我的語法有什麼問題？ （SQLite）

Question

那麼我在我的表中進行了一些更改，現在正在向我顯示此錯誤。我嘗試調試但沒有運氣。任何想法？

「android.database.sqlite.SQLiteException：沒有這樣的表：表名（代碼1）：在編譯：SELECT * FROM表名」

 import java.util.ArrayList; 
     import java.util.HashMap; 
     import java.util.Hashtable; 
     import android.content.ContentValues; 
     import android.content.Context; 
     import android.database.Cursor; 
     import android.database.DatabaseUtils; 
     import android.database.sqlite.SQLiteOpenHelper; 
     import android.database.sqlite.SQLiteDatabase; 

public class DBHelper extends SQLiteOpenHelper { 

    public static final String DATABASE_NAME = "MyDBName.db"; 
    public static final String CONT_TABLE_NAME = "tablename"; 
    public static final String CONT_COLUMN_ID = "id"; 
    public static final String CONT_COLUMN_CONDUCTIVITY = "conductivity"; 
    public static final String CONT_COLUMN_MOISTURE = "moisture"; 
    public static final String CONT_COLUMN_OXYGEN = "oxygen"; 
    public static final String CONT_COLUMN_PH = "ph"; 

    private HashMap hp; 

    public DBHelper(Context context) 
    { 
     super(context, DATABASE_NAME , null, 1); 
    } 

    @Override 
    public void onCreate(SQLiteDatabase db) { 
     // TODO Auto-generated method stub 
     db.execSQL(
       "create table tablename " + 
         "(id integer primary key, conductivity text,ph text,oxygen text, moisture text)" 
     ); 
    } 

    @Override 
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
     // TODO Auto-generated method stub 
     db.execSQL("DROP TABLE IF EXISTS tablename"); 
     onCreate(db); 
    } 

    public boolean insertContact (String conductivity, String ph, String oxygen, String moisture) 
    { 
     SQLiteDatabase db = this.getWritableDatabase(); 
     ContentValues contentValues = new ContentValues(); 
     contentValues.put("conductivity", conductivity); 
     contentValues.put("ph", ph); 
     contentValues.put("oxygen", oxygen); 
     contentValues.put("moisture", moisture); 

     db.insert("tablename", null, contentValues); 
     return true; 
    } 

    public Cursor getData(int id){ 
     SQLiteDatabase db = this.getReadableDatabase(); 
     Cursor res = db.rawQuery("select * from tablename where id="+id+"", null); 
     return res; 
    } 

    public int numberOfRows(){ 
     SQLiteDatabase db = this.getReadableDatabase(); 
     int numRows = (int) DatabaseUtils.queryNumEntries(db, CONT_TABLE_NAME); 
     return numRows; 
    } 

    public boolean updateContact (Integer id, String conductivity, String ph, String oxygen, String moisture) 
    { 
     SQLiteDatabase db = this.getWritableDatabase(); 
     ContentValues contentValues = new ContentValues(); 
     contentValues.put("conductivity", conductivity); 
     contentValues.put("ph", ph); 
     contentValues.put("oxygen", oxygen); 
     contentValues.put("moisture", moisture); 

     db.update("tablename", contentValues, "id = ? ", new String[] { Integer.toString(id) }); 
     return true; 
    } 

    public Integer deleteContact (Integer id) 
    { 
     SQLiteDatabase db = this.getWritableDatabase(); 
     return db.delete("tablename", 
       "id = ? ", 
       new String[] { Integer.toString(id) }); 
    } 

    public ArrayList<String> getAllCotacts() 
    { 
     ArrayList<String> array_list = new ArrayList<String>(); 

     //hp = new HashMap(); 
     SQLiteDatabase db = this.getReadableDatabase(); 
     Cursor res = db.rawQuery("select * from tablename", null); 
     res.moveToFirst(); 

     while(res.isAfterLast() == false){ 
      array_list.add(res.getString(res.getColumnIndex(CONT_COLUMN_CONDUCTIVITY))); 
      res.moveToNext(); 
     } 
     return array_list; 
    } 
} 

Answer 1

@Shree奎師那是正確的，你有沒有這樣的表現在在你的數據庫中。

嘗試刪除應用程序並重新安裝 - 然後onCreate(SQLiteDatabase db)將被自動調用，並且會再次創建表。

提示。如果您使用CursorLoader，請考慮使用_id字段而不是id。