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在这个 CG 教程挑战中，我们被要求在 for 循环中增加在视图上绘制的圆圈的颜色。为此，我设置了一个带有颜色的数组，然后尝试在前循环中实现颜色，使用递增的 i++ 移动到索引中的下一个对象。在模拟器中，我看到所有圆圈都具有相同的颜色。

如何设置 for 循环以增加颜色以每个圆圈绘制一种颜色。 

    //set array of colors up
NSArray *colors = [[NSArray alloc]initWithObjects:[UIColor greenColor], [UIColor redColor], [UIColor blueColor], [UIColor purpleColor], [UIColor orangeColor], [UIColor greenColor], [UIColor redColor], [UIColor blueColor], [UIColor purpleColor], [UIColor orangeColor], [UIColor greenColor], [UIColor redColor], [UIColor blueColor], [UIColor purpleColor], [UIColor orangeColor], [UIColor greenColor], [UIColor redColor], [UIColor blueColor], [UIColor purpleColor], nil];

CGRect bounds = [self bounds];

//figure out center point 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 fo the circle should be nearly as big as the view
float maxRadius = hypot(bounds.size.width, bounds.size.height)/2.0;

UIBezierPath *path = [[UIBezierPath alloc]init];

int i = 0;

for (float currentRadius = maxRadius; currentRadius > 0; currentRadius -= 20) {

    //we have to add this because when drawing several arcs UIBezierPath does not pick up the pencil between arcs and this moves the starting point of the next "stroke"
    [path moveToPoint:CGPointMake(center.x + currentRadius, center.y)];

    [path addArcWithCenter:center radius:currentRadius //note this is the current radius!
                startAngle:0.0 endAngle:M_PI*2.0 clockwise:YES];

        [self setCircleColor:[colors objectAtIndex:i]];
    i++;


}
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1 回答 1

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贝塞尔路径只有一种笔画颜色。您应该在循环的每次迭代中创建路径、设置颜色和描边。看起来您正在将每个同心圆添加到路径中，这意味着所有圆都将使用您的最终笔触颜色绘制（或过度绘制）。

于 2013-05-29T05:39:28.000 回答