如何在 Android 中使用 Assets 中预加载的 SQLite 数据库

我想用preloaded database在我的应用程序中意味着尝试在安装 apk 时获取数据库，以便可以使用已保存在其中的数据。我复制了“成分.db”文件位于资产文件夹中。并使用以下代码 但这会出现错误“从资源文件复制数据库时出现问题”

我怎么解决这个问题？ 请建议我可能的方法

我的数据库助手类是这样的

class IngredientHelper extends SQLiteOpenHelper {
        private static final String DATABASE_PATH = "/data/data/com.example.preloadeddatabase/databases/";
        private static final String DATABASE_NAME = "ingredients.db";

        private static final String TABLE_NAME = "Ingredients";
        private static final String COLUMN_ID = "_id";
        private static final String COLUMN_TITLE = "ingredient_name";

        private static final int SCHEMA_VERSION = 1;

        public SQLiteDatabase dbSqlite;
        private final Context myContext;

        public IngredientHelper(Context context) {
            super(context, DATABASE_NAME, null, SCHEMA_VERSION);
            this.myContext = context;

        }

        @Override
        public void onCreate(SQLiteDatabase db) {

        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

        }

        public void createDatabase() {

            createDB();
        }

        public void createDB() {

            boolean dbExist = DbExists();

            if (!dbExist) {
                this.getReadableDatabase();
                copyDataBase();

            }
        }

        private boolean DbExists() {
            SQLiteDatabase db = null;
            try {
                String databasePath = DATABASE_PATH + DATABASE_NAME;
                db = SQLiteDatabase.openDatabase(databasePath, null,
                        SQLiteDatabase.OPEN_READWRITE);

                db.setLocale(Locale.getDefault());
                db.setLockingEnabled(true);
                db.setVersion(1);

            }

            catch (SQLiteException e) {
                Log.e("SqlHelper", "Database Not Found");
            }

            if (db != null) {
                db.close();
            }

            return db != null ? true : false;
        }

        private void copyDataBase() {
            InputStream iStream = null;
            OutputStream oStream = null;
            String outFilePath = DATABASE_PATH + DATABASE_NAME;
            try {
                iStream = myContext.getAssets().open(DATABASE_NAME);
                oStream = new FileOutputStream(outFilePath);
                byte[] buffer = new byte[2048];
                int length;
                while ((length = iStream.read(buffer)) > 0) {
                    oStream.write(buffer, 0, length);
                }
                oStream.flush();
                oStream.close();
                iStream.close();
            }

            catch (IOException e) {
                throw new Error("Problem Copying Database From Resource File");
            }
        }

        public void openDatabase() throws SQLException {

            String myPath = DATABASE_PATH + DATABASE_NAME;
            dbSqlite = SQLiteDatabase.openDatabase(myPath, null,
                    SQLiteDatabase.OPEN_READWRITE);
        }

        @Override
        public synchronized void close() {

            if (dbSqlite != null) {
                dbSqlite.close();
            }
            super.close();

        }

        public Cursor getCursor() {
            SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
            queryBuilder.setTables(TABLE_NAME);
            String[] asColumnsToReturn = new String[] { COLUMN_ID, COLUMN_TITLE };

            Cursor mCursor = queryBuilder.query(dbSqlite, asColumnsToReturn,
                    null, null, null, null, "ingredient_name ASC");

            return mCursor;
        }

        public String getName(Cursor c) {
            return (c.getString(1));
        }

在将资源文件复制到数据库目录之前，不要打开可读数据库。您可能会遇到异常，因为您试图写入已打开的文件（因为当您调用 getReadableDatabase() 时它会被打开）。