Getting Null pointer exception while running my app

Question

Following is the error that I am getting while running my app. My app crashes only when I am trying to open my room activity. Hereby attaching my logcat result and room activity code for your persual........................................... .............................................................................................

    Process: com.example.tictactoe, PID: 5976
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.tictactoe/com.example.tictactoe.RoomActivity}: java.lang.NullPointerException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3616)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3780)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2251)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:233)
        at android.app.ActivityThread.main(ActivityThread.java:8068)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:631)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:978)
     Caused by: java.lang.NullPointerException
        at com.example.tictactoe.RoomActivity.onCreate(RoomActivity.kt:22)
        at android.app.Activity.performCreate(Activity.java:8006)
        at android.app.Activity.performCreate(Activity.java:7990)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1329)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3589`

Room Activity looks like this

package com.example.tictactoe

import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Toast
import com.google.firebase.auth.FirebaseAuth
import com.google.firebase.database.FirebaseDatabase
import kotlinx.android.synthetic.main.activity_room.*


class RoomActivity : AppCompatActivity() {


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_room)
        var mAuth: FirebaseAuth?=null // my authnetication variable

        var database = FirebaseDatabase.getInstance()
        var myRef = database.reference
        var currentUser = mAuth!!.currentUser
        mAuth = FirebaseAuth.getInstance()
        buLoginEvent()
    }

    fun buLoginEvent(){
       LoginToFirebase(email.text.toString(), password.text.toString());

    }

    fun LoginToFirebase(email:String, password:String){
        var mAuth: FirebaseAuth?=null // my authnetication variable

        var database = FirebaseDatabase.getInstance()
        var myRef = database.reference
        var currentUser = mAuth!!.currentUser
        mAuth!!.createUserWithEmailAndPassword(email,password)
            .addOnCompleteListener(this){
                task->
                if(task.isSuccessful){
                    Toast.makeText(applicationContext,"Successfull Login", Toast.LENGTH_LONG).show()
                    //saving in database
                    myRef.child("Users").child(splitString(currentUser?.email.toString())).setValue(
                        currentUser?.uid
                    )//creating current node iin relatime database
                    LoadMain()
                }
                else{
                    Toast.makeText(applicationContext,"Failed Login", Toast.LENGTH_LONG).show()
                }
            }

    }

    override fun onStart() {//2nd time when the application is started then call this method
        super.onStart()
        LoadMain()
    }
    fun  LoadMain(){
        var mAuth: FirebaseAuth?=null // my authnetication variable

        var database = FirebaseDatabase.getInstance()
        var myRef = database.reference
        var currentUser = mAuth!!.currentUser

        if(currentUser!=null) {// doing this only when the user is not null


            var intent = Intent(this, OnlineGameActivity::class.java)
            intent.putExtra("email", currentUser!!.email)
            intent.putExtra("uid", currentUser!!.uid)

            startActivity(intent)
            finish()
        }
    }
    fun splitString(str:String):String{
        var split=str.split("@")
        return split[0]
    }
}

score 0 · Answer 1 · answered Jan 19 '22 at 06:22

0

Please initialize mAuth before use it thatswhy you are getting this exception,also check the json file have you put in app directory or not from firebase account where you have registered the app with package,and please try the below way may help you

var mAuth: FirebaseAuth?=null // my authnetication variable

    var database = FirebaseDatabase.getInstance()
    var myRef = database.reference
    mAuth = FirebaseAuth.getInstance()
    var currentUser = mAuth!!.currentUser

answered Jan 19 '22 at 06:22

gpuser

1,143
1
9
6

Tried doing it but still getting the error – Divyanshu Dobriyal Jan 19 '22 at 06:51
Please try to flow and call this in asynchtask doinbackground and then process next in onPostExecute method,,, you can use any loader here may help you – gpuser Jan 27 '22 at 13:26

score 0 · Answer 2 · answered Jan 19 '22 at 07:40

you are creating null variable named mAuth

var mAuth: FirebaseAuth?=null // my authnetication variable

few lines below you are trying to get user from this instance with line

var currentUser = mAuth!!.currentUser

!! means "this variable isn't null for shure". but it is always. you are getting FirebaseAuth instance in next line. just initialize mAuth at the beginning before using any method of it

val mAuth: FirebaseAuth = FirebaseAuth.getInstance() // my authnetication variable
...
var currentUser = mAuth!!.currentUser // !! is redundant in here

same problem is in LoginToFirebase and LoadMain methods - trying to call method of null object (not initialized mAuth in all cases)

Getting Null pointer exception while running my app

2 Answers2