iOS 7.0中的水平CAGradientLayer

Question

在我的应用程序中,我使用a CAGradientLayer来设置我的单元格的背景,这样:

retValue = [tableView dequeueReusableCellWithIdentifier:@"Cells" forIndexPath:indexPath];
UIView *bgColorView = [[UIView alloc] init];
bgColorView.backgroundColor = [UIColor blueColor];
bgColorView.layer.masksToBounds = YES;
id startColor = (id)[[UIColor colorWithWhite:0.75 alpha:1] CGColor];
id endColor = (id)[[UIColor blueColor] CGColor];
CAGradientLayer* gradientLayer = [CAGradientLayer layer];
gradientLayer.frame = retValue.contentView.bounds;
gradientLayer.colors = @[startColor,startColor,endColor,endColor];
gradientLayer.locations = @[[NSNumber numberWithFloat:0],
    [NSNumber numberWithFloat:0.95],
    [NSNumber numberWithFloat:0.95],
    [NSNumber numberWithFloat:1]];
[gradientLayer setStartPoint:CGPointMake(0,0.5)];
[gradientLayer setEndPoint:CGPointMake(1,0.5)];
[bgColorView.layer addSublayer:gradientLayer];
retValue.selectedBackgroundView = bgColorView;

(此代码在里面- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath)

它在iOS 6上工作正常但在iOS 7上不起作用,在新的iOS中,渐变始终是垂直的(忽略startPoint和endPoint)

有没有人在同一个问题上遇到过？

谢谢,

佩里

Answer 1

这个问题相当陈旧,但我遇到过它,所以其他人也可能会这样.以下代码将生成在版本为7.0.3的iPhone模拟器上运行的水平渐变

+ (void)drawGradientOverContainer:(UIView *)container
{
    UIColor *transBgColor = [UIColor colorWithWhite:1.0 alpha:0.0];
    UIColor *black = [UIColor blackColor];
    CAGradientLayer *maskLayer = [CAGradientLayer layer];
    maskLayer.opacity = 0.8;
    maskLayer.colors = [NSArray arrayWithObjects:(id)black.CGColor, 
    (id)transBgColor.CGColor, (id)transBgColor.CGColor, (id)black.CGColor, nil];

    // Hoizontal - commenting these two lines will make the gradient veritcal
    maskLayer.startPoint = CGPointMake(0.0, 0.5);
    maskLayer.endPoint = CGPointMake(1.0, 0.5);

    NSNumber *gradTopStart = [NSNumber numberWithFloat:0.0];
    NSNumber *gradTopEnd = [NSNumber numberWithFloat:0.4];
    NSNumber *gradBottomStart = [NSNumber numberWithFloat:0.6];
    NSNumber *gradBottomEnd = [NSNumber numberWithFloat:1.0];
    maskLayer.locations = @[gradTopStart, gradTopEnd, gradBottomStart, gradBottomEnd];

    maskLayer.bounds = container.bounds;
    maskLayer.anchorPoint = CGPointZero;
    [container.layer addSublayer:maskLayer];
}

我不确定为什么你的代码不起作用,但如果我没有设置锚点,我会得到奇怪的行为 - 渐变仍然是水平的.也许它与单元格背景视图有关 - 您可以尝试将渐变应用于基础表.

Answer 2

在Swift 4中,我实现了一个很好的工作扩展:

extension UIView {

    enum GradientColorDirection {
        case vertical
        case horizontal
    }

    func showGradientColors(_ colors: [UIColor], opacity: Float = 1, direction: GradientColorDirection = .vertical) {
        let gradientLayer = CAGradientLayer()
        gradientLayer.opacity = opacity
        gradientLayer.colors = colors.map { $0.cgColor }

        if case .horizontal = direction {
            gradientLayer.startPoint = CGPoint(x: 0.0, y: 0.0)
            gradientLayer.endPoint = CGPoint(x: 1.0, y: 0.0)
        }

        gradientLayer.bounds = self.bounds
        gradientLayer.anchorPoint = CGPoint.zero
        self.layer.addSublayer(gradientLayer)
    }

}