Android：从服务器获取SQLite文件并替换现有的 [英] Android: Get SQLite file from server and replace the existing

问题描述

我已经开发了一个本地基于SQLite的数据库的Android应用程序。
现在我试图用一个简单的文件替换这个SQLite .db数据库与服务器 - 只是从服务器下载.db并替换当前。

我已经创建了一个带有true / false的JSON响应来检查联机.db文件是否比本地.db文件更新，所以我的问题是：如何从www.domain.com/获取.db sqlite.db，并从我的应用程序中替换现有的Android sqlite .db文件。试试这个代码来检查数据库的版本：

解决方案

  class CheckDb扩展AsyncTask< String，Void，String> {
 $ b $ @覆盖
保护字符串doInBackground（String ... params）{
 //创建新的JSON解析器
 JSONParser jParser = new JSONParser（）; 
 
 //从URL获取JSON 
 c = jParser.getJSONFromUrl（url）; 
 
尝试{
 //获取JSON数组; 
 
 //在变量中存储JSON项目
 final String id = c.getString（verzija）.toString（）。trim（）; 
 
 $ b catch（JSONException e）{
 e.printStackTrace（）; 
} 
返回null; 
 
 $ b @Override 
 protected void onPostExecute（String s）{
 //导入TextView 
 final TextView json =（TextView）findViewById（R。 id.textView）; 
 //在TextView中设置JSON数据
 try {
 json.setText（c.getString（verzija）.toString（）。trim（））; 
 String db_version = c.getString（verzija）.toString（）。trim（）; 
 String current_version =3; 
 if（！db_version.equals（current_version））{
 
 new Thread（new Runnable（）{
 public void run（）{
 downloadFile（）; 
} 
}）。start（）; 
 
} 
 else {
 dialog.hide（）; 
 Toast.makeText（MainActivity.this，您有数据库的有效版本，Toast.LENGTH_SHORT）.show（）; 
} 
} catch（JSONException e）{
 e.printStackTrace（）; 
} 
 super.onPostExecute（s）; 
 
 
 
 
 $ b $ p 
 $ b 
下载新版本并替换现有的版本： 
 
 
  void downloadFile（）{
 
尝试{
 URL url = new URL dwnload_file_path）; 
 HttpURLConnection urlConnection =（HttpURLConnection）url.openConnection（）; 
 
 urlConnection.setRequestMethod（GET）; 
 urlConnection.setDoOutput（true）; 
 
 // connect 
 urlConnection.connect（）; 
 
 //设置我们要保存文件的路径
文件SDCardRoot = Environment.getExternalStorageDirectory（）; 
 //创建一个新文件，保存下载的文件
文件文件=新建文件（SDCardRoot，download_db.db）; 
 
 FileOutputStream fileOutput = new FileOutputStream（file）; 
 
 //用于从互联网读取数据的流
 InputStream inputStream = urlConnection.getInputStream（）; 
 
 //这是我们正在下载的文件的总大小
 totalSize = urlConnection.getContentLength（）; 
 
 runOnUiThread（new Runnable（）{
 public void run（）{
 pb.setMax（totalSize）; 
} 
}）; 
 
 //创建缓冲区... 
 byte [] buffer = new byte [1024]; 
 int bufferLength = 0; （（bufferLength = inputStream.read（buffer））> 0）{
 fileOutput.write（buffer，0，bufferLength）; 
 
 while 
 downloadedSize + = bufferLength; 
 //更新进度条// 
 runOnUiThread（new Runnable（）{
 public void run（）{
 pb.setProgress（downloadedSize）; 
 float per = （（float）downloadedSize / totalSize）* 100; 
 cur_val.setText（Downloaded+ downloadedSize +KB /+ totalSize +KB（+（int）per +％））; 
} 
}）; 
 
