permanent images in android studio

Hi everybody! I have started using android studio. When i try to run sketches there, if i put a rect in draw() for example it remains forever in that position even if i change it's coordinates. Do you have any idea what i am missing? I have followed steps described in tutorial "Developing with Android Studio". Here is a code example:

public class Sketch2 extends PApplet {

 ball MainBall;//= new ball();

public void settings() {
    size(600, 600,P2D);
    //fullScreen();

}

public void setup() {
    background(150,50,50);
   // MainBall= new ball();
    //MainBall.display();

w10 = width/10; System.out.println("K: "+k); }

int k,w10,rh=10;
public void draw() {

    if(MainBall!=null){
        MainBall.display();
        MainBall.fingerForce();
    }

    fill(30,60,k);
    rect(random(0,width),rh,80,30);

//HERE THERE WLL APPEAR ONE RECT FOR EACH LOOP //sphere(30);

/*    if(mousePressed){ rh+=40;
        rect(random(0,width),random(0,height),random(0,40),random(0,40));
        System.out.println("MPPPPPPPP");
    }*/

    if((k+=10) < 255)
    k+=10;
    else k=0;
}

@Override
public void mouseClicked() {
    super.mouseClicked();
    System.out.println("mouseClicked");
    println("println");
}

class ball {
    private int R;
    PVector coord;
    PVector fingerVector;

    ball(){
        R=30;
        this.coord= new PVector (130, 50);
        fingerVector =new PVector(2,2);

    }
    ball(int R){
        this.R = R;
        this.coord= new PVector (width/2, height/4);
        fingerVector =new PVector(0,0);
    }
    void fingerForce(){
        if(mousePressed){
            fingerVector.add(mouseX-pmouseX,mouseY-pmouseY,0);
            coord.x +=2;
            coord.y+=1;
        }
       // coord.add(fingerVector);
    }

    void display(){
        //pushMatrix();
       // translate(this.coord.x,this.coord.y);
        sphere(this.R);
        //rect(100,20,80,80);

       // popMatrix();

        rect(this.coord.x+20,this.coord.y+20,10,10);
    }



}

}

Additional info: same thing happens when using P3D or using none of them. here something from gradle if matters anything
minSdkVersion 15 targetSdkVersion 23 maxSdkVersion 25