title: android database: the method open() is undefined for the type databasehelper class
body: <p>i want to authenticate user id and password from sqlite database. The user table is saved in sqlite db, i want to compare the edittext value with the value saved in the sqlite db, when i initialize and open the database i get error that the method open() is undefined for the Db_getUserDetail (name of my database helper class). </p>
  
  <p>code of main activity </p>
  
  <pre><code>@Override
  public void onClick(View v) {
  
  ffCode = ed_login.getText().toString();
  password = ed_password.getText().toString();
  // check if any of edit text is empty
       if(ffCode.equals(""))
           {
           Toast.makeText(getApplicationContext(), "Please enter your FF code",    Toast.LENGTH_LONG).show();
                 return;
            }
  
       else if (password.equals(""))
           {
           Toast.makeText(getApplicationContext(), "Please enter your password", Toast.LENGTH_LONG).show();
                  return;
            }
                Log.e("opening database", "yes");
                Db_getUserDetail  myDb= new Db_getUserDetail(MainActivity.this);
                myDb.open();
                //this is the method to query
                String storedffcode=Db_getUserDetail.getCodeAndPassword(ffCode);
                myDb.close(); 
  
                if(ffCode.equals(storedffcode))
                  {
                  Toast.makeText(getApplicationContext(), "Congrats: Login Successfull", Toast.LENGTH_LONG).show();
  
                  }
                  else
                  {
                      Toast.makeText(getApplicationContext(), "User Name or Password does not match", Toast.LENGTH_LONG).show();
                  }
  
          }
  
      });
  </code></pre>
  
  <p>code for getting values from database</p>
  
  <pre><code>    public static  String getCodeAndPassword(String ffCode)
      {
         Log.e("retrieving ff code", "yes");
         SQLiteDatabase db = null;
         Cursor cursor =   db.query("user_detail", null, " ff_code=?" , new String[]{ffCode}, null, null, null);
         if(cursor.getCount()&lt;1)
          {
              cursor.close();
              return "Not Exist";
          }
          Log.e("found ff code", "yes");
          cursor.moveToFirst();
          String ffcode= cursor.getString(cursor.getColumnIndex("ff_code"));
          return ffcode;
      }
  </code></pre>
  
  <p>log cat:<br>
      java.lang.NullPointerException
      at com.example.db_client.Db_getUserDetail.getCodeAndPassword(Db_getUserDetail.java:135)
      at com.example.db_client.UserDetailActivity$1.onClick(UserDetailActivity.java:75)
      at android.view.View.performClick(View.java:4438)
      at android.view.View$PerformClick.run(View.java:18422)
      at android.os.Handler.handleCallback(Handler.java:733)
      at android.os.Handler.dispatchMessage(Handler.java:95)
      at android.os.Looper.loop(Looper.java:136)enter code here</p>
  
  <p>code of db helper class</p>
  
  <pre><code>public class Db_getUserDetail extends SQLiteOpenHelper {
  
  public static final String DATABASE_NAME = "CRM";
  public static final String CONTACTS_TABLE_NAME =          "user_detail";
  public static final String CONTACTS_COLUMN_USER_ID =      "user_id";
  public static final String CONTACTS_COLUMN_USER_PWD =     "user_pwd";
  public static final String CONTACTS_COLUMN_FF_CODE=        "ff_code";
  public static final String CONTACTS_COLUMN_FF_NAME =       "ff_name";
  public static final String CONTACTS_COLUMN_TERR_CODE =     "terr_code";
  public static final String CONTACTS_COLUMN_DG_CODE=       "dg_code";
  public static final String CONTACTS_COLUMN_DIST_CODE =     "dist_code";
  public static final String CONTACTS_COLUMN_FF_MOB =         "ff_mob";
  public static final String CONTACTS_COLUMN_IMEI_NO =        "imeino";
  
    //constructor for database class DBHelper....
      public Db_getUserDetail(Context context)
      {
          super(context, DATABASE_NAME , null, 1);
      }
  
        String ff_code;   
        String ff_name;
        String terr_code;
        String dg_code;
        String dist_code;
        String  ff_mob;
        String imeino;
  
