标签：style blog io ar color os 使用 sp for
很多应用中为了美观和让视图过渡的时候显得尽量平滑,使用了渐变的效果.八国如果美工没时间给作图的话,我们可以自己去实现
使用渐变CAGradientLayer
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];
用上面的代码就欧克了
至于为什么要用CGColor然后再转为id,因为CAGradientLayer说明里面是这么写的
/* The array of CGColorRef objects defining the color of each gradient * stop. Defaults to nil. Animatable. */ @property(copy) NSArray *colors;
还有startPoint和endPoint不是实际的坐标点,而是类似于锚点anchorPoint的一种点[范围是0-1],头文件里是这么写的
/* 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;
point第一个元素代表左右方向,第二个元素代表上下方向.
此外CAGradientLayer还有一个属性是可以实现更高级的渐变效果,可以控制各个颜色区域所占的比例等,有兴趣的可以设置一下看看效果~
/* 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;
标签：style blog io ar color os 使用 sp for
原文地址：http://www.cnblogs.com/xyzaijing/p/4151370.html
