android - 复制数据库文件到本地存储

Question

我在 assete 文件夹中有一个 sqlite 数据库。

我想将其复制到本地存储。

我使用这段代码，它复制没有表的数据库。当我想在 sqlliteeditor 中打开数据库时，出现错误 14。

  private void copyDataBase2() throws IOException {
    OutputStream os = new FileOutputStream(  "/data/data/pakagename/Learning.db");
    InputStream is = context.getAssets().open("databases/Learning.db");
    byte[] buffer = new byte[1024];
    int length;
    while ((length = is.read(buffer)) > 0) {
        os.write(buffer, 0, length);
    }
    is.close();
    os.flush();
    os.close();
}

Answer 1

尝试像这样复制数据库文件:

public class DbHelper extends SQLiteOpenHelper {
    private static String DB_PATH = new File(getFilesDir(), "databases").getPath();
    private static String DB_NAME = "test_db.db";
    private SQLiteDatabase dataBase;
    private final Context fContext;
    public DbHelper(Context context) {
        super(context, DB_NAME, null, 1);
        this.fContext = context;
    }
    public void createDataBase() throws IOException {
        boolean dbExist = checkDataBase();
        if (dbExist) {
            //ничего не делаем – файл базы данных уже есть
        } 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) {
            //файл базы данных отсутствует
        }
        if (checkDB != null) {
            checkDB.close();
        }
        return checkDB != null ? true : false;
    }
    private void copyDataBase() throws IOException {
        InputStream input = fContext.getAssets().open(DB_NAME);
        String outFileName = DB_PATH + DB_NAME;
        OutputStream output = new FileOutputStream(outFileName);
        byte[] buffer = new byte[1024];
        int length;
        while ((length = input.read(buffer)) > 0) {
            output.write(buffer, 0, length);
        }
        output.flush();
        output.close();
        input.close();
    }
    public void openDataBase() throws SQLException {
        String path = DB_PATH + DB_NAME;
        dataBase = SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READONLY);
    }
    @Override
    public synchronized void close() {
        if (dataBase != null)
            dataBase.close();
        super.close();
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    }
}

如果您使用 API 19 或更高版本:

String db_path = fContext.getDatabasePath(DB_NAME);

When i want to open database in sqlliteeditor, i get error 14.

此外，我建议您检查数据库文件。如果在编辑器中打开时出现错误，很可能不是文件复制算法的问题。