在Android应用程序中，可以将预先准备好的数据库文件复制到设备上的特定位置以供使用。下面是一个解决该问题的示例代码：

1. 首先，在项目的assets文件夹中放置要复制的数据库文件，例如mydatabase.db。

2. 创建一个用于复制数据库文件的辅助类DatabaseHelper：

import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class DatabaseHelper extends SQLiteOpenHelper {
    private static final String DB_NAME = "mydatabase.db";
    private static final int DB_VERSION = 1;
    private static String DB_PATH;

    private Context mContext;

    public DatabaseHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
        mContext = context;
        DB_PATH = mContext.getApplicationInfo().dataDir + "/databases/";
    }

    public void createDatabase() throws IOException {
        boolean dbExist = checkDatabase();

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

            try {
                copyDatabase();
            } catch (IOException e) {
                throw new Error("Error copying database");
            }
        }
    }

    private boolean checkDatabase() {
        SQLiteDatabase checkDB = null;

        try {
            String path = DB_PATH + DB_NAME;
            checkDB = SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READONLY);
        } catch (SQLiteException e) {
            // Database doesn't exist yet
        }

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

        return checkDB != null;
    }

    private void copyDatabase() throws IOException {
        InputStream inputStream = mContext.getAssets().open(DB_NAME);
        String outFileName = DB_PATH + DB_NAME;
        OutputStream outputStream = new FileOutputStream(outFileName);

        byte[] buffer = new byte[1024];
        int length;
        while ((length = inputStream.read(buffer)) > 0) {
            outputStream.write(buffer, 0, length);
        }

        outputStream.flush();
        outputStream.close();
        inputStream.close();
    }

    public void openDatabase() throws SQLException {
        String path = DB_PATH + DB_NAME;
        SQLiteDatabase database = SQLiteDatabase.openDatabase(path, null, SQLiteDatabase.OPEN_READONLY);
        database.setVersion(DB_VERSION);
    }

    @Override
    public synchronized void close() {
        super.close();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
    }

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

3. 在使用数据库之前，调用createDatabase()方法复制数据库文件：

DatabaseHelper databaseHelper = new DatabaseHelper(context);
try {
    databaseHelper.createDatabase();
} catch (IOException e) {
    e.printStackTrace();
}

4. 现在可以通过openDatabase()方法打开数据库并使用它：

try {
    databaseHelper.openDatabase();
    SQLiteDatabase database = databaseHelper.getReadableDatabase();
    // 执行数据库操作...
} catch (SQLException e) {
    e.printStackTrace();
}

通过这种方式，您可以确保数据库文件正确地复制到设备上的数据库文件夹中，并且可以在应用程序中使用。