 //完成后关闭输出流// 
 fileOutput.close（）; 
 runOnUiThread（new Runnable（）{
 public void run（）{
 // pb.dismiss（）; //如果要关闭它.. 
} 
}）; 
 $ b} catch（final MalformedURLException e）{
 showError（Error：MalformedURLException+ e）; 
 e.printStackTrace（）; 
 catch（final IOException e）{
 showError（Error：IOException+ e）; 
 e.printStackTrace（）; 
 
 catch（final Exception e）{
 showError（错误：请检查您的网络连接+ e）; 
 
 
 $ / code $ / pre 
 
 
另外，你需要改变你想要的路径保存文件并将Internet权限添加到 AndroidManifest 。
 
I have developed an Android app with a local SQLite based database.
Now I'm trying to sync this SQLite .db database with a server with a simple file replace - Just to download .db from server and replace the current one.

I have already created an JSON response with true/false just to check if the online .db file is newer than the local .db file so my question is: How to get the .db from the www.domain.com/sqlite.db and replace the existing Android sqlite .db file from my app.
解决方案
Try this code to check version of database: 
class CheckDb extends AsyncTask<String, Void, String> {

    @Override
    protected String doInBackground(String... params) {
        // Creating new JSON Parser
        JSONParser jParser = new JSONParser();

        // Getting JSON from URL
        c = jParser.getJSONFromUrl(url);

        try {
            // Getting JSON Array;

            // Storing  JSON item in a Variable
           final String id = c.getString(verzija).toString().trim();

      }
        catch (JSONException e) {
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(String s) {
        //Importing TextView
        final TextView json = (TextView)findViewById(R.id.textView);
        //Set JSON Data in TextView
        try {
            json.setText(c.getString(verzija).toString().trim());
            String db_version = c.getString(verzija).toString().trim();
            String current_version = "3";
            if(!db_version.equals(current_version)) {

                new Thread(new Runnable() {
                    public void run() {
                        downloadFile();
                    }
                }).start();

            }
            else {
                dialog.hide();
                Toast.makeText(MainActivity.this, "You have valid version of database", Toast.LENGTH_SHORT).show();
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
        super.onPostExecute(s);
    }
}
And this for downloading the new version and replacing the existing:
void downloadFile(){

    try {
        URL url = new URL(dwnload_file_path);
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

        urlConnection.setRequestMethod("GET");
        urlConnection.setDoOutput(true);

        //connect
        urlConnection.connect();

        //set the path where we want to save the file
        File SDCardRoot = Environment.getExternalStorageDirectory();
        //create a new file, to save the downloaded file
        File file = new File(SDCardRoot,"download_db.db");

        FileOutputStream fileOutput = new FileOutputStream(file);

        //Stream used for reading the data from the internet
        InputStream inputStream = urlConnection.getInputStream();

        //this is the total size of the file which we are downloading
        totalSize = urlConnection.getContentLength();

        runOnUiThread(new Runnable() {
            public void run() {
                pb.setMax(totalSize);
            }
        });

        //create a buffer...
        byte[] buffer = new byte[1024];
        int bufferLength = 0;

        while ( (bufferLength = inputStream.read(buffer)) > 0 ) {
            fileOutput.write(buffer, 0, bufferLength);
            downloadedSize += bufferLength;
            // update the progressbar //
            runOnUiThread(new Runnable() {
                public void run() {
                    pb.setProgress(downloadedSize);
                    float per = ((float)downloadedSize/totalSize) * 100;
                    cur_val.setText("Downloaded " + downloadedSize + "KB / " + totalSize + "KB (" + (int)per + "%)" );
                }
            });
        }
        //close the output stream when complete //
        fileOutput.close();
        runOnUiThread(new Runnable() {
            public void run() {
                // pb.dismiss(); // if you want close it..
            }
        });

    } catch (final MalformedURLException e) {
        showError("Error : MalformedURLException " + e);
        e.printStackTrace();
    } catch (final IOException e) {
        showError("Error : IOException " + e);
        e.printStackTrace();
    }
    catch (final Exception e) {
        showError("Error : Please check your internet connection " + e);
    }
}
Also, you need to change path where you want to save the file and add internet permission to your AndroidManifest.

                        
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