1.//隐藏返回按钮的Back文字
[[UIBarButtonItem appearance] setBackButtonTitlePositionAdjustment:UIOffsetMake(0, -60) forBarMetrics:UIBarMetricsDefault];
2.UISegmentedControl选中时
//定义选中状态的样式selected，类型为字典
NSDictionary *selected =@{NSFontAttributeName:[UIFont systemFontOfSize:20],
NSForegroundColorAttributeName:[UIColor whiteColor]};
//定义未选中状态下的样式normal，类型为字典
NSDictionary *normal =@{NSFontAttributeName:[UIFont systemFontOfSize:20],
NSForegroundColorAttributeName:[UIColor grayColor]};
/*
NSFontAttributeName ->系统宏定义的特殊键，用来给格式字典中的字体赋值
NSForegroundColorAttributeName ->系统宏定义的特殊键，用来给格式字典中的字体颜色赋值
*/
//通过setTitleTextAttributes: forState:方法来给test控件设置文字内容的格式
[segMent setTitleTextAttributes:normal forState:UIControlStateNormal];
[segMent setTitleTextAttributes:selected forState:UIControlStateSelected];
