在SQLiteOpenHelper中調用onUpgrade（）

Question

我知道這已被問了一百萬次。但是，我沒有找到一個方法來內我subclass

叫onUpgrade()我已經內置了SQLite Manager其正常工作的SQLite DataBase。我希望用戶在應用程序內創建一個附加表格。所以，就我讀過，我必須這樣做，在onUpgrade

這裏是我的代碼：

String DB_PATH =null; 

private static String DB_NAME = "CompositionFoodTable_LatinAmerica"; 

private SQLiteDatabase myDataBase; 

private final Context myContext; 

public FoodDataBaseHelper(Context context) { 

    super(context, DB_NAME, null, 2); //Constructor with newer version 
    //However I am not sure about this because when I run a query within the manager 
    //to check the version, it throws 0 
    this.myContext = context; 
    DB_PATH = context.getApplicationInfo().dataDir + "/databases/"; 
    // I am not calling getReadableDatabase() or getWriteable(). They destroy my 
    //current version 

} 

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

    //NOT BEING CALLED 
    // Drop older plates table if existed 
    String CREATE_PRODUCT_TABLE = null; 
    try { 
     db.beginTransaction(); 
     for (int i = oldVersion + 1; i <= newVersion; i++) { 


      CREATE_PRODUCT_TABLE = "CREATE TABLE IF NOT EXISTS PRODUCTS (" + 
        "ID INTEGER PRIMARY KEY AUTOINCREMENT, " + 
        "NAME TEXT, " + 
        "DATE TEXT, " + 
        "SERVING_SIZE_G TEXT, " + 

        "H20_PERC TEXT, " + 
        "ENERGY_KCAL TEXT, " + 
        "PROTEIN_G TEXT, " + 
        "TOTAL_FAT_G TEXT, " + 

        "CARBS_G TEXT, " + 
        "TOT_DIET_FIBER_G TEXT, " + 
        "ASH_G TEXT, " + 
        "CALCIUM_MG TEXT, " + 

        "PHOSPHORUS_MG TEXT, " + 
        "IRON_MG TEXT, " + 
        "THIAMINE_MG TEXT, " + 
        "RIBOFLAVIN_MG TEXT, " + 

        "NIACIN_MG TEXT, " + 
        "VIT_C_MG TEXT, " + 
        "VIT_A_EQUIV_RETINOL_MCG TEXT, " + 
        "MUFA_G TEXT, " + 

        "PUFA_G TEXT, " + 
        "SATURATED_FATTY_ACIDS_G TEXT, " + 
        "CHOLESTEROL_MG TEXT, " + 
        "POTASSIUM_MG TEXT, " + 

        "SODIUM_MG TEXT, " + 
        "ZINC_MG TEXT, " + 
        "MAGNESIUM_MG TEXT, " + 
        "VIT_B6_MG TEXT, " + 

        "VIT_B12_MCG TEXT, " + 
        "FOLIC_AC_MCG TEXT, " + 
        "FOLATE_EQUIV_FD_MCG TEXT, " + 
        "EDIBLE_FRACTION_PERC TEXT)"; 

      db.execSQL(CREATE_PRODUCT_TABLE); 

      // create plates table 
      db.setTransactionSuccessful(); 
     } 
     } finally{ 

      db.endTransaction(); 
     } 
      // Future schema changes has to go into this loop 


} 

休息的我的方法：

/** 
* Creates a empty database on the system and rewrites it with your own database. 
* */ 
public void createDataBase() throws IOException{ 

    boolean dbExist = checkDataBase(); 

    if(dbExist){ 
     //do nothing - database already exist 
    }else{ 

     //By calling this method and empty database will be created into the default system path 
      //of your application so we are going to be able to overwrite that database with our database. 
     this.getReadableDatabase(); 

     try { 
      copyDataBase(); 

     } catch (IOException e) { 

      throw new Error("Error copying database"); 

     } 
    } 

} 

/** 
* Check if the database already exist to avoid re-copying the file each time you open the application. 
* @return true if it exists, false if it doesn't 
*/ 
private boolean checkDataBase(){ 
    boolean checkdb = false; 
    try{ 
     String myPath = myContext.getFilesDir().getAbsolutePath().replace("files", "databases")+File.separator + DB_NAME; 
     File dbfile = new File(myPath);     
     checkdb = dbfile.exists(); 
    } 
    catch(SQLiteException e){ 
     System.out.println("Database doesn't exist"); 
    } 

    return checkdb; 
} 

/** 
* Copies your database from your local assets-folder to the just created empty database in the 
* system folder, from where it can be accessed and handled. 
* This is done by transferring bytestream. 
* */ 
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 output stream 
    OutputStream myOutput = new FileOutputStream(outFileName); 

    //transfer bytes from the inputfile to the outputfile 
    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 database 
    String myPath = DB_PATH + DB_NAME; 
    myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE); 

} 

@Override 
public synchronized void close() { 

     if(myDataBase != null) 
      myDataBase.close(); 

     super.close(); 

} 

@Override 
public void onCreate(SQLiteDatabase db) { 
    // SQL statement to create plate table 

} 

Answer 1

不過，我找不到在我的子類中調用onUpgrade（）的方法

You不要自己撥打onUpgrade()。 SQLiteOpenHelper將在需要時調用onUpgrade()。

我有一個SQLite數據庫已經內置在一個SQLite管理器，它可以正常工作。

如果你想打包一個SQLite數據庫與你的應用程序，請考慮switching to SQLiteAssetHelper。

我想用戶在應用程序內創建一個額外的表。所以，就我讀過，我必須這樣做，在onUpgrade

onUpgrade()號是當開發商船舶應用程序的新版本，需要一個新的數據庫模式。它不是基於用戶輸入而動態添加表格，索引或其他任何內容。爲此，請在適當的位置自行撥打execSQL()，電話SQLiteDatabase。