如何将 RSS 提要数据保存到 Android 中的 SQLite？

Question

我能够在 android studio 中成功解析 RSS 提要，但我想将解析后的数据保存到数据库中，所以如果我离线，我仍然可以从保存的数据中检索。

这是我的MainActivity

package com.jjurrius.simplerssvideo;

import android.app.ProgressDialog;
import android.content.Intent;
import android.net.Uri;
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import org.xmlpull.v1.XmlPullParserFactory;

import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.sql.SQLException;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    ListView lvRss;
    ArrayList<String> titles;
    ArrayList<String> links;
    private DatabaseHandler db;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lvRss = (ListView) findViewById(R.id.lvRss);

        titles = new ArrayList<String>();
        links = new ArrayList<String>();
        db = new DatabaseHandler(this);

        try {
            db.open();
            NewsInformation item = new NewsInformation();
            item.completeTextLink = "Your Link of news";
            item.title            = "title of news";
            item.writerName       = "writer of news";
            item.dateWriten       = "1999";
            item.source           = "something";
            item.smallBody        = "news body";
            item.bigBody          = "news text";
            item.page             = "1";
            db.insertNewsInfo(item);
            db.close();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }


        lvRss.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
                Uri uri = Uri.parse(links.get(position));
                Intent intent = new Intent(Intent.ACTION_VIEW, uri);
                startActivity(intent);
            }
        });

        new ProcessInBackground().execute();
    }

    public InputStream getInputStream(URL url)
    {
        try
        {
            return url.openConnection().getInputStream();
        }
        catch (IOException e)
        {
            return null;
        }
    }

    public class ProcessInBackground extends AsyncTask<Integer, Void, Exception>
    {
        ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);

        Exception exception = null;
        @Override
        protected void onPreExecute() {
            progressDialog.setMessage("Fetching Latest News!");
            progressDialog.show();

        }

        @Override
        protected Exception doInBackground(Integer... integers) {
            try
            {

                // rss feed site here
                URL url = new URL("https://moxie.foxnews.com/feedburner/world.xml");
                // factory new instance
                XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
                factory.setNamespaceAware(false);
                XmlPullParser xpp = factory.newPullParser();
                xpp.setInput(getInputStream(url),"UTF_8");

                boolean insideItem = false;

                int eventType = xpp.getEventType();

                while (eventType != XmlPullParser.END_DOCUMENT)
                {
                    if(eventType == XmlPullParser.START_TAG)
                    {
                        if(xpp.getName().equalsIgnoreCase("item"))
                        {
                            insideItem = true;
                        }
                        else if (xpp.getName().equalsIgnoreCase("title"))
                        {
                            if(insideItem)
                            {
                                titles.add(xpp.nextText());

                            }
                        }

                    }
                    else if(eventType == XmlPullParser.START_TAG && xpp.getName().equalsIgnoreCase("item"))
                    {
                        insideItem = false;
                    }

                    eventType = xpp.next();
                }
            }
            catch (MalformedURLException e)
            {
                exception = e;
            }
            catch (XmlPullParserException e)
            {
                exception = e;
            }
            catch (IOException e)
            {
                exception = e;
            }
            return null;
        }

        @Override
        protected void onPostExecute(Exception s) {
            super.onPostExecute(s);

            ArrayAdapter<String> adapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1,titles);

            lvRss.setAdapter(adapter);
            progressDialog.dismiss();

        }
    }
}

我的NewsInformation.java

package com.jjurrius.simplerssvideo;

public class NewsInformation
{
    public String completeTextLink;
    public String title;
    public String writerName;
    public String dateWriten;
    public String source;
    public String smallBody;
    public String bigBody;
    public String page;
}

我的DabaseHelper.java

package com.jjurrius.simplerssvideo;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class DatabaseHelper extends SQLiteOpenHelper {

    private final String TAG = "DatabaseHelper";
    private static final String DATABASE_NAME = "db_for_news";

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, 10);

