我正在使用这个DataBaseHelper.class,我被困在onUpgrade()方法上.我不知道如何弄清楚数据库的版本号是什么.我可以将版本设置为1,第一次发布它,当我发布更新时,我只需将版本设置为2(myDataBase.setVersion(2);).但只要应用程序正在运行,它就只有2.下次启动它再次为1.私有静态int DATABASE_VERSION也是如此.我在考虑将版本号存储在一个额外的表中,但在我看来,这似乎不是最佳实践.

那么如何确保版本号在升级后增加并且保留它(分配给私有静态int DATABASE_VERSION或myDataBase.getVersion();)的值？

DataBaseHelper类：

public class DataBaseHelper extends sqliteOpenHelper {
 
    //The Android's default system path of your application database.
    private static String DB_PATH = "/data/data/com.mydatabase.db/databases/";
 
    private static String DB_NAME = "database.sl3";
 
    private sqliteDatabase myDataBase;
 
    private final Context myContext;
 
 
    // Do you need this?
    private static int DATABASE_VERSION = 2;
    // or is this correct:
    // private static int DATABASE_VERSION = myDataBase.getVersion();
 
 
    /**
     * Constructor
     * Takes and keeps a reference of the passed context in order to access to
     * the application assets and resources.
     * 
     * @param context
     */
    public DataBaseHelper(Context context) {
 
        super(context,DB_NAME,null,DATABASE_VERSION);
        this.myContext = context;
    }
 
    /**
     * Creates an empty database on the system and rewrites it with your own
     * database.
     * */
    public void
        createDataBase() throws IOException {
        boolean dbExist = checkDataBase();
 
        if (dbExist) {
 
 
        }
        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.getWritableDatabase();
 
 
            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() {
 
        sqliteDatabase checkDB = null;
 
        try {
            String myPath = DB_PATH + DB_NAME;
            checkDB = sqliteDatabase.openDatabase(myPath,sqliteDatabase.OPEN_READWRITE);
 
        } catch (sqliteException e) {
 
            //database does't exist yet.
 
        }
 
        if (checkDB != null) {
 
            checkDB.close();
 
        }
        return checkDB != null ? true : false;
    }
 
    /**
     * 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 transfering 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,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,sqliteDatabase.OPEN_READWRITE);
 
 
 
        // Which parameters do I have to pass?
        onUpgrade(myDataBase,DATABASE_VERSION,2);
    }
 
    @Override
    public synchronized void
        close() {
 
        if (myDataBase != null)
            myDataBase.close();
 
        super.close(); 
 
    }
 
    @Override
    public void
        onCreate(sqliteDatabase db) {
 
    }
 
   @Override
   public void
        onUpgrade(  sqliteDatabase db,int oldVersion,int newVersion) {
 
    Log.d ("onUpgrade first log",Integer.toString(myDataBase.getVersion()));
 
 
 
 
    if (oldVersion == 1) {
 
        // do something
 
 
        // And then do this!?
        DATABASE_VERSION = 2;
        // or do this
        myDataBase.setVersion(2);
        Log.d ("onUpgrade sedond log",Integer.toString(myDataBase.getVersion()));
 
    }
 
    else {
        Log.d("onUpgrade","else-clause: Already upgraded!");
    }
 
 
 
}

// Do you need this?
private static int DATABASE_VERSION = 2;