HELP! pset3 breakout ball not bouncing

Question

I have been having serious issues with this particular project. Somehow I followed all the instructions in the bounce video and I have written all my codes but my ball is not bouncing off ANYTHING T____T... can someone please help tell me what I'm doing wrong?

while (lives > 0 && bricks > 0)
{
    // TODO


   while (true)
   {
    GEvent event = getNextEvent(MOUSE_EVENT);

    if (event != NULL)
    {
        if (getEventType(event) == MOUSE_MOVED)
        {
            double x = getX(event) - getWidth(paddle);
            double y = getY(event) - getWidth(paddle);
            setLocation(paddle,x,530);

        }
    }

    double x_velocity = 2.0;
    double y_velocity = 1.5;


        move(ball, x_velocity,y_velocity);
        pause(10);

        if (getX(ball) + getWidth(ball) >= getWidth(window))
        {
        x_velocity = -x_velocity;
        }

        else if (getX(ball) <=0)
        {
        x_velocity = -x_velocity;
        }

        else if (getY(ball) <=0)
        {
        y_velocity = -y_velocity;
        }

        GObject object = detectCollision(window,ball);

        if(object != NULL)
        {

        if (object == paddle)
        {
        y_velocity= -y_velocity;
        }

        if (strcmp(getType(object),"GRect") ==0)
        {
        y_velocity= -y_velocity;
        bricks--;
        }
        }

}
}

// wait for click before exiting
waitForClick();

// game over
closeGWindow(window);
return 0;
}

/**
 * Initializes window with a grid of bricks.
 */
void initBricks(GWindow window)
{
// TODO

int setRectx = 5;
int setRecty = 37;

for ( int i = 0; i < ROWS; i++)
{

for ( int n = 0; n < COLS; n++)
{
GRect bricks = newGRect(setRectx,setRecty,36,10);
setColor(bricks,"BLUE");
setFilled(bricks,true);
setRectx = setRectx + 38;
add (window, bricks);
}
setRectx = 5;
setRecty = setRecty + 20;


}

}

/**
* Instantiates ball in center of window.  Returns ball.
*/
GOval initBall(GWindow window)
{
// TODO

GOval ball = newGOval(200,300,20,20);

add (window, ball);


return ball;

}

/**
 * Instantiates paddle in bottom-middle of window.
 */
GRect initPaddle(GWindow window) 
{
// TODO 
GRect paddle = newGRect(200,530,36,10);
setColor(paddle,"BLACK");
setFilled(paddle,true);

add(window, paddle);

return paddle;
}

/**
* Instantiates, configures, and returns label for scoreboard.
*/
GLabel initScoreboard(GWindow window)
{
// TODO
return NULL;
}

/**
* Updates scoreboard's label, keeping it centered in window.
*/
void updateScoreboard(GWindow window, GLabel label, int points)
{
// update label
char s[12];
sprintf(s, "%i", points);
setLabel(label, s);

// center label in window
double x = (getWidth(window) - getWidth(label)) / 2;
double y = (getHeight(window) - getHeight(label)) / 2;
setLocation(label, x, y);
}

/**
* Detects whether ball has collided with some object in window
* by checking the four corners of its bounding box (which are
* outside the ball's GOval, and so the ball can't collide with
* itself).  Returns object if so, else NULL.
*/
GObject detectCollision(GWindow window, GOval ball)
{
// ball's location
double x = getX(ball);
double y = getY(ball);

// for checking for collisions
GObject object;

// check for collision at ball's top-left corner
object = getGObjectAt(window, x, y);
if (object != NULL)
{
    return object;
}

// check for collision at ball's top-right corner
object = getGObjectAt(window, x + 2 * RADIUS, y);
if (object != NULL)
{
    return object;
}

// check for collision at ball's bottom-left corner
object = getGObjectAt(window, x, y + 2 * RADIUS);
if (object != NULL)
{
    return object;
}

// check for collision at ball's bottom-right corner
object = getGObjectAt(window, x + 2 * RADIUS, y + 2 * RADIUS);
if (object != NULL)
{
    return object;
}

// no collision
return NULL;

Answer 1

The problem is simple.

double x_velocity = 2.0;
double y_velocity = 1.5;
move(ball, x_velocity,y_velocity);

You initialize your velocities immediately before the move() call. It doesn't matter what you do to detect a collision in later code, when the while loop comes back around, you redeclare and reinitialize the velocities, so the ball will always move in the same direction and at the same speed.

Now if you had declared the velocities before starting the while loop instead, things might be a little different. ;-)

If this answers your question, please click on the check mark to accept. Let's keep up on forum maintenance. ;-)