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

Question

I'm new to Android Studio, since the past 3 months. Any ideas on my error below? Thanks! Notification will be receive once the status of rider application is equal to 0.

Below is my error, Service java class and model java class. I already call service in MainActivity.java but app crashes once entering MainActvity with errors below.

E/AndroidRuntime: FATAL EXCEPTION: main
              Process: com.example.mariamsyafiqah.coolblogserver, PID: 6206
              java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
                  at com.example.mariamsyafiqah.coolblogserver.Service.ListenRiderApplication.onChildAdded(ListenRiderApplication.java:56)
                  at com.google.android.gms.internal.zzbox.zza(Unknown Source)
                  at com.google.android.gms.internal.zzbqx.zzZS(Unknown Source)
                  at com.google.android.gms.internal.zzbra$1.run(Unknown Source)
                  at android.os.Handler.handleCallback(Handler.java:751)
                  at android.os.Handler.dispatchMessage(Handler.java:95)
                  at android.os.Looper.loop(Looper.java:154)
                  at android.app.ActivityThread.main(ActivityThread.java:6119)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

ListenRiderApplication.java

public class ListenRiderApplication extends Service implements ChildEventListener {
FirebaseDatabase db;
DatabaseReference riderApplication;

@Override
public void onCreate() {
    super.onCreate();
    db = FirebaseDatabase.getInstance();
    riderApplication = db.getReference("Rider");
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    riderApplication.addChildEventListener(this);
    return super.onStartCommand(intent, flags, startId);
}

public ListenRiderApplication() {
}

@Override
public IBinder onBind(Intent intent) {
    return null;
}

@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
    //Trigger here
    RiderApplication request = dataSnapshot.getValue(RiderApplication.class);
    if(request.getStatus().equals("0"))
        showNotification(dataSnapshot.getKey(), request);
}

private void showNotification(String key, RiderApplication request) {
    Intent intent = new Intent(getBaseContext(), RiderAppStatus.class);
    //intent.putExtra("userPhone", request.getPhone());
    PendingIntent contentIntent = PendingIntent.getActivity(getBaseContext(),0,intent,0);

    NotificationCompat.Builder builder = new NotificationCompat.Builder(getBaseContext());

    builder.setAutoCancel(true)
            .setDefaults(Notification.DEFAULT_ALL)
            .setTicker("Rider Coolblog")
            .setContentInfo("New rider registration")
            .setContentText("You have new rider registered #"+key)
            .setSmallIcon(R.mipmap.ic_launcher)
            .setContentIntent(contentIntent);

    NotificationManager manager = (NotificationManager)getBaseContext().getSystemService(Context.NOTIFICATION_SERVICE);

    //If you want to many notification show, you need to give uniqie ID for each Notification
    int randomInt = new Random().nextInt(9999-1)+1;
    manager.notify(randomInt,builder.build());

}

@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {

}

@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {

}

@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {

}

@Override
public void onCancelled(DatabaseError databaseError) {

}
}

RiderApplication.java

public class RiderApplication {
private String phone, name, availability, noPlate;
private String status;

public RiderApplication() {}

public RiderApplication(String phone, String availability, String name, String noPlate) {
    this.phone = phone;
    this.availability = availability;
    this.name = name;
    this.noPlate = noPlate;
    this.status = "0";
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public String getStatus() { return status; }
public void setStatus(String status) { this.status = status; }

public String getAvailability() {
    return availability;
}

public void setAvailability(String availability) {
    this.availability = availability;
}

public String getNoPlate() {
    return noPlate;
}

public void setNoPlate(String noPlate) {
    this.noPlate = noPlate;
}
}

Answer 1

Try following code in onChildAdded method

if(request.getStatus()!=null && request.getStatus().equals("0"))
        showNotification(dataSnapshot.getKey(), request);