RecyclerView“无法解析符号"错误-Android Studio

我无法解决所有RecyclerView上的符号错误.到底是怎么回事?由于RecyclerView出现错误，因此LayoutManager上也出现了错误.我的最后四个Override语句在错误的位置，我不知道该去哪里.我是一个初学者，并且具有非常基础的编程知识，所以我不知道如何解决此问题.我正在上课，但教授根本没有帮助.

I am getting cannot resolve symbol errors on all my RecyclerView's. What is going on? Because I have an error with RecyclerView, I also have errors on LayoutManager. My last four Override statements are in the wrong place and I don't know where they go. I am a beginner and have a very basic knowledge of programming so I don't know how to fix this. I am taking a class but the professor isn't helpful at all.

package com.bignerdranch.android.criminalintent;

import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.CheckBox;
import android.widget.TextView;
import android.widget.Toast;

import java.util.List;


public class CrimeListFragment extends Fragment {

    private RecyclerView mCrimeRecyclerView;
    private CrimeAdapter mAdapter;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_crime_list, container, false);

        mCrimeRecyclerView = (RecyclerView) view
                .findViewById(R.id.crime_recycler_view);
        mCrimeRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));

        return view;
    }

    @Override
    public void onResume() {
        super.onResume();
        updateUI();
    }

    private void updateUI(){
        CrimeLab crimeLab = CrimeLab.get(getActivity());
        List<Crime> crimes = crimeLab.getCrimes();

        if (mAdapter == null) {
            mAdapter = new CrimeAdapter(crimes);
            mCrimeRecyclerView.setAdapter(mAdapter);
        } else {
            mAdapter.notifyDataSetChanged();
        }
    }
        private class CrimeAdapter extends RecyclerView.Adapter<CrimeHolder> {
            private List<Crime> mCrimes;
            public CrimeAdapter(List<Crime> crimes) {
                mCrimes = crimes;
            }
        }
        private class CrimeHolder extends RecyclerView.ViewHolder
                implements View.OnClickListener {
            private TextView mTitleTextView;
            private TextView mDateTextView;
            private CheckBox mSolvedCheckBox;
            private Crime mCrime;

            public CrimeHolder(View itemView) {
                super(itemView);

                mTitleTextView = (TextView)
                        itemView.findViewById(R.id.list_item_crime_title_text_view);
                mDateTextView = (TextView)
                        itemView.findViewById(R.id.list_item_crime_date_text_view);
                mSolvedCheckBox = (CheckBox)
                        itemView.findViewById(R.id.list_item_crime_solved_check_box);
            }

            public void bindCrime(Crime crime) {
                mCrime = crime;
                mTitleTextView.setText(mCrime.getTitle());
                mDateTextView.setText(mCrime.getDate().toString());
                mSolvedCheckBox.setChecked(mCrime.isSolved());
            }

            @Override
            public CrimeHolder onCreateViewHolder(ViewGroup parent, int viewType) {
                LayoutInflater layoutInflater = LayoutInflater.from(getActivity());
                View view = layoutInflater.inflate(R.layout.list_item_crime, parent, false);
                return new CrimeHolder(view);
            }

            @Override
            public void onBindViewHolder(CrimeHolder holder, int position) {
                Crime crime = mCrimes.get(position);
                holder.bindCrime(crime);
            }

            @Override
            public int getItemCount() {
                return mCrimes.size();
            }

            @Override
            public void onClick(View v) {
                Intent intent = CrimeActivity.newIntent(getActivity(), mCrime.getId());
                startActivity(intent);
            }
        }
}