Develop Reference

Libgdx viewport not stretching

I'm currently having a problem creating a stretchedViewPort in libgdx.
As you can see in the image I added the gamescreen is not stretched over the whole screen and there are black spaces. I'm wondering what I'm doing wrong.
I provided the relevant parts of the code below.
Furthermore I also tried to use asign the viewport in to the stage in the oncreate function like this: m_stage = new Stage(m_viewport); But in that case I got a black screen and nothing was rendered (tough there were no compile errors).
Can someone point out what I'm doing wrong or what I'm missing.
Thanks in advance!
Kind regards,
Cavasta
package com.block.it;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.Screen;
import com.badlogic.gdx.graphics.PerspectiveCamera;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.scenes.scene2d.InputEvent;
import com.badlogic.gdx.scenes.scene2d.Stage;
import com.badlogic.gdx.scenes.scene2d.ui.Image;
import com.badlogic.gdx.scenes.scene2d.utils.ClickListener;
import com.badlogic.gdx.utils.viewport.StretchViewport;
public class GameMenu implements Screen {
private BlockIt m_blockIt;
private Texture m_btexture = new Texture(Gdx.files.internal("mainmenu1.png"));
private Image m_background = new Image(m_btexture);
private Texture m_starttexture = new Texture(Gdx.files.internal("buttons/c_start.png"));
private Image m_startGame = new Image(m_starttexture);
private Texture m_optionstexture = new Texture(Gdx.files.internal("buttons/c_controls.png"));
private Image m_options = new Image(m_optionstexture);
private Texture m_highscoretexture = new Texture(Gdx.files.internal("buttons/c_highscores.png"));
private Image m_highscore = new Image(m_highscoretexture);
private Texture m_continueTexture = new Texture(Gdx.files.internal("buttons/c_resume_game.png"));
private Image m_continue = new Image(m_continueTexture);
private Texture m_playerIcon = new Texture(Gdx.files.internal("player/player_move_front.png"));
private Image m_player = new Image(m_playerIcon);
private int m_buttonPressed = -1;
private boolean m_gameInProgress = false;
private StretchViewport m_viewport;
private PerspectiveCamera m_camera;
private Stage m_stage = new Stage();
public GameMenu(BlockIt blockIt, boolean gameInProgress) {
m_blockIt = blockIt;
m_camera = new PerspectiveCamera();
m_viewport = new StretchViewport(Gdx.graphics.getWidth(), Gdx.graphics.getHeight(), m_camera);
m_viewport.update(Gdx.graphics.getWidth(), Gdx.graphics.getHeight(), true);
m_stage = new Stage();
}
#Override
public void show() {
if (!m_gameInProgress) {
m_startGame.setX(227);
m_startGame.setY(270);
m_startGame.addListener(new ClickListener() {
#Override
public void touchUp(InputEvent event, float x, float y, int pointer, int button) {
// m_blockIt.startNewGame();
}
#Override
public boolean touchDown(InputEvent event, float x, float y, int pointer, int button) {
// switch to a new texture
/*Texture newTexture = new Texture(Gdx.files.internal("buttons/c_new_game.png"));
m_startGame.setDrawable(new SpriteDrawable(new Sprite(newTexture)));
*/
m_player.setX(-64);
m_player.setY(300);
m_stage.addActor(m_player);
m_buttonPressed = 0;
return true;
}
});
} else {
m_continue.setX(227);
m_continue.setY(270);
m_continue.addListener(new ClickListener() {
#Override
public void touchUp(InputEvent event, float x, float y, int pointer, int button) {
}
});
}
m_stage.addActor(m_background); //adds the image as an actor to the stage
if (m_gameInProgress) {
m_stage.addActor(m_continue);
} else {
m_stage.addActor(m_startGame);
}
Gdx.input.setInputProcessor(m_stage);
}
#Override
public void render(float delta) {
m_camera.update();
Gdx.gl.glClearColor(0, 0, 0, 1); //sets clear color to black
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT); //clear the batch
m_stage.act(); //update all actors
m_stage.draw(); //draw all actors on the Stage.getBatch()
}
#Override
public void resize(int width, int height
) {
}
#Override
public void pause() {
}
#Override
public void resume() {
}
#Override
public void hide() {
}
#Override
public void dispose() {
}
}

