login to firebase in kotlin android studio

Question

I'm using firebase in my android project. But this is what get when user trying to sign up in firebase using my application.

My errors log

09-15 13:54:23.992 2716-2716/com.example.err0r1096.tikteck E/AndroidRuntime: FATAL EXCEPTION: main
                                                                         Process: com.example.err0r1096.tikteck, PID: 2716

java.lang.IllegalStateException: Could not execute method for android:onClick
     at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
     at android.view.View.performClick(View.java:5637)
     at android.view.View$PerformClick.run(View.java:22429)
     at android.os.Handler.handleCallback(Handler.java:751)
     at android.os.Handler.dispatchMessage(Handler.java:95)
     at android.os.Looper.loop(Looper.java:154)
     at android.app.ActivityThread.main(ActivityThread.java:6119)
     at java.lang.reflect.Method.invoke(Native Method)
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
  Caused by: java.lang.reflect.InvocationTargetException
     at java.lang.reflect.Method.invoke(Native Method)
     at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
     at android.view.View.performClick(View.java:5637) 
     at android.view.View$PerformClick.run(View.java:22429) 
     at android.os.Handler.handleCallback(Handler.java:751) 
     at android.os.Handler.dispatchMessage(Handler.java:95) 
     at android.os.Looper.loop(Looper.java:154) 
     at android.app.ActivityThread.main(ActivityThread.java:6119) 
     at java.lang.reflect.Method.invoke(Native Method) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 
  Caused by: kotlin.KotlinNullPointerException
     at com.example.err0r1096.tikteck.Login.LoginToFireBase(Login.kt:26)
     at com.example.err0r1096.tikteck.Login.OneC(Login.kt:20)
     at java.lang.reflect.Method.invoke(Native Method) 
     at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
     at android.view.View.performClick(View.java:5637) 
     at android.view.View$PerformClick.run(View.java:22429) 
     at android.os.Handler.handleCallback(Handler.java:751) 
     at android.os.Handler.dispatchMessage(Handler.java:95) 
     at android.os.Looper.loop(Looper.java:154) 
     at android.app.ActivityThread.main(ActivityThread.java:6119) 
     at java.lang.reflect.Method.invoke(Native Method) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

and this my code :

package com.example.err0r1096.tikteck

import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.Toast
import com.google.firebase.auth.FirebaseAuth
import kotlinx.android.synthetic.main.activity_login.*


class Login : AppCompatActivity() {

    private val mAuth: FirebaseAuth? = null
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_login)
    }
    fun OneC(view: View){

        LoginToFireBase(etEmail.text.toString(),etPassword.text.toString())

    }

    fun LoginToFireBase(email:String,password:String){

        mAuth!!.createUserWithEmailAndPassword(email,password)
                .addOnCompleteListener(this){ task ->

                    if (task.isSuccessful){
                        Toast.makeText(applicationContext,"Successful login",Toast.LENGTH_LONG).show()
}
                else
                {
                    Toast.makeText(this,"Login UnSuccessful",Toast.LENGTH_LONG).show()
                }
        }
    }
}

My application is crashing when user click on start button .

I think the problem is in my code and not on the firebase.

Your code is throwing a `NullPointerException` on `LoginToFireBase(Login.kt:26)`. Did you initialize `mAuth` anywhere? If not, the [`mAuth!!` will throw a `NullPointerException`](https://stackoverflow.com/questions/34342413/what-is-the-kotlin-double-bang). — Frank van Puffelen, Sep 15 '17 at 10:36
"mAuth!!" - try to never use it, if you're not 100% sure it's not null. Also avoid nullable objects as much as possible. This will lead to much cleaner and crash-free code. — Pavlo Zin, Sep 15 '17 at 11:13

score 0 · Answer 1 · edited Jun 20 '20 at 09:12

You can check the official doc:

Kotlin's type system is aimed to eliminate NullPointerException's from our code. The only possible causes of NPE's may be:

An explicit call to throw NullPointerException();

Usage of the !! operator that is described below;

External Java code has caused it;

There's some data inconsistency with regard to initialization (an uninitialized this available in a constructor is used somewhere).

Using: b!! it will return a non-null value of b or throw an NPE if b is null

Check your code (you are using kotlin as java)

mAuth!!.createUserWithEmailAndPassword(email,password)

Did you initialize mAuth anywhere? If not, the mAuth!! will throw a NullPointerException

score 0 · Answer 2 · answered Jan 06 '18 at 07:02

Try declaring the widgets by,

fun onC (view: View) {
val emailTxt = findViewById<View>(R.id.etEmail) as EditText
val passwordTxt = findViewById<View>(R.id.etPassword) as EditText
val email = emailTxt.text.toString.trim()
val password = passwordTxt.text.toString.trim()
LoginToFireBase (email, password)
}

This may resolve your problem :)

login to firebase in kotlin android studio

2 Answers2