Question

I’m trying to make a camera for an android app that moves by dragging on the touch screen to drag the camera across. I’m using the Cocos2D engine for my development.

The problem is, whenever you moved your finger on the screen, everything on the screen just disappears instead of moving.

My code is below, I hope someone can help me with this 🙂 Thanks for your time.

@Override
public boolean ccTouchesMoved(MotionEvent event)
        {
            CGPoint location = CCDirector.sharedDirector().convertToGL(CGPoint.ccp(event.getX(), event.getY()));
            CGPoint movement = CGPoint.ccpSub(location, previousLocation);
            previousLocation = location;
            //Update the camera
            float[] x = new float[1];
            float[] y = new float[1];
            float[] z = new float[1];
            this.getCamera().getCenter(x, y, z);
            CameraPos.x = x[0];
            CameraPos.y = y[0];
            this.getCamera().getEye(x, y, z);
            movement.x = 2 * movement.x * (1 + (z[0]/832));
            movement.y = 2 * movement.y * (1 + (z[0]/832));
            CameraPos.x = CameraPos.x - Math.round(movement.x);
            CameraPos.y = CameraPos.y - Math.round(movement.y);
            this.getCamera().setCenter(CameraPos.x, CameraPos.y, 0);
            this.getCamera().setEye(CameraPos.x, CameraPos.y, z[0]);
            return true;
        }

Answer 1

Its fine I got it working nevertheless.

For any who want to know this, I created a class called CameraControls that controls the basic functions of the camera. It isnt finished yet (I’ll probably update the code as I make changes such as zoom functionality) but this one allows me to track the touch input perfectly.

import org.cocos2d.nodes.CCDirector;
import org.cocos2d.types.CGPoint;
import org.cocos2d.types.CGSize;

public class CameraControls {

CGSize winSize = CCDirector.sharedDirector().displaySize();
CGPoint CameraPos = CGPoint.ccp(winSize.width, winSize.height);
CGPoint previousLocation;
double minX;
double maxX;
double minY;
double maxY;

public CameraControls(World world)
{
    this.loadCamera(world);
}

public void setCameraLimit(float minX, float maxX, float minY, float maxY)
{
    this.minX = minX;
    this.maxX = maxX;
    this.minY = minY;
    this.maxY = maxY;
}

public void loadCamera(World world)
{
    float[] x = new float[1];
    float[] y = new float[1];
    float[] z = new float[1];
    world.getCamera().getCenter(x, y, z);
    CameraPos.x = x[0];
    CameraPos.y = y[0]; 
}

public void trackTouchMovement(CGPoint location, World world)
{
    if(previousLocation == null)
    {
        previousLocation = location;
    }
    CGPoint movement = CGPoint.ccpSub(previousLocation, location);
    previousLocation = location;
    float[] x1 = new float[1];
    float[] y1 = new float[1];
    float[] z1 = new float[1];
    world.getCamera().getEye(x1, y1, z1);
    CameraPos.x = CameraPos.x + movement.x;
    CameraPos.y = CameraPos.y + movement.y;

    try
    {
        if(CameraPos.x >= maxX || CameraPos.x <= minX || CameraPos.y >=  maxY || CameraPos.y <= minY)
        {
            CameraPos = CGPoint.ccpSub(CameraPos, movement);
        }
    }
    catch (NullPointerException e)
    {
        System.out.println("Invalid values for camera Limits. No Limits applied.");
    }

    world.getCamera().setCenter(CameraPos.x, CameraPos.y, 0);
    world.getCamera().setEye(CameraPos.x, CameraPos.y, z1[0]);
}

public void storePositionAsPrevious(CGPoint pos)
{
    previousLocation = pos;
}

public void resetPrevious()
{
    previousLocation = null;
}
}

Now that I have a class, I simply create an instance of CameraControls in my class and then do the necessary configuration.

CameraControls camera = new CameraControls(this);

In this case, I want the total area my camera can view to be 3 x the width of the camera, and 3 times the height of the camera, so I set the limits of the camera as the negative width of the camera, the width of the camera, the negative height of the camera and the height of the camera, as the camera starts at (0, 0).

    camera.setCameraLimit(-winSize.width, winSize.width, -winSize.height, winSize.height);

Finally, I just add the necessary method calling in ccTouchesBegan, ccTouchesMoved and ccTouchesEnded

@Override
public boolean ccTouchesMoved(MotionEvent event)
        {
            CGPoint location = CCDirector.sharedDirector().convertToGL(CGPoint.ccp(event.getX(), event.getY()));
            camera.trackTouchMovement(location, this);
            return true;
        }
@Override
public boolean ccTouchesEnded(MotionEvent event)
{
            camera.resetPrevious();
            return true;
}
@Override
public boolean ccTouchesBegan(MotionEvent event)
{
            CGPoint location = CCDirector.sharedDirector().convertToGL(CGPoint.ccp(event.getX(), event.getY()));
            camera.storePositionAsPrevious(location);
            return true;
}