在Android的数据文件夹拷贝数据库 [英] copy data base in android data folder

问题描述

我用这code从资产复制我的SQLite数据库中的数据机器人。

 私有静态字符串DB_PATH =/data/data/com.project.writing/databases/;
私有静态字符串DB_NAME =Fonts.sqlite;
私人SQLiteDatabase schoolDataBase;


    / **
    *在系统上创建一个空数据库，并与自己的数据库重写它。
    * * /
    公共无效的CreateDatabase（）抛出IOException异常{
        布尔dbExist = checkDataBase（）;
        如果（dbExist）{
            //什么也不做 - 数据库中已存在
        }其他{

            //通过调用这个方法和空的数据库将被创建到系统​​默认路径
               //你的应用程序，所以我们要能够覆盖数据库，我们的数据库。
            this.getReadableDatabase（）;
            尝试 {
                copyDataBase（）;
            }赶上（IOException异常E）{
                抛出新的错误（错误复制数据库）;
            }
        }
    }

    / **
     *检查数据库中已存在，以避免重新复制每次打开应用程序时，该文件。
     * @返回true，如果它存在，虚假的，如果它不
    * /
    私人布尔checkDataBase（）{
        SQLiteDatabase CHECKDB = NULL;
        尝试{
            字符串mypath中= DB_PATH + DB_NAME;

            CHECKDB = SQLiteDatabase.openDatabase（mypath中，空，SQLiteDatabase.OPEN_READONLY）;
        }赶上（SQLiteException E）{
            //数据库的简化版，存在。
            的System.out.println（数据库不存在+ E）;
        }
        如果（CHECKDB！= NULL）{
            checkDB.close（）;
        }
        返回CHECKDB！= NULL？真假;
    }
    / **
     *复制你的数据库从当地的资产文件夹在刚才创建的空数据库
     *系统文件夹，从那里它可以被访问和处理。
     *这是通过transfering字节流进行。
     *
     * * /


    私人无效copyDataBase（）抛出IOException异常{
        //打开本地数据库作为输入流
        InputStream的myInput = myContext.getAssets（）开（DB_NAME）。
        //路径刚刚创建的空分贝
        字符串outFileName = DB_PATH + DB_NAME;
        //打开空分贝的输出流
        的OutputStream myOutput =新的FileOutputStream（outFileName）;
        //传输的字节从inputfile中的OUTPUTFILE
        byte []的缓冲区=新的字节[1024];
        INT长;
        而（（长度= myInput.read（缓冲液））大于0）{
            myOutput.write（缓冲液，0，长度）;
        }
        //关闭流
        myOutput.flush（）;
        myOutput.close（）;
        myInput.close（）;

        //Toast.makeText(myContext，复制完成，300）.show（）;
    }
 

解决方案

不要推倒重来。有好的包，确实要在2号线的code什么： https：//开头github.com/jgilfelt/android-sqlite-asset-helper

I am using this code copy my sqlite database from asset to data in android .

private static String DB_PATH= "/data/data/com.project.writing/databases/";
private static String DB_NAME = "Fonts.sqlite";
private SQLiteDatabase schoolDataBase;


    /**
    * Creates a empty database on the system and rewrites it with your own database.
    * */
    public void createDataBase() throws IOException{
        boolean dbExist = checkDataBase();
        if(dbExist){
            //do nothing - database already exist
        }else{

            //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.
            this.getReadableDatabase();
            try {
                copyDataBase();
            } 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;
        try{
            String myPath = DB_PATH + DB_NAME;

            checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
        }catch(SQLiteException e){
            //database does't exist yet.
            System.out.println("data base does not exist"+e);
        }
        if(checkDB != null){
            checkDB.close();
        }
        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
        myOutput.flush();
        myOutput.close();
        myInput.close();

        //Toast.makeText(myContext, "Copy Done", 300).show();
    }

解决方案

Do not reinvent the wheel. There's nice package that does what you want in 2 lines of code: https://github.com/jgilfelt/android-sqlite-asset-helper

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