DataSnapshot value doesn't get stored in the variable

Question

I'm trying to get a boolean value from firebase database into my Android application. I've got it in a boolean variable but when I use this boolean value, it says a null object reference.

I'm trying to start a particular Intent based on the data in the firebase database. But It gives me this following error


public class SplashScreen extends AppCompatActivity {

Boolean rec_res;
@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_splash_screen);
        FirebaseDatabase database = FirebaseDatabase.getInstance();
        DatabaseReference rootRef = database.getReference();

        rootRef.child("rec_res").addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                rec_res = dataSnapshot.getValue(Boolean.class);
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });

        int SPLASH_TIME_OUT = 2000;
        new Handler().postDelayed(new Runnable() {

            /*
             * Showing splash screen with a timer. This will be useful when you
             * want to show case your app logo / company
             */

            @Override
            public void run() {
                // This method will be executed once the timer is over
                // Start your app main activity



                ConnectivityManager connectivityManager
                        = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
                NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
                boolean isConnected = activeNetworkInfo != null && activeNetworkInfo.isConnected();


               /* if(String.valueOf(rec_res).equals("true")) {
                    Intent k = new Intent(SplashScreen.this, RecruitRegActivity.class);
                    startActivity(k);
                }*/

                if (rec_res && isConnected) {

                        Intent i = new Intent(SplashScreen.this, RecruitRegActivity.class);
                        startActivity(i);

                } else if(!isConnected){
                    Intent i = new Intent(SplashScreen.this, NoInternet.class);
                    startActivity(i);
                } else {
                    Intent i = new Intent(SplashScreen.this, HomePage.class);
                    startActivity(i);
                }

                // close this activity
                finish();
            }
        }, SPLASH_TIME_OUT);

This is the error I get

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.smec.tam, PID: 12815
    java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.Boolean.booleanValue()' on a null object reference
        at com.smec.tam.SplashScreen$2.run(SplashScreen.java:99)
        at android.os.Handler.handleCallback(Handler.java:751)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:154)
        at android.app.ActivityThread.main(ActivityThread.java:6316)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:872)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:762)

You are trying to use the value of `rec_res` before it has been set. Move your "start intent" logic inside the `onDataChange` event handler — samthecodingman, Dec 30 '19 at 15:19
Check this link below ........... https://stackoverflow.com/a/46998849/7209777 — Hagar Magdy, Dec 30 '19 at 15:21

score 0 · Accepted Answer · answered Dec 30 '19 at 15:24

The problem is that you are doing this if (rec_res && isConnected) before your task is completed, so that's why it throws a NullPointerException.

You can put your logic inside the onDataChange so you'll do the logic once your task is done and you have initialised your rec_res stuff.

rootRef.child("rec_res").addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                rec_res = dataSnapshot.getValue(Boolean.class);
                int SPLASH_TIME_OUT = 2000;
        new Handler().postDelayed(new Runnable() {

            /*
             * Showing splash screen with a timer. This will be useful when you
             * want to show case your app logo / company
             */

            @Override
            public void run() {
                // This method will be executed once the timer is over
                // Start your app main activity



                ConnectivityManager connectivityManager
                        = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
                NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
                boolean isConnected = activeNetworkInfo != null && activeNetworkInfo.isConnected();


               /* if(String.valueOf(rec_res).equals("true")) {
                    Intent k = new Intent(SplashScreen.this, RecruitRegActivity.class);
                    startActivity(k);
                }*/

                if (rec_res && isConnected) {

                        Intent i = new Intent(SplashScreen.this, RecruitRegActivity.class);
                        startActivity(i);

                } else if(!isConnected){
                    Intent i = new Intent(SplashScreen.this, NoInternet.class);
                    startActivity(i);
                } else {
                    Intent i = new Intent(SplashScreen.this, HomePage.class);
                    startActivity(i);
                }

                // close this activity
                finish();
            }
        }, SPLASH_TIME_OUT);
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });

DataSnapshot value doesn't get stored in the variable

1 Answers1