带有GradientLayer的UIButton模糊图像并使渐变变暗

Question

我有一个UIButton在这里，我想有一个渐变作为背景下的图像(透明背景的符号)，但我面临两个不同的问题。

无论我如何添加，第一个CAGradientLayer似乎都覆盖在图像的顶部，使图像完全模糊。

其次，渐变本身似乎变暗了很多，就像按钮被禁用一样，它不是。

下面是我的代码:

self.backButton = [[UIButton alloc] initWithFrame:CGRectMake(15, 35, 28, 28)];
[backButton addTarget:self
               action:@selector(goBack)
     forControlEvents:UIControlEventTouchUpInside];
[backButton setBackgroundColor:[UIColor clearColor]];
CAGradientLayer *buttonGradient = [CAGradientLayer layer];
buttonGradient.frame = backButton.bounds;
buttonGradient.colors = [NSArray arrayWithObjects:
                         (id)[[UIColor colorWithRed:.0
                                              green:.166
                                               blue:.255
                                              alpha:1] CGColor], 
                         (id)[[UIColor colorWithRed:.0
                                              green:.113
                                               blue:.255
                                              alpha:1] CGColor], 
                         nil];
[buttonGradient setCornerRadius:backButton.frame.size.width / 2];
[backButton.layer insertSublayer:buttonGradient
                         atIndex:0];
[backButton setImage:[UIImage imageNamed:@"backarrow.png"]
            forState:UIControlStateNormal];
[backButton setEnabled:NO];
[topbarView addSubview:backButton];

Answer 1

所以我设法通过做一个[button bringSubviewToFront:button]来解决这个问题。添加渐变后的imageView。似乎无论我做什么，新图层都会添加到imageView的顶部，所以我需要把它推到前面。

objective - c

:

[button bringSubviewToFront:button.imageView] 

迅速4.1:

button.bringSubview(toFront:button.imageView!)

Answer 2

或者，你可以在图像视图的图层

下面插入渐变图层

CAGradientLayer* gradient = [CAGradientLayer layer];
// ...
[button.layer insertSublayer:gradient below:button.imageView.layer];

Answer 3

SWIFT 3

下面是一个例子:(根据尼尔的回答)

    let layer = CAGradientLayer()
    layer.frame = CGRect(x: 0, y: 0, width: myButtonOutlet.layer.frame.size.width, height: myButtonOutlet..layer.frame.size.height)
    layer.colors = [UIColor.white.cgColor, pixelColorReceta.cgColor]
    layer.masksToBounds = true
    layer.cornerRadius = myButtonOutlet.layer.cornerRadius
    myButtonOutlet.layer.insertSublayer(layer, below: myButtonOutlet..imageView?.layer)

快乐编码:)

Answer 4

Swift 3

你可以将图片移动到渐变上方:

button.imageView?.layer.zPosition = 1

或者在图片下面插入渐变:

button.layer.insertSublayer(gradientLayer, below: button.imageView?.layer)