CodeTextField | 验证码文本框、密码框、等

I have a ComboBox and a Textfield, I need that when I select 'letters' in the ComboBox the Textfield accepts only letters and when I select 'numbers' in the ComboBox the Textfield accepts only numbers

JDK jdk1.8.0_201:

Here is image of view I have following problem. I created a sample user information form for user. He fills some details and submits. See the first sub image in above screenshot.

I am entering first name and last name here, normal keyboard will appear when I switch first name to last name manually by scrolling a view or by using keyboard next button on keyboard.

Then, when click code textfield, a uipickerview/UIActionsheet will appear. Plase see previous image.

It is working fine. When I move one firstname textfield to last name text field and from lastname to code text field.

Problem : My problem is that, suppose currently I am lastname textfield i.e I am entering my last name and I clicked on code textfield following issue is coming. seen the below image.Here is my problem

So here, keyboard is appearing as well as uipickerview/UIactionsheet is also coming but in behing keyboard. I don't know it is coming. Not only last name to code textfield form first name tp code textfield or email textfield to code textfield...same issue is coming only when I move to one textfield to next field by scrolling/switching. If I use next button from keyboard it is moving and working file.

Anybody help me to sort out this problem.

Here my code,

I finally managed to get the SignUp to work, but when trying to confirm the signup, I'm reaching a problem. Here is my code: