如何从Android设备下载SQLite数据库？ [英] How to download an SQLite database from an Android device?

问题描述

在花费几个小时试图弄清楚这一点，也许我可以用别人的专长;才有可能产生一个（网络）服务器上的SQLite数据库，并将其下载到Android设备，然后使用它？

Before spending hours trying to figure this out, maybe I can use someone's expertise; would it be possible to generate an SQLite database on a (web)server and download it to an Android device and then use it?

我需要同步的数据，但它可能会更快完全创建数据库和发送二进制。

I need to sync data, but it probably would be much faster to create the database completely and send that as binary.

推荐答案

下面是我实现的：

     private static boolean downloadDatabase(Context context) {
                try {
                       // Log.d(TAG, "downloading database");
                        URL url = new URL("http://some-url.com/db/" + "db_name.s3db");
                        /* Open a connection to that URL. */
                        URLConnection ucon = url.openConnection();
                        /*
                         * Define InputStreams to read from the URLConnection.
                         */
                        InputStream is = ucon.getInputStream();
                        BufferedInputStream bis = new BufferedInputStream(is);
                        /*
                         * Read bytes to the Buffer until there is nothing more to read(-1).
                         */
                        ByteArrayBuffer baf = new ByteArrayBuffer(50);
                        int current = 0;
                        while ((current = bis.read()) != -1) {
                                baf.append((byte) current);
                        }

                        /* Convert the Bytes read to a String. */
                        FileOutputStream fos = null;
                        // Select storage location
                        fos = context.openFileOutput("db_name.s3db", Context.MODE_PRIVATE); 

                        fos.write(baf.toByteArray());
                        fos.close();
                       // Log.d(TAG, "downloaded");
                } catch (IOException e) {
                        Log.e(TAG, "downloadDatabase Error: " , e);
                        return false;
                }  catch (NullPointerException e) {
                        Log.e(TAG, "downloadDatabase Error: " , e);
                        return false;
                } catch (Exception e){
                        Log.e(TAG, "downloadDatabase Error: " , e);
                        return false;
                }
                return true;
        }

此下载数据库到应用程序专用存储<一href="http://developer.android.com/reference/android/content/Context.html#openFileOutput%28java.lang.String,%20int%29">see这里

This downloads the database into your applications private storage see here

不要忘了你所需要的网络许可，您的清单。

Don't forget you need the internet permission in your manifest.

要然后得到一个实际的数据库从这个文件，你可以这样做：

To then get an actual database from this file you can do this:

   /**
     * Copies your database from your local downloaded database that is copied from the server 
     * into 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 copyServerDatabase() {
            // by calling this line an empty database will be created into the default system path
            // of this app - we will then overwrite this with the database from the server
            SQLiteDatabase db = getReadableDatabase();
            db.close();


                OutputStream os = null;
                InputStream is = null;
                try {
                      // Log.d(TAG, "Copying DB from server version into app");
                        is = mContext.openFileInput("db_name.s3db");
                        os = new FileOutputStream("/data/data/your.package.name/databases/"); // XXX change this

                        copyFile(os, is);
                } catch (Exception e) {
                        Log.e(TAG, "Server Database was not found - did it download correctly?", e);                          
                } finally {
                        try {
                                //Close the streams
                                if(os != null){
                                        os.close();
                                }
                                if(is != null){
                                        is.close();
                                }
                        } catch (IOException e) {
                                Log.e(TAG, "failed to close databases");
                        }
                }
                  // Log.d(TAG, "Done Copying DB from server");
        }




     private void copyFile(OutputStream os, InputStream is) throws IOException {
            byte[] buffer = new byte[1024];
            int length;
            while((length = is.read(buffer))>0){
                    os.write(buffer, 0, length);
            }
            os.flush();
    }

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