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：

@H_301_6@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!"); } }