This document discusses screens, fonts, and preferences in libGDX. It describes how to create and switch between screens to structure a game. It also explains how to use bitmap fonts instead of trueType fonts for performance, and tools to generate bitmap fonts. Finally, it provides an overview of libGDX's preferences system for persistent storage of game data.

1. libGDX:
Screens,
Fonts
and
Pref
Jussi
Pohjolainen
Tampere
University
of
Applied
Sciences

2. SCREENS

3. Screen
and
Game
• Screen
– Use
to
add
different
screens
to
your
game
– Screen
is
a
interface
and
contains
all
the
same
methods
than
ApplicationListener.
Also
show() and
hide() when
screen
is
shown
and
hidden
• Game
– Game
is
an
ApplicationListener
that
holds
also
methods
for
changing
the
screen:
setScreen(Screen s)

4. public class ScreensFontsPref extends Game {
private MainMenuScreen mainmenu;
// Common objects to all screens!
private SpriteBatch batch;
// Returns the SpriteBatch
public SpriteBatch getBatch() {
return batch;
}
@Override
public void create () {
batch = new SpriteBatch();
// Create MainMenuScreen
mainmenu = new MainMenuScreen(this);
// Set it visible
setScreen(mainmenu);
}
@Override
public void render () {
super.render(); // Remember this, otherwise nothing is shown!
}
}

5. public class GameScreen implements Screen {
private ScreensFontsPref game;
private SpriteBatch batch;
private OrthographicCamera camera;
public GameScreen(ScreensFontsPref g) {
game = g;
batch = game.getBatch();
camera = new OrthographicCamera();
camera.setToOrtho(false, 800, 480);
}
@Override
public void render(float delta) {
batch.setProjectionMatrix(camera.combined);
Gdx.gl.glClearColor(1, 0, 0, 1);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
batch.begin();
// Do same drawing
Gdx.app.log("GameScreen", "render");
batch.end();
if (Gdx.input.isTouched()) {
game.setScreen(new GameScreen(game));
}
}

6. FONTS

7. About
Fonts
• libGDX
does
not
support
TrueType
Fonts
(TTF)
– Rendering
vector
graphics
is
costly
• libGDX
makes
use
of
bitmap
files
(pngs)
to
render
fonts
• Use
external
tool
to
convert
TTF
to
PNG!
• Each
glyph
in
the
font
has
a
corresponding
TextureRegion
• Default
font
Arial
provided,
other
fonts
you
have
to
create!
• If
you
use
same
font
in
different
screens,
create
font
once
and
share
it
with
other
screens.

8. Simple
to
Use
BitmapFont f = new BitmapFont();
f.draw(batch, "Hello World", 10, 10);
f.dispose();

9. Tools
for
CreaPng
own
Fonts
• Hiero
(http://bit.ly/16EpREP)
– Free
and
buggy?
Java
app
• Glyphite
(https://www.glyphite.com/)
– Free
web
app
• LiFera
(http://kvazars.com/littera/)
– Free
web
app

10. LiFera
Usage
1. Upload
some
.S
font
2. Export
format
.txt
3. Add
to
assets
(.png
and
.txt)
to
libGDX
project

11. Simple
to
Use
BitmapFont f = new new
BitmapFont(Gdx.files.internal("font.txt"));
f.draw(batch, "Hello World", 10, 10);
f.dispose();

12. Calculate
PosiPon
Libgdx
getAscent()
getDescent()
getLineHeight()

13. Calculate
PosiPon
String fontText = "Main Menu";
float fontX = game.getDefaultFont().getBounds(fontText).width;
float fontY = game.getDefaultFont().getBounds(fontText).height;

14. PREF

15. Persistent
Storage
• Simple
preferences
mechanism
for
storing
and
retrieving
• Windows,
Linux,
OS
X:
xml-­‐file
in
home
dir
– Windows:
%UserProfile%/.prefs/My Preferences
– Mac:
~/.prefs/My Preferences
• On
Android,
the
system's
SharedPreferences
class
is
used.
– Preferences
will
survive
app
updates,
but
are
deleted
when
the
app
is
uninstalled.

16. Usage
Preferences prefs =
Gdx.app.getPreferences("MyPreferences");
prefs.putString("name", "Donald Duck");
String name = prefs.getString("name", "No name stored");
prefs.putBoolean("soundOn", true);
prefs.putInteger("highscore", 10);
prefs.flush();

17. file
<?xml version="1.0" encoding="UTF-8"
standalone="no"?>
<!DOCTYPE properties SYSTEM "http://java.sun.com/
dtd/properties.dtd">
<properties>
<entry key="score">221</entry>
</properties>