Problems calling Android's getSharedPreferences(); from SQLiteOpenHelper class

First I want to describe my situation briefly.开发者_如何学JAVA

I have two classes, one MainClass and one DataBaseHelper class, which extends SQLiteOpenHelper.

From my MainClass I call a method in the DataBaseHelper class to open a data base. Before opening the data base I want to check the users data base version (this is important as soon as I want to update the data base and push it to the Android market). So from the DataBaseHelper class I call the following method, which is in the MainClass.

 public int checkCurrentDbVersion(){
        // Restore preferences
        SharedPreferences settings = getSharedPreferences(PREFERENCES, 0);
        int dbUpgradeVar = settings.getInt("dbUpgradeVar", 1);
        return dbUpgradeVar;        
    }

I call the checkCurrentDbVersion() method from the DataBaseHelper class like so:

    MainClass currentDbVersion = new MainClass(); 

    int oldDbVersion = currentDbVersion.checkCurrentDbVersion();

As soon as the debugger runs the following line, it stops.

SharedPreferences settings = getSharedPreferences(PREFERENCES, 0);

What am I doing wrong? I have no constructor defined. Could that be the failure?

Best Regards Johe

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I found a solution, which I wanna share. It can be found here:

Passing data through intents instead of constructors

I forgot the context (I am still not 100% sure what the context is all about, but anyways...).

So to get the code working I changed it like so:

 public int checkCurrentDbVersion(Context context){
        // Restore preferences
        SharedPreferences settings = context.getSharedPreferences(PREFERENCES, 0);
        int dbUpgradeVar = settings.getInt("dbUpgradeVar", 1);
        return dbUpgradeVar;        
    }

Call the method

private final Context myContext;

/*
*do some other stuff here
*/

    MainClass currentDbVersion = new MainClass(); 

    int oldDbVersion = currentDbVersion.checkCurrentDbVersion(myContext);

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Here is my solution 1.my app can not use.

import androidx.appcompat.app.AppCompatActivity;

SharedPreferences settings = new AppCompatActivity().getSharedPreferences(PREFERENCES, 0);

2.works fine in my app

    public static boolean isLoggedIn(AppCompatActivity activity) {
        final SharedPreferences loggedSP = activity.getSharedPreferences(SP_name.get_Logged_SPname(), MODE_PRIVATE);
        return loggedSP.getBoolean(SP_name.get_Logged_SPkey(),false);
    }

to execute it in my main activity

boolean a = LoginRepository.isLoggedIn(this);