IOS TabBar小知识（不断更新中。。。）

1.调整TabBar上Title的位置

[childNav.tabBarItem setTitlePositionAdjustment:UIOffsetMake(-5, -5)];

2.设置abBar上Title的字体

[childNav.tabBarItem setTitleTextAttributes:@{NSFontAttributeName:[UIFont systemFontOfSize:12]} forState:UIControlStateNormal];

3.阻止系统对TabBar选中后的图片进行渲染

UIImage *selectedImage = [UIImage imageNamed:selectedImageName];
selectedImage          = [selectedImage imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
childNav.tabBarItem.selectedImage = selectedImage;