如何在构建时修复 "cannot find symbol" 错误？

Question

我正在尝试按照一个教程进行操作，在该教程中，您构建了一个带有回收站视图的笔记应用程序。在我添加适配器并在我的 HomeFragment 中引用它之后，我开始收到两个错误。

我还仔细检查了 classes/variables 等的情况。尝试了小写和大写。也尝试导入 R。这是我不断收到的两个错误：

error: cannot find symbol
public final NotesAdapter getNotesAdapter() {
         ^symbol:   
class NotesAdapter 
location: class HomeFragment  

error: cannot find symbol
    private NotesAdapter notesAdapter;
            ^
  symbol:   class NotesAdapter
  location: class HomeFragment

这是我导入的 HomeFragment：

package com.denizgocer.notetakingfinal

import com.denizgocer.notetakingfinal.R
import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.SearchView
import android.widget.Toast
import androidx.recyclerview.widget.StaggeredGridLayoutManager
import com.denizgocer.notetakingfinal.database.NotesDatabase
import com.denizgocer.notetakingfinal.entities.Notes
import kotlinx.android.synthetic.main.fragment_create_note.*
import kotlinx.android.synthetic.main.fragment_home.*
import kotlinx.coroutines.launch
import NotesAdapter
import java.util.*
import kotlin.collections.ArrayList

class HomeFragment : BaseFragment() {

    var arrNotes = ArrayList<Notes>()
    var notesAdapter: NotesAdapter = NotesAdapter()
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        arguments?.let {
        }
    }

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        // Inflate the layout for this fragment


        return inflater.inflate(
            R.layout.fragment_home,
            container,
            false
        )

    }

    companion object {
        @JvmStatic
        fun newInstance() =
            HomeFragment().apply {
                arguments = Bundle().apply {
                }
            }
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        recycler_view.setHasFixedSize(true)

        recycler_view.layoutManager = StaggeredGridLayoutManager(2,StaggeredGridLayoutManager.VERTICAL)

        launch {
            context?.let {
                var notes = NotesDatabase.getDatabase(it).noteDao().getAllNotes()
                notesAdapter!!.setData(notes)
                arrNotes = notes as ArrayList<Notes>
                recycler_view.adapter = notesAdapter
            }
        }

        notesAdapter!!.setOnClickListener(onClicked)

        fabCreateNote.setOnClickListener {
            replaceFragment(CreateNoteFragment.newInstance(),false)
        }

        search_view.setOnQueryTextListener( object : SearchView.OnQueryTextListener{
            override fun onQueryTextSubmit(p0: String?): Boolean {
                return true
            }

            override fun onQueryTextChange(p0: String?): Boolean {

                var tempArr = ArrayList<Notes>()

                for (arr in arrNotes){
                    if (arr.title!!.toLowerCase(Locale.getDefault()).contains(p0.toString())){
                        tempArr.add(arr)
                    }
                }

                notesAdapter.setData(tempArr)
                notesAdapter.notifyDataSetChanged()
                return true
            }

        })


    }


    private val onClicked = object :NotesAdapter.OnItemClickListener{
        override fun onClicked(notesId: Int) {


            var fragment :Fragment
            var bundle = Bundle()
            bundle.putInt("noteId",notesId)
            fragment = CreateNoteFragment.newInstance()
            fragment.arguments = bundle

            replaceFragment(fragment,false)
        }

    }


    fun replaceFragment(fragment:Fragment, istransition:Boolean){
        val fragmentTransition = activity!!.supportFragmentManager.beginTransaction()

        if (istransition){
            fragmentTransition.setCustomAnimations(android.R.anim.slide_out_right,android.R.anim.slide_in_left)
        }
        fragmentTransition.replace(R.id.frame_layout,fragment).addToBackStack(fragment.javaClass.simpleName).commit()
    }


}

这是我的 NotesAdapter，包括导入：

import android.graphics.BitmapFactory
import android.graphics.Color
import android.graphics.drawable.GradientDrawable
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import com.denizgocer.notetakingfinal.R
import com.denizgocer.notetakingfinal.entities.Notes
import kotlinx.android.synthetic.main.item_rv_notes.view.*
import java.util.*
import kotlin.collections.ArrayList

class NotesAdapter :
    RecyclerView.Adapter<NotesAdapter.NotesViewHolder>() {
    var listener: OnItemClickListener? = null
    var arrList = ArrayList<Notes>()
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): NotesViewHolder {
        return NotesViewHolder(
            LayoutInflater.from(parent.context).inflate(R.layout.item_rv_notes, parent, false)
        )
    }

    override fun getItemCount(): Int {
        return arrList.size
    }

    fun setData(arrNotesList: List<Notes>) {
        arrList = arrNotesList as ArrayList<Notes>
    }

    fun setOnClickListener(listener1: OnItemClickListener) {
        listener = listener1
    }

    override fun onBindViewHolder(holder: NotesViewHolder, position: Int) {

        holder.itemView.tvTitle.text = arrList[position].title
        holder.itemView.tvDesc.text = arrList[position].noteText
        holder.itemView.tvDateTime.text = arrList[position].dateTime

        if (arrList[position].color != null) {
            holder.itemView.cardView.setCardBackgroundColor(Color.parseColor(arrList[position].color))
        } else {
            holder.itemView.cardView.setCardBackgroundColor(Color.parseColor(R.color.ColorLightBlack.toString()))
        }

        if (arrList[position].pathImage != null) {
            holder.itemView.imgNote.setImageBitmap(BitmapFactory.decodeFile(arrList[position].pathImage))
            holder.itemView.imgNote.visibility = View.VISIBLE
        } else {
            holder.itemView.imgNote.visibility = View.GONE
        }

        if (arrList[position].webLink != "") {
            holder.itemView.tvWebLink.text = arrList[position].webLink
            holder.itemView.tvWebLink.visibility = View.VISIBLE
        } else {
            holder.itemView.tvWebLink.visibility = View.GONE
        }

        holder.itemView.cardView.setOnClickListener {
            listener!!.onClicked(arrList[position].pld!!)
        }

    }

    class NotesViewHolder(view: View) : RecyclerView.ViewHolder(view)


    interface OnItemClickListener {
        fun onClicked(noteId: Int)
    }

}

Answer 1

似乎 NotesAdapter 在默认包中。这意味着您没有明确地放入包中，而是直接放入源文件夹中。

只有默认包中的classes可以使用默认包中的其他classes。你不能 import class 在里面。

为了解决这个问题，请将 NotesAdapter 放入一个包中并正确导入。

此外，如果将 class 移动到包后错误仍然存在，您可能需要使用 File>Invalidate Caches and Restart>Invalidate and Restart，因为 AndroidStudio 并不总是正确的探测并处理源文件的移动（以我的经验）。

如何在构建时修复 "cannot find symbol" 错误？

How do I fix the "cannot find symbol" error while building?

java

android

kotlin

compiler-errors

build-error