Android Studio “ Attempt To Invoke Virtual Method Android.database.cursor On A Null Object Reference” Problem

I built a gridview with SQLite database, and used cursor to uptade Imageview. It worked well in my last project, but when I combine it with customized toolbar,error shows up java

Solution 1:

Your AddNewMedicine.sqLiteHelper is null & that's why you're getting NullPointerException(Because your AddNewMedicine is already destroyed).

You should create new instance of SqLiteHelper in MainActivity instead.

So replace

Cursorcursor= AddNewMedicine.sqLiteHelper.getData("SELECT * FROM MEDICINE");

to

SQLiteHelpersqLiteHelper=newSQLiteHelper(this, "MedicineDB.sqlite", null, 1);
Cursorcursor= sqLiteHelper.getData("SELECT * FROM MEDICINE");