You have to set the camera and viewport to the value u used to program the world:
eg. If your world is 800*480:
camera = new OrthographicCamera(800,480);
fitViewport = new FitViewport(800, 480, camera);

You have to update the viewport when the window is resized:
#Override
public void resize(int width, int height) {
m_viewport.update(width, height, true);
}

How fix in libgdx blinks screen in Desktop Mode?

when i run emulator and start application i see blinks screen, but on a PC in DesktopLauncher screen is normal.
I can not understand where I made mistakes.
render method override but it does not help.
class starter:
public class Drop extends Game {
Camera cam;
Game game;
SpriteBatch batch;
int tempGameScore = 0;
int dropsGatchered = 0;
Preferences preferences;//сохраняем игру
#Override
public void create() {
batch = new SpriteBatch();
this.setScreen(new MainMenuScreen(this));
}
#Override
public void render() {
super.render();
}
#Override
public void dispose() {
batch.dispose();
}
MainMenu:
I think I'm working wrong with the scene tool.
Can it is necessary as otherwise to draw a scene?
public class MainMenuScreen implements Screen {
Sprite texture;
final Drop game;
Skin skin;
Stage stage;
OrthographicCamera camera;
ImageButton newGameButton, exit, highScore;
Table table;
ImageButton.ImageButtonStyle btnplayStyle, btnscoreStyle, btnexitStyle;
private static TextureAtlas atlas, backAtlas;
public MainMenuScreen(final Drop gam) {
this.game = gam;
atlas = new TextureAtlas(Gdx.files.internal("texture/texture.pack"), true);
backAtlas = new TextureAtlas(Gdx.files.internal("texture/background.pack"), true);
texture = new Sprite(backAtlas.findRegion("background"));
skin = new Skin();
skin.addRegions(atlas);
table = new Table();
camera = new OrthographicCamera();
camera.setToOrtho(false, 800, 480);
stage = new Stage();
stage.addActor(table);
Gdx.input.setInputProcessor(stage);// Make the stage consume events
table();
}
private void table() {
btnplayStyle = new ImageButton.ImageButtonStyle();
btnplayStyle.up = skin.getDrawable("play");//кнопка не нажата
btnplayStyle.over = skin.getDrawable("play");
btnplayStyle.down = skin.getDrawable("play"); // кнопка нажата
newGameButton = new ImageButton(btnplayStyle);
newGameButton.setSize(300, 200);
stage.addActor(newGameButton);
newGameButton.addListener(new ClickListener() {
#Override
public void clicked(InputEvent event, float x, float y) {
game.setScreen(new GameScreen(game));
}
});
//Button score
btnscoreStyle = new ImageButton.ImageButtonStyle();
btnscoreStyle.up = skin.getDrawable("records");//кнопка не нажата
btnscoreStyle.over = skin.getDrawable("records");
btnscoreStyle.down = skin.getDrawable("records"); // кнопка нажата
highScore = new ImageButton(btnscoreStyle);
highScore.setSize(300, 200);
stage.addActor(highScore);
highScore.addListener(new ClickListener() {
#Override
public void clicked(InputEvent event, float x, float y) {
game.setScreen(new Score(game) {
});
}
});
//Button EXIT
btnexitStyle = new ImageButton.ImageButtonStyle();
btnexitStyle.up = skin.getDrawable("exit");//кнопка не нажата
btnexitStyle.over = skin.getDrawable("exit");
btnexitStyle.down = skin.getDrawable("exit"); // кнопка нажата
exit = new ImageButton(btnexitStyle);
exit.setSize(300, 200);
stage.addActor(exit);
exit.addListener(new ClickListener() {
#Override
public void clicked(InputEvent event, float x, float y) {
Gdx.app.exit();
}
});
table.setBounds(0, 0, Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
game.batch.begin();
game.batch.draw(texture, 0, 0, Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
table.add(newGameButton).width(400).height(120);
table.getCell(newGameButton).spaceBottom(30);
table.row();
table.add(highScore).width(400).height(120);
table.getCell(highScore).spaceBottom(30);
table.row();
table.add(exit).width(400).height(120);
table.getCell(exit).spaceBottom(30);
table.row();
game.batch.end();
}
#Override
public void render(float delta) {
stage.act();
stage.draw();
}
#Override
public void resize(int width, int height) {
}
#Override
public void show() {
}
#Override
public void pause() {
}
#Override
public void resume() {
}
#Override
public void hide() {
}
#Override
public void dispose() {
stage.dispose();
skin.dispose();
}
}
I think I'm working wrong with the scene tool

