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24. November 2014

 

In this video tutorial, we look at handling Keyboard, Mouse and Touch input in LibGDX.  We look at both handling input via polling as well as an event driven approach.

 

You can see the video in full 1080p definition here.  Once again, all the code included in the video is available below:

 

 

Polled Input Sample

package com.gamefromscratch;

import com.badlogic.gdx.ApplicationAdapter;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.Input;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.Sprite;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;

public class PolledInputDemo extends ApplicationAdapter {
   SpriteBatch batch;
   Texture img;
   Sprite sprite;
   
   @Override
   public void create () {
      batch = new SpriteBatch();
      img = new Texture("badlogic.jpg");
      sprite = new Sprite(img);
      sprite.setPosition(Gdx.graphics.getWidth()/2 - sprite.getWidth()/2,
            Gdx.graphics.getHeight()/2 - sprite.getHeight()/2);
   }

   @Override
   public void render () {

      // Keyboard events
      if(Gdx.input.isKeyPressed(Input.Keys.LEFT))
         sprite.translateX(-1f);
      if(Gdx.input.isKeyPressed(Input.Keys.RIGHT))
         sprite.translateX(1f);
      if(Gdx.input.isKeyPressed(Input.Keys.SPACE))
         sprite.setPosition(Gdx.graphics.getWidth()/2 - sprite.getWidth()/2,
               Gdx.graphics.getHeight()/2 - sprite.getHeight()/2);

      if(Gdx.input.isButtonPressed(Input.Buttons.RIGHT))
         sprite.setPosition(Gdx.input.getX(),Gdx.graphics.getHeight() - Gdx.input.getY());


      Gdx.gl.glClearColor(0, 0, 0, 1);
      Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
      batch.begin();
      batch.draw(sprite, sprite.getX(), sprite.getY());
      batch.end();
   }

   @Override
   public void dispose(){
      img.dispose();
   }
}

Event Driven Input Sample

package com.gamefromscratch;

import com.badlogic.gdx.ApplicationAdapter;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.Input;
import com.badlogic.gdx.InputProcessor;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.Sprite;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;

public class EventDrivenInputDemo extends ApplicationAdapter implements InputProcessor {
   SpriteBatch batch;
   Texture img;
   Sprite sprite;
   boolean movingRight = false;
   
   @Override
   public void create () {
      batch = new SpriteBatch();
      img = new Texture("badlogic.jpg");
      sprite = new Sprite(img);
      sprite.setPosition(Gdx.graphics.getWidth()/2-sprite.getWidth()/2,
            Gdx.graphics.getHeight()/2 - sprite.getHeight()/2);

      Gdx.input.setInputProcessor(this);
   }

   @Override
   public void render () {

      if(movingRight)
         sprite.translateX(1f);
      Gdx.gl.glClearColor(0, 0, 0, 1);
      Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
      batch.begin();
      batch.draw(sprite, sprite.getX(),sprite.getY());
      batch.end();
   }

   @Override
   public boolean keyDown(int keycode) {
      if(keycode == Input.Keys.RIGHT)
         movingRight = true;
      return true;
   }

   @Override
   public boolean keyUp(int keycode) {
      if(keycode == Input.Keys.LEFT)
         sprite.translateX(-1f);
      if(keycode == Input.Keys.RIGHT)
         movingRight = false;
      return true;
   }

   @Override
   public boolean keyTyped(char character) {
      return false;
   }

   @Override
   public boolean touchDown(int screenX, int screenY, int pointer, int button) {
      return false;
   }

   @Override
   public boolean touchUp(int screenX, int screenY, int pointer, int button) {
      return false;
   }

   @Override
   public boolean touchDragged(int screenX, int screenY, int pointer) {
      // If the user is holding down ( or was holding down, and hasnt released ) three fingers, move the sprite
      if(pointer ==2)
         sprite.setPosition(screenX,Gdx.graphics.getHeight()-screenY);
      return true;
   }

   @Override
   public boolean mouseMoved(int screenX, int screenY) {
      sprite.setPosition(screenX,Gdx.graphics.getHeight()-screenY);
      return true;
   }

   @Override
   public boolean scrolled(int amount) {
      if(amount > 0)
         sprite.translateY(1f);
      if(amount < 0)
         sprite.translateY(-1f);

      return true;
   }
}

Programming , , ,

21. November 2014

 

In the last video tutorial we used a graphic instead of text to create a Hello World.  This is because drawing text is actually a multi step process in LibGDX and not really appropriate for a first tutorial.  It is however perfect for a second tutorial, so here we are! ;)

 

In this video we explore the difference between TTF and Bitmap fonts, show how to run the Hiero font generation tool in both Eclipse and IntelliJ IDEA then create and save a bitmap font.  We then explore the code needed to show a bitmap font on screen, including how to measure the results, apply color and text justification.

