Android SQLiteOpenHelper Error - Call to super must be the first statement in contructor

Question

Let me start by saying that before asking this question, I have already read many similar questions, but I couldn't find any possible solution for my situation.

I am trying to extend SQLiteOpenHelper class, but with 2 significant differences -

I am using SQLCipher (using it doesn't bother, if I use super on the top in constructor)
I am getting my database location from SharedPreferences (this is why, I have to put it before super)

For e.g., following constructor works fine (I have excluded the imports and functions which are not relevant to my question)-

import net.sqlcipher.Cursor;
import net.sqlcipher.SQLException;
import net.sqlcipher.database.SQLiteDatabase;
import net.sqlcipher.database.SQLiteOpenHelper;

public class LocalDBHelper extends SQLiteOpenHelper {
    public static String DB_LOCAL_NAME = "localdata.db";
    public static SQLiteDatabase myDataBase;
    private final Context myContext;

    public LocalDBHelper(Context context) {
        super(context, Environment.getExternalStorageDirectory().toString()+File.separator + "myFolder"
                + "/" + DB_LOCAL_NAME, null, 1);
        this.myContext = context;
        SQLiteDatabase.loadLibs(context);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int i, int i1) {
        onCreate(db);
    }
}

But, in my case, I want to allow the database location to be variable (e.g. user can use it from Downloads folder or if user does not give permission to use external storage(as in case of Android 6.0), then use internal storage or use getExternalFilesDir() depending upon the situation) -> So, long thing short, I am saving database location in Shared Preferences, and tried to use it by modifying the constructor as following -

public QuestionBankDBHelper(Context context) {
        SharedPreferences getPrefs = PreferenceManager
                .getDefaultSharedPreferences(NoContextAvailable); //What should I use here for the context ?
        String getDBLocation = getPrefs.getString("MY_DATABASE_LOCATION", Environment.getExternalStorageDirectory().toString()+File.separator + "myFolder"
                + "/" + DB_LOCAL_NAME);
        super(context, getDBLocation, null, 1);
        this.myContext = context;
        SQLiteDatabase.loadLibs(context);
    }

Obviously the above modified constructor doesn't work, and gives following two errors -

What Context can be used with getDefaultSharedPreferences?
Call to super must be the first statement in Constructor.

Even after a lot of trials and search, I couldn't figure how to work around these two problems, and have my database location as variable.

Oleg Khalidov · Accepted Answer · 2016-05-10T07:45:18.500

3

move getDBLocation code into a static method:

private static String getDBLocation(Context context) {
    SharedPreferences getPrefs = PreferenceManager.getDefaultSharedPreferences(context);
    String getDBLocation = getPrefs.getString("MY_DATABASE_LOCATION", 
            Environment.getExternalStorageDirectory().toString() 
                + File.separator + "myFolder" + "/" + DB_LOCAL_NAME);
    return getDBLocation;
}

public QuestionBankDBHelper(Context context) {
    super(context, getDBLocation(context), null, 1);
    this.myContext = context;
    SQLiteDatabase.loadLibs(context);
}

edited May 10 '16 at 07:45

answered May 10 '16 at 07:10

Oleg Khalidov

5,108
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What should be the context of `getDefaultSharedPreferences`, I can't seem to use, `myContext` in a static function. – Dr. Atul Tiwari May 10 '16 at 07:12
@OlegKhalidov Thanks for the updated answer, I am testing it now, and will get back to you shortly. – Dr. Atul Tiwari May 10 '16 at 07:19
@OlegKhalidov It worked, thanks. I think you forgot to add `return getDBLocation;` in the static method – Dr. Atul Tiwari May 10 '16 at 07:35

score 2 · Answer 2 · answered May 10 '16 at 07:12

Simple answer:

create static function that accepts context as parameter and returns DB path
Put super as the first statement and use static function return as path parameter

The proper solution would be to remove any kind of knowledge about finding the path to database in this class. Before you construct this class you should do all checks, calculations, questions and only call constructor of this class with defined path

Android SQLiteOpenHelper Error - Call to super must be the first statement in contructor

2 Answers2