CALayer-CAGradientLayer(梯度图层)

** CAGradientlayer可以绘制一个充满整个图层的颜色梯度(包括原型图层等图层)在一个背景颜色上 **

在了解CAGradientLayer之前,我们先要了解一下CALayer的坐标,如下图,一个Layer的左上角为(0,0),其右下角坐标为(1,1),中心点是(0.5,0.5),任何图层都是如此,和父图层以及自身的形状无关.

CALayer坐标

属性

• colors
  var colors: [AnyObject]?
  一个内部是CGColorRef的数组,规定所有的梯度所显示的颜色,默认为nil

• locations
  var locations: [NSNumber]?
  一个内部是NSNumber的可选数组,规定所有的颜色梯度的区间范围,选值只能在0到1之间,并且数组的数据必须单增,默认值为nil

• endPoint
  var endPoint: CGPoint
  图层颜色绘制的终点坐标,也就是阶梯图层绘制的结束点,默认值是(0.5,1.0)

• startPoint
  var startPoint: CGPoint
  与endPoint相互对应,就是绘制阶梯图层的起点坐标,绘制颜色的起点,默认值是(0.5,0.0)

• type
  var type:String
  绘制类型,默认值是kCAGradientLayerAxial,也就是线性绘制,各个颜色阶层直接的变化是线性的

---

实例

通过属性大家都差不多知道该如何使用阶梯图层了,接下来我们看一下普通的例子,然后讨论几种情况

//
//  ViewController.swift
//  CALayer-CAGradientLayer
//
//  Created by 蔡士林 on 6/16/16.
//  Copyright © 2016 BZ. All rights reserved.
//

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // 创建阶梯图层
        let gradientLayer = CAGradientLayer()
        // 设置阶梯图层的背景
        //gradientLayer.backgroundColor = UIColor.grayColor().CGColor
        // 图层的颜色空间(阶梯显示时按照数组的顺序显示渐进色)
        gradientLayer.colors = [UIColor.redColor().CGColor,UIColor.blueColor().CGColor,UIColor.greenColor().CGColor]
        // 各个阶梯的区间百分比
        gradientLayer.locations = [0.1,0.6,1]
        gradientLayer.frame = CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.width)
        gradientLayer.position = self.view.center
        // 绘图的起点(默认是(0.5,0))
        gradientLayer.startPoint = CGPointMake(1, 0)
        // 绘图的终点(默认是(0.5,1))
![Uploading (0,0.5)(1,0.5)@2x_114834.png . . .]

        gradientLayer.endPoint = CGPointMake(0, 1)
        self.view.layer.addSublayer(gradientLayer)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

}

系统默认的绘制方向,从上往下的

![Uploading (0.5,0)(0.5,1)@2x_161190.png . . .]

这是起点为(0,0.5),终点(1,0.5),时横向绘制

(0,0.5)(1,0.5)@2x.png

以起点和终点所画出来的直线做中心轴绘制

(1,0)(0,1)@2x.png

动画

CAGradientLayer的所有属性都能产生隐式动画我们可以通过NSTimer来定时修改Location(其他的也可以(⊙o⊙)哦)

CAGradientLayer.gif

//
//  ViewController.swift
//  CALayer-CAGradientLayer
//
//  Created by 蔡士林 on 6/16/16.
//  Copyright © 2016 BZ. All rights reserved.
//

import UIKit

class ViewController: UIViewController {
    
    var graLayer:CAGradientLayer!
    var index = 0.1

    override func viewDidLoad() {
        super.viewDidLoad()
        
        let gradientLayer = CAGradientLayer()
        gradientLayer.backgroundColor = UIColor.grayColor().CGColor
        gradientLayer.colors = [UIColor.redColor().CGColor,UIColor.blueColor().CGColor,UIColor.greenColor().CGColor]
        gradientLayer.locations = [0.1,0.15,1]
        gradientLayer.frame = CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.width)
        gradientLayer.position = self.view.center
        gradientLayer.startPoint = CGPointMake(1, 0)
        gradientLayer.endPoint = CGPointMake(0, 1)
        self.graLayer = gradientLayer
        self.view.layer.addSublayer(gradientLayer)
        
        
        
    }
    
    override func touchesBegan(touches: Set, withEvent event: UIEvent?) {
        NSTimer.scheduledTimerWithTimeInterval(0.02, target: self, selector: #selector(ViewController.change), userInfo: nil, repeats: true)
    }
    
    func change(){
        index = index + 0.01
        let twoIndex = index + 0.05
        graLayer.locations = [index,twoIndex,1]
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

}

当然了你也可以设置它的其他属性来实现各种各样的动画,你可以充分发挥你的想象力~

有帮助的希望大家点个❤,也是对我的一点点鼓励~