Question

我正在使用此代码将我的sqlite数据库从资产复制到android中的数据。

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();
    }

Answer 1

不要重新发明轮子。有一个很好的软件包可以在两行代码中完成你想要的工作：https://github.com/jgilfelt/android-sqlite-asset-helper

在android数据文件夹中复制数据库

1 个答案: