Cannot resolve symbol in findViewById()

Question

I've looked through various other similar posts, but cannot figure out why I'm getting this issue.

Here's the xml file-

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.apple.nooneleftbehind.RecordPackage.AllRecordsActivity">


    <ListView
        android:id="@+id/list_view_for_me"
        android:layout_width="0dp"
        android:layout_height="0dp"
        tools:layout_constraintTop_creator="1"
        tools:layout_constraintRight_creator="1"
        tools:layout_constraintBottom_creator="1"
        android:layout_marginStart="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        android:layout_marginEnd="8dp"
        app:layout_constraintRight_toRightOf="parent"
        android:layout_marginTop="8dp"
        tools:layout_constraintLeft_creator="1"
        android:layout_marginBottom="8dp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>

The Activity that I'm using (AllRecordsActivity) is inside a package called RecordPackage. Which seems quite alright in the tools:context definition of the xml file.

Here's my Activity-

package com.example.apple.nooneleftbehind.RecordPackage;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;

import com.example.apple.nooneleftbehind.R;
import com.firebase.ui.database.FirebaseListAdapter;
import com.google.firebase.database.ChildEventListener;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

import java.util.ArrayList;

public class AllRecordsActivity extends AppCompatActivity {

    private ListView mRecordsListView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_all_records);

        mRecordsListView = (ListView) findViewById(R.id.list_view_for_me); //This line has the unresolved symbol error for list_view_for_me
    }
}

Answer 1

there is no error so first clean your project than rebuild your project when it happens again.

Answer 2

Try Clean Project then Rebuild Project.