IOS TabBar小知識（不斷更新中。。。）

1.調整TabBar上Title的位置

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

2.設置abBar上Title的字體

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

3.阻止系統對TabBar選中後的圖片進行渲染

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