UIAlertController添加输入框问题？

[qq_32270687]

ViewController * vc = (id)self.parentViewController;
UIAlertController * alertController = [UIAlertController alertControllerWithTitle:@"Create Wishlist" message:@"" preferredStyle:UIAlertControllerStyleAlert];
// 创建文本框
[alertController addTextFieldWithConfigurationHandler:^(UITextField *textField){
textField.placeholder = @"登录";
}];
UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:nil];

UIAlertAction *createAction = [UIAlertAction actionWithTitle:@"Create" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {

//读取收入框的内容的方法
UITextField *login = alertController.textFields.firstObject;

}];

[alertController addAction:cancelAction];
[alertController addAction:createAction];

[vc presentViewController:alertController animated:YES completion:nil];

为什么对话框弹出来，不显示输入框？？控制台报一堆的debugger
The relevant UICollectionViewFlowLayout instance is <_UIAlertControllerCollectionViewFlowLayout: 0x7ff4630e4000>, and it is attached to <UICollectionView: 0x7ff461828600; frame = (0 104.667; 270 44); clipsToBounds = YES; gestureRecognizers = <NSArray: 0x7ff4630e4cd0>; layer = <CALayer: 0x7ff4630e4640>; contentOffset: {0, 0}; contentSize: {0, 0}> collection view layout: <_UIAlertControllerCollectionViewFlowLayout: 0x7ff4630e4000>

这是什么情况？？

[看_灰机]

UIAlertView *alertView//创建alertView，title什么的自己写； [alertView setAlertViewStyle:UIAlertViewStylePlainTextInput]; //style，带文本框的 UITextField *evaluate = [alertView textFieldAtIndex:0]; //evaluate 就是文本框了，可以获取里面输入的内容，也可设置属性。

[看_灰机]

http://blog.csdn.net/w582324909/article/details/52539421