ACM_Someone like you

    //實現背景漸變
    //初始化我們需要改變背景色的UIView，并添加在視圖上
    self.theView = [[UIView alloc] initWithFrame:CGRectMake(0, 64, [UIScreen mainScreen].bounds.size.width, self.view.hf_width)];
    [self.view addSubview:self.theView];
    //初始化CAGradientlayer對象，使它的大小為UIView的大小
    self.gradientLayer = [CAGradientLayer layer];
    self.gradientLayer.frame = self.theView.bounds;
    //將CAGradientlayer對象添加在我們要設置背景色的視圖的layer層
    [self.theView.layer addSublayer:self.gradientLayer];
    //設置漸變區域的起始和終止位置（范圍為0-1）
    //不設置默認從上到下漸變，如果使用startPoint endPoint 就是右下角對角線 方向漸變 也可以自定義方向
   // self.gradientLayer.startPoint = CGPointMake(0, 0);
   // self.gradientLayer.endPoint = CGPointMake(1, 1);
    //設置顏色數組(我寫的是白色的漸變)
    CGColorRef color1 = [UIColor colorWithWhite:1.000 alpha:0.7].CGColor;
    CGColorRef color2 = [UIColor colorWithWhite:1.000 alpha:0.0].CGColor;
    [_gradientLayer setColors:@[(__bridge id)color1,(__bridge id)color2]];//設置顏色分割點（范圍：0-1）
    self.gradientLayer.locations = @[@(0.0f), @(0.9f)];

//給漸變層設置 mask 屬性
    {
        // 設置只顯示一個三角形范圍的漸變色
        UIBezierPath *shapeLayerPath = [[UIBezierPath alloc] init];
        // 點的坐標是相對于漸變層的
        [shapeLayerPath moveToPoint:CGPointMake(0,self.view.hf_width)];//第一個點
        [shapeLayerPath addLineToPoint:CGPointMake(self.view.hf_width/2, 0)];//第二個點
        [shapeLayerPath addLineToPoint:CGPointMake(self.view.hf_width, self.view.hf_width)];//第三個點
        CAShapeLayer *shapeLayer = [CAShapeLayer layer];
        shapeLayer.path = shapeLayerPath.CGPath;
        self.gradientLayer.mask = shapeLayer; 
    }