_showImageView.center = self.center;

_showImageView.size = _showImage.size;

NSLog(@"第一種: _showImageView.frame === %@", NSStringFromCGRect(_showImageView.frame));

_showImageView.center = self.center;

_showImageView.bounds = (CGRect){CGPointZero, _showImage.size};

NSLog(@"第二種: _showImageView.frame === %@", NSStringFromCGRect(_showImageView.frame));

2014-09-23 10:41:59.311 NeiHanShe[6205:60b] 第一種: _showImageView.frame === {{160, 284}, {265, 146.13971}}

2014-09-23 10:41:59.311 NeiHanShe[6205:60b] 第二種: _showImageView.frame === {{27.5, 210.93015}, {265, 146.13971}}

所有正確設置,應該選擇第二種,否則不會居中, 第一種的self.center 會當做_showImageView.frame 的 x y