      //override onCreate method to create Database table...
      @Override
      public void onCreate(SQLiteDatabase db)
      {
          // TODO Auto-generated method stub.
          Log.e("DB created", "yes");
          db.execSQL("create table user_detail" + "(user_id text, user_pwd text,ff_code text,ff_name text,terr_code text,dg_code text, dist_code text,ff_mob text,imeino text) ");
      }
  
      //Upgrade new Table...
      @Override
      public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
          // TODO Auto-generated method stub
          db.execSQL("DROP TABLE IF EXISTS user_detail");
          onCreate(db);
      }
      //to insert new records in table...
      public boolean insertUserData (String user_id, String user_pwd, String ff_code ,String ff_name,String terr_code,String dg_code, String dist_code,
                                String ff_mob, String imeino)                                                                                     
  
      {
          Log.e("DB insert call", "yes");
  
          SQLiteDatabase db = this.getWritableDatabase();
          ContentValues contentValues = new ContentValues();
  
          Log.e("content values", "yes");
          contentValues.put("user_id", user_id);
          contentValues.put("user_pwd", user_pwd);    
          contentValues.put("ff_code", ff_code);
          contentValues.put("ff_name",ff_name);   
          contentValues.put("terr_code", terr_code);  
          contentValues.put("dg_code", dg_code);  
          contentValues.put("dist_code", dist_code);  
          contentValues.put("ff_mob", ff_mob);    
          contentValues.put("imeino", imeino);    
  
          db.insert("user_detail", null, contentValues);
          return true;
      }
  
      //get data from table...
      public Cursor getData(String id)
      {
          SQLiteDatabase db = this.getReadableDatabase();
          Cursor res =  db.rawQuery( "select * from user_detail", null );
          return res;
      }
  
      //get no of rows in table...
      public int numberOfRows(){
          SQLiteDatabase db = this.getReadableDatabase();
          int numRows = (int) DatabaseUtils.queryNumEntries(db, CONTACTS_TABLE_NAME);
          return numRows;
      }
  
      //to delete data from table at particular id....
      public Integer deleteContact (String id)
      {
          SQLiteDatabase db = this.getWritableDatabase();
          return db.delete("user_detail","id = '"+id+"'", null);
      }
      //to get all data from database...
      public ArrayList getAllCotacts() 
      {
          ArrayList array_list = new ArrayList();
          //hp = new HashMap();
          SQLiteDatabase db = this.getReadableDatabase();
          Cursor res =  db.rawQuery( "select * from user_detail", null );
          res.moveToFirst();
          while(res.isAfterLast() == false)
          {
              array_list.add(res.getString(res.getColumnIndex(CONTACTS_COLUMN_USER_ID)));
              array_list.add(res.getString(res.getColumnIndex(CONTACTS_COLUMN_USER_PWD)));
              array_list.add(res.getString(res.getColumnIndex(CONTACTS_COLUMN_FF_CODE)));
              array_list.add(res.getString(res.getColumnIndex(CONTACTS_COLUMN_FF_NAME)));
              array_list.add(res.getString(res.getColumnIndex(CONTACTS_COLUMN_TERR_CODE)));
              array_list.add(res.getString(res.getColumnIndex(CONTACTS_COLUMN_DG_CODE)));
              array_list.add(res.getString(res.getColumnIndex(CONTACTS_COLUMN_DIST_CODE)));
              array_list.add(res.getString(res.getColumnIndex(CONTACTS_COLUMN_FF_MOB)));
              array_list.add(res.getString(res.getColumnIndex(CONTACTS_COLUMN_IMEI_NO)));
  
              res.moveToNext();
          }
          return array_list;
      }
  
      public static  String getCodeAndPassword(String ffCode)
      {
         Log.e("retrieving ff code", "yes");
         SQLiteDatabase db = null;
         //SQLiteDatabase db = getWritableDatabse();
         Cursor cursor =   db.query("user_detail", null, " ff_code=?" , new String[]{ffCode}, null, null, null);
         if(cursor.getCount()&lt;1)
          {
              cursor.close();
              return "Not Exist";
          }
          Log.e("found ff code", "yes");
          cursor.moveToFirst();
          String ffcode= cursor.getString(cursor.getColumnIndex("ff_code"));
          return ffcode;
      }
  </code></pre>