In MainMenuScreen you have to draw things in the render() method, not in the show() method. Like this:
#Override
public void render() {
stage.draw();
// ... possibly more drawing code
}

LibGDX application crash: "batch cannot be null"

i'm creating a 2D platform game with Android Studio and LibGDX.
Right now, I'm implementing an on-screen controller to move the character, but when I start the launcher, it closes automatically.
When I run the launcher, this is what the console shows:
Exception in thread "LWJGL Application" java.lang.IllegalArgumentException: batch cannot be null.
at com.badlogic.gdx.scenes.scene2d.Stage.<init>(Stage.java:108)
at com.globapps.supermarioclon.Tools.Controles.<init>(Controles.java:30)
at com.globapps.supermarioclon.Screens.PantallaJuego.<init>(PantallaJuego.java:57)
at com.globapps.supermarioclon.MarioBros.create(MarioBros.java:34)
at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:147)
at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:124)
This is the code from the controller class:
public class Controles {
Viewport viewport;
Stage stage;
boolean salto, izquierda, derecha;
OrthographicCamera cam;
public Controles() {
cam = new OrthographicCamera();
viewport = new FitViewport(800, 480, cam);
stage = new Stage(viewport, PantallaJuego.batch);
Gdx.input.setInputProcessor(stage);
Table table1 = new Table();
Table table2 = new Table();
table1.left().bottom();
table2.right().bottom();
Image flechaizquierda = new Image(new Texture("flechaIzquierda.png"));
flechaizquierda.setSize(50, 50);
flechaizquierda.addListener(new InputListener() {
#Override
public boolean touchDown(InputEvent event, float x, float y, int pointer, int button) {
izquierda = true;
return true;
}
#Override
public void touchUp(InputEvent event, float x, float y, int pointer, int button) {
izquierda = false;
}
});
final Image flechaderecha = new Image(new Texture("flechaDerecha.png"));
flechaderecha.setSize(50, 50);
flechaderecha.addListener(new InputListener() {
#Override
public boolean touchDown(InputEvent event, float x, float y, int pointer, int button) {
derecha = true;
return true;
}
#Override
public void touchUp(InputEvent event, float x, float y, int pointer, int button) {
derecha = false;
}
});
Image flechasalto = new Image(new Texture("flechaIzquierda.png"));
flechasalto.setSize(50, 50);
flechasalto.addListener(new InputListener() {
#Override
public boolean touchDown(InputEvent event, float x, float y, int pointer, int button) {
salto = true;
return true;
}
#Override
public void touchUp(InputEvent event, float x, float y, int pointer, int button) {
}
});
table1.add();
table1.add(flechaizquierda).size(flechaizquierda.getWidth(), flechaizquierda.getHeight());
table1.add();
table1.row().pad(0, 5, 0, 5);
table1.add();
table1.add(flechaderecha).size(flechaderecha.getWidth(), flechaderecha.getHeight());
table2.add();
table2.add(flechasalto).size(flechasalto.getWidth(), flechasalto.getHeight());
table2.row().padRight(5);
table2.add();
stage.addActor(table1);
stage.addActor(table2);
}
public void draw() {
stage.draw();
}
