Ch6: Change the color of the blocks instead of destroying them

bostonCode · July 18th, 2012, 12:25 PM

Hi there,
I'm somewhat new to objective-c/core graphics, but I'm curious if after initializing and calling the drawRect routine, would it be possible to change the color of the blocks dynamically without destroying them? I believe my issue(s) are mainly to do with the context, but I'm unsure if the inputColor member can be changed past initialization. My function updateColor() is below and would be called when collision is detected on a block. Everything else is verbatim of the CH6 project. Any help or advice considering would be highly appreciated.
Thanks,
J

Code:

- (id)initWithFrame:(CGRect)frame color:(int) inputColor;
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
        self.color = inputColor;
    }
    return self;
}

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
    // Drawing code
    float viewWidth, viewHeight;
    viewWidth = self.bounds.size.width;
    viewHeight = self.bounds.size.height;
    
    //Get the drawing context
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    //define a rect in the shape of a block
    CGRect blockRect = CGRectMake(0, 0, viewWidth, viewHeight);
    
    //define a path using the rect
    UIBezierPath* path = [UIBezierPath bezierPathWithRect:blockRect];
    
    //set the line width of the path
    path.lineWidth = 0.0;
    
    //define a gradient to use to fill the blocks
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGFloat locations[2] = { 0.0, 1.0 };
    
    CGFloat components[8] = { 0.0, 0.0, 0.0, 1.0, //start color
        1.0, 1.0, 1.0, 1.0 }; //end color
    
    //determine gradient color based on color property
    switch (self.color) {
        case RED_COLOR:
            //red block
            components[0] = 1.0;
            break;
        case GREEN_COLOR:
            //red block
            components[1] = 1.0;
            break;
        case BLUE_COLOR:
            //red block
            components[2] = 1.0;
            break;
        default:
            break;
    }

    CGGradientRef myGradient = CGGradientCreateWithColorComponents(colorSpace, components, locations, sizeof(locations)/sizeof(CGFloat));
    
    CGContextDrawLinearGradient(context, myGradient, CGPointMake(0, 0), CGPointMake(viewWidth, 0), 0);

    //clean up the color space and gradient
    CGColorSpaceRelease(colorSpace);
    CGGradientRelease(myGradient);
    
    //stroke the path
    [path stroke];
}

-(void)updateColor:(int) inputColor
{
    self.color = inputColor;
    //Get the drawing context
    CGContextRef context = UIGraphicsGetCurrentContext();
    //define a gradient to use to fill the blocks
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGFloat components[8] = { 0.0, 0.0, 0.0, 1.0, //start color
        1.0, 1.0, 1.0, 1.0 }; //end color
    CGFloat locations[2] = { 0.0, 1.0 };
    CGGradientRef myGradient = CGGradientCreateWithColorComponents(colorSpace, components, locations, sizeof(locations)/sizeof(CGFloat));
    
    CGContextDrawLinearGradient(context, myGradient, CGPointMake(0, 0), CGPointMake(self.bounds.size.width, 0), 0);

}