CAGradientLayer *topLayer = [[CAGradientLayer alloc] init];    topLayer.frame = CGRectMake(0, 0, 320, 100);    topLayer.colors = @[(id)[UIColor colorWithWhite:1.0 alpha:0.0].CGColor,(id)self.view.backgroundColor.CGColor];    topLayer.startPoint = CGPointMake(0.0, 1);    topLayer.endPoint = CGPointMake(0.0f, 0.0f);            [self.view.layer addSublayer:topLayer];

/* The array of CGColorRef objects defining the color of each gradient * stop. Defaults to nil. Animatable. */@property(copy) NSArray *colors;

/* 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, endPoint;

/* 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(copy) NSArray *locations;