public boolean isDerecha() {
return derecha;
}
public boolean isIzquierda() {
return izquierda;
}
public boolean isSalto() {
return salto;
}
public void resize(int ancho, int alto) {
viewport.update(ancho, alto);
}
}
And this is the PlayScreen class:
public class PantallaJuego extends ApplicationAdapter implements Screen {
private MarioBros game;
public static SpriteBatch batch;
private TextureAtlas atlas;
private OrthographicCamera gamecam, cam;
private Viewport gamePort, viewport;
private HUD hud;
private TmxMapLoader maploader;
private TiledMap map;
private OrthogonalTiledMapRenderer renderer;
private World world;
private Box2DDebugRenderer b2dr;
Controles controles;
private Mario player;
private Music musica;
public PantallaJuego(MarioBros game) {
atlas = new TextureAtlas("MarioyEnemigos.pack");
this.game = game;
gamecam = new OrthographicCamera();
gamePort = new FitViewport(MarioBros.V_WIDTH / MarioBros.PPM, MarioBros.V_HEIGHT / MarioBros.PPM, gamecam);
hud = new HUD(game.batch);
controles = new Controles();
batch = new SpriteBatch();
maploader = new TmxMapLoader();
map = maploader.load("nivel1mario.tmx");
renderer = new OrthogonalTiledMapRenderer(map, 1/MarioBros.PPM);
gamecam.position.set(gamePort.getWorldWidth()/2, gamePort.getWorldHeight()/2, 0);
world = new World(new Vector2(0,-10), true);
b2dr = new Box2DDebugRenderer();
player = new Mario(world, this);
new B2WorldCreator(world, map);
world.setContactListener(new WorldContactListener());
musica = MarioBros.manager.get("Audio/Música/Super Mario World - Overworld Theme Music (FULL VERSION).mp3", Music.class);
musica.setLooping(true);
musica.play();
}
public TextureAtlas getAtlas() {
return atlas;
}
#Override
public void show() {
}
public void handleInput(float dt) {
if(controles.isDerecha())
player.b2body.applyLinearImpulse(new Vector2(0.1f, 0), player.b2body.getWorldCenter(), true);
if(controles.isSalto())
MarioBros.manager.get("Audio/Sonidos/Super Mario Bros- Mario Jump Sound Effect.mp3", Sound.class).play();
player.b2body.applyLinearImpulse(new Vector2(0, 4f), player.b2body.getWorldCenter(), true);
if(controles.isIzquierda())
player.b2body.applyLinearImpulse(new Vector2(-0.1f, 0), player.b2body.getWorldCenter(), true);
}
public void update(float dt) {
handleInput(dt);
world.step(1 / 60f, 6, 2);
gamecam.position.x = player.b2body.getPosition().x;
cam.position.set(viewport.getWorldWidth() / 2, viewport.getWorldHeight() / 2, 0);
player.update(dt);
hud.update(dt);
if(Gdx.app.getType() == Application.ApplicationType.Android)
controles.draw();
gamecam.update();
cam.update();
renderer.setView(gamecam);
}
#Override
public void render(float delta) {
update(delta);
Gdx.gl.glClearColor(0, 0, 0, 1);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
renderer.render();
b2dr.render(world, cam.combined);
b2dr.render(world, gamecam.combined);
game.batch.setProjectionMatrix(gamecam.combined);
game.batch.begin();
player.draw(game.batch);
game.batch.end();
game.batch.setProjectionMatrix(hud.stage.getCamera().combined);
hud.stage.draw();
}
If someone could help me, I'd be very grateful. Thank you.

