Question

My On Boot Receiver keeps crashing :

   01-06 03:20:13.861: E/AndroidRuntime(15832): FATAL EXCEPTION: main
01-06 03:20:13.861: E/AndroidRuntime(15832): java.lang.RuntimeException: Unable to start receiver com.example.prva.OnBootReceiver: java.lang.NullPointerException
01-06 03:20:13.861: E/AndroidRuntime(15832):    at android.app.ActivityThread.handleReceiver(ActivityThread.java:2043)
01-06 03:20:13.861: E/AndroidRuntime(15832):    at android.app.ActivityThread.access$2400(ActivityThread.java:132)
01-06 03:20:13.861: E/AndroidRuntime(15832):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1098)
01-06 03:20:13.861: E/AndroidRuntime(15832):    at android.os.Handler.dispatchMessage(Handler.java:99)
01-06 03:20:13.861: E/AndroidRuntime(15832):    at android.os.Looper.loop(Looper.java:143)
01-06 03:20:13.861: E/AndroidRuntime(15832):    at android.app.ActivityThread.main(ActivityThread.java:4277)
01-06 03:20:13.861: E/AndroidRuntime(15832):    at java.lang.reflect.Method.invokeNative(Native Method)
01-06 03:20:13.861: E/AndroidRuntime(15832):    at java.lang.reflect.Method.invoke(Method.java:507)
01-06 03:20:13.861: E/AndroidRuntime(15832):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
01-06 03:20:13.861: E/AndroidRuntime(15832):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
01-06 03:20:13.861: E/AndroidRuntime(15832):    at dalvik.system.NativeStart.main(Native Method)
01-06 03:20:13.861: E/AndroidRuntime(15832): Caused by: java.lang.NullPointerException
01-06 03:20:13.861: E/AndroidRuntime(15832):    at com.example.prva.DatabaseManager.getAllData(DatabaseManager.java:91)
01-06 03:20:13.861: E/AndroidRuntime(15832):    at com.example.prva.OnBootReceiver.onReceive(OnBootReceiver.java:32)
01-06 03:20:13.861: E/AndroidRuntime(15832):    at android.app.ActivityThread.handleReceiver(ActivityThread.java:2028)
01-06 03:20:13.861: E/AndroidRuntime(15832):    ... 10 more

Broadcast receiver :

@Override
    public void onReceive(Context context, Intent intent) {
        // TODO Auto-generated method stub
        Calendar c2 = Calendar.getInstance();               
        int hour = c2.get(Calendar.HOUR_OF_DAY);
        int minute = c2.get(Calendar.MINUTE);
        int sek = c2.get(Calendar.SECOND);

        int dan;
        int dodaj;

        milivreme = ((hour * 60 * 60 * 1000)+ (minute * 60 * 1000) + (sek * 1000));

        Cursor cursor = DatabaseManager.getAllData();

        cursor.moveToFirst();
        if (!cursor.isAfterLast())
        {
            do
            {               
        milibaza = cursor.getInt(2);
        razlika = milibaza - milivreme;

        Intent intent1 = new Intent(context, AlarmReceiver.class);
        PendingIntent pendingintent = PendingIntent.getService(context, 3, intent1, PendingIntent.FLAG_CANCEL_CURRENT);
        AlarmManager am = (AlarmManager) context.getSystemService(context.ALARM_SERVICE);

        am.set(AlarmManager.RTC_WAKEUP, System.currentTimeMillis() + razlika, pendingintent);
            }
            while (cursor.moveToNext());
        }
        cursor.close(); 
    }

The getAllData method :

public static Cursor getAllData() {

        return db.query(TABLE_NAME, new String[] { TABLE_COLUMN_ID, TABLE_COLUMN_ONE, TABLE_COLUMN_TWO }, 
                null, null, null, null, null);       

    }   

Databse has records :

I have a button which displays last value from the database in a textview :

public void onClick(View v) {
                // TODO Auto-generated method stub
                String BazaDan;
                int BazaVrijeme;
                DatabaseManager.Cursoric();

                BazaDan = DatabaseManager.getDan();
                BazaVrijeme = DatabaseManager.getVrijeme();
                textbaza.setText(new StringBuilder(BazaDan).append(", ").append(BazaVrijeme).toString());
            }
        });

Method for Cursor that button is using :

public static void Cursoric(){

        Cursor cursor;
        cursor = db.query
                (
                        TABLE_NAME,
                        new String[] { TABLE_COLUMN_ID, TABLE_COLUMN_ONE, TABLE_COLUMN_TWO },                       
                        null, null, null, null, null
                );
        cursor.moveToFirst();
        if (!cursor.isAfterLast())
        {
            do
            {
                BazaDan = cursor.getString(1);
                BazaVrijeme = cursor.getInt(2);
            }
            while (cursor.moveToNext());
        }    

        cursor.close(); 
    }

As you can see its almost the same thing I’m using in BroadcastReceiver.
The textview after that button click displays from the database (last time I tested) :

1, 12120000 

Its day number, and miliseconds.

So records are being stored in the database, and they can be retrieved but OnBootReceiver keeps getting null pointer exception when booting while he is doing almost the same thing with cursor as that button.

Answer 1

as in log :

Caused by: java.lang.NullPointerException

because db instance is null inside getAllData method so just make null check before using it as :

public static Cursor getAllData()
{
       Cursor cursor=null;
    if(db!=null)
    {
      cursor=db.query(TABLE_NAME, new String[] 
              { TABLE_COLUMN_ID, TABLE_COLUMN_ONE, 
              TABLE_COLUMN_TWO }, null,
               null, null, null, null);
    }

return cursor;
}

and also check cursor for NULL before using it inside onReceive method of BroadcastReceiver