I am trying to create a ListMenu using data from an SQLite database to

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Asked: June 14, 20262026-06-14T03:06:33+00:00 2026-06-14T03:06:33+00:00

I am trying to create a ListMenu using data from an SQLite database to

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I am trying to create a ListMenu using data from an SQLite database to define the name of each MenuItem. So in a class called menu.java I have defined the array

String classes [] = {};

which should hold each menu item name.

In a DBAdapter class I created a function so the user can insert info to a table (This all works fine btw).

public long insertContact(String name, String code, String location, String comments, int days, int start, int end, String type) 
    {
        ContentValues initialValues = new ContentValues();
        initialValues.put(KEY_NAME, name);
        initialValues.put(KEY_CODE, code);
        initialValues.put(KEY_LOCATION, location);
        initialValues.put(KEY_COMMENTS, comments);
        initialValues.put(KEY_DAYS, days);
        initialValues.put(KEY_START, start);
        initialValues.put(KEY_END, end);
        initialValues.put(KEY_TYPE, type);
        return db.insert(DATABASE_TABLE, null, initialValues);
    }

It would be the Strings inserted into KEY_NAME that I need to populate that String array with. Does anyone know if this is possible?

Thanks so much for the help guys.

If I implement that function by Sam/Mango the program crashes, am I using it incorrectly or is the error due to the unknown size of the array?

DBAdapter db = new DBAdapter(this);
String classes [] = db.getClasses();

edit: I should mention that if I manually define the array:

String classes [] = {"test1", "test2", "test3", etc};

It works fine. The error is a NullPointerException

Here’s the logcat (sorry about the formatting). I hadn’t initialized with db = helper.getReadableDatabase(); in the getClasses() function but unfortunately it didn’t fix the problem.

11-11 22:53:39.117: D/dalvikvm(17856): Late-enabling CheckJNI
11-11 22:53:39.297: D/TextLayoutCache(17856): Using debug level: 0 - Debug Enabled: 0
11-11 22:53:39.337: D/libEGL(17856): loaded /system/lib/egl/libGLES_android.so
11-11 22:53:39.337: D/libEGL(17856): loaded /system/lib/egl/libEGL_adreno200.so
11-11 22:53:39.357: D/libEGL(17856): loaded /system/lib/egl/libGLESv1_CM_adreno200.so
11-11 22:53:39.357: D/libEGL(17856): loaded /system/lib/egl/libGLESv2_adreno200.so
11-11 22:53:39.387: I/Adreno200-EGLSUB(17856): <ConfigWindowMatch:2078>: Format RGBA_8888.
11-11 22:53:39.407: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x5c66d000 size:36593664 offset:32825344 fd:65
11-11 22:53:39.417: E/(17856): Can't open file for reading
11-11 22:53:39.417: E/(17856): Can't open file for reading
11-11 22:53:39.417: D/OpenGLRenderer(17856): Enabling debug mode 0
11-11 22:53:39.477: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x5ecd3000 size:40361984 offset:36593664 fd:68
11-11 22:53:40.507: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x61451000 size:7254016 offset:3485696 fd:71
11-11 22:53:41.077: I/Adreno200-EGLSUB(17856): <ConfigWindowMatch:2078>: Format RGBA_8888.
11-11 22:53:41.077: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x61c4c000 size:7725056 offset:7254016 fd:74
11-11 22:53:41.097: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x623aa000 size:8196096 offset:7725056 fd:80
11-11 22:53:41.937: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x62b7b000 size:8667136 offset:8196096 fd:83
11-11 22:53:41.977: D/memalloc(17856): /dev/pmem: Unmapping buffer base:0x61c4c000 size:7725056 offset:7254016
11-11 22:53:41.977: D/memalloc(17856): /dev/pmem: Unmapping buffer base:0x623aa000 size:8196096 offset:7725056
11-11 22:53:41.977: D/memalloc(17856): /dev/pmem: Unmapping buffer base:0x62b7b000 size:8667136 offset:8196096
11-11 22:53:42.167: I/Adreno200-EGLSUB(17856): <ConfigWindowMatch:2078>: Format RGBA_8888.
11-11 22:53:42.177: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x61c5d000 size:17084416 offset:13316096 fd:74
11-11 22:53:42.317: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x63853000 size:20852736 offset:17084416 fd:80
11-11 22:53:42.357: D/OpenGLRenderer(17856): Flushing caches (mode 0)
11-11 22:53:42.357: D/memalloc(17856): /dev/pmem: Unmapping buffer base:0x5c66d000 size:36593664 offset:32825344
11-11 22:53:42.357: D/memalloc(17856): /dev/pmem: Unmapping buffer base:0x5ecd3000 size:40361984 offset:36593664
11-11 22:53:42.367: D/memalloc(17856): /dev/pmem: Unmapping buffer base:0x61451000 size:7254016 offset:3485696
11-11 22:53:42.757: D/memalloc(17856): /dev/pmem: Mapped buffer base:0x5c56d000 size:24621056 offset:20852736 fd:65
11-11 22:53:44.247: D/AndroidRuntime(17856): Shutting down VM
11-11 22:53:44.247: W/dalvikvm(17856): threadid=1: thread exiting with uncaught exception (group=0x40ac3210)
11-11 22:53:44.257: E/AndroidRuntime(17856): FATAL EXCEPTION: main
11-11 22:53:44.257: E/AndroidRuntime(17856): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{x.x.timetable/x.x.timetable.menu}: java.lang.NullPointerException
11-11 22:53:44.257: E/AndroidRuntime(17856):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1891)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1992)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at android.app.ActivityThread.access$600(ActivityThread.java:127)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1158)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at android.os.Handler.dispatchMessage(Handler.java:99)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at android.os.Looper.loop(Looper.java:137)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at android.app.ActivityThread.main(ActivityThread.java:4441)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at java.lang.reflect.Method.invokeNative(Native Method)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at java.lang.reflect.Method.invoke(Method.java:511)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:823)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:590)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at dalvik.system.NativeStart.main(Native Method)
11-11 22:53:44.257: E/AndroidRuntime(17856): Caused by: java.lang.NullPointerException
11-11 22:53:44.257: E/AndroidRuntime(17856):    at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:221)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:157)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at x.x.timetable.DBAdapter.getClasses(DBAdapter.java:151)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at x.x.timetable.menu.<init>(menu.java:15)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at java.lang.Class.newInstanceImpl(Native Method)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at java.lang.Class.newInstance(Class.java:1319)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at android.app.Instrumentation.newActivity(Instrumentation.java:1023)
11-11 22:53:44.257: E/AndroidRuntime(17856):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1882)
11-11 22:53:44.257: E/AndroidRuntime(17856):    ... 11 more
11-11 22:53:46.527: I/Process(17856): Sending signal. PID: 17856 SIG: 9



package x.x.timetable;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class DBAdapter {
    static final String KEY_ROWID = "_id";
    static final String KEY_NAME = "name";
    static final String KEY_CODE = "code";
    static final String KEY_LOCATION = "location";
    static final String KEY_COMMENTS = "comments";
    static final String KEY_DAYS = "days";
    static final String KEY_START = "start";
    static final String KEY_END = "end";
    static final String KEY_TYPE = "type";


    static final String TAG = "DBAdapter";

    static final String DATABASE_NAME = "MyDB";
    static final String DATABASE_TABLE = "timetable";
    static final int DATABASE_VERSION = 2;

    static final String DATABASE_CREATE =
        "create table timetable (_id integer primary key autoincrement, "
        + "name text not null, code text not null, location text not null, comments text not null, days INTEGER not null, start INTEGER not null, end INTEGER not null, type text not null);";

    final Context context;

    DatabaseHelper DBHelper;
    SQLiteDatabase db;

    public DBAdapter(Context ctx)
    {
        this.context = ctx;
        DBHelper = new DatabaseHelper(context);
    }

    private static class DatabaseHelper extends SQLiteOpenHelper
    {
        DatabaseHelper(Context context)
        {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
        }

