Question

我正在学习Android。我有一个SQLite数据库的Quote应用程序。我需要给这个应用程序提供数据库版本，所以每当我更新应用程序时，用户数据库也可以得到更新。我需要做些什么改变？

我的数据库Helper / Handler Class如下所示。

public class DataBaseHandler extends SQLiteOpenHelper {
    private static String DB_PATH;
    private static String DB_NAME = "SuccessQuotesNew";
    private SQLiteDatabase myDataBase;
    private final Context myContext;
    public DataBaseHandler(Context context) {

        super(context, DB_NAME, null, 1);
        this.myContext = context;
        DB_PATH = context.getDatabasePath(DB_NAME).toString();
        Log.e("path", DB_PATH);
    }

    public void createDataBase() throws IOException {

        boolean dbExist = checkDataBase();

        if (dbExist) {

        } 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;
            checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

        } catch (SQLiteException e) {

        }

        if (checkDB != null) {

            checkDB.close();

        }

        return checkDB != null ? true : false;
    }

    private void copyDataBase() throws IOException {

        InputStream myInput = myContext.getAssets().open(DB_NAME);
        String outFileName = DB_PATH;
        OutputStream myOutput = new FileOutputStream(outFileName);
        byte[] buffer = new byte[1024];
        int length;
        while ((length = myInput.read(buffer)) > 0) {
            myOutput.write(buffer, 0, length);
        }
        myOutput.flush();
        myOutput.close();
        myInput.close();

    }

    // ==============================================================================

    public void openDataBase() throws SQLException {

        // Open the database
        String myPath = DB_PATH;
        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) {

    }


}

Answer 1

构造函数的最后一个参数是数据库的版本代码。 super(context, DB_NAME, null, 1);更改该号码并检查更新方法将被调用，因此当您想要更新数据库更改它时，应用程序将在您创建该对象后调用更新方法。

此处参考检查 - Android SQLite database and app update

数据库版本SQLite Android

1 个答案: