The document discusses LibGDX's support for internationalization and scene 2D. It describes how to create property files for different languages to support internationalization in LibGDX games. It then provides an overview of Scene2D, describing it as an optional higher-level framework for creating 2D games and UIs using stages, actors, and events. It includes code examples of creating a stage and adding an actor, as well as handling input events with actors.

1. LibGDX:
Internaliza1on
and
Scene
2D
Jussi
Pohjolainen
Tampere
University
of
Applied
Sciences

2. INTERNALIZATION

3. Support
for
Mul1ple
Languages
• Create
defaults
proper1es
file:
– MyBundle.properties
• Create
other
language
files:
– MyBundle.fi_FI.properties

4. MyBundle.proper1es
title=My Game
score=You score {0}

5. MyBundle_fi.proper1es
title=Pelini
score=Pisteesi {0}

6. In
Java
Locale locale = new Locale("fi");
I18NBundle myBundle =
I18NBundle.createBundle(Gdx.files.internal("MyBundle"), locale);
String title = myBundle.get("title");
String score = myBundle.get("score", 50);

7. Notes
• If
you
don't
specify
locale,
default
locale
is
used
• Charset
is
UTF-­‐8
(without
BOM)
• See:
– hVps://github.com/libgdx/libgdx/wiki/
Interna1onaliza1on-­‐and-­‐Localiza1on

8. SCENE2D

9. Scene2D?
• It’s
op1onal,
you
don’t
need
it.
But
you
may
want
to
use
it.
• May
be
useful
for
"board
games"
• Higher
level
framework
for
crea>ng
games
• Provides
UI
Toolkit
also:
Scene2d.ui
• Tutorial
– https://github.com/libgdx/libgdx/wiki/Scene2d

10. Concepts
• Stage
– “Screens”,
“Stages”,
“Levels”
– Camera
watching
the
stage
– Contains
group
of
actors
• Actors
– “Sprites”

11. Roughly
the
Idea
in
Code
Stage gameStage = new Stage();
// PlayerActor extends Actor { .. }
PlayerActor player = new PlayerActor();
// Let's add the actor to the stage
gameStage.addActor(player);

12. Possibili1es
• Event
system
for
actors;
when
actor
is
touched,
dragged
..
– Hit
detec>on;
dragging
/
touching
within
the
bounds
of
actor
• Ac>on
system:
rotate,
move,
scale
actors
in
parallel
– Also
rota1on
and
scaling
of
group
of
actors

13. Stage
• Stage
implements
InputProcessor,
so
it
can
directly
input
events
from
keyboard
and
touch
• Add
to
your
Applica1onAdapter
– Gdx.input.setInputProcessor(myStage);
• Stage
distributes
input
to
actors
• Use
setViewport
to
set
the
camera
– myStage.setViewPort(...);
• Stage
has
act
method,
by
calling
this,
every
act
method
of
every
actor
is
called

14. Actors
• Actor
has
an
posi1on,
rect
size,
scale,
rota1on…
• Posi1on
is
the
leb
corner
of
the
actor
• Posi1on
is
rela1ve
to
the
actor’s
parent
• Actor
may
have
ac>ons
– Change
the
presenta>on
of
the
actor
(move,
resize)
• Actor
can
react
to
events

15. public class StageGame extends ApplicationAdapter {
// Stage contains hierarcy of actors
private Stage stage;
// We will have player actor in the stage
private BlueBirdActor playerActor;
@Override
public void create () {
// Creating the stage
stage = new Stage();
// Creating the actors
playerActor = new BlueBirdActor();
// add actors to stage
stage.addActor(playerActor);
}
@Override
public void render () {
Gdx.gl.glClearColor(1, 0, 0, 1);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
// Call act on every actor
stage.act(Gdx.graphics.getDeltaTime());
// Call draw on every actor
stage.draw();
}
}

16. public class BlueBirdActor extends Actor {
private Texture texture;
public BlueBirdActor() {
texture = new Texture(Gdx.files.internal("blue-bird-icon.png"));
}
@Override
public void draw(Batch batch, float alpha) {
batch.draw(texture, getX(), getY());
}
@Override
public void act(float delta) {
super.act(delta);
}
}

17. Event
System
• Stage
will
be
responsible
for
gedng
user
input
– Gdx.input.setInputProcessor(stage);
• Stage
will
fire
events
to
actors
• Actor
may
receive
events
if
it
has
a
listener
– actor.addListener(new InputListener()
{ … } );
• Actor
must
specify
bounds
in
order
to
receive
input
events
within
those
bounds!
• To
handle
key
input,
actor
has
to
have
keyboard
focus

18. public class StageGame extends ApplicationAdapter {
// Stage contains hierarcy of actors
private Stage stage;
// We will have player actor in the stage
private BlueBirdActor playerActor;
@Override
public void create () {
// Creating the stage
stage = new Stage();
// Sets the InputProcessor that will receive all touch and key input events.
// It will be called before the ApplicationListener.render() method each frame.
//
// Stage handles the calling the inputlisteners for each actor.
Gdx.input.setInputProcessor(stage);
// Creating the actors
playerActor = new BlueBirdActor();
// add actors to stage
stage.addActor(playerActor);
stage.setKeyboardFocus(playerActor);
}
@Override
public void render () {
Gdx.gl.glClearColor(1, 0, 0, 1);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
// Call act on every actor
stage.act(Gdx.graphics.getDeltaTime());
// Call draw on every actor
stage.draw();
}
}

