#import <UIKit/UIKit.h>@interface RootViewController : UIViewController@end

#import "RootViewController.h"#import "NIDropDown.h"@interface RootViewController ()@end@implementation RootViewController- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil{  self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];  if (self) {    // Custom initialization  }  return self;}- (void)viewDidLoad{  [super viewDidLoad];  // Do any additional setup after loading the view.    self.title=@"DropDown";    UIButton *button=[UIButton buttonWithType:UIButtonTypeRoundedRect];  button.frame=CGRectMake(10, 100, 150,30);  button.backgroundColor=[UIColor redColor];  [button addTarget:self action:@selector(doClickAction:) forControlEvents:UIControlEventTouchUpInside];  [self.view addSubview:button];       }-(void)doClickAction:(UIButton *)btn{   NSArray *dataArray=[NSArray arrayWithObjects:@"1",@"2",@"3",@"4",@"5", nil];    NIDropDown *dropDown=[[NIDropDown alloc]init];  [dropDown showDropDown:btn andHeight:[dataArray count]*36 andData:dataArray];  [self.view addSubview:dropDown];}- (void)didReceiveMemoryWarning{  [super didReceiveMemoryWarning];  // Dispose of any resources that can be recreated.}