Question

我在谷歌商店已有一个应用程序。我正在使用一个内置数据库，有3个表格并在首次启动应用程序时复制它。现在我想升级到应用程序并添加另一个表。以下是我的代码。

public DataBaseHelper(Context context) 
{
    super(context, DB_NAME, null, 1);
    DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
    this.mContext = context;
}   

public void createDataBase() throws IOException
{
    //If database not exists copy it from the assets

    boolean mDataBaseExist = checkDataBase();
    if(!mDataBaseExist)
    {
        this.getReadableDatabase();
        this.close();
        try 
        {
            //Copy the database from assests
            copyDataBase();
            Log.e(TAG, "createDatabase database created");
        } 
        catch (IOException mIOException) 
        {
            throw new Error("ErrorCopyingDataBase");
        }
    }
}
    //Check that the database exists here: /data/data/your package/databases/Da Name
    private boolean checkDataBase()
    {
        File dbFile = new File(DB_PATH + DB_NAME);
        return dbFile.exists();
    }

    //Copy the database from assets
    private void copyDataBase() throws IOException
    {
        InputStream mInput = mContext.getAssets().open(DB_NAME);
        String outFileName = DB_PATH + DB_NAME;
        OutputStream mOutput = new FileOutputStream(outFileName);
        byte[] mBuffer = new byte[1024];
        int mLength;
        while ((mLength = mInput.read(mBuffer))>0)
        {
            mOutput.write(mBuffer, 0, mLength);
        }
        mOutput.flush();
        mOutput.close();
        mInput.close();
    }

    //Open the database, so we can query it
    public boolean openDataBase() throws SQLException
    {
        String mPath = DB_PATH + DB_NAME;
        //Log.v("mPath", mPath);
        mDataBase = SQLiteDatabase.openDatabase(mPath, null, SQLiteDatabase.CREATE_IF_NECESSARY);
        //mDataBase = SQLiteDatabase.openDatabase(mPath, null, SQLiteDatabase.NO_LOCALIZED_COLLATORS);
        return mDataBase != null;
    }

    @Override
    public synchronized void close() 
    {
        if(mDataBase != null)
            mDataBase.close();
        super.close();
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) 
    {
        Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
                + newVersion + ", which will destroy all old data");
        String sql = "CREATE TABLE IF NOT EXISTS CKRecordings (" +
                "_id INTEGER PRIMARY KEY AUTOINCREMENT, " + 
                "name TEXT , filepath TEXT , creationDate TEXT)";
        db.execSQL(sql);
        db.execSQL("DROP TABLE IF EXISTS data");
        onCreate(db);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub

    }

我想问几个问题。上面的代码没有升级。

现在，如果我是应用程序的新用户，是否必须编辑旧数据库并制作另一个CKRecording表并将其替换为资产或以上代码中的当前数据库，这对新用户也有效？

Answer 1

super(context, DB_NAME, null, 1);

在此声明中，最后一个参数是数据库版本.. 将其设置为2 以获取新更新的APK。所以现有用户可以新添加表或列。

更新后的apk onUpgrade会调用。在那里你可以从资产中复制数据库。但是现有用户将丢失数据..所以最好的选择是在数据库中动态添加表。

升级数据库

1 个答案: