在SQLiteOpenHelper中创建新版本的数据库时不调用onUpgrade（）和onCreate（）方法

Question

我正在尝试在我的Android应用中创建一个新的版本数据库。但是，虽然我将数据库的版本从以前的版本（2）更改为新版本（3），但它并没有调用onUpgrade（）和onCreate（）。它只调用构造函数的三倍。我不明白为什么构造函数被调用三次，以及为什么onUpgrade（）和onCreate（）没有调用？

我也试过新的数据库版本代码，但结果是一样的。

这是我的代码。

public class DatabaseHelper extends SQLiteOpenHelper {

    private static String PACKAGE_NAME;

    private static String DB_PATH;

    private static String DB_NAME = "mydata.db";

    private SQLiteDatabase myDataBase;

    private final Context myContext;

    public DatabaseHelper(Context context) {

        super(context, DB_NAME, null, 3);
        this.myContext = context;

        Log.e("UPDATED3", "CONSTRUCTOR");

        PACKAGE_NAME = myContext.getPackageName();
        DB_PATH = "/data/data/" + PACKAGE_NAME + "/databases/";
    }

    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 gonna be able to overwrite that
            // database with our database.
            this.getReadableDatabase();

            try {

                copyDataBase();

            } catch (IOException e) {

                throw new Error("Error copying database");

            }
        }

    }

    private boolean checkDataBase() {

        SQLiteDatabase checkDB = null;

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

        } catch (SQLiteException e) {

            // database does't exist yet.

        }

        if (checkDB != null) {

            checkDB.close();

        }

        return checkDB != null ? true : false;
    }

    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) {

        Log.e("UPDATED3", "ONCREATE");
    }

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

        Log.e("UPDATED3", "UPDATED THE DATABASE");
    }

}

我在任何活动中使用我的数据库（如下所示）。

DatabaseHelper databaseHelper = new DatabaseHelper(getApplicationContext());

        try {
            databaseHelper.createDataBase();
            databaseHelper.openDataBase();
        } catch (IOException e) {

            Toast.makeText(getApplicationContext(), "Error: " + e.getMessage(),
                    Toast.LENGTH_LONG).show();
            e.printStackTrace();
        }