将资产文件夹中的数据库文件附加到我自己在 Android 中的 SQLite 数据库

Question

我正在制作一个应用程序，它需要在应用程序启动时初始化大量数据，所以我想用资产文件夹中的 apk 文件导出初始数据库。我可以将该数据库复制到我的工作目录，但是当我尝试向该数据库写入/更新任何内容时，问题就出现了。

我不知道为什么它说它不可写。我知道资产中的数据库不能被重写。所以现在我想将数据库与我内部创建的数据库（通过代码编写）连接起来，这样我就可以一次性复制带有数据的表。我没有得到任何代码帮助。

Answer 1

可以按照此代码进行操作，可能会对您有所帮助：

public class PrepopulatedDBOpenHelper extends SQLiteOpenHelper {
    public static final String DB_NAME = "task_management";
    public static String DB_PATH;
    private SQLiteDatabase database;
    private Context context;

    public static final String EMPLOYEE_TABLE = "employee";
    public static final String ID_FIELD = "_id";
    public static final String NAME_FIELD = "name";
    public static final String EMAIL_FIELD = "email";
    public static final String PHONE_FIELD = "phone";
    public static final String DESIGNATION_FIELD = "designation";

    public PrepopulatedDBOpenHelper(Context context) {
        super(context, DB_NAME, null, 1);
        this.context = context;

        // database path /data/data/pkg-name/databases/
        String packageName = context.getPackageName();
        DB_PATH = "/data/data/" + packageName + "/databases/";
        this.database = openDatabase();

    }

    public SQLiteDatabase getDatabase() {
        return this.database;
    }

    public SQLiteDatabase openDatabase() {
        String path = DB_PATH + DB_NAME;
        if (database == null) {
            createDatabase();
            database = SQLiteDatabase.openDatabase(path, null,
                    SQLiteDatabase.OPEN_READWRITE);
        }
        return database;
    }

    private void createDatabase() {
        boolean dbExists = checkDB();
        if (!dbExists) {
            this.getReadableDatabase();
            Log.e(getClass().getName(),
                    "Database doesn't exist. Copying database from assets...");
            copyDatabase();
        } else {
            Log.e(getClass().getName(), "Database already exists");
        }
    }

    private void copyDatabase() {
        try {
            InputStream dbInputStream = context.getAssets().open(DB_NAME);
            String path = DB_PATH + DB_NAME;
            OutputStream dbOutputStream = new FileOutputStream(path);
            byte[] buffer = new byte[4096];
            int readCount = 0;
            while ((readCount = dbInputStream.read(buffer)) > 0) {
                dbOutputStream.write(buffer, 0, readCount);
            }

            dbInputStream.close();
            dbOutputStream.close();

        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    private boolean checkDB() {
        String path = DB_PATH + DB_NAME;
        File file = new File(path);
        if (file.exists()) {
            Log.e(getClass().getName(), "Database already exists");
            return true;
        }
        Log.e(getClass().getName(), "Database does not exists");
        return false;
    }

    public synchronized void close() {
        if (this.database != null) {
            this.database.close();
        }
    }
   }

Answer 2

你可以试试这个：

database = SQLiteDatabase.openDatabase(path, null,
                SQLiteDatabase.OPEN_READWRITE);