转载：http://blog.csdn.net/iunion/article/details/7494511 UIViewContentMode
typedef enum { UIViewContentModeScaleToFill, UIViewContentModeScaleAspectFit, // contents scaled to fit with fixed aspect. remainder is transparent UIViewContentModeScaleAspectFill, // contents scaled to fill with fixed aspect. some portion of content may be clipped. UIViewContentModeRedraw, // redraw on bounds change (calls -setNeedsDisplay) UIViewContentModeCenter, // contents remain same size. positioned adjusted. UIViewContentModeTop, UIViewContentModeBottom, UIViewContentModeLeft, UIViewContentModeRight, UIViewContentModeTopLeft, UIViewContentModeTopRight, UIViewContentModeBottomLeft, UIViewContentModeBottomRight, } UIViewContentMode;
