Hello everyone,
Can any of you please demonstrate a simple example on how to use groups in libGdx ? so if i move the parent, then all the children will move with it and same goes for rotation and scaling.
Thank you
Well, all you would do is create a “Member” Class and have different instances of that (like the Component classes in Swing):
Very rough code:
public class Member{
private ArrayList<Member> children=new ArrayList<Member>();//only needed if the parent ever needs to access any children
Member parent;
Vector2 position,scale; // just a simple vector class
public Member(Member parent, Vector2 position, Vector2 scale){
this.parent=parent;
this.position=Vector2.combine(parent.getPosition(), position);// "combine" method just combines the x and y values and returns a new Vector2. also, position based on parent position
this.scale=parent.getScale();// notice this is scale, not size so the children will scale with the parent and not just be the same size as it
}
public Member(Vector2 position, Vector2 scale){//this would be and un-parented "Member"
this.parent=parent;
this.position=position;
this.scale=scale;
}
public void update(){
if(parent==null){
//update position based on world coordinates
}else{
//update position based on parent coordinates
}
}
/**put getters and setters here**/
}
And there you have it, now every class that “extends” that class will be able to be parented to one another
and now for the Vector2 class:
public class Vector2{
float x,y;//doesn't just have to be used for coordinates
float velx,vely;// velocity variables
public Vector2(float x,float y){
this.x=x;
this.y=y;
}
public void update(){
//update stuff here
x+=velx;
y+=vely;
}
/*getters and setters here*/
/*Also, to make life easier, put in some tween (is that the word?) functions (translate,rotate,moveTo,moveOnAngle,moveToVector)*/
public static Vector2 combine(Vector2 first,Vector2 second){
return new Vector2(first.getX()+second.getX(), first.getY()+second.getY());
}
}
Hope this helps in any way
Wait what, he’s talking about libgdx Group. It’s a specific class. And libgdx has its own Vector2 class too…]
@OP http://www.gamefromscratch.com/post/2013/12/11/LibGDX-Tutorial-3C-Scene-management.aspx
@kingroka123
thank’s for the input but as Jimmt said, am talking about libGdx Group.
@Jimmt
i already checked that tutorial before posting, and it seems that it’s a bit old.
this gave me an error :
stage = new Stage(Gdx.graphics.getWidth(),Gdx.graphics.getHeight(),true);
because according to the docs a Stage take a viewport as a parameter and there is also other things that seemed outdated in that tutorial, that’s why i asked for a quick example here 
thank you
I have no Idea but maybe try out this:
stage = new Stage(new Viewport());
oh ._. I thought he just meant hierarchical grouping. oh well, at least i tried ;D
ps: I wrote that code at about 12 am and I don’t think I even thought about it being in LibGDX 
The part with stage and viewport has been introduced sometime before the 1.0 release of libgdx. Viewport is just an interface as far as I know, so you can’t create it directly. Check the libgdx docs which viewport would suit you best (I tend to use the ScalingViewport): https://github.com/libgdx/libgdx/wiki/Viewports
Thnx everyone, here is exactly what i needed to have ;D
public class LearnGdx extends ApplicationAdapter {
public static final int WIDTH = 800;
public static final int HEIGHT = 480;
private Stage stage;
private Group group;
private float rotSpeed = 5;
@Override
public void create() {
// Create a stage
stage = new Stage(new StretchViewport(WIDTH, HEIGHT));
// Create a group and add it to the stage.
group = new Group();
stage.addActor(group);
// Create images and add them to the group.
final Texture region = new Texture(Gdx.files.internal("circle.png"));
Image img = new Image(region);
Image img2 = new Image(region);
Image img3 = new Image(region);
img2.setColor(new Color(1, 0, 0, 1));
img3.setColor(new Color(0, 0, 1, 1));
group.addActor(img2);
group.addActor(img3);
group.addActor(img);
// Images are positioned relative to the group...
img.setPosition(0, 0);
img2.setPosition(img.getWidth()/2, 0);
img3.setPosition(-img.getWidth()/2, 0);
// Group is positioned relative to the stage...
group.setPosition(WIDTH / 2 - img.getWidth() / 2,
HEIGHT / 2 - img.getHeight() / 2);
group.setOrigin(img.getWidth()/2,img.getHeight()/2);
}
@Override
public void render() {
Gdx.gl.glClearColor(0, 0, 0, 1);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
stage.act(Gdx.graphics.getDeltaTime());
stage.draw();
if (Gdx.input.isKeyPressed(Keys.LEFT)) {
group.rotateBy(rotSpeed);
}
if (Gdx.input.isKeyPressed(Keys.RIGHT)) {
group.rotateBy(-rotSpeed);
}
}
}