AndEngine Tutorial 06 – Platform – 01

Posted by Vexillum on November 11, 2012

In the 6th AndEngine tutorial we will learn how to create platforms and check when our player collides with them.

Let’s get started

Just like when we created “Player.java” (AndEngine Tutorial 03 – Player Movement 01), we now have to create a new class for the platforms called “Platform.java”, into com.PerleDevelopment.AndEngine.tutorial.objects, and extend the class by “GameObject”.
Now Eclipse wants us to define a constructor, the quick fix Eclipse suggests is not the constructor we want. We want:

public Platform(int pX, int pY, TextureRegion pTextureRegion, VertexBufferObjectManager pVertexBufferObjectManager) {
	super(pX, pY, pTextureRegion, pVertexBufferObjectManager);
}

Some Information about the code:

Platform( pX, pY, pTextureRegion, pVertexBufferObjectManager)

• pX & pY
  • determines the position of the Platform
• pTextureRegion
  • we are going to load a “TextureRegion”
• pVertexBufferObjectManager
  • this is some OpenGL stuff http://www.opengl.org/wiki/Vertex_Buffer_Object
  •  just input “getVertexBufferObjectManager()”

After we added the constructor Ecplise also wants us to implement the “move()” method.
Just add this method using “quick fix”.

Your “Platform.java” should look something like this:

Platform.java

package com.PerleDevelopment.AndEngine.tutorial.objects;

import org.andengine.opengl.texture.region.TextureRegion;
import org.andengine.opengl.vbo.VertexBufferObjectManager;

public class Platform extends GameObject {

	// ===========================================================
	// Constants
	// ===========================================================

	// ===========================================================
	// Fields
	// ===========================================================

	// ===========================================================
	// Constructors
	// ===========================================================

	public Platform(int pX, int pY, TextureRegion pTextureRegion, VertexBufferObjectManager pVertexBufferObjectManager) {
		super(pX, pY, pTextureRegion, pVertexBufferObjectManager);
	}

	// ===========================================================
	// Getter & Setter
	// ===========================================================

	// ===========================================================
	// Methods for/from SuperClass/Interfaces
	// ===========================================================

	@Override
	public void move() {
		// TODO Auto-generated method stub

	}

	// ===========================================================
	// Methods
	// ===========================================================

}

Now that we created the platform class we have to go back to “Player.java” to check whether the player is colliding with the platform.
In “Player.java” we create an “ArrayList” which later should contain all the platforms.

private ArrayList mPlatforms;

I order to access the private variable “mPlatforms”, we can Eclipse generate Getters and Setters or just copy this code:

public ArrayList getmPlatforms() {
	return mPlatforms;
}

public void setmPlatforms(ArrayList mPlatforms) {
	this.mPlatforms = mPlatforms;
}

To check whether the player is colliding or not we can use the “collidesWith(IShape pOtherShape)” method.
Just add the code, which checks if the player collides with a platform, below into the move method.

for (Platform Platform : getmPlatforms()) {
	if (this.collidesWith(Platform)) {
		Log.v("objects.Player", "just collided with platform ;)");
	}
}

Your “Player.java” should look something like this:

Player.java

package com.PerleDevelopment.AndEngine.tutorial.objects;

import java.util.ArrayList;

import org.andengine.opengl.texture.region.TextureRegion;
import org.andengine.opengl.vbo.VertexBufferObjectManager;

import android.util.Log;

import com.PerleDevelopment.AndEngine.tutorial.AndEngineTutorialActivity;
import com.PerleDevelopment.AndEngine.tutorial.helper.AccelerometerHelper;

public class Player extends GameObject {

	// ===========================================================
	// Constants
	// ===========================================================

	final int DEFAULT_VELOCITY = 200;

	// ===========================================================
	// Fields
	// ===========================================================

	boolean jumping = false;
	private ArrayList mPlatforms;

	// ===========================================================
	// Constructors
	// ===========================================================

	public Player(final float pX, final float pY, final TextureRegion pTextureRegion, final VertexBufferObjectManager pVertexBufferObjectManager) {
		super(pX, pY, pTextureRegion, pVertexBufferObjectManager);
	}

