Iphone iOS的自定义渐变背景视图不工作

我有以下UIView自定义类：

@implementation BackgroundView

- (void)drawRect:(CGRect)rect 
{

    CGContextRef currentContext = UIGraphicsGetCurrentContext();

    CGGradientRef glossGradient;
    CGColorSpaceRef rgbColorspace;
    size_t num_locations = 2;
    CGFloat locations[2] = { 0.0, 1.0 };

    float r = (255.0)/(255.0);
    float g = (165.0)/(255.0);
    float b = (0.0)/(255.0);

    float rr = (238.0)/(255.0);
    float gg = (118.0)/(255.0);
    float bb = (0.0)/(255.0);

    CGFloat components[8] = { r, g, b, 1.0,  // Start color
        rr, gg, bb, 1.0 }; // End color

    rgbColorspace = CGColorSpaceCreateDeviceRGB();
    glossGradient = CGGradientCreateWithColorComponents(rgbColorspace, components, locations, num_locations);

    CGRect currentBounds = self.bounds;
    CGPoint topCenter = CGPointMake(CGRectGetMidX(currentBounds), 0.0f);
    CGPoint midCenter = CGPointMake(CGRectGetMidX(currentBounds), CGRectGetMidY(currentBounds));
    CGContextDrawLinearGradient(currentContext, glossGradient, topCenter, midCenter, 0);

    CGGradientRelease(glossGradient);
    CGColorSpaceRelease(rgbColorspace); 
}


@end

基本上，它应该是一个橙色的梯度。值r、g和b表示浅橙色，值rr、gg、bb表示深橙色。但它不起作用。只有框架顶部为橙色，框架底部为黑色。我似乎无法摆脱黑色

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我会用什么值来表示橙色的渐变呢。有人能找出错误吗？我找不到。非常感谢

这是因为您指定渐变的终点位于currentBounds的中间-请参见此行：

CGPoint midCenter = CGPointMake(CGRectGetMidX(currentBounds), CGRectGetMidY(currentBounds));

要去除黑色，请确保y坐标位于视图的底部

或者，您可以使用此代码在端点之后扩展渐变

 CGContextDrawLinearGradient(currentContext, glossGradient, topCenter, midCenter, kCGGradientDrawsAfterEndLocation);