Game Development Reference
In-Depth Information
In Figure
5-10
, on the left we see the game area and on the right is the
CGRect
that describes the
actorView
's
frame
. The circle on the left is an
Actor02
that needs to be converted into
CGRect
on
actorView
. We start by figuring out the origin of the
GCFrame
by first finding the upper-left point of the
Actor02
. We find the X value of the upper-left point by subtracting the
radius
of the
Actor02
from
the
Actor02
's
center
X value. To find the Y value, we subtract the
radius
from the
Actor02
's
center
Y value. To convert these points into the coordinate space of
actorView
, we simply multiple by the
X value of the upper left point by
xFactor
and multiple the Y value by
yFactor
. The values
xFactor
and
yFactor
are the ratios between the
gameAreaSizes
width and height and the
actorView
's
frame
's
width and height. To find the size of
actorView
's frame, we simply multiply the radius by
xFactor
and
yFactor
to find the width and height.
When the user touches the
UIView actorView
, we have to do this process in reverse: convert
the point on the
actorView
to a point with our game space. This conversion happens in the task
tapGesture:
, as shown in Listing 5-18.
Listing 5-18. Example02Controller.h (tapGuesture:)
- (void)tapGesture:(UIGestureRecognizer *)gestureRecognizer{
UITapGestureRecognizer* tapRecognizer = (UITapGestureRecognizer*)gestureRecognizer;
CGPoint pointOnView = [tapRecognizer locationInView:actorView];
float xFactor = actorView.frame.size.width/self.gameAreaSize.width;
float yFactor = actorView.frame.size.height/self.gameAreaSize.height;
CGPoint pointInGame = CGPointMake(pointOnView.x/xFactor, pointOnView.y/yFactor);
[viper setMoveToPoint:pointInGame];
}
In Listing 5-18, we find where the user touched by calling
locationInView:
on
tapRecognizer
and passing in
actorView
and storing the result in
pointOnView
. After recalculating
xFactor
and
yFactor
values, we simply divide
pointOnView
's X and Y values by
xFactor
and
yFactor
, giving us
pointInGame
. Using this value we simply, set the
moveToPoint
property of viper with
pointInGame
.
To wrap up this example, let's take a look at the code that changes the size of
actorView
, as shown
in Listing 5-19.
Listing 5-19. Example02Controller.m (sliderValueChanged:)
- (IBAction)sliderValueChanged:(id)sender {
UISlider* slider = (UISlider*)sender;
float newWidth = [slider value];
float newHeight = gameAreaSize.height/gameAreaSize.width*newWidth;
CGRect parentFrame = [[actorView superview] frame];
float newX = (parentFrame.size.width-newWidth)/2.0;
float newY = (parentFrame.size.height-newHeight)/2.0;
CGRect newFrame = CGRectMake(newX, newY, newWidth, newHeight);
[actorView setFrame:newFrame];
}
