SQLiteDatabase.OpenDatabase 在 Fragment 中是 NullPointerException

Question

This works outside of fragment onCreateView but not in that static method.

SQLiteDatabase checkDB = SQLiteDatabase.openDatabase(path_to + DATABASE_NAME, null, SQLiteDatabase.OPEN_READWRITE);

I have a DataBaseHelper which is initialized outside the static method as

FeedReaderHelper mHelper = new FeedReaderHelper(this);

whereas for fragment, I use

if (getActivity() != null)
    FeedReaderHelper xHelper = new FeedReaderHelper(getActivity());
else
    Log.d(TAG, "Null");

I know that getActivity is not null and the error persists even if I only try to open and close the database. My logcat goes like this:

java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference

I don't get what Resources means here and how to avoid the error altogether.

Also, I've tried opening the database before onContentView is called; it still resolves to NullPointer upon checkDB.close

Answer 1

I was using FeedReederHelper only to call db.exec() statements whereupon the same Helper should have been used to open database without the hard-coded path in checkDB call. mHelper.getWriteableDatabase(); solved the issue.