代码:

UIImage *normal = [[UIImage imageNamed:@"tabbar_home_default"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];

UIImage *selected = [[UIImage imageNamed:@"tabbar_home_selected"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];

self.navigationController.tabBarItem.image = normal;

self.navigationController.tabBarItem.selectedImage = selected;

以上代码设置之后, 出现tabBarItem图片过大, 后来检查才发现, 原来图片发在了Images.xcassets中的x1位置, 改为x2位置之后就恢复正常了.

还有就是看看Images.xcassets中是不是有重复的图片.