[self.view addSubview:view];
//初始化
CAGradientLayer *gradLayer = [CAGradientLayer layer];
//渐变颜色数组
gradLayer.colors = @[(__bridge id)[UIColor redColor].CGColor,(__bridge id)[UIColor greenColor].CGColor,(__bridge id)[UIColor purpleColor].CGColor];
//渐变色分段
gradLayer.locations = @[@0.3,@0.6,@1];
//从左上角到右下角
gradLayer.startPoint = CGPointMake(0, 0);
gradLayer.endPoint = CGPointMake(1, 1);
//从左到右
gradLayer.startPoint = CGPointMake(0, 0.5);
gradLayer.endPoint = CGPointMake(0.5, 0.5);
//farme
gradLayer.frame = view.bounds;
[view.layer addSublayer:gradLayer];
效果图：从左到右
Snip20170928_2.png
