Question

Main Activity:

private Button btnSubmit;
private DataSource mDataSource;
private Context mContext;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    final EditText first_name = (EditText) findViewById(R.id.first_name);
    final Spinner relation = (Spinner) findViewById(R.id.relation);
    final EditText address = (EditText) findViewById(R.id.address);
    Button  mSubmitButton = (Button) findViewById(R.id.btnSubmit);
    relation.setOnItemSelectedListener(new CustomOnItemSelectedListener());
    mSubmitButton.setOnClickListener(new View.OnClickListener() {

           @Override
           public void onClick(View v) {
                 String fName = first_name.getText().toString();
                 String re_lation = (String) relation.getSelectedItem(); 
                 String add_ress = address.getText().toString();
                 if ((fName.length() <=0) || (re_lation.length()<=0) || (add_ress.length()<=0)) {
                        Toast.makeText(MyAndroidAppActivity.this, "please fill the data", Toast.LENGTH_SHORT).show();
                 } else{
                        Log.i("name",fName);
                        Log.i("rel",re_lation);
                        Log.i("e",add_ress);
                        mDataSource.addUser(fName, re_lation, add_ress);

                 }
           }
     });
}

DataSource.java

private SQLiteDatabase mSQLiteDatabase;
private MySQLiteHelper mSQLiteHelper;
private String[] mAllColumns = {
      MySQLiteHelper.COLUMN_ID, MySQLiteHelper.COLUMN_FIRST_NAME, MySQLiteHelper.COLUMN_RELATION, MySQLiteHelper.COLUMN_ADDRESS
};

public DataSource (Context context){
      mSQLiteHelper = new MySQLiteHelper(context);
}

public void open() throws SQLiteException {
      mSQLiteDatabase = mSQLiteHelper.getWritableDatabase();
}

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

public void addUser(String first_name, String relation, String address){
      ContentValues values = new ContentValues();
      Log.i("name",first_name);
      values.put(MySQLiteHelper.COLUMN_FIRST_NAME, first_name);
      values.put(MySQLiteHelper.COLUMN_RELATION, relation);
      values.put(MySQLiteHelper.COLUMN_ADDRESS, address);
      mSQLiteDatabase.insert(MySQLiteHelper.TABLE_USERS, null, values);
      //Cursor cursor = mSQLiteDatabase.query(MySQLiteHelper.TABLE_USERS, allcolumns, selection, selectionArgs, groupBy, having, orderBy)
}

MySQLiteHelper.java

public class MySQLiteHelper extends SQLiteOpenHelper {
        public static final String TABLE_USERS = "users";
        public static final String COLUMN_ID = "_id";
        public static final String COLUMN_FIRST_NAME = "first_name";
        public static final String COLUMN_RELATION = "relation";
        public static final String COLUMN_ADDRESS = "address";



        private static final String DATABASE_NAME = "users.db";
        private static final int DATABASE_VERSION = 1;

        // Database creation sql statement
        private static final String DATABASE_CREATE = "create table "
                + TABLE_USERS + "( " + COLUMN_ID
                + " integer primary key autoincrement, " + COLUMN_FIRST_NAME
                + " text not null," + COLUMN_RELATION + " text not null," +
                COLUMN_ADDRESS + " text not null);";



        public MySQLiteHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
        }

        @Override
        public void onCreate(SQLiteDatabase db) {
            db.execSQL(DATABASE_CREATE);

        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            db.execSQL("DROP TABLE IF EXISTS "+TABLE_USERS);
            onCreate(db);

        }
}

Error Logcat:

06-20 11:26:02.043: E/AndroidRuntime(342): FATAL EXCEPTION: main
06-20 11:26:02.043: E/AndroidRuntime(342): java.lang.NullPointerException
06-20 11:26:02.043: E/AndroidRuntime(342):  at com.mkyong.android.MyAndroidAppActivity$1.onClick(MyAndroidAppActivity.java:62)
06-20 11:26:02.043: E/AndroidRuntime(342):  at android.view.View.performClick(View.java:2485)
06-20 11:26:02.043: E/AndroidRuntime(342):  at android.view.View$PerformClick.run(View.java:9080)
06-20 11:26:02.043: E/AndroidRuntime(342):  at android.os.Handler.handleCallback(Handler.java:587)
06-20 11:26:02.043: E/AndroidRuntime(342):  at android.os.Handler.dispatchMessage(Handler.java:92)
06-20 11:26:02.043: E/AndroidRuntime(342):  at android.os.Looper.loop(Looper.java:123)
06-20 11:26:02.043: E/AndroidRuntime(342):  at android.app.ActivityThread.main(ActivityThread.java:3683)
06-20 11:26:02.043: E/AndroidRuntime(342):  at java.lang.reflect.Method.invokeNative(Native Method)
06-20 11:26:02.043: E/AndroidRuntime(342):  at java.lang.reflect.Method.invoke(Method.java:507)
06-20 11:26:02.043: E/AndroidRuntime(342):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
06-20 11:26:02.043: E/AndroidRuntime(342):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)

Here i got the null pointer exeception while inserting the spinner and other text values in sqlite database,in the error line mDataSource.addUser(fName, re_lation, add_ress);

i got the three values.but the database is not created here.i point out the error line and while submiting the values into database,it throws the null pointer exception.what is the error in my program.anybody can tell me?

thanks in advance

Answer 1

mDataSource is not yet initialized

you should initialize it on your onCreate() callback

protected void onCreate(Bundle savedInstanceState)
{

setContentView(R.layout.layout);
mDataSource = new DataSource(getBaseContext());

// ... The Rest of your code
}

and in your DataSource’s Constructor call also the open() method

public DataSource (Context context){

mSQLiteHelper = new MySQLiteHelper(context);
open();
}

public void open() throws SQLiteException {
        mSQLiteDatabase = mSQLiteHelper.getWritableDatabase();
}