InputField.shouldHideMobileInput

public bool shouldHideMobileInput ;

Description

Should the mobile keyboard input be hidden.

using UnityEngine;
using System.Collections;
using UnityEngine.UI; // Required when Using UI elements.

public class Example : MonoBehaviour
{
    public InputField mainInputField;

    public void Start()
    {
        //This setting can be toggled in the inspector.
        mainInputField.shouldHideMobileInput = true;
    }
}