Question

I know how to do SQLite Database, when doing it specifically in its own dedicated java class. But whenever i want it to be inside of something, in this case, an Intent Service, it always give me errors, and i can’t debug it.

package my.skul;


    import android.app.IntentService;
    import android.app.Notification;
    import android.app.NotificationManager;
    import android.app.PendingIntent;
    import android.content.Context;
    import android.content.Intent;
    import android.database.Cursor;
    import android.database.sqlite.SQLiteDatabase;
    import android.database.sqlite.SQLiteOpenHelper;

    public class CheckClassroom extends IntentService {

                /**
                 * A constructor is required, and must call the super IntentService(String)
                 * constructor with a name for the worker thread.
                 */
                public CheckClassroom() {
                    super("CheckClassroom");
                }

                /**
                 * The IntentService calls this method from the default worker thread with
                 * the intent that started the service. When this method returns,
                 * IntentService stops the service, as appropriate.
                 */
                @Override
                protected void onHandleIntent(Intent intent) {





                }
                private DbHelper ourHelper;
                private final Context ourContext;
                private SQLiteDatabase ourDatabase;

                private static class DbHelper extends SQLiteOpenHelper {

                    public DbHelper(Context context) {
                        super(context, "myschool", null, 1);
                        // TODO Auto-generated constructor stub
                    }

                    @Override
                    public void onCreate(SQLiteDatabase arg0) {
                        // TODO Auto-generated method stub

                    }

                    @Override
                    public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
                        // TODO Auto-generated method stub

                    }

                    public CheckClassroom(Context c) {
                        ourContext = c;
                    }

                    public CheckClassroom open() {
                        ourHelper = new DbHelper(ourContext);
                        ourDatabase = ourHelper.getWritableDatabase();

                        return this;

                    }

                    public void close() {
                        ourHelper.close();
                    }

            }
                getColumns()
                {
                    //retrieve sqlitedatabase data

                }


    }

I’ve been reading a lot about constructor, but i can’t really fully understand it, explaining all my errors here would really give me a better understanding of this. Thanks..

Answer 1

when i hover in public CheckClassroom() { super(“CheckClassroom”);
}The blank final field ourContext may not have been initialized

Because you declared the DbHelper class static, it will create an instance as soon as the CheckClassroom is instantiated. At that time, ourContext is still not initialized.

To fix this, remove the static for the DbHelper class and make one instance to be a static field instead. Then in the constructor you can initialize that (after you initialize ourContext).

private static DbHelper myDbHelper;

public CheckClassroom() {
    super("CheckClassroom");
    ourContext = this;
    myDbHelper = new DbHelper();
}

And instead of using ourContext, you can just use CheckClassroom.this in the DbHelper class.

Also…

The public CheckClassroom(Context c) { ourContext = c; } function has nothing to do inside the DbHelper class….

Also that open and close functions do not seem right, instead I think you should override onCreate and onDestroy

Here is your code, fixed:

package my.skul;

import android.app.IntentService;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class CheckClassroom extends IntentService {

            /**
             * A constructor is required, and must call the super IntentService(String)
             * constructor with a name for the worker thread.
             */
            public CheckClassroom() {
                super("CheckClassroom");
            }

            /**
             * The IntentService calls this method from the default worker thread with
             * the intent that started the service. When this method returns,
             * IntentService stops the service, as appropriate.
             */
            @Override
            protected void onHandleIntent(Intent intent) {





            }
            private DbHelper ourHelper;
            private SQLiteDatabase ourDatabase;

            @Override
            public void onCreate() {
                ourHelper = new DbHelper();
                ourDatabase = ourHelper.getWritableDatabase();
            }

            @Override
            public void onDestroy() {
                ourHelper.close();
            }

            private class DbHelper extends SQLiteOpenHelper {

                public DbHelper() {
                    super(CheckClassroom.this, "myschool", null, 1);
                    // TODO Auto-generated constructor stub
                }

                @Override
                public void onCreate(SQLiteDatabase arg0) {
                    // TODO Auto-generated method stub

                }

                @Override
                public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
                    // TODO Auto-generated method stub

                }
            }
            /* not sure what that is... 
            getColumns()
            {
                //retrieve sqlitedatabase data

            }
            */
}