java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.auth.FirebaseUser.getUid()'

Question

Process: com.example.vicevirus.myapplication, PID: 13471  
    java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.auth.FirebaseUser.getUid()' on a null object reference
              at com.example.vicevirus.myapplication.RegisterActivity$1.onComplete(RegisterActivity.java:48)
              at com.google.android.gms.tasks.zzc$1.run(Unknown Source)
              at android.os.Handler.handleCallback(Handler.java:751)
              at android.os.Handler.dispatchMessage(Handler.java:95)
              at android.os.Looper.loop(Looper.java:154)
              at android.app.ActivityThread.main(ActivityThread.java:6119)
              at java.lang.reflect.Method.invoke(Native Method)
              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

This is on android monitor. How do I solve this?

package com.example.vicevirus.myapplication;

import android.app.ProgressDialog;
         import android.support.annotation.NonNull;
         import android.support.v7.app.AppCompatActivity;
         import android.os.Bundle;
         import android.view.View;
         import android.widget.EditText;
         import android.widget.Toast;
         import com.google.android.gms.tasks.OnCompleteListener;
         import com.google.android.gms.tasks.OnSuccessListener;
         import com.google.android.gms.tasks.Task;
         import com.google.firebase.auth.AuthResult;
         import com.google.firebase.auth.FirebaseAuth;
         import com.google.firebase.database.DatabaseReference;
         import com.google.firebase.database.FirebaseDatabase;

public class RegisterActivity extends AppCompatActivity {
    private EditText email,name,password;
    DatabaseReference databaseReference;
    FirebaseAuth mAuth;
    private DatabaseReference userIdRef;
    ProgressDialog registerDialog;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_register);
        email=(EditText)findViewById(R.id.email);
        name=(EditText)findViewById(R.id.name);
        password=(EditText)findViewById(R.id.password);
        databaseReference= FirebaseDatabase.getInstance().getReference().child("chat_users");
        mAuth=FirebaseAuth.getInstance();
        registerDialog=new ProgressDialog(this);
        registerDialog.setMessage("Registering..");
    }
    public void submit(View view) {
        registerDialog.show();
        mAuth.createUserWithEmailAndPassword(email.getText().toString(),password.getText().toString()).addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
            @Override
            public void onComplete(@NonNull Task<AuthResult> task) {
                if(task.isComplete())
                {
                    registerDialog.dismiss();
                    Toast.makeText(getApplicationContext(),"Registered successfully",Toast.LENGTH_SHORT).show();
                    userIdRef=databaseReference.child(mAuth.getCurrentUser().getUid());
                    userIdRef.child("name").setValue(name.getText().toString());
                    finish();
                }
                registerDialog.dismiss();
            }
        });
    }
}

mAuth.getCurrentUser() returns null which is why you get the NullPointerException — M0CH1R0N, Jul 07 '17 at 21:45
sorry i dont quite understand can u please explain it in details? im quite new to this — vicevirus, Jul 07 '17 at 21:54

score 8 · Accepted Answer · answered Jul 07 '17 at 22:05

8

The problem seems to be that your user is not yet logged in or even registered. So calling mAuth.getCurrentUser() returns null.

Check out this page of the FireBase documentation about how you need to implement the registering of users. It could be that this is failing. The check task.isSuccessful() is necessary to check this.

answered Jul 07 '17 at 22:05

M0CH1R0N

756
9
19

tqvm it worked now – vicevirus Jul 07 '17 at 23:58
Could you mark this as the answer if it helped you. – M0CH1R0N Jul 08 '17 at 08:42

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.google.firebase.auth.FirebaseUser.getUid()'

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