        @Override
        public void onCreate(SQLiteDatabase db)
        {
            try {
                db.execSQL(DATABASE_CREATE);
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
        {
            Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
                    + newVersion + ", which will destroy all old data");
            db.execSQL("DROP TABLE IF EXISTS timetable");
            db.execSQL("DROP TABLE IF EXISTS contacts");
            onCreate(db);
        }
    }

    //---opens the database---
    public DBAdapter open() throws SQLException 
    {
        db = DBHelper.getWritableDatabase();
        return this;
    }

    //---closes the database---
    public void close() 
    {
        DBHelper.close();
    }

    public int count(){
        db = DBHelper.getWritableDatabase();
        String count = "SELECT count(*) FROM table";
        Cursor mcursor = db.rawQuery(count, null);
        int icount = mcursor.getInt(0);
        return icount;
    }

    //---insert a contact into the database---
    public long insertContact(String name, String code, String location, String comments, int days, int start, int end, String type) 
    {
        ContentValues initialValues = new ContentValues();
        initialValues.put(KEY_NAME, name);
        initialValues.put(KEY_CODE, code);
        initialValues.put(KEY_LOCATION, location);
        initialValues.put(KEY_COMMENTS, comments);
        initialValues.put(KEY_DAYS, days);
        initialValues.put(KEY_START, start);
        initialValues.put(KEY_END, end);
        initialValues.put(KEY_TYPE, type);
        return db.insert(DATABASE_TABLE, null, initialValues);
    }

    //---deletes a particular contact---
    public boolean deleteContact(long rowId) 
    {
        return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
    }

    //---retrieves all the Timetable---
    public Cursor getAllTimetable()
    {
        return db.query(DATABASE_TABLE, new String[] {KEY_ROWID, KEY_NAME,
                KEY_CODE, KEY_LOCATION, KEY_COMMENTS, KEY_DAYS, KEY_START, KEY_END, KEY_TYPE}, null, null, null, null, null);
    }

    //---retrieves a particular contact---
    public Cursor getContact(long rowId) throws SQLException 
    {
        Cursor mCursor =
                db.query(true, DATABASE_TABLE, new String[] {KEY_ROWID,
                KEY_NAME, KEY_CODE, KEY_LOCATION, KEY_COMMENTS, KEY_DAYS, KEY_START, KEY_END, KEY_TYPE}, KEY_ROWID + "=" + rowId, null,
                null, null, null, null);
        if (mCursor != null) {
            mCursor.moveToFirst();
        }
        return mCursor;
    }

    //---updates a contact---
    public boolean updateContact(long rowId, String name, String code, String location, String comments, int days, int start, int end, String type) 
    {
        ContentValues args = new ContentValues();
        args.put(KEY_NAME, name);
        args.put(KEY_CODE, code);
        args.put(KEY_LOCATION, location);
        args.put(KEY_COMMENTS, comments);
        args.put(KEY_DAYS, days);
        args.put(KEY_START, start);
        args.put(KEY_END, end);
        args.put(KEY_TYPE, type);
        return db.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0;
    }

    public String[] getClasses() {

        db = DBHelper.getWritableDatabase();
        String[] columns = {KEY_NAME};
        Cursor c = db.query(DATABASE_TABLE, columns, null, null, null, null, null);
        String[] classes = new String [c.getCount()];
        int i = 0;
        while (c.moveToNext()) {
            classes[i] = c.getString(0);
            i++;
        }
        c.close();
        return classes; 
    }
}

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1 Answer

Editorial Team · Answer 1 · 2026-06-14T03:06:34+00:00

Absolutely it’s possible. you could just make a method in your database class that returns your values in a string array.

public String[] getClasses() {
    String[] columns = {KEY_NAME};
    Cursor c = db.query(DATABASE_TABLE, columns, null, null, null, null, null);
    String[] classes = new String [c.getCount()];
    int i = 0;
    while (c.moveToNext()) {
        classes[i] = c.getString(0);
        i++;
    }
    c.close();
    return classes; 
}

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