开发学院手机开发Android 开发 在android项目里使用自带的SQLite数据库 阅读


 2012-07-07 07:42:05 来源:WEB开发网   
核心提示:最近在研究android,使用android默认的访问sqlite的方法,在android项目里使用自带的SQLite数据库,访问的是:data/data/你的项目package/database/数据库名称 下的数据库,假如要在项目中打包db文件

最近在研究android,使用android默认的访问sqlite的方法,访问的是:data/data/你的项目package/database/数据库名称 下的数据库,假如要在项目中打包db文件,该怎么弄呢?
publicclass DataBaseHelper extends SQLiteOpenHelper{

//The Android's default system path of your application database.

    private static String DB_PATH = "/data/data/你的项目package/databases/";


    private static String DB_NAME = "数据库名称";


    private SQLiteDatabase myDataBase; 


    private final Context myContext;



     * Constructor

     * Takes and keeps a reference of the passed context in order to access to the application assets and resources.

     * @param context


    public DataBaseHelper(Context context) {


        super(context, DB_NAME, null, 1);

        this.myContext = context;




     * Creates a empty database on the system and rewrites it with your own database.

     * */

    public void createDataBase() throws IOException{


        boolean dbExist = checkDataBase();



            //do nothing - database already exist



            //By calling this method and empty database will be created into the default system path

               //of your application so we are gonna be able to overwrite that database with our database.



            try {




            } catch (IOException e) {


                throw new Error("Error copying database");








     * Check if the database already exist to avoid re-copying the file each time you open the application.

     * @return true if it exists, false if it doesn't


    private boolean checkDataBase(){


        SQLiteDatabase checkDB = null;



            String myPath = DB_PATH + DB_NAME;

            checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);


        }catch(SQLiteException e){


            //database does't exist yet.




        if(checkDB != null){






        return checkDB != null ? true : false;




     * Copies your database from your local assets-folder to the just created empty database in the

     * system folder, from where it can be accessed and handled.

     * This is done by transfering bytestream.

     * */

    private void copyDataBase() throws IOException{


        //Open your local db as the input stream

        InputStream myInput = myContext.getAssets().open(DB_NAME);


        // Path to the just created empty db

        String outFileName = DB_PATH + DB_NAME;


        //Open the empty db as the output stream

        OutputStream myOutput = new FileOutputStream(outFileName);


        //transfer bytes from the inputfile to the outputfile

        byte[] buffer = new byte[1024];

        int length;

        while ((length = myInput.read(buffer))>0){

            myOutput.write(buffer, 0, length);



        //Close the streams







    public void openDataBase() throws SQLException{


        //Open the database

        String myPath = DB_PATH + DB_NAME;

        myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);





    public synchronized void close() {


            if(myDataBase != null)








    public void onCreate(SQLiteDatabase db) {





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




        // Add your public helper methods to access and get content from the database.

       // You could return cursors by doing "return myDataBase.query(....)" so it'd be easy

       // to you to create adapters for your views.}

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