My guess is that I need to somehow make my two-step animation into some kind of Drawable.
Thanks!
— Bill

Imprecise Box2d coordinates using LibGDX

I am using LibGDX and Box2d to build my first Android game. Yay!
But I am having some serious problems with Box2d.
I have a simple stage with a rectangular Box2d body at the bottom representing the ground, and two other rectangular Box2d bodies both at the left and right representing the walls.
A Screenshot
Another Screenshot
I also have a box. This box can be touched and it moves using applyLinearImpulse, like if it was kicked. It is a DynamicBody.
What happens is that in my draw() code of the Box object, the Box2d body of the Box object is giving me a wrong value for the X axis. The value for the Y axis is fine.
Those blue "dots" on the screenshots are small textures that I printed on the box edges that body.getPosition() give me. Note how in one screenshot the dots are aligned with the actual DebugRenderer rectangle and in the other they are not.
This is what is happening: when the box moves, the alignment is lost in the movement.
The collision between the box, the ground and the walls occur precisely considering the area that the DebugRenderer renders. But body.getPosition() and fixture.testPoint() considers that area inside those blue dots.
So, somehow, Box2d is "maintaining" these two areas for the same body.
I thought that this could be some kind of "loss of precision" between my conversions of pixels and meters (I am scaling by 100 times) but the Y axis uses the same technique and it's fine.
So, I thought that I might be missing something.
Edit 1
I am converting from Box coordinates to World coordinates. If you see the blue debug sprites in the screenshots, they form the box almost perfectly.
public static final float WORLD_TO_BOX = 0.01f;
public static final float BOX_TO_WORLD = 100f;
The box render code:
public void draw(Batch batch, float alpha) {
x = (body.getPosition().x - width/2) * TheBox.BOX_TO_WORLD;
y = (body.getPosition().y - height/2) * TheBox.BOX_TO_WORLD;
float xend = (body.getPosition().x + width/2) * TheBox.BOX_TO_WORLD;
float yend = (body.getPosition().y + height/2) * TheBox.BOX_TO_WORLD;
batch.draw(texture, x, y);
batch.draw(texture, x, yend);
batch.draw(texture, xend, yend);
batch.draw(texture, xend, y);
}
Edit 2
I am starting to suspect the camera. I got the DebugRenderer and a scene2d Stage. Here is the code:
My screen resolution (Nexus 5, and it's portrait):
public static final int SCREEN_WIDTH = 1080;
public static final int SCREEN_HEIGHT = 1920;
At the startup:
// ...
stage = new Stage(SCREEN_WIDTH, SCREEN_HEIGHT, true);
camera = new OrthographicCamera();
camera.setToOrtho(false, SCREEN_WIDTH, SCREEN_HEIGHT);
debugMatrix = camera.combined.cpy();
debugMatrix.scale(BOX_TO_WORLD, BOX_TO_WORLD, 1.0f);
debugRenderer = new Box2DDebugRenderer();
// ...
Now, the render() code:
public void render() {
Gdx.gl.glClearColor(0, 0, 0, 1);
Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
camera.update();
world.step(1/45f, 6, 6);
world.clearForces();
stage.act(Gdx.graphics.getDeltaTime());
stage.draw();
debugRenderer.render(world, debugMatrix);
}

Looks like the answer to that one was fairly simple:
stage.setCamera(camera);
I was not setting the OrthographicCamera to the stage, so the stage was using some kind of default camera that wasn't aligned with my stuff.
It had nothing to do with Box2d in the end. Box2d was returning healthy values, but theses values were corresponding to wrong places in my screen because of the wrong stage resolution.

Box2D(LibGDX) - strange behaviour of ball

I am trying to create simple tennis game. Each side has a wall. There are also a box and a ball. My environment doesn't have gravity. The box and the ball don't have any velocity. When the box contacts the ball(I move this by mouse with different speed), it(the ball) just changes its position and doesn't continue moving and sometimes these objects don't collide with each other:
I want the box can strike the ball using different angle and strength.
How can I do this? What should I change in the properties of the ball and the box?
The code snippet is below:
public void createBall(Vector2 position, Vector2 velocity, float angle, Object userData){
// First we create a body definition
BodyDef bodyDef = new BodyDef();
// We set our body to dynamic, for something like ground which doesnt move we would set it to StaticBody
bodyDef.type = BodyType.DynamicBody;
// Set our body's starting position in the world
bodyDef.position.set(position);
// Create our body in the world using our body definition
Body body = world.createBody(bodyDef);
body.setUserData(userData);
// Create a circle shape and set its radius to 6
CircleShape circle = new CircleShape();
circle.setRadius(10f);
PolygonShape poly = new PolygonShape();
poly.setAsBox(12, 12);
// Create a fixture definition to apply our shape to
FixtureDef fixtureDef = new FixtureDef();
fixtureDef.shape = circle;
fixtureDef.density = 0.0f;
fixtureDef.friction = 0.2f;
fixtureDef.restitution = 1f; // Make it bounce a little bit
fixtureDef.isSensor=false;
// Create our fixture and attach it to the body
Fixture f = body.createFixture(fixtureDef);
f.setUserData("ball");
circle.dispose();
}
private Body createBox(World world, float width, float height, float density) {
BodyDef def = new BodyDef();
def.type = BodyType.KinematicBody;
Body box = world.createBody(def);
PolygonShape poly = new PolygonShape();
poly.setAsBox(width/2, height/2);
FixtureDef fixtureDef = new FixtureDef();
fixtureDef.shape = poly;
fixtureDef.density = 0.0f;
fixtureDef.friction = 0.3f;
fixtureDef.restitution = 0.1f; // Make it bounce a little bit
fixtureDef.isSensor=false;
// Create our fixture and attach it to the body
Fixture f = box.createFixture(fixtureDef);
f.setUserData("platform");
poly.dispose();
return box;
}
public void createWall(World world, Vector2 position, float hx, float hy){
// Create our body definition
BodyDef groundBodyDef =new BodyDef();
// Set its world position
groundBodyDef.position.set(position);
groundBodyDef.type=BodyType.StaticBody;
// Create a body from the defintion and add it to the world
Body groundBody = world.createBody(groundBodyDef);
// Create a polygon shape
PolygonShape groundBox = new PolygonShape();
// Set the polygon shape as a box which is twice the size of our view port and 20 high
// (setAsBox takes half-width and half-height as arguments)
groundBox.setAsBox(hx, hy);
// Create a fixture from our polygon shape and add it to our ground body
groundBody.createFixture(groundBox, 0.0f);
// Clean up after ourselves
groundBox.dispose();
}

