Chapter 5 带颜色的同心圆

一、重写 DrwaRect

-(void)drawRect:(CGRect)rect
{
    CGRect bounds = self.bounds;

    CGPoint center;
    center.x = bounds.origin.x + bounds.size.width / 2.0;
    center.y = bounds.origin.y + bounds.size.height / 2.0;

    float maxRadius = MAX(bounds.size.width, bounds.size.height);
    　　// 画圆
    UIBezierPath *path = [[UIBezierPath alloc] init];
    for(float currentRadius = maxRadius; currentRadius > 0; currentRadius -= 20)
    {
        [path moveToPoint:CGPointMake(center.x + currentRadius, center.y)];
        [path addArcWithCenter:center
                        radius:currentRadius
                    startAngle:0.0
                      endAngle:M_PI * 2.0
                     clockwise:YES];
    }
    path.lineWidth = 10;

    // Configure the drawing color of light gray
    [self.circleColor setStroke];
    [path stroke];

    /*
    CGContextRef currentContext = UIGraphicsGetCurrentContext();
    CGContextSaveGState(currentContext);
    [path addClip];

    // Gradient triangle
    CGFloat location[2] = {0.0, 1.0};
    CGFloat components[8] = {1.0, 0.0, 0.0, 1.0, 1.0, 1.0, 0.0, 1.0};
    CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
    CGGradientRef gradient = CGGradientCreateWithColorComponents(colorspace, components, location, 2);
    CGPoint startPoint = CGPointMake(rect.size.width / 2.0, rect.size.height / 4.0);
    CGPoint endPoint = CGPointMake(rect.size.width / 2.0 , rect.size.height * 0.75);
    CGContextDrawLinearGradient(currentContext, gradient, startPoint, endPoint, 0);
    CGColorSpaceRelease(colorspace);
    CGGradientRelease(gradient);

    // Add shadow of image
    CGContextSetShadow(currentContext, CGSizeMake(4.0, 7.0), 3);
    // Draw stuff here, it will appear with a shadow

    // Add logo image
    UIImage *logoImage = [UIImage imageNamed:@"logo.png"];
    CGRect logoRect = CGRectMake(rect.size.width / 4.0, rect.size.height / 4.0, rect.size.width/2.0, rect.size.height / 2.0);
    [logoImage drawInRect:logoRect];

    CGContextRestoreGState(currentContext);
    // Draw stuff here, it will apear with no shadow;

    CGContextRelease(currentContext);
     */
}

二、重写 touchesBegin:withEvent

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
//    NSLog(@"%@ was touched", self);

    // Get 3 random numbers between 0 and 1
    float red = (arc4random() % 100) / 100.0;
    float blue = (arc4random() % 100) / 100.0;
    float green = (arc4random() % 100) / 100.0;

    UIColor *randomColor = [UIColor colorWithRed:red green:green blue:blue alpha:1.0];
    self.circleColor = randomColor;
}

三、重绘 View

[self setNeedsDisplay];