Keyboard is going out while moving one text field to another text field

I have two textfields as emailTextField and passwordTextField.

I have written the following textfield delegate methods for moving one text field to another:

- (BOOL)textFieldShouldReturn:(UITextField *)textField
{

    if (textField == emailTextField) {

        [textField resignFirstResponder];
        [passwordTextField becomeFirstResponder];
    } else if (textField == passwordTextField) {

        [textField resignFirstResponder];

    }

    return YES;
}

When I click to next button after entering email then it will go to password textfield but within a fraction of a second, the keyboard will disappear.

What is the solution for this? Is there a mistake in the code?

Try this

- (BOOL)textFieldShouldReturn:(UITextField *)textField
{

   if (textField == emailTextField) { 

      [passwordTextField becomeFirstResponder];

  } else if (textField == passwordTextField) {

       [textField resignFirstResponder];

  }

  return YES;
}