Android的sqlite選擇[] args

Question

尋找任何人可以使用sqlite查詢生成器中的select args []通過舉例。下面的代碼無法正常工作。

public class DatabaseHelper extends SQLiteOpenHelper{ 

    public static String DB_PATH = "/data/data/yourpath/databases/"; 
    public static String DB_NAME ="your_sqlite"; 
    private static final int DATABASE_VERSION = 1; 


    private final Context myContext; 
    private SQLiteDatabase mydb; 
    //private Cursor aliases; 
    private Cursor m; 

    public DatabaseHelper(Context ctx){ 
     super(ctx,DB_NAME,null,DATABASE_VERSION); 
     this.myContext = ctx; 

    } 


    /** 
    * creates an empty database and rewrites it with you own 
    * */ 
    public void createDatabase() throws IOException{ 
     boolean dbExists = checkDatabase(); 

     if(dbExists){ 
      //do nothing 
     }else{ 
      // by calling this method an empty database will be created into default system path 
      this.getReadableDatabase(); 

      try{ 
       copyDatabase(); 
      } 
      catch(IOException e){ 
       throw new Error("Error copying database"); 
      } 
     } 

    } 

/* 
* check if database exists to prevent re-copying the file each time you open the application 
* return true if exists otherwise false 
*/ 
private boolean checkDatabase(){ 
    SQLiteDatabase checkDB = null; 

    try{ 
     String myPath = DB_PATH + DB_NAME; 
     checkDB = SQLiteDatabase.openDatabase(myPath, null,SQLiteDatabase.OPEN_READONLY); 

    }catch(SQLiteException e){ 

    } 

    if (checkDB != null){ 
     checkDB.close(); 
    } 
    return checkDB != null ? true : false; 
} 

/** 
    * copies your database from local assets folder to just created empty database 
    * in the system folder from where it can be accessed and handled 
    * */ 
private void copyDatabase() throws IOException{ 
    //open your local db as the input stream 
    InputStream myInput = myContext.getAssets().open(DB_NAME); 

    //path to the just created empty db 
    String outFileName = DB_PATH + DB_NAME; 

    //open the empty db as the outputStream 
    OutputStream myOutput = new FileOutputStream(outFileName); 

    //transfers bytes from the input file to output file 
    byte[] buffer = new byte[1024]; 

    int length; 

    while((length = myInput.read(buffer))>0){ 
     myOutput.write(buffer, 0, length); 
    } 
    //close the streams 
    myOutput.flush(); 
    myOutput.close(); 
    myInput.close(); 
} 
public void openDatabase() throws SQLException{ 
    //open the db 
    String myPath = DB_PATH + DB_NAME; 
    mydb = SQLiteDatabase.openDatabase(myPath, null,SQLiteDatabase.OPEN_READONLY); 
} 
public synchronized void close(){ 
    if(mydb != null){ 
     mydb.close(); 
    } 
    super.close(); 
} 




    @Override 
public void onOpen(SQLiteDatabase db) { 
    super.onOpen(db); 
} 


    @Override 
    public void onCreate(SQLiteDatabase db) { 

    } 

    @Override 
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 

    } 



public Cursor getAllCharacters(){ 

    return mydb.query("char",new String[]{"_id","gender_id","race_id","name"}, 
      null, null, null,null,null); 
} 
public void setCharacter(long id){ 
    m = mydb.query("char",new String[]{"gender_id","race_id"},"_id =" + id,null,null,null,null,null); 
    if (m == null){ 
     System.out.print("Cursor is empty"); 
    } 
} 


public Cursor getAliases(){ 
    String gender_id = m.getString(0); 
    String race_id = m.getString(1); 
    String where = "_id=? AND _id=?"; 
    String[] args ={gender_id,race_id}; 

    Cursor alias = mydb.query("alias",new String[]{"_id","gender_id","race_id","alias"}, 
      where,args,null,null,null); 
    return alias; 
} 

} 

我試圖擺脫getAliases（）

Answer 1

String where = "_id=? AND _id=?"; 

它看起來像你想查詢兩列具有相同名稱的光標？ SQLite表只能有唯一的列名，所以不能有兩列名爲_id。