 

The video is available in up to 1080P on YouTube by clicking here.

 

The source code:

Initial Example – Loading a font and drawing text:

package com.gamefromscratch;

import com.badlogic.gdx.ApplicationAdapter;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.Color;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.g2d.BitmapFont;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;

public class gdxtext extends ApplicationAdapter {
   SpriteBatch batch;
    BitmapFont font;

   @Override
   public void create () {
      batch = new SpriteBatch();
        font = new BitmapFont(Gdx.files.internal("Papy.fnt"));
   }

   @Override
   public void render () {
      Gdx.gl.glClearColor(0, 0, 0, 1);
      Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
      batch.begin();

        //Example One -- Drawing Text
        font.draw(batch,"Hello World",Gdx.graphics.getWidth()/2,Gdx.graphics.getHeight()/2);

        batch.end();
   }
}

 

Example 2 – Measuring and centering text:

BitmapFont.TextBounds bounds = font.getBounds("Hello World");
font.draw(batch,"Hello World",
       Gdx.graphics.getWidth()/2 - bounds.width/2,
       Gdx.graphics.getHeight()/2 + bounds.height/2);

Example 3 – Multi-line Text

String debugString = "I took one, one cause you left me\n"
           + "Two, two for my family\n"
           + "Three, three for my heartache\n"
           + "Four, four for my headaches\n"
           + "Five, five for my sorrow\n";
   BitmapFont.TextBounds bounds = font.getMultiLineBounds(debugString);

 

Example 4 -- Center justified text in the colour purple

    font.setColor(Color.PURPLE);
    font.drawMultiLine(batch,
            debugString,
            0,
            Gdx.graphics.getHeight()/2 + bounds.height/2,
            Gdx.graphics.getWidth(),
            BitmapFont.HAlignment.CENTER
            );

Programming , , ,

18. November 2014

 

In this video tutorial, we create our first LibGDX project.  This tutorial covers that basic layout of a LibGDX application, adding new assets to a project and looks at how the initial project is composed and how multiple platforms are supported.  We then go through the initial code, then look in depth at coordinate systems, then move on to creating a sprite.  Finally we look at positioning, scaling and rotating a sprite with a SpriteBatch.

 

This tutorial assumes you already have your development environment setup and know how to run a LibGDX application in your chosen IDE.  If you do no, please watch these videos first.

 

The following is the video tutorial.  It was recorded in 1080p and the complete version can be viewed here.

 

 

The following is the final code generated:

 

package com.gamefromscratch;

import com.badlogic.gdx.ApplicationAdapter;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.Sprite;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;

public class HelloWorld extends ApplicationAdapter {
   SpriteBatch batch;
   Texture img;
   Sprite sprite;
   
   @Override
   public void create () {
      batch = new SpriteBatch();
      img = new Texture("HelloWorld.png");
      sprite = new Sprite(img);
      sprite.setPosition(
            Gdx.graphics.getWidth()/2 - sprite.getWidth()/2,
            Gdx.graphics.getHeight()/2 - sprite.getHeight()/2);
      sprite.setScale(1.0f,2.0f);
   }

   @Override
   public void render () {
      Gdx.gl.glClearColor(0, 0, 0, 1);
      Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
      batch.begin();
      batch.draw(sprite, sprite.getX(),sprite.getY(),sprite.getWidth()/2,
            sprite.getHeight()/2,sprite.getWidth(),
            sprite.getHeight(),sprite.getScaleX(),
            sprite.getScaleY(),sprite.getRotation());
      batch.end();
   }
}

 

Here is the image that was used in this tutorial:

HelloWorld

Programming , , ,

12. November 2014

 

The title pretty much says it all.  The installation process to get a fully working Java, Android and GWT development environment up and running can be a bit tricky at times.  These three videos walk through the entire process, from downloading and installing a Java JDK, then the Android SDK and GWT then finally creating your first LibGDX project.  The second video then looks at working with IntelliJ IDEA with LIbGDX, the third video shows the same thing for Eclipse.  Each of these videos walks through loading a project, then running a Desktop, Android then HTML5 project.  Each of the videos is hosted on YouTube and is available in 1080p.  Click the link above the video below to open it directly in YouTube.

