在HoloLens中使用UGUI InputField组件时，存在一个问题。当点击一次InputField时，将弹出的键盘关掉，再点击其它地方，又会因InputField再次获得焦点而弹出键盘。

解决方法：
将InputField的interactable字段设置为false。添加PointerHandler脚本来响应点击事件，然后另外写脚本来调出输入键盘。
TouchScreenKeyboard.Open("",TouchScreenKeyboardType.ASCIICapable);//打开系统键盘
TTouchScreenKeyboard.hideInput字段在HoloLens中不起作用。

示例：自己调用输入键盘

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using Microsoft.MixedReality.Toolkit.Input;

[RequireComponent(typeof(PointerHandler))]
public class InputFieldKeyboard : MonoBehaviour
{
    [SerializeField]
    private InputField m_InputField;
    [SerializeField]
    private TouchScreenKeyboardType keyboardType = TouchScreenKeyboardType.Default;
    private TouchScreenKeyboard m_Keyboard;

    private void Awake()
    {
        if (m_InputField == null)
            m_InputField = this.GetComponent<InputField>();
#if UNITY_EDITOR
        m_InputField.interactable = true;
#else
        m_InputField.interactable = false;
#endif
    }

#if !UNITY_EDITOR
    void Update()
    {

        if (m_Keyboard == null)
            return;

        switch(m_Keyboard.status)
        {
            case TouchScreenKeyboard.Status.Visible:
                m_InputField.text = m_Keyboard.text;
                break;
            default:
                m_Keyboard = null;
                break;
        }
    }
#endif

    public void Open()
    {
#if !UNITY_EDITOR
        m_InputField.caretPosition = m_InputField.text == null ? 0 : m_InputField.text.Length;
        TouchScreenKeyboard.hideInput = false;
        m_Keyboard = TouchScreenKeyboard.Open(m_InputField.text, keyboardType);
#endif
    }
}