For iOS, tabs will appear at the bottom of the screen. For Android, tabs will be at the top of the screen, below the nav-bar. This follows each OS‘s design specification, but can be configured with the
$ionicConfigProvider.
文档中说明，对于android,默认在顶部，ios在底部。具体配置参考
http://www.ionicframework.com/docs/api/provider/$ionicConfigProvider/
原文：http://my.oschina.net/liangzhenghui/blog/501040