 

Part 1: Configuring a Java Development Environment for LibGDX and Android Development

 

 

Part 2: Using IntelliJ IDEA with LibGDX

 

 

Part 3: Using Eclipse with LibGDX

 

Programming , ,

25. September 2014

 

Remember in our earlier example where we used a ContactListener to check for a collision between two types of FixtureDef and how ungainly the check was?  Remember when I said there was a much better way of doing this?  Well, welcome the the better way, Filters.

 

Filters are actually rather simple, except they use bitmasking, a concept that might be somewhat new to you.  I actually went into some detail on the use of bitmasks in this tutorial if you need some details.  Basically its about using individual bits in a number as “on/off” flags.  Basically it allows you to track multiple values in a single variable.  In Box2D, there are a pair of bitmask, the categoryBits and maskBits.  Those names can be a bit confusing but don’t worry about that.

 

Basically you can think of categoryBits as saying “This is what I am” and maskBits as “This is what I collide with”.  Keep in mind, you can set multiple bits for either, so you can both be multiple things and collide with multiple things.  That may still sound somewhat confusing, so let’s look at an example.  This is a modification of the code from the previous tutorial.  In this case, we want our two sprites to NOT collide with each other, but to collide with the edge that represents the ground in the world.

package com.gamefromscratch;

import com.badlogic.gdx.ApplicationAdapter;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.OrthographicCamera;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.Sprite;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.math.MathUtils;
import com.badlogic.gdx.math.Matrix4;
import com.badlogic.gdx.math.Vector2;
import com.badlogic.gdx.physics.box2d.*;

public class Physics4 extends ApplicationAdapter {
    SpriteBatch batch;
    Sprite sprite,sprite2;
    Texture img;
    World world;
    Body body,body2;
    Body bodyEdgeScreen;

    Matrix4 debugMatrix;
    OrthographicCamera camera;

    final float PIXELS_TO_METERS = 100f;


    final short PHYSICS_ENTITY = 0x1;    // 0001
    final short WORLD_ENTITY = 0x1 << 1; // 0010 or 0x2 in hex

    @Override
    public void create() {
        batch = new SpriteBatch();
        img = new Texture("badlogic.jpg");

        // Create two identical sprites slightly offset from each other vertically
        sprite = new Sprite(img);
        sprite.setPosition(-sprite.getWidth()/2,-sprite.getHeight()/2 +200);
        sprite2 = new Sprite(img);
        sprite2.setPosition(-sprite.getWidth()/2 + 20,-sprite.getHeight()/2 + 400);

        world = new World(new Vector2(0, -1f),true);

        // Sprite1's Physics body
        BodyDef bodyDef = new BodyDef();
        bodyDef.type = BodyDef.BodyType.DynamicBody;
        bodyDef.position.set((sprite.getX() + sprite.getWidth()/2) /
                        PIXELS_TO_METERS,
                (sprite.getY() + sprite.getHeight()/2) / PIXELS_TO_METERS);

        body = world.createBody(bodyDef);


        // Sprite2's physics body
        BodyDef bodyDef2 = new BodyDef();
        bodyDef2.type = BodyDef.BodyType.DynamicBody;
        bodyDef2.position.set((sprite2.getX() + sprite2.getWidth()/2) /
                        PIXELS_TO_METERS,
                (sprite2.getY() + sprite2.getHeight()/2) / PIXELS_TO_METERS);

        body2 = world.createBody(bodyDef2);

        // Both bodies have identical shape
        PolygonShape shape = new PolygonShape();
        shape.setAsBox(sprite.getWidth()/2 / PIXELS_TO_METERS, sprite.getHeight()
                /2 / PIXELS_TO_METERS);

        // Sprite1
        FixtureDef fixtureDef = new FixtureDef();
        fixtureDef.shape = shape;
        fixtureDef.density = 0.1f;
        fixtureDef.restitution = 0.5f;
        fixtureDef.filter.categoryBits = PHYSICS_ENTITY;
        fixtureDef.filter.maskBits = WORLD_ENTITY;