I think you should instantiate your batch in PantallaJueago class before instantiating controles field.
public PantallaJuego(MarioBros game) {
atlas = new TextureAtlas("MarioyEnemigos.pack");
this.game = game;
gamecam = new OrthographicCamera();
gamePort = new FitViewport(MarioBros.V_WIDTH / MarioBros.PPM, MarioBros.V_HEIGHT / MarioBros.PPM, gamecam);
hud = new HUD(game.batch);
batch = new SpriteBatch();
controles = new Controles();
Because it is null while you instantiating your "controles". You are getting this error for your line
stage = new Stage(viewport, PantallaJuego.batch);
PantallaJuego.batch is null.

Well you should learn some more of the basics before you continue. This is related to a a NullPointerException and is usually very easy to fix. It tells you that you are trying to access a method or variable in nothing since you did not initialize it. Let's take your stack and find whats wrong.
Exception in thread "LWJGL Application" java.lang.IllegalArgumentException: batch cannot be null.
//Great! So let's fix this.
at com.badlogic.gdx.scenes.scene2d.Stage.<init>(Stage.java:108)
//This is a LibGDX class so there is probably nothing wrong with this
at com.globapps.supermarioclon.Tools.Controles.<init>(Controles.java:30)
//This is your class so let's go to this specific line, you can double click it.
stage = new Stage(viewport, PantallaJuego.batch);
//So either viewport or batch is null in this line.
//You can put a breakpoint here and run a debug,
//your program will stop on this line and you can hover
//to see what is in the variables. You will see that batch
// is null. Why, you may ask.
In the constructor of your main class you first set new Controles()
controles = new Controles();
Now the constructor of Controles will run and comes to this line:
stage = new Stage(viewport, PantallaJuego.batch);
And since your code did not reach batch = new SpriteBatch(); in PantallaJuego batch is still null and since stage does not accept that it will throw a NullPointer. A quick fix is to turn around new SpriteBatch() and new Controles().
The reason I say you should start learning the basics first is because your code is very poorly formed. You should format your code in a neat way and use much smaller methods since right now certain methods and constructors do all kind of stuff and it is very hard to read. Apart from this you are picking up very bad habits like making a global from that SpriteBatch (public static). There is really no need for this and it is partly responsible for your failure here.
Have a look at What is a NullPointerException, and how do I fix it? although your error is not a NullPointerException it is very related. Stage() does a check of it's own for it to be null and throws another exception before it tries to access it and get a nullpointer then.

Libgdx adding a UI button separated from the gamescreen

I've got a GameScreen where I have 100 "dots" randomly bounce around the screen. I'm currently adding a UI button in order to rotate the screen; one on the left and one on the right. The button works, however, the button is "linked" to the camera because as the screen rotates (the playing field for the dots spins because the camera rotates), the button rotates with it. I want the button(s) to be fixed to the device screen, and not rotate with the underlying field of dots.
Do I have to unproject the button somehow, or create a separate stage for any UI elements (buttons, statusbar title alone the top, etc)? Many thanks.
Here's my code:
public class GameScreen implements Screen {
final jGdxDots game;
final MyGestureListener myGestureListener;
OrthographicCamera camera;
private Skin skin;
final int NUMBER_OF_DOTS = 100;
int dotTotal;
private Stage stage;
FPSLogger fpsLogger;
float cameraRotate = 0f;
public GameScreen(final jGdxDots gam) {
this.game = gam;
fpsLogger = new FPSLogger();
camera = new OrthographicCamera();
camera.setToOrtho(false, 800, 480); //boolean = YDOWN or YUP axis.
//create stage
stage = new Stage(Gdx.graphics.getWidth(),Gdx.graphics.getHeight(),true);
//set stage to handle the inputs
//Gdx.input.setInputProcessor(stage);
stage.setCamera(camera);
//stage.setViewport(800, 480, true);
//multiplex the gesture listeners (both for stage and my listener)
myGestureListener = new MyGestureListener();
GestureDetector gd = new GestureDetector(myGestureListener);
InputMultiplexer im = new InputMultiplexer(gd, stage); // Order matters here!
Gdx.input.setInputProcessor(im);
//UI button
skin = new Skin(Gdx.files.internal("data/uiskin.json"));
final TextButton button = new TextButton("Rotate", skin, "default");
button.setWidth(100f); //200f
button.setHeight(100f); //20f
button.setPosition(10f, 10f);
button.addListener(new ClickListener(){
#Override
public boolean touchDown(InputEvent event, float x, float y,
int pointer, int button) {
// TODO Auto-generated method stub
cameraRotate = 1f;
return super.touchDown(event, x, y, pointer, button);
}
#Override
public void touchUp(InputEvent event, float x, float y,
int pointer, int button) {
// TODO Auto-generated method stub
super.touchUp(event, x, y, pointer, button);
cameraRotate = 0f;
}
});
stage.addActor(button);
spawnDots(stage);
}
private void spawnDots(Stage theStage) {
//Rectangle raindrop = new Rectangle();
for (int i=0; i < NUMBER_OF_DOTS; i++) {
DotActor dot = new DotActor();
dot.setOrigin(8,8); //(dot.getWidth()/2, dot.getHeight()/2);
dot.vector.set(MathUtils.random(1,4), MathUtils.random(1,4));
dot.actorX = MathUtils.random(0, 800 - dot.getWidth());
dot.actorY = MathUtils.random(0, 480 - dot.getHeight());
stage.addActor(dot);
}
dotTotal = NUMBER_OF_DOTS;
}
#Override
public void dispose() {
stage.dispose();
}
#Override
public void render(float delta) {
//clear screen
Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
//logger
fpsLogger.log();
//camera.zoom += 0.005f;
camera.rotate(cameraRotate); //(1.0f);
camera.update();
//run act() method of each actor
stage.act(Gdx.graphics.getDeltaTime());
//run each actor's draw() method who are members of this stage
stage.draw();
}
}

I had this problem too. Create a separate stage, or you might just want to draw directly with a sprite batch in a 'renderer' class
Mine looks something like this:
public OverlayRenderer()
{
this.spriteBatch = new SpriteBatch();
this.loadTextures();
}
public void render(String _message)
{
this.spriteBatch.begin();
this.spriteBatch.draw(TEXTURES.UI, 0, 0);
....
}
and directly after your
stage.draw();
line, I would add
overLayRenderer.render();

LibGDX Tablelayout Menu does not show

I'm writing a new program in LibGDX handling Backgroundtextures and have just begun to implement the screens. But when I test it, it just shows me a black cleared screen with the given resolution.
I call the screen with the setScreen(screen)- Method in an implemented Game class.
So here is the code:
public class MenuScreen implements Screen{
Table table;
Stage stage;
TextButton button;
TextField textField;
Texture texture;
Pic2Box2d game;
public MenuScreen(Pic2Box2d gameH)
{
this.game = gameH;
stage = new Stage(0, 0, true);
table = new Table();
}
public void create()
{
final TextFieldStyle fieldStyle = new TextFieldStyle(new BitmapFont(), Color.WHITE, new BitmapFont(), Color.GRAY, null, null, null);
textField = new TextField("path", fieldStyle);
final TextButtonStyle buttonStyle = new TextButtonStyle();
buttonStyle.font = new BitmapFont();
buttonStyle.fontColor = Color.WHITE;
buttonStyle.pressedOffsetY = 1f;
buttonStyle.downFontColor = new Color(0.8f, 0.8f, 0.8f, 1f);
button = new TextButton("Übernehmen", buttonStyle);
button.setClickListener(new ClickListener() {
#Override
public void click(Actor actor, float x, float y) {
if(textField.getText() != "" && textField.getText() != "path")
{
texture = new Texture(textField.getText());
game.setScreen(new Workscreen(texture));
}
}
});
table.row();
table.add(textField);
table.add(button);
stage.addActor(table);
}
#Override
public void render(float delta) {
Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
Gdx.gl.glClearColor(0, 0, 0, 1);
stage.act(Gdx.graphics.getDeltaTime());
stage.draw();
}
}

#idaNakav is correct about using show() and setting the Stage dimensions. However, that will still give you a black screen because your table doesn't have any size. Try changing your show() code to include table.setFillParent(true).
It should look something like this (code based on the example that you provided).
#Override
public void show() {
final TextFieldStyle fieldStyle = new TextFieldStyle(new BitmapFont(), Color.WHITE, null, null, null);
textField = new TextField("path", fieldStyle);
final TextButtonStyle buttonStyle = new TextButtonStyle();
buttonStyle.font = new BitmapFont();
buttonStyle.fontColor = Color.WHITE;
buttonStyle.pressedOffsetY = 1f;
buttonStyle.downFontColor = new Color(0.8f, 0.8f, 0.8f, 1f);
button = new TextButton("Übernehmen", buttonStyle);
button.addListener(new ClickListener() {
#Override
public void clicked(InputEvent event, float x, float y) {
if (textField.getText() != "" && textField.getText() != "path") {
texture = new Texture(textField.getText());
game.setScreen(new Workscreen(texture));
}
}
});
table.row();
table.add(textField);
table.add(button);
// Make the table fill the stage.
table.setFillParent(true);
stage.addActor(table);
}

When screen is becoming the current screen show method is called (not create like in your case), try changing your create method to show
also you are init the stage wrong , you should send it width and height , you sent 0,0
try something like
stage = new Stage(Gdx.graphics.getWidth(),Gdx.graphics.getHeight(),false);