如何使新闻阅读器应用正常且快速地工作

Question

我正在尝试在android studio上构建新闻阅读器应用程序，但该应用程序显示空白屏幕或有时加载2或5个新闻标题。如何使其正常，快速地工作！

public class MainActivity extends AppCompatActivity {

    ArrayList<String> titles=new ArrayList<>();
    ArrayList<String> contents=new ArrayList<>();
    ArrayAdapter<String> adapter;
    SQLiteDatabase articlesDB;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ListView listView=(ListView) findViewById(R.id.listView);
        adapter=new ArrayAdapter<>(this,android.R.layout.simple_list_item_1,titles);
        listView.setAdapter(adapter);

        articlesDB=this.openOrCreateDatabase("Articles",MODE_PRIVATE,null);
        articlesDB.execSQL("CREATE TABLE IF NOT EXISTS articles(id INTEGER PRIMARY KEY,articleId INTEGER,title VARCHAR,content VARCHAR)");

        updateListView();

        DownloadTask task=new DownloadTask();
        try {
            task.execute("https://hacker-news.firebaseio.com/v0/topstories.json?print=pretty");
        }
        catch (Exception e){
            e.printStackTrace();
        }

    }

    public void updateListView(){
        Cursor c=articlesDB.rawQuery("SELECT * FROM articles",null);

        int titleIndex=c.getColumnIndex("title");
        int contentIndex=c.getColumnIndex("content");

        if(c.moveToFirst()){
            titles.clear();
            contents.clear();

            do{
                titles.add(c.getString(titleIndex));
                contents.add(c.getString(contentIndex));
            }
            while (c.moveToNext());

            adapter.notifyDataSetChanged();
        }
    }

    public class DownloadTask extends AsyncTask<String,Void,String>{

        @Override
        protected String doInBackground(String... urls) {
            String result="";
            URL url;
            HttpURLConnection conn=null;
            try {
                url=new URL(urls[0]);
                conn=(HttpURLConnection) url.openConnection();
                InputStream inputStream=conn.getInputStream();
                InputStreamReader reader=new InputStreamReader(inputStream);
                int data=reader.read();
                while (data!=-1){
                    char current=(char) data;
                    result=result+current;
                    data=reader.read();
                }

                JSONArray jsonArray=new JSONArray(result);
                int numberOfItems=20;
                if(jsonArray.length()<20){
                    numberOfItems=jsonArray.length();
                }

                articlesDB.execSQL("DELETE FROM articles");
                for(int i=1;i<numberOfItems;i++){

                    String articleId=jsonArray.getString(i);
                    url=new URL("https://hacker-news.firebaseio.com/v0/item/"+articleId+".json?print=pretty");
                    conn=(HttpURLConnection) url.openConnection();
                    inputStream=conn.getInputStream();
                    reader=new InputStreamReader(inputStream);
                    data=reader.read();
                    String artcileInfo="";
                    while (data!=-1){
                        char current=(char) data;
                        artcileInfo=artcileInfo+current;
                        data=reader.read();
                    }

                    JSONObject jsonObject=new JSONObject(artcileInfo);
                    //Dont trust API might be possible there is no url or no title then it would throw an exception
                    if(!jsonObject.isNull("title") && !jsonObject.isNull("url")){
                        String articleTitle=jsonObject.getString("title");
                        String articleURL=jsonObject.getString("url");

                        url=new URL(articleURL);
                        conn=(HttpURLConnection) url.openConnection();
                        inputStream=conn.getInputStream();
                        reader=new InputStreamReader(inputStream);
                        data=reader.read();
                        String articleActualContent="";
                        while (data!=-1){
                            char current=(char) data;
                            articleActualContent=articleActualContent+current;
                            data=reader.read();
                        } 

                        String sql="INSERT INTO articles(articleID,title,content) VALUES(? , ? , ?)";
                        SQLiteStatement statement=articlesDB.compileStatement(sql);
                        statement.bindString(1,articleId);
                        statement.bindString(2,articleTitle);
                        statement.bindString(3,articleURL);
                        statement.execute();
                    }
                }
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } catch (JSONException e) {
                e.printStackTrace();
            }
            return null;
        }

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

            updateListView();
        }
    }
}

GC中的输出释放了日志中持续出现的错误。 我的模拟器中需要19个新闻标题。