Question

我的项目中有一个数据库，现在我将数据库更改为新内容，但数据库没有更改，请帮我解决这个问题

我只是替换assets文件夹中的数据库文件我的源代码：

public class MovieDB extends SQLiteOpenHelper {
    String DB_PATH = null;
    public static String DB_NAME = "db_movie";
    private SQLiteDatabase myDataBase;
    private final Context myContext;

    /**
     * Constructor Takes and keeps a reference of the passed context in order to
     * access to the application assets and resources.
     * 
     * @param context
     */
    public MovieDB(Context context) {

        super(context, DB_NAME, null, 3);
        this.myContext = context;
        DB_PATH = "/data/data/" + context.getPackageName() + "/" + "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_READONLY);

        } 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, 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;
        // SQLiteDatabase.NO_LOCALIZED_COLLATORS
        myDataBase = SQLiteDatabase.openDatabase(myPath, null,
                SQLiteDatabase.OPEN_READONLY
                        | SQLiteDatabase.NO_LOCALIZED_COLLATORS
                        | SQLiteDatabase.CREATE_IF_NECESSARY);

    }

    @Override
    public synchronized void close() {

        if (myDataBase != null)
            myDataBase.close();

        super.close();

    }

    // return cursor
    public Cursor query(String table, String[] columns, String selection,
            String[] selectionArgs, String groupBy, String having,
            String orderBy) {
        return myDataBase.query("pwp_singers", null, null, null, null, null,
                null);

    }

    @Override
    public void onCreate(SQLiteDatabase arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
        // TODO Auto-generated method stub

    }

}

Answer 1

如果更改了列或表，则除了行之外的数据库表中的任何内容反映您必须具备的已安装应用程序的更改在案例更改数据库版本3中升级数据库版本到4。

super(context, DB_NAME, null, 3); - > super(context, DB_NAME, null, 4);

如何在android项目中升级SQLite数据库？

1 个答案: