显示alertView键盘打不开

Question

创建AlertView ：

UIAlertView * alert = [[UIAlertView alloc] initWithTitle:nil message:@"The person you selected does not have an email address on file. Please enter their email address below." delegate:self cancelButtonTitle:nil otherButtonTitles:@"Cancel",@"Submit",nil];
alert.tag = 1;
alert.alertViewStyle = UIAlertViewStylePlainTextInput;
UITextField * alertTextField = [alert textFieldAtIndex:0];
alertTextField.keyboardType = UIKeyboardTypeEmailAddress;
alertTextField.placeholder = @"Enter Email address";
[alert show];

在ios6中键盘可以正常打开，但是在ios5中就有问题

这是在ios5.1中的截图：

Answer 1

becomefirstresponder