在iPhone应用程序中手动绘制渐变?

If I have two UIColors, what's the best way to draw an even gradient between them over an arbitrarily-sized area?

如果我有两个UIColors，在一个任意大小的区域中，在它们之间画一个均匀梯度的最好方法是什么?

I am guessing you would create a UIView subclass and use the CG drawing methods in the drawRect method. I just don't know which ones, or if there are any pitfalls to watch out for, like performance. Has anyone done this?

我猜你会创建一个UIView子类并在drawRect方法中使用CG绘图方法。我只是不知道是哪一个，或者如果有什么陷阱要注意，比如性能。有人做过吗?

7 个解决方案

#1

You'll want to use CGGradient. See the iPhone Dev Center "CGGradient Reference" document.

你需要使用CGGradient。参见iPhone开发中心“CGGradient参考”文档。

#2

#import <QuartzCore/QuartzCore.h>    
- (void) setGradient {
    CAGradientLayer *gradient = [CAGradientLayer layer];
    gradient.frame = self.view.bounds;
    gradient.colors = [NSArray arrayWithObjects:(id)[[UIColor whiteColor] CGColor], (id)[[UIColor blackColor] CGColor], nil];
    [self.view.layer insertSublayer:gradient atIndex:0];     
}

Don't forget to add QuartzCore library to your project.

不要忘记在项目中添加QuartzCore库。

#3

The Swift way to add Gradient is :

快速增加渐变的方法是:

    var view : UIView = UIView(frame: CGRectMake(0, 0, 320, 100))
    var g : CAGradientLayer = CAGradientLayer()
    g.frame = gradientView.bounds
    g.colors = ["000000".UIColor.CGColor , "111111".UIColor.CGColor]
    view.layer.insertSublayer(g, atIndex: 0)

UIColor() is a helper class for Swift to convert hex color to rgb color, highly recommended.

UIColor()是快速转换hex颜色到rgb颜色的助手类，强烈推荐。

#4

Same-ish solution as @Anton Chikin but a little more robust. Notice the override of layerClass... this way, you don't have to worry about setting the frame and the frame is automatically updated upon rotation & resize.

同样的解决方案是@Anton Chikin，但是有点健壮。请注意layerClass的覆盖…这样，您不必担心设置框架和框架会自动更新在旋转和调整大小。

class GradientView: UIView {

    var colorA : UIColor = UIColor.greenColor() {
        didSet { updateGradient() }
    }
    var colorB : UIColor = UIColor.blueColor() {
        didSet { updateGradient() }
    }

    override class func layerClass() -> AnyClass {
        return CAGradientLayer.self
    }

    required init(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        updateGradient()
    }

    func updateGradient() {
        if let gLayer = layer as? CAGradientLayer {
            gLayer.colors = [colorA.CGColor, colorB.CGColor]
        }
    }

}

If you're using IB, you can set the properties via "User Defined Runtime Attributes".

如果使用IB，则可以通过“用户定义的运行时属性”设置属性。

If you're not using IB, use the other initializer.

如果您没有使用IB，请使用其他初始化器。

#5

I found that using CAGradientLayer produced a gradient with noticeable stepping Ended up using this

我发现使用CAGradientLayer会产生一个渐变，并且使用这个渐变效果。

http://evilrockhopper.com/tag/cggradient/

http://evilrockhopper.com/tag/cggradient/

As per this question Gradients on UIView and UILabels On iPhone

根据这个问题，UIView和UILabels在iPhone上的梯度。

#6

hi you can use following to to apply gradient on view

你好，你可以使用以下的方法在视图上应用渐变。

-(void)applyGradientEffecttoView:(UIView *)aView
 {
     // Create the colors

     UIColor *darkOp = [UIColor colorWithRed:0.0f green:0.0f blue:0.0f alpha:1.0];
     UIColor *lightOp =[UIColor colorWithRed:255.0f green:255.0f blue:255.0f alpha:0.0];

      // Create the gradient
      CAGradientLayer *gradient = [CAGradientLayer layer];

      // Set colors
      gradient.colors = [NSArray arrayWithObjects:
                        (id)lightOp.CGColor,
                        (id)darkOp.CGColor,
                        nil];
     gradient.locations = [NSArray arrayWithObjects:
                          [NSNumber numberWithFloat:0.0f],
                          [NSNumber numberWithFloat:0.5],
                          nil];

    // Set bounds
     gradient.frame = aView.bounds;

   // Add the gradient to the view

  [aView.layer insertSublayer:gradient atIndex:0];
}

#7

For views that draw text, such as UILabel, UITextView, and UITextField, you should add the gradient inside the drawRect function. (see this post for an example).

对于绘制文本的视图，如UILabel、UITextView和UITextField，应该在drawRect函数中添加渐变。(参见本文中的示例)。

There are some great subclasses of UILabel, UITextView, and UITextField that allow you to add a gradient pretty easily (see JBGradient on GitHub).

UILabel、UITextView和UITextField有一些很好的子类，可以很容易地添加一个渐变(见GitHub上的jb渐变)。

#1