	// ===========================================================
	// Getter & Setter
	// ===========================================================

	public ArrayList getmPlatforms() {
		return mPlatforms;
	}

	public void setmPlatforms(ArrayList mPlatforms) {
		this.mPlatforms = mPlatforms;
	}

	// ===========================================================
	// Methods for/from SuperClass/Interfaces
	// ===========================================================

	@Override
	public void move() {

		this.mPhysicsHandler.setVelocityX(-AccelerometerHelper.TILT * DEFAULT_VELOCITY);
		setRotation(-AccelerometerHelper.TILT * 7);
		OutOfScreenX();

		Jumping();

		for (Platform Platform : getmPlatforms()) {
			if (this.collidesWith(Platform)) {
				Log.v("objects.Player", "just collided with platform ;)");
			}
		}

	}

	// ===========================================================
	// Methods
	// ===========================================================

	private void Jumping() {
		if (jumping) {
			Jump();
		} else {
			Fall();
		}
	}

	private void Jump() {
		if (mY <= AndEngineTutorialActivity.CAMERA_HEIGHT / 2) { // mY <= 400
			jumping = false;
		} else {
			this.mPhysicsHandler.setVelocityY(-DEFAULT_VELOCITY);
		}
	}

	private void Fall() {
		if (mY >= AndEngineTutorialActivity.CAMERA_HEIGHT) { // mY >= 800
			jumping = true;
		} else {
			this.mPhysicsHandler.setVelocityY(DEFAULT_VELOCITY);
		}
	}

	private void OutOfScreenX() {
		if (mX > AndEngineTutorialActivity.CAMERA_WIDTH) { // OutOfScreenX (right)
			mX = 0;
		} else if (mX < 0) { // OutOfScreenX (left)
			mX = AndEngineTutorialActivity.CAMERA_WIDTH;
		}
	}
}

The last thing we have to do is loading the texture, creating the platforms and adding them into the game.
For this we have to go back into “AndEngineTutorialActivity.java”, and create a new ArrayList

private ArrayList mPlatforms = new ArrayList();

Next thing to do it loading the texture (https://raw.github.com/Perle-Development/AndEngine-Tutorial/master/assets/platform.png), just like we did in “AndEngine Tutorial 02 – Textures and Sprites” (since your texture is 64p*32p, we have to make your TextureAtlas 64p*64p).

/* Texture for platform */
this.mPlatformBitmapTextureAtlas = new BitmapTextureAtlas(this.getTextureManager(), 64, 64);
this.mPlatformTextureRegion = BitmapTextureAtlasTextureRegionFactory.createFromAsset(this.mPlatformBitmapTextureAtlas, this, "platform.png", 0, 0);
this.mPlatformBitmapTextureAtlas.load();

Don’t forget to create the BitmapTextureAtlas and the TextureRegion.
In order to add the platforms into the game copy this code into the onCreateScene.method.

mPlatforms.add(new Platform(100, 500, this.mPlatformTextureRegion, this.getVertexBufferObjectManager()));
mPlatforms.add(new Platform(200, 600, this.mPlatformTextureRegion, this.getVertexBufferObjectManager()));
mPlatforms.add(new Platform(300, 700, this.mPlatformTextureRegion, this.getVertexBufferObjectManager()));
oPlayer.setmPlatforms(mPlatforms); // Adds platforms, so we can work with them (Player.java)

for (Platform Platform : mPlatforms) {
	this.mMainScene.attachChild(Platform);
}

Platforms.add(new Platform(pX, pY, pTextureRegion, pVertexBufferObjectManager));

• pX & pY
  • determines the position of the platform
• pTextureRegion
  • This tells AndEngien which texture to load
• pVertexBufferObjectManager
  • this is some OpenGL stuff http://www.opengl.org/wiki/Vertex_Buffer_Object
  • just input “getVertexBufferObjectManager()”

oPlayer.setmPlatforms(mPlatforms);

• Send the new created Platforms to “Player.java”, so we can check whether the player collides with them or not.

for (Platform Platform : mPlatforms) {this.mMainScene.attachChild(Platform);}

• A simple “For-Each Loop” which adds every platform to the scene.