        // Sprite2
        FixtureDef fixtureDef2 = new FixtureDef();
        fixtureDef2.shape = shape;
        fixtureDef2.density = 0.1f;
        fixtureDef2.restitution = 0.5f;
        fixtureDef2.filter.categoryBits = PHYSICS_ENTITY;
        fixtureDef2.filter.maskBits = WORLD_ENTITY;

        body.createFixture(fixtureDef);
        body2.createFixture(fixtureDef2);

        shape.dispose();

        // Now the physics body of the bottom edge of the screen
        BodyDef bodyDef3 = new BodyDef();
        bodyDef3.type = BodyDef.BodyType.StaticBody;

        float w = Gdx.graphics.getWidth()/PIXELS_TO_METERS;
        float h = Gdx.graphics.getHeight()/PIXELS_TO_METERS;

        bodyDef3.position.set(0,0);
        FixtureDef fixtureDef3 = new FixtureDef();
        fixtureDef3.filter.categoryBits = WORLD_ENTITY;
        fixtureDef3.filter.maskBits = PHYSICS_ENTITY;

        EdgeShape edgeShape = new EdgeShape();
        edgeShape.set(-w/2,-h/2,w/2,-h/2);
        fixtureDef3.shape = edgeShape;


        bodyEdgeScreen = world.createBody(bodyDef3);
        bodyEdgeScreen.createFixture(fixtureDef3);
        edgeShape.dispose();

        camera = new OrthographicCamera(Gdx.graphics.getWidth(),Gdx.graphics.
                getHeight());
    }

    @Override
    public void render() {
        camera.update();
        // Step the physics simulation forward at a rate of 60hz
        world.step(1f/60f, 6, 2);

        sprite.setPosition((body.getPosition().x * PIXELS_TO_METERS) - sprite.
                        getWidth()/2 ,
                (body.getPosition().y * PIXELS_TO_METERS) -sprite.getHeight()/2 );


        sprite.setRotation((float)Math.toDegrees(body2.getAngle()));
        sprite2.setPosition((body2.getPosition().x * PIXELS_TO_METERS) - sprite2.
                        getWidth()/2 ,
                (body2.getPosition().y * PIXELS_TO_METERS) -sprite2.getHeight()/2 );
        sprite2.setRotation((float)Math.toDegrees(body.getAngle()));

        Gdx.gl.glClearColor(1, 1, 1, 1);
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

        batch.setProjectionMatrix(camera.combined);
        batch.begin();

        batch.draw(sprite, sprite.getX(), sprite.getY(),sprite.getOriginX(),
                sprite.getOriginY(),
                sprite.getWidth(),sprite.getHeight(),sprite.getScaleX(),sprite.
                        getScaleY(),sprite.getRotation());
        batch.draw(sprite2, sprite2.getX(), sprite2.getY(),sprite2.getOriginX(),
                sprite2.getOriginY(),
                sprite2.getWidth(),sprite2.getHeight(),sprite2.getScaleX(),sprite2.
                        getScaleY(),sprite2.getRotation());
        batch.end();
    }

    @Override
    public void dispose() {
        img.dispose();
        world.dispose();
    }
}

 

When a collision occurs, the collider will check it’s categoryBits against the collided’s maskBits.  If both are true, a collision occurs.  So in this example, both sprites will fall, completely ignoring each other.  However when they run in to the WORLD_ENTITY, a collision will occur.

 

Now, taking the same scenario, if you wanted to have the sprites collide with each other AND WORLD_ENTITY objects, you would simply change to

fixtureDef.filter.maskBits = WORLD_ENTITY|PHYSICS_ENTITY;

 

Now this object will have collisions with either kind of entity.

There is one other kind of filter in Box2D, and it's confusing as hell in my opinion. It's basically an override for grouping entities together called groupIndex.  I will let someone else explain how it works:

 

When checking two fixtures to see if they should collide:

  • if either fixture has a groupIndex of zero, use the category/mask rules as above
  • if both groupIndex values are non-zero but different, use the category/mask rules as above
  • if both groupIndex values are the same and positive, collide
  • if both groupIndex values are the same and negative, don't collide

 

The default value for the groupIndex is zero

 

So, if you want to have fine tune control over which entities interact with each other, Filter is how you do it.  Ok, let’s keep this part short and sweet.

Programming , ,

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