我有一个包含 CALayer ("layerPlot_") 的 UIView 当您调用以下方法时它可以工作，但它会在两个方向（向上和向下）上扩展高度我想指定是否要向下或向上扩展高度以及该层的其他边缘保持在同一位置。
代码如下：
/**
* Resizes the layer to a new height.
*
* @param newHeight the new height of the layer
*/
-(void)resizeLayerTo:(CGFloat)newHeight {
// Create animation
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"bounds.size.height"];
[animation setFromValue:[NSNumber numberWithFloat:0.0f]];
[animation setToValue:[NSNumber numberWithFloat:newHeight]];
[animation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn]];
[animation setFillMode:kCAFillModeForwards];
[animation setDuration:1.2f];
// Update the layer's bounds so the layer doesn't snap back when the animation completes.
CGRect newSize = [layerPlot_ bounds];
newSize.size.height = newHeight;
layerPlot_.bounds = newSize;
// Add the animation, overriding the implicit animation.
[layerPlot_ addAnimation:animation forKey:@"bounds"];
}
谢谢。