Question

我在drawRect方法中有一个for循环，它绘制了一些圆圈来填充屏幕。我试图这样做，所以每个圈子都有一个新的随机笔画。出于某种原因，没有任何东西出现。这是我的randomColor方法：

    -(UIColor *) randomColor
{
    int red, green, blue, alpha;

    red = arc4random_uniform(255);
    green = arc4random_uniform(255);
    blue = arc4random_uniform(255);
    alpha = arc4random_uniform(255);

    UIColor *colorToReturn = [[UIColor alloc] initWithRed:red green:green blue:blue alpha:alpha];

    return colorToReturn;
}

我试着在这里实现它：

-(void) drawRect:(CGRect)rect
{
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    CGRect bounds = [self bounds];

    // Firgure out the center of the bounds rectangle
    CGPoint center;
    center.x = bounds.origin.x + bounds.size.width / 2.0;
    center.y = bounds.origin.y + bounds.size.height / 2.0;

    // The radius of the circle should be nearly as big as the view
    float maxRadius = hypot(bounds.size.width, bounds.size.height) / 2.0;

    // The thickness of the line should be 10 points wide
    CGContextSetLineWidth(ctx, 10);

    // The color of the line should be gray (red/green/blue = 0.6, alpha = 1.0)
//    CGContextSetRGBStrokeColor(ctx, 0.6, 0.6, 0.6, 1.0);
    // The same as
//    [[UIColor colorWithRed:0.6 green:0.6 blue:0.6 alpha:1.0] setStroke];
    // The same as

//    [[UIColor redColor] setStroke];

    // Draw concentric circles from the outside in
    for (float currentRadius = maxRadius; currentRadius > 0; currentRadius -= 20) {
        // Add a path to the context
        CGContextAddArc(ctx, center.x, center.y, currentRadius, 0.0, M_PI * 2.0, YES);

        [[self randomColor] setStroke];

        // Perform drawing instructions; removes path
        CGContextStrokePath(ctx);
    }

Answer 1

UIColor将0到1之间的浮点值作为其RGB分量的值：

 UIColor *colorToReturn = [[UIColor alloc] initWithRed:red/255.0 green:green/255.0 blue:blue/255.0 alpha:alpha];

Answer 2

我使用下面的两个宏来获得随机颜色。第一个是我在设置颜色时经常使用的简单宏。第二个使用它返回一个随机颜色：

#define _RGB(r,g,b,a) [UIColor colorWithRed:r/255.0 green:g/255.0 blue:b/255.0 alpha:a]
#define kCLR_RANDOM_COLOR _RGB(arc4random()%255, arc4random()%255, arc4random()%255, 1)

为什么这种随机颜色方法不起作用？

2 个答案: