iOS封装的下拉列表控件，调用简单，在tableview上使用也不会遮挡，会自动选择向上或向下弹出选项，不会被屏幕遮挡
EBDropdownListItem *item1 = [[EBDropdownListItem alloc] initWithItem:@"1" itemName:@"item1"];
EBDropdownListItem *item2 = [[EBDropdownListItem alloc] initWithItem:@"2" itemName:@"item2"];
EBDropdownListItem *item3 = [[EBDropdownListItem alloc] initWithItem:@"3" itemName:@"item3"];
EBDropdownListItem *item4 = [[EBDropdownListItem alloc] initWithItem:@"4" itemName:@"item4"];
// 弹出框向上
EBDropdownListView *dropdownListView = [[EBDropdownListView alloc] initWithDataSource:@[item1, item2, item3, item4]];
dropdownListView.frame = CGRectMake(20, 100, 130, 30);
[dropdownListView setViewBorder:0.5 borderColor:[UIColor grayColor] cornerRadius:2];
[self.view addSubview:dropdownListView];
[dropdownListView setDropdownListViewSelectedBlock:^(EBDropdownListView *dropdownListView) {
NSString *msgString = [NSString stringWithFormat:
@"selected name:%@ id:%@ index:%ld"
, dropdownListView.selectedItem.itemName
, dropdownListView.selectedItem.itemId
, dropdownListView.selectedIndex];
msgLabel.text = msgString;
}];
