Question

我知道这已被问了一百万次。但是，我找不到在onUpgrade()

中拨打subclass的方法

我已经在SQLite DataBase中内置了SQLite Manager，它可以正常使用。我希望用户在应用程序中创建一个额外的表。所以，据我所知，我必须在onUpgrade

中完成

这是我的代码：

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


}

我的其他方法：

 /**
 * 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

但是，我找不到在我的子类
中调用onUpgrade（）的方法

您不要自己致电onUpgrade()。如果需要，SQLiteOpenHelper会致电onUpgrade()。

我已经在SQLite Manager中构建了一个正常运行的SQLite数据库。

如果您想在应用中打包SQLite数据库，请考虑switching to SQLiteAssetHelper。

我希望用户在应用中创建一个额外的表。所以，据我所知，我必须在onUpgrade中执行此操作

没有。 onUpgrade()适用于开发人员发布需要新数据库架构的应用程序的新版本。它不适用于表，索引或基于用户输入动态添加的任何其他内容。为此，请在execSQL()上，在适当的时间点自己致电SQLiteDatabase。

在SQLiteOpenHelper中调用onUgrade（）

1 个答案: