在片段中启动recyclerview时获取错误findViewById

Question

我在另一个没有使用fragment的项目中测试了这段代码，并在MainActivity.kt中编写了它，它很有效。但是当我用fragment做另一个项目时，问题来了，所以我把它写在一个新的类(HerbalFragment.kt(中。它在initiate Recyclerview的"findViewById"中出错，在"this"中也出错。这是我的代码(HerbalFragment.kt(

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
/**
* A simple [Fragment] subclass.
*/
class HerbalFragment : Fragment() {
private lateinit var rvHerbal: RecyclerView
private var list: ArrayList<Herbal> = arrayListOf()
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
super.onViewCreated(view, savedInstanceState)
return inflater.inflate(R.layout.fragment_herbal, container, false)
rvHerbal = findViewById(R.id.rv_herbal)
rvHerbal.setHasFixedSize(true)
list.addAll(HerbalData.listData)
showRecyclerList()
}
private fun showRecyclerList() {
rvHerbal.layoutManager = LinearLayoutManager(this)
val listHerbalAdapter = ListHerbalAdapter(list)
rvHerbal.adapter = listHerbalAdapter
}
}[![enter image description here][1]][1]

请帮帮我，谢谢

Answer 1

据我所知，您的代码无法访问，

override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
super.onViewCreated(view, savedInstanceState)
return inflater.inflate(R.layout.fragment_herbal, container, false)
// unreachable code you are already return the view so below code will never execute
rvHerbal = findViewById(R.id.rv_herbal)
rvHerbal.setHasFixedSize(true)
list.addAll(HerbalData.listData)
showRecyclerList()
}

要解决这个问题，你需要按照我的建议更改你的代码。

override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return  inflater.inflate(R.layout.fragment_herbal, container, false)

}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
// do what ever you want here like find view ids and etc...
rvHerbal = findViewById(R.id.rv_herbal)
rvHerbal.setHasFixedSize(true)
list.addAll(HerbalData.listData)
showRecyclerList()
}
}
private fun showRecyclerList() {
rvHerbal.layoutManager = LinearLayoutManager(activity!!)
val listHerbalAdapter = ListHerbalAdapter(list)
rvHerbal.adapter = listHerbalAdapter
}

Answer 2

如果通过这种简单的方法使用kotlin数据绑定，则不必查找视图

为此添加导入(fragment_herbal是您的xml布局视图文件名(

import kotlinx.android.synthetic.main.fragment_herbal.*

然后

override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
return inflater.inflate(R.layout.fragment_herbal, container, false)
}

然后在没有findviewbyid 的情况下使用您的视图项目

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
rvHerbal.setHasFixedSize(true)
list.addAll(HerbalData.listData)
showRecyclerList()
}