在Activity中建立一個RecyclerView可以正常建立以及顯示，然後換了在Fragment中一直報錯說不能為空。

然後上網查了一下：

結論得出，我們通常把initView方法寫在onCreateView方法中，但是這個時候view可能並沒有返回，所以就找不到了，所以我們可以把初始化操作放在onActivityCreated或onViewCreated中

只要把RecyclerView放到 onViewCreated 中初始化即可：

override fun onViewCreated(view: View?, savedInstanceState: Bundle?) {
        
 
super.onViewCreated(view, savedInstanceState)
        //模擬資料
        var user1 = UserData()
        user1.age = "23"
        user1.sex = "男"
        user1.userName = "張三"

        var user2 = UserData()
        user2.age = "30"
        user2.sex = "女"
        user2.userName = "李四"

        var user3 = UserData()
        user3.age 
 
= "25"
        user3.sex = "保密"
        user3.userName = "劉柳"

        arrayList.add(user1)
        arrayList.add(user2)
        arrayList.add(user3)


        val takePhotoAdapter = TakePhotoAdapter(arrayList)
        recycler_View.adapter = takePhotoAdapter

        val gridlayout = GridLayoutManager(context!!, 2)
        recycler_View.layoutManager
 
=gridlayout
    }