gistfile1.m

-(void)drawcagradientlayer:(CGRect)rect{
    CAGradientLayer *gradient = [CAGradientLayer layer];
    gradient.colors = @[(id)[UIColor colorWithRed:0 green:0.8 blue:0 alpha:1.0].CGColor,  // light gray
                        (id)[UIColor colorWithRed:0 green:0.8 blue:0 alpha:0.3].CGColor]; // lighter gray
    
    // 创建一个Path句柄
    CGMutablePathRef pathRef = CGPathCreateMutable();
    // 初始化该path到一个初始点
    CGPathMoveToPoint(pathRef, &CGAffineTransformIdentity, kYAxisLabelWidth, rect.size.height/2);
    // 添加一条直线，从初始点到该函数指定的坐标点
    CGPathAddLineToPoint(pathRef, &CGAffineTransformIdentity, rect.size.width-kMarginRight, rect.size.height/3);
    CGPathAddLineToPoint(pathRef, &CGAffineTransformIdentity, rect.size.width-kMarginRight, rect.size.height/2);
    CGPathAddLineToPoint(pathRef, &CGAffineTransformIdentity, kYAxisLabelWidth, rect.size.height/2);
    // 关闭该path
    CGPathCloseSubpath(pathRef);
    gradient.frame = CGPathGetBoundingBox(pathRef);
    gradient.startPoint=CGPointMake(0, 0);
    gradient.endPoint=CGPointMake(1, 0);
    
    CAShapeLayer *mask = [CAShapeLayer layer];
    CGAffineTransform translation = CGAffineTransformMakeTranslation(-CGRectGetMinX(gradient.frame),
                                                                     -CGRectGetMinY(gradient.frame));
    mask.path = CGPathCreateCopyByTransformingPath(pathRef,
                                                   &translation);
    gradient.mask = mask;
    
    [self.layer addSublayer:gradient];
}