Android外部数据库的引用

    private void copydatabase(String dbname) {
        //getFilesDir:拿到data-data当前目录下的files文件夹的绝对路径
        File file = new File(getFilesDir(), dbname);
        if (!file.exists()){//判断db是否存在
            AssetManager assets = getAssets();
            FileOutputStream fos = null;
            InputStream is = null;
            try {
                //拿到输入流
                is = assets.open(dbname);
                //读写
                fos = new FileOutputStream(file);
                //缓冲区
                byte[] b = new byte[1024];
                int len = -1;
                while ((len = is.read(b)) != -1) {
                    fos.write(b, 0, len);
                }
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                try {
                    is.close();
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }