CAGradientLayer学习

最新推荐文章于 2017-07-04 20:28:00 发布

Asong_ge

最新推荐文章于 2017-07-04 20:28:00 发布

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分类专栏： iOS

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这个东西很简单，这里只做基本的使用，以此作为笔记，俗话说好记性不如烂笔头嘛。

CAGradientLayer这个鬼东西也是继承layer，下面将通过两个例子来说明具体的使用。

首先

这里先看一下这里面的东西

/* The array of CGColorRef objects defining the color of each gradient
 * stop. Defaults to nil. Animatable. */

@property(nullable, copy) NSArray *colors;

/* An optional array of NSNumber objects defining the location of each
 * gradient stop as a value in the range [0,1]. The values must be
 * monotonically increasing. If a nil array is given, the stops are
 * assumed to spread uniformly across the [0,1] range. When rendered,
 * the colors are mapped to the output colorspace before being
 * interpolated. Defaults to nil. Animatable. */

@property(nullable, copy) NSArray<NSNumber *> *locations;

/* The start and end points of the gradient when drawn into the layer's
 * coordinate space. The start point corresponds to the first gradient
 * stop, the end point to the last gradient stop. Both points are
 * defined in a unit coordinate space that is then mapped to the
 * layer's bounds rectangle when drawn. (I.e. [0,0] is the bottom-left
 * corner of the layer, [1,1] is the top-right corner.) The default values
 * are [.5,0] and [.5,1] respectively. Both are animatable. */

@property CGPoint startPoint;
@property CGPoint endPoint;

colors和location都是支持隐私动画的，通过上面 .h文件可以看出，CAGradientLayer的基本用法。

实例

先来看一个例子：

代码如下：

- (void)test{
    UILabel * label = [[UILabel alloc]initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, 40)];
    label.center = self.view.center;
    label.font = [UIFont systemFontOfSize:35];
    label.backgroundColor = [UIColor clearColor];
    label.textAlignment = NSTextAlignmentCenter;
    label.text = @"吴松——Asong";
    //这里是label是用来做文字裁剪作用
    [self.view addSubview:label];
    
    CAGradientLayer *gradientLayer1 =  [CAGradientLayer layer];
    gradientLayer1.frame = label.frame;
    CGColorRef red = [UIColor redColor].CGColor;
    CGColorRef purple = [UIColor purpleColor].CGColor;
    CGColorRef yellow = [UIColor yellowColor].CGColor;
    CGColorRef orange = [UIColor orangeColor].CGColor;
    //添加颜色变化，NSArray *colors;是个数组
    [gradientLayer1 setColors:@[(__bridge id)red, (__bridge id)purple, (__bridge id)yellow, (__bridge id)orange]];
    
    //用来划分显示颜色的区间，不设置的话，会是平均值
    [gradientLayer1 setLocations:@[@0.3, @0.6, @0.8, @1.0]];
   //Default: StartPoint ：[.5,0]
    [gradientLayer1 setStartPoint:CGPointMake(0, 0)];
    //Default: EndPoint ：[.5,1]
    [gradientLayer1 setEndPoint:CGPointMake(1, 1)];
    //label作为遮罩层 :简单的理解就是有对象（不透明）的地方就显示下面的内容。
    gradientLayer1.mask = label.layer;
    //因为只要这位mask，label的就是从原来的superView移除了，从新粘到gradientLayer1，所以要重置位置
    label.frame = gradientLayer1.bounds;

    [self.view.layer addSublayer:gradientLayer1];
}