How to fix app crash caused due to attempt of reading field from a null reference?

Question

I am creating a sample app that sends notification to the driver when a rider requests pickup (like the uber app) I have a button for that functionality in the app.The app works fine and gets the driver but when i click on the button to call the driver the app crashes showing a nullpointerexception at if (response.body().success == 1) Toast.makeText(Home.this, "Request Failed!", Toast.LENGTH_SHORT).show();

this is the code

private void sendRequestToDriver(String driverId) {

    DatabaseReference tokens = FirebaseDatabase.getInstance().getReference(Common.token_tbl);

    tokens.orderByKey().equalTo(driverId)
            .addListenerForSingleValueEvent(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    for (DataSnapshot postSnapshot:dataSnapshot.getChildren())
                    {
                        Token token = postSnapshot.getValue(Token.class);

                        String json_lat_lng = new Gson().toJson(new LatLng(mLastLocation.getLatitude(),mLastLocation.getLongitude()));

                        Notification data = new Notification("SKYLAKE",json_lat_lng);
                        Sender content = null;
                        if (token != null) {
                            content = new Sender(token.getToken(),data);
                        }

                        mService.sendMessage(content)
                                .enqueue(new Callback<FCMResponse>() {
                                    @Override
                                    public void onResponse(@NonNull Call<FCMResponse> call, Response<FCMResponse> response) {

                                        if (response.body().success == 1)
                                            Toast.makeText(Home.this, "Request Failed!", Toast.LENGTH_SHORT).show();
                                        else {
                                            Toast.makeText(Home.this, "Request Sent!", Toast.LENGTH_SHORT).show();
                                        }
                                    }

                                    @Override
                                    public void onFailure(Call<FCMResponse> call, Throwable t) {
                                        Log.e("ERROR",t.getMessage());

                                    }
                                });
                    }
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });
}

ERROR LOG

03-23 16:46:35.606 18150-18150/com.joy.skylake.enlyftrider E/UncaughtException: java.lang.NullPointerException: Attempt to read from field 'int com.joy.skylake.enlyftrider.Model.FCMResponse.success' on a null object reference
at com.joy.skylake.enlyftrider.Home$3$1.onResponse(Home.java:192)
at retrofit2.ExecutorCallAdapterFactory$ExecutorCallbackCall$1$1.run(ExecutorCallAdapterFactory.java:70)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5438)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:762)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:652)

check whether `response` and `response.body()` are null before trying to access their member. — DrNachtschatten, Mar 23 '18 at 11:46
Are you debug what is the value of `response.body().success`. — Ekta Bhawsar, Mar 23 '18 at 11:46
public interface IFCMService { @Headers({ "Content-Type:application/json", "Authorization:key=MyAuthorizationKey" }) @POST("fcm/send") Call sendMessage(@Body Sender body); } — Joy Dey, Mar 23 '18 at 11:49
Possible duplicate of [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — ADM, Mar 23 '18 at 11:51
You can check the value of `response.body().success` by showing a toast and It should be an integer. If it is a string then firstly you parse this string to integer. — Ekta Bhawsar, Mar 23 '18 at 11:53
So, did you get what value is having `response.body().success` — Ekta Bhawsar, Mar 23 '18 at 11:57

score 0 · Answer 1 · answered Mar 23 '18 at 11:58

0

if (response.body() != null && response.body().success == 1) {
   ...
}

answered Mar 23 '18 at 11:58

y.allam

1,446
13
24

Please provide some explanation to your answers to give context to the code – Ricardo Mar 23 '18 at 14:13

Ekta Bhawsar · Answer 2 · 2018-03-23T12:41:23.117

0

You can try yoda condition Yoda Conditions

if (null != response.body() && 1 == response.body().success) {
   ...
}

Error Code 400 means an Invalid JSON in your request.

Please check this possible duplicate

edited Mar 23 '18 at 12:41

answered Mar 23 '18 at 12:07

Ekta Bhawsar

746
11
26

it seems the body is still null. I have another app that should receive a notification once the request is sent but the notification isnt comming – Joy Dey Mar 23 '18 at 12:34
yup body is null and code = 400. please check my updated answer. it has a link. – Ekta Bhawsar Mar 23 '18 at 12:42
what should i change to fix it? – Joy Dey Mar 23 '18 at 12:48
See your message is blank. – Ekta Bhawsar Mar 23 '18 at 12:50
no its not. as i said i hve two apps (like uber driver and uber rider) when one clicks on Request Driver it sends a request to the driver app and this activity would start. the code is here http://txt.do/dg70p – Joy Dey Mar 23 '18 at 12:57
I'll be greatful to you if you kindly help me in sorting out this. – Joy Dey Mar 23 '18 at 13:06

How to fix app crash caused due to attempt of reading field from a null reference?

2 Answers2