Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference at

Question

 This is the errror, tried a few things but still to no avail.

java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference at com.dllibrary.cart.SigninMainActivity$1$1.onDataChange(SigninMainActivity.java:56) at com.google.android.gms.internal.zzegf.zza(Unknown Source) at com.google.android.gms.internal.zzeia.zzbyc(Unknown Source) at com.google.android.gms.internal.zzeig.run(Unknown Source) at android.os.Handler.handleCallback(Handler.java:815) at android.os.Handler.dispatchMessage(Handler.java:104) at android.os.Looper.loop(Looper.java:194) at android.app.ActivityThread.main(ActivityThread.java:5637) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:960) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)

code for my sign in method

     signin.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

           final ProgressDialog mdialog = new       ProgressDialog(SigninMainActivity.this);
            mdialog.setMessage("Please waiting");
            mdialog.show();
            table_user.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    //check if user not exist
                    if (dataSnapshot.child(phone.getText().toString()).exists()) {
                        //Get User Information
                        mdialog.dismiss();

                        User user = dataSnapshot.child(phone.getText().toString()).getValue(User.class);
                       if (user.getPassword().equals(password.getText().toString())) {
                            Intent homeIntent= new Intent(SigninMainActivity.this, home.class);
                            Common.currentUser = user;
                            startActivity(homeIntent);
                            finish();
                        } else {

                            Toast.makeText(SigninMainActivity.this, "Sign in failed", Toast.LENGTH_SHORT).show();


                        }
                    }else{
                        mdialog.dismiss();
                        Toast.makeText(SigninMainActivity.this, "User Does Not exist", Toast.LENGTH_SHORT).show();
                    }
                }

line 56 is at "if(user.getPassword.equals)"

Try to use if ( user.getPassword() != null && password.getText() != null && user.getPassword().equals(password.getText().toString())) instead of if (user.getPassword().equals(password.getText().toString())) — Prathibha Chiranthana, Feb 08 '18 at 07:19
https://stackoverflow.com/questions/44873766/null-pointer-exception-attempt-to-invoke-virtual-method-void?rq=1 — Prathibha Chiranthana, Feb 08 '18 at 07:25

score 2 · Accepted Answer · answered Feb 08 '18 at 07:22

Check the below code I implement with the change I expected.

    signin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

               final ProgressDialog mdialog = new       ProgressDialog(SigninMainActivity.this);
                mdialog.setMessage("Please waiting");
                mdialog.show();
                table_user.addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {
                        //check if user not exist
                        if (dataSnapshot.child(phone.getText().toString()).exists()) {
                            //Get User Information
                            mdialog.dismiss();

                            User user = dataSnapshot.child(phone.getText().toString()).getValue(User.class);
//Check the null
                           if (user.getPassword() != null && password.getText() != null && user.getPassword().equals(password.getText().toString())) {
                                Intent homeIntent= new Intent(SigninMainActivity.this, home.class);
                                Common.currentUser = user;
                                startActivity(homeIntent);
                                finish();
                            } else {

                                Toast.makeText(SigninMainActivity.this, "Sign in failed", Toast.LENGTH_SHORT).show();


                            }
                        }else{
                            mdialog.dismiss();
                            Toast.makeText(SigninMainActivity.this, "User Does Not exist", Toast.LENGTH_SHORT).show();
                        }
                    }

score 2 · Answer 2 · answered Feb 08 '18 at 07:32

The following error:

Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference

Tells you what is all about. It means that in this line of code:

if (user.getPassword().equals(password.getText().toString()))

That exists at line 56, user.getPassword() returns null.

This is happening because the User object that you are trying to get from the database has the value of null. So to solve this, make sure you get the correct User object. Also, check this object for nullity before actually using it:

if(user != null) {}

Good point @alex, thanks for the precise explanation, on how i can approach the process once more. — Dalton Kim, Feb 08 '18 at 07:47

Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference at

2 Answers2