升级我从assets文件夹复制的sqlite数据库(Android)

我用这个教程:
Tutorial Custom database

我从assets文件夹复制数据库并将其复制到我的设备(或模拟器).一切都是正确的.我在DDMS透视图中看到了我的数据库.但是我想要升级我的数据库,所以我做了:

super(context, DB_NAME, null, 2); //changed version from 1 to 2

并修改onUpgrade方法:

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    if(newVersion > oldVersion){
        this.myContext.deleteDatabase(DB_NAME);
        try {
            this.copyDataBase();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

但运行后我的设备上仍然有旧版本的数据库.我如何删除旧版本的数据库并复制新的. DB_NAME是我的数据库名称(格式,但不是路径),copyDataBase()是将数据库复制到设备的方法(它的工作原理).

我粘贴我的所有代码:

public class DataBaseHelper extends SQLiteOpenHelper{

    private static String DB_PATH = "/data/data/sitcom.quiz/databases/";

    private static String DB_NAME = "sitcoms.sqlite";

    private SQLiteDatabase myDataBase; 

    private final Context myContext;

    public DataBaseHelper(Context context) {

        super(context, DB_NAME, null, 4);
        this.myContext = context;
    }   

    public void createDataBase() throws IOException{

        boolean dbExist = checkDataBase();

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

            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_READONLY);

        }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_READONLY);

    }

    @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("adas", "dasd");

        if(newVersion > oldVersion){
            String myPath = DB_PATH + DB_NAME;
            this.myContext.deleteDatabase(myPath);
            try {
                this.copyDataBase();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }


}

和我的活动:

DataBaseHelper myDbHelper = new DataBaseHelper(this);
        myDbHelper = new DataBaseHelper(this);

        try {
            myDbHelper.createDataBase();
        } catch (IOException ioe) {
            throw new Error("Unable to create database");
        }
        try {
            myDbHelper.openDataBase();
        }catch(SQLException sqle){
            throw sqle;
        }

谢谢,如果你能给我理由或只是暗示为什么这不起作用.

当调用函数onUpgrade()时,android已经打开了db.我不认为此时可以删除它.查看日志以获取更多信息.如果你想这样做,你需要将删除和复制代码移动到数据库尚未打开的地方.
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