通过渲染改变tabBarItem的背景图片

p.p1 { margin: 0.0px 0.0px 0.0px 0.0px; font: 18.0px Menlo; color: #703daa }
p.p2 { margin: 0.0px 0.0px 0.0px 0.0px; font: 18.0px Menlo }
p.p3 { margin: 0.0px 0.0px 0.0px 0.0px; font: 18.0px Menlo; color: #3d1d81 }
span.s1 { }
span.s2 { color: #000000 }
span.s3 { color: #3d1d81 }
span.s4 { color: #4f8187 }
span.s5 { color: #d12f1b }
span.s6 { font: 18.0px "PingFang SC"; color: #d12f1b }
span.s7 { color: #703daa }

UITabBarController *tabVC = [[UITabBarController alloc] init];

TestVC *vc = [TestVC new];

tabVC.tabBar.tintColor = [UIColor greenColor];

UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:vc];

nav.tabBarItem.title = @"第一页";

UIImage *img = [UIImage imageNamed:@"service_sel"];

nav.tabBarItem.selectedImage = [img imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];

nav.tabBarItem.image = [img imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];