用自定义控件设置导航栏的titleView

UIButton * button =[UIButton buttonWithType:UIButtonTypeCustom];
button.frame=CGRectMake(20, 20, 100, 40);
[button setTitle:@"1/3" forState:UIControlStateNormal];
[button addTarget:self action:@selector(showAllQuestions:) forControlEvents:UIControlEventTouchUpInside];
 
self.navigationItem.titleView = button;