只需加這么一段代碼，如下：

imageView.contentMode = UIViewContentModeScaleAspectFit;

imageView.autoresizesSubviews = YES;

imageView.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;