iOS View颜色渐变

UIView *backView = [[UIView alloc]initWithFrame:CGRectMake(100, 100, 200, 200)];

        backView.backgroundColor = [UIColor redColor];

        [_selectStationView addSubview:backView];

        

        CAGradientLayer *gradient = [CAGradientLayer layer];

        gradient.frame = backView.bounds;

        gradient.colors = [NSArray arrayWithObjects:(id)[UIColorredColor].CGColor,

                           (id)[UIColor greenColor].CGColor,

                           (id)[UIColor cyanColor].CGColor,nil];

        [backView.layer insertSublayer:gradient atIndex:0];