Android中对assets目录下数据库操作

1.先写一个对本地数据的管理类AssetsDatabaseManager

/** * This is a Assets Database Manager * Use it, you can use a assets database file in you application * It will copy the database file to "/data/data/[your application package name]/database" when you first time you use it * Then you can get a SQLiteDatabase object by the assets database file * @author smartTop * @time 2012-09-20 * * * How to use: * 1. Initialize AssetsDatabaseManager * 2. Get AssetsDatabaseManager * 3. Get a SQLiteDatabase object through database file * 4. Use this database object * * Using example: * AssetsDatabaseManager.initManager(getApplication()); // this method is only need call one time * AssetsDatabaseManager mg = AssetsDatabaseManager.getManager();  // get a AssetsDatabaseManager object * SQLiteDatabase db1 = mg.getDatabase("db1.db");  // get SQLiteDatabase object, db1.db is a file in assets folder * db1.??? // every operate by you want * Of cause, you can use AssetsDatabaseManager.getManager().getDatabase("xx") to get a database when you need use a database */public class AssetsDatabaseManager {    private static String tag = "AssetsDatabase"; // for LogCat    private static String databasepath = "/data/data/%s/database"; // %s is packageName    // A mapping from assets database file to SQLiteDatabase object    private Map<String, SQLiteDatabase> databases = new HashMap<String, SQLiteDatabase>();    // Context of application    private Context context = null;    // Singleton Pattern    private static AssetsDatabaseManager mInstance = null;    /**     * Initialize AssetsDatabaseManager     * @param context, context of application     */    public static void initManager(Context context){        if(mInstance == null){            mInstance = new AssetsDatabaseManager(context);        }    }    /**     * Get a AssetsDatabaseManager object     * @return, if success return a AssetsDatabaseManager object, else return null     */    public static AssetsDatabaseManager getManager(){        return mInstance;    }    private AssetsDatabaseManager(Context context){        this.context = context;    }    /**     * Get a assets database, if this database is opened this method is only return a copy of the opened database     * @param dbfile, the assets file which will be opened for a database     * @return, if success it return a SQLiteDatabase object else return null     */    public SQLiteDatabase getDatabase(String dbfile) {        if(databases.get(dbfile) != null){            Log.i(tag, String.format("Return a database copy of %s", dbfile));            return (SQLiteDatabase) databases.get(dbfile);        }        if(context==null)            return null;        Log.i(tag, String.format("Create database %s", dbfile));        String spath = getDatabaseFilepath();        String sfile = getDatabaseFile(dbfile);        File file = new File(sfile);        SharedPreferences dbs = context.getSharedPreferences(AssetsDatabaseManager.class.toString(), 0);        boolean flag = dbs.getBoolean(dbfile, false); // Get Database file flag, if true means this database file was copied and valid        if(!flag || !file.exists()){            file = new File(spath);            if(!file.exists() && !file.mkdirs()){                Log.i(tag, "Create \""+spath+"\" fail!");                return null;            }            if(!copyAssetsToFilesystem(dbfile, sfile)){                Log.i(tag, String.format("Copy %s to %s fail!", dbfile, sfile));                return null;            }            dbs.edit().putBoolean(dbfile, true).commit();        }        SQLiteDatabase db = SQLiteDatabase.openDatabase(sfile, null, SQLiteDatabase.NO_LOCALIZED_COLLATORS);        if(db != null){            databases.put(dbfile, db);        }        return db;    }    private String getDatabaseFilepath(){        return String.format(databasepath, context.getApplicationInfo().packageName);    }    private String getDatabaseFile(String dbfile){        return getDatabaseFilepath()+"/"+dbfile;    }    private boolean copyAssetsToFilesystem(String assetsSrc, String des){        Log.i(tag, "Copy "+assetsSrc+" to "+des);        InputStream istream = null;        OutputStream ostream = null;        try{            AssetManager am = context.getAssets();            istream = am.open(assetsSrc);            ostream = new FileOutputStream(des);            byte[] buffer = new byte[1024];            int length;            while ((length = istream.read(buffer))>0){                ostream.write(buffer, 0, length);            }            istream.close();            ostream.close();        }        catch(Exception e){            e.printStackTrace();            try{                if(istream!=null)                    istream.close();                if(ostream!=null)                    ostream.close();            }            catch(Exception ee){                ee.printStackTrace();            }            return false;        }        return true;    }    /**     * Close assets database     * @param dbfile, the assets file which will be closed soon     * @return, the status of this operating     */    public boolean closeDatabase(String dbfile){        if(databases.get(dbfile) != null){            SQLiteDatabase db = (SQLiteDatabase) databases.get(dbfile);            db.close();            databases.remove(dbfile);            return true;        }        return false;    }    /**     * Close all assets database     */    static public void closeAllDatabase(){        Log.i(tag, "closeAllDatabase");        if(mInstance != null){            for(int i=0; i<mInstance.databases.size(); ++i){                if(mInstance.databases.get(i)!=null){                    mInstance.databases.get(i).close();                }            }            mInstance.databases.clear();        }    }}

2.初始化数据库

// 初始化，只需要调用一次AssetsDatabaseManager.initManager(getApplicationContext());// 获取管理对象，因为数据库需要通过管理对象才能够获取AssetsDatabaseManager mg = AssetsDatabaseManager.getManager();// 通过管理对象获取数据库addressDB = mg.getDatabase("address.db");注意：初始化话，只能初始化一次，最好在application中初始化