19. public class BlueBirdActor extends Actor {
private boolean up, down, left, right
public BlueBirdActor() {
addListener(new PlayerListener());
}
@Override
public void act(float delta) {
if(up) {
setY(getY() + speed * delta);
}
}
// InputListener implements EventListener, just override the methods you need
// Also ActorGestureListener available: fling, pan, zoom, pinch..
class PlayerListener extends InputListener {
@Override
public boolean keyDown(InputEvent event, int keycode) {
if(keycode == Input.Keys.UP) {
up = true;
}
return true;
}
@Override
public boolean keyUp(InputEvent event, int keycode) {
if(keycode == Input.Keys.UP) {
up = false;
}
return true;
}
}
}

20. Ac1ons
• Each
actor
has
a
list
of
ac1ons
• Updated
on
every
frame
(act-­‐method)
• Many
ac1ons
available
– MoveToAction
– RotateToAction
– ScaleToAction
• Example
– MoveToAction action = new MoveToAction();
– action.setPosition(300f, 700f);
– action.setDuration(2f);
– actor.addAction(action);

21. Grouping
Ac1ons
in
Sequence
SequenceAction sequenceAction = new SequenceAction();
MoveToAction moveAction = new MoveToAction();
RotateToAction rotateAction = new RotateToAction();
ScaleToAction scaleAction = new ScaleToAction();
moveAction.setPosition(200f, 400f);
moveAction.setDuration(1f);
rotateAction.setRotation(rotate);
rotateAction.setDuration(1f);
scaleAction.setScale(0.5f);
scaleAction.setDuration(1f);
sequenceAction.addAction(moveAction);
sequenceAction.addAction(rotateAction);
sequenceAction.addAction(scaleAction);
actor.addAction(sequenceAction);

22. Grouping
Ac1ons
in
Parallel
ParallelAction parallel = new ParallelAction ();
MoveToAction moveAction = new MoveToAction();
RotateToAction rotateAction = new RotateToAction();
ScaleToAction scaleAction = new ScaleToAction();
moveAction.setPosition(200f, 400f);
moveAction.setDuration(1f);
rotateAction.setRotation(rotate);
rotateAction.setDuration(1f);
scaleAction.setScale(0.5f);
scaleAction.setDuration(1f);
parallel.addAction(moveAction);
parallel.addAction(rotateAction);
parallel.addAction(scaleAction);
actor.addAction(parallel);

23. Ac1ons
Complete?
SequenceAction sequenceAction = new SequenceAction();
ParallelAction parallelAction = new ParallelAction();
MoveToAction moveAction = new MoveToAction();
RotateToAction rotateAction = new RotateToAction();
RunnableAction runnableAction = new RunnableAction();
moveAction.setPosition(200f, 400f);
moveAction.setDuration(1f);
moveAction.setInterpolation(Interpolation.bounceOut);
rotateAction.setRotation(rotate);
rotateAction.setDuration(1f);
runnableAction.setRunnable(new Runnable() {
public void run() {
System.out.println("done!");
}
});
parallelAction.addAction(rotateAction);
parallelAction.addAction(moveAction);
sequenceAction.addAction(parallelAction);
sequenceAction.addAction(runnableAction);

24. Enable
rotate
and
scale
in
drawing
@Override
public void draw(Batch batch, float alpha){
batch.draw(texture,
this.getX(), this.getY(),
this.getOriginX(),
this.getOriginY(),
this.getWidth(),
this.getHeight(),
this.getScaleX(),
this.getScaleY(),
this.getRotation(),0,0,
texture.getWidth(), texture.getHeight(), false, false);
}

25. Grouping
Group group = new Group();
group.addActor(playerActor);
group.addActor(monsterActor);
group.addAction( ... );
stage.addActor(group);

26. CREATING
UI:
SCENE2D.UI

27. Scene2D.UI
• Tutorial
– hVps://github.com/libgdx/libgdx/wiki/Scene2d.ui
• To
quickly
get
started,
add
following
to
your
project
– uiskin.png,
uiskin.atlas,
uiskin.json,
default.fnt
– hVps://github.com/libgdx/libgdx/tree/master/
tests/gdx-­‐tests-­‐android/assets/data
• Tutorial
and
examples
– hVps://github.com/libgdx/libgdx/wiki/Scene2d.ui

28. TextBuVon
example
Skin skin = new Skin( Gdx.files.internal("uiskin.json") );
final TextButton button = new TextButton("Hello", skin);
button.setWidth(200f);
button.setHeight(20f);
button.setPosition(Gdx.graphics.getWidth() /2 - 100f, Gdx.graphics.getHeight()/2
- 10f);
startStage.addActor(button);
Gdx.input.setInputProcessor(startStage);
button.addListener(new ClickListener(){
@Override
public void clicked(InputEvent event, float x, float y){
whichScreen = !whichScreen;
Gdx.input.setInputProcessor(gameStage);
}
});