        //fdd
        Log.i(TAG, "Object created.");
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE news ( page TEXT ," +
                " completeTextLink TEXT  ,title TEXT , writerName TEXT , dateWriten TEXT ," +
                " source TEXT ,  smallBody TEXT , bigBody TEXT);");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        Log.w(DatabaseHelper.class.getName(), "Upgrading database from version "
                + oldVersion + " to " + newVersion + ", which will destroy all old data");
        db.execSQL("Drop table if exists news" );
        onCreate(db);
    }
}

我的DatabaseHandler.java

package com.jjurrius.simplerssvideo;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class DatabaseHandler {

    private DatabaseHelper dbHelper;
    private SQLiteDatabase database;


    public DatabaseHandler(Context context) {
        dbHelper = new DatabaseHelper(context);
    }

    //methods for all table
    public void open() throws SQLException {
        database = dbHelper.getWritableDatabase();
    }

    public void close() {
        dbHelper.close();
    }

    public void clearTable(String tableName) {
        database.delete( tableName, null, null);
    }

    //news table method

    public void insertNewsInfo(NewsInformation newsInfo) {
        ContentValues cv = new ContentValues();
        cv.put("bigBody"          ,  newsInfo.bigBody );
        cv.put("completeTextLink" ,  newsInfo.completeTextLink );
        cv.put("dateWriten"       ,  newsInfo.dateWriten );
        cv.put("source"            ,  newsInfo.source );
        cv.put("smallBody"        ,  newsInfo.smallBody );
        cv.put("title"            ,  newsInfo.title );
        cv.put("writerName"       ,  newsInfo.writerName );
        cv.put("page"             ,  newsInfo.page );

        database.insert("news" , "writerName", cv);
    }


    public List<NewsInformation> getAllNewsForPage(String page) {
        List<NewsInformation> NewsInfoList = new ArrayList<NewsInformation>();

        Cursor cursor = database.rawQuery("select completeTextLink " +
                " , title , writerName , dateWriten , source , smallBody , bigBody" +
                " FROM news where page = ?", new String[]{page});


        cursor.moveToFirst();
        while (!cursor.isAfterLast()) {
            NewsInformation newsInfo = new NewsInformation();

            newsInfo.completeTextLink = cursor.getString(0);
            newsInfo.title = cursor.getString(1);
            newsInfo.writerName = cursor.getString(2);
            newsInfo.dateWriten = cursor.getString(3);
            newsInfo.source = cursor.getString(4);
            newsInfo.smallBody = cursor.getString(5);
            newsInfo.bigBody = cursor.getString(6);
            newsInfo.page = page;

            NewsInfoList.add(newsInfo);
            cursor.moveToNext();
        }

        // Make sure to close the cursor
        cursor.close();

        return NewsInfoList;
    }

    public String getBigBody(String completeBodyLink) {
        Cursor cursor = database.rawQuery("select bigBody FROM news where completeTextLink = ?", new String[]{completeBodyLink});
        cursor.moveToFirst();
        String bigBody = cursor.getString(0);
        cursor.close();
        return bigBody;
    }
}

当我运行该应用程序时，它会向我显示 rss 提要，但我无法保存它们。我不知道错误在哪里。

这是我的 github 仓库：SimpleRssFeed

Answer 1

你好，我的朋友； 我更改了您的代码，为了更好地理解，我使用 Document、Element、NodeList 对象来获取 Rss。 在 doInBackground 方法中，我们获取 rss 中的所有必需字段并创建 NewsInformation 对象，最后我们得到 NewsInformation 列表，并在 onPostExecute 方法中将它们添加到 DB 和 Listview 适配器， 这是我对您的代码所做的更改：

您的数据对象

    public class NewsInformation
{
    public String link;
    public String title;
    public String pubdate;
    public String category;

}

和您的活动：

    import android.app.ProgressDialog;
import android.content.Intent;
import android.net.Uri;
import android.os.AsyncTask;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import androidx.appcompat.app.AppCompatActivity;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;


import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.sql.SQLException;
import java.util.ArrayList;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

public class RssReader extends AppCompatActivity {

    ListView lvRss;
    ArrayList<String> titles;
    ArrayList<String> links;
    ArrayList<NewsInformation> news =new ArrayList<>();
    private DatabaseHandler db;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.rss_reader);
        lvRss = (ListView) findViewById(R.id.lvRss);

        titles = new ArrayList<String>();
        links = new ArrayList<String>();
        db = new DatabaseHandler(this);


        lvRss.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int position, long id) {
                Uri uri = Uri.parse(links.get(position));
                Intent intent = new Intent(Intent.ACTION_VIEW, uri);
                startActivity(intent);
            }
        });

        new ProcessInBackground().execute();
    }

    public InputStream getInputStream(URL url) {
        try {
            return url.openConnection().getInputStream();
        } catch (IOException e) {
            return null;
        }
    }

    public class ProcessInBackground extends AsyncTask<Integer, Void, Exception> {
        ProgressDialog progressDialog = new ProgressDialog(RssReader.this);

        Exception exception = null;

        @Override
        protected void onPreExecute() {
            progressDialog.setMessage("Fetching Latest News!");
            progressDialog.show();

        }

        @Override
        protected Exception doInBackground(Integer... integers) {
            try {
                // rss feed site here
                URL url = new URL("https://moxie.foxnews.com/feedburner/world.xml");

                DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
                DocumentBuilder db = dbf.newDocumentBuilder();

                Document doc = db.parse(getInputStream(url));

                doc.getDocumentElement().normalize();
                NodeList nodeList = doc.getElementsByTagName("item");
                Log.e("node size:", String.valueOf(nodeList.getLength()));
                //// fetch every node item in RSS and create news_item list
                for (int i = 0; i < nodeList.getLength(); i++) {
                    NewsInformation news_item = new NewsInformation();
                    Node node = nodeList.item(i);
                    Element parentItem = (Element) node;

                    NodeList links = parentItem.getElementsByTagName("link");
                    Element element_link = (Element) links.item(0);
                    NodeList element_link_childNodes = element_link.getChildNodes();
                    news_item.link = element_link_childNodes.item(0).getNodeValue();


                    NodeList titles = parentItem.getElementsByTagName("title");
                    Element element_title = (Element) titles.item(0);
                    NodeList element_title_childNodes = element_title.getChildNodes();
                    news_item.title = element_title_childNodes.item(0).getNodeValue();


                    NodeList pubDates = parentItem.getElementsByTagName("pubDate");
                    Element element_pubDate = (Element) pubDates.item(0);
                    NodeList element_pubDate_childNodes = element_pubDate.getChildNodes();
                    news_item.pubdate = element_pubDate_childNodes.item(0).getNodeValue();


                    NodeList categorys = parentItem.getElementsByTagName("pubDate");
                    Element element_category = (Element) categorys.item(0);
                    NodeList element_category_childNodes = element_category.getChildNodes();
                    news_item.category = element_category_childNodes.item(0).getNodeValue();

                    news.add(news_item);

                   //////////////////////////////////////////////////////////////////////////////////////////////

                }


            } catch (MalformedURLException e) {
                exception = e;
                Log.e("nerror1:", String.valueOf(e));
            } catch (IOException e) {
                exception = e;
                Log.e("nerror2:", String.valueOf(e));
            } catch (ParserConfigurationException e) {
                e.printStackTrace();
                Log.e("nerror3:", String.valueOf(e));
            } catch (SAXException e) {
                e.printStackTrace();
                Log.e("nerror4:", String.valueOf(e));
            }
            return null;
        }

        @Override
        protected void onPostExecute(Exception s) {
            super.onPostExecute(s);
            ArrayAdapter<String> adapter = new ArrayAdapter<String>(RssReader.this, android.R.layout.simple_list_item_1, titles);
            lvRss.setAdapter(adapter);

//////////// after fetching data insert to db///////////////////////////////////////////
                try {
                    db.open();
                    for (int i = 0; i < news.size(); ++i) {
                        db.insertNewsInfo(news.get(i));
                    }
                    db.close();

                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }

/////////////////////////////////////////////////////////////////////////////
            progressDialog.dismiss();

        }
    }
}

作为建议，我向您推荐：

• 使用协程库而不是 AsyncTask 类（阅读协程）

• 对于 http/https 请求使用改造库

• 使用 Room 代替 dataBaseHandler