//在Image Xcassets中appicon的名字已改成AppIcon~x~.png
NSDictionary *infoPlist = [[NSBundle mainBundle] infoDictionary];
NSString *icon = [[infoPlist valueForKeyPath:@"CFBundleIcons.CFBundlePrimaryIcon.CFBundleIconFiles"] lastObject];
UIImage *shareImage= [UIImage imageNamed:icon];