You are moving your box by changing its position. But an important part of collision resolution is velocity. And your box's velocity is always zero (from box2d look point). Thus you experience strange collision resolution

I think your screen width and height are too large... if that's the case try using world width and height ... 20x12 units.. not 800x480 something .

Box2D doesn't like bodies, which fixtures has density 0. Usual, simulation performs somehow, but behaviour is not correct. Try value 0.3 for example.
Overlap problem may be solved by setting flag b2BodyDef::bullet. There description from Box2D reference:
bool b2BodyDef::bullet
Is this a fast moving body that should be prevented from tunneling through other moving bodies? Note that all bodies are prevented from tunneling through kinematic and static bodies. This setting is only considered on dynamic bodies.
Warning:
You should use this flag sparingly since it increases processing time.

Sprite Jump in my Game Play Andengine

Hy, I have started a Game in andengine for android, I want to apply a jump functionality on a sprite which will be like some projectile motion , up and forward as well . I have applied move modifier to gain that functionality. But that is not in projectile motion.
How can i achieve that and while the jump of my sprite by tapping again it cant jump again until it completes it jump.i dont want to use delay function on scene touch .any help .
final Entity playerEntity = move;
final float jumpDuration = 1;
final float startX = playerEntity.getX();
final float jumpHeight = 60;
move.getTextureRegion().setFlippedVertical(true);
final MoveModifier jumpForwardUp = new MoveModifier(jumpDuration/2, startX, startX - jumpHeight, playerEntity.getY(), playerEntity.getY() + 130);
final MoveModifier jumpForwardDown = new MoveModifier(jumpDuration/2, startX - jumpHeight, startX, playerEntity.getY() + 130, playerEntity.getY() + 170);
final SequenceEntityModifier modifier = new SequenceEntityModifier(jumpForwardUp ,jumpForwardDown);
playerEntity.registerEntityModifier(modifier);

Try using JumpModifier and for some real physics work, go for Box2d Extension of AndEngine and go through some of AndEngine examples code.
Edit:
AndEngine have list of modifiers. JumpModifier is one of them. Maintain a class level or project level flag that is true when your object is in jump and is false when object is in normal state.
Every modifier takes an object of IModifierListner set that flag to true in onStart of IModifierListner and set that to false at onEnd of IModifierListner. at every tap check if that flag is true then simple return and do nothing.

Change Sprite Position onAccelerometerChanged

I am new in AndEngine. I use animatedSprite and Sprite Object. I want to move Sprite on the basis of accelerometer but i dont want to move animatedSprite also. I want physicsworld implementation
private void addBottomFace(final float pX, final float pY) {
myBottomSticFace = new Sprite(pX, pY, myBottomStickTextureRegion);
myBottomStickBody = PhysicsFactory.createBoxBody(this.myPhysicsWorld, myBottomSticFace, BodyType.DynamicBody, myFixtureDef);
this.myScene.attachChild(myBottomSticFace);
this.myPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(myBottomSticFace, myBottomStickBody, true, true));
}
#Override
public void onAccelerometerChanged(AccelerometerData pAccelerometerData) {
final Vector2 gravity = Vector2Pool.obtain(pAccelerometerData.getX(), pAccelerometerData.getY());
myBottomSticFace.setPosition(myBottomSticFace,getX() + pAccelerometerData.getX(), myBottomSticFace,getY());
Vector2Pool.recycle(gravity);
}
With this code mBottomSticFace will move according to accelerometer but body does not moves.

You should create two different bodies and attach it to your sprites.
The Body you want to be moved should be set as BodyType.DynamicBody, and the other one should be BodyType.StaticBody.
To see accelerometer and body examples, check this:
http://code.google.com/p/andengineexamples/source/browse/src/org/anddev/andengine/examples/PhysicsExample.java