URLから画像をロードするときのパフォーマンスの問題

Question

RSSフィードのデータを表示するリストビューがあります。私はすべてをうまく取得し、それは私がそれをどのように表示されます。問題は、スクロールするときのパフォーマンスです。たいていのラグが非常に遅く、アプリが実際にクラッシュすることもあります。私がイメージを取り除くと、すべてがスムーズでうまくいく。これを修正して画像を保存するにはどうすればよいですか？

フラグメント：

package kyfb.android.kyfb.com.kyfb; 

import android.app.Fragment; 
import android.app.ListFragment; 
import android.content.Context; 
import android.content.Intent; 
import android.content.res.Configuration; 
import android.graphics.Color; 
import android.graphics.drawable.ColorDrawable; 
import android.media.Image; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.support.v4.app.FragmentActivity; 
import android.util.Log; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.AdapterView; 
import android.widget.AdapterView.OnItemClickListener; 
import android.widget.ListView; 
import android.widget.ProgressBar; 
import android.widget.TextView; 

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

import java.io.IOException; 
import java.lang.reflect.Array; 
import java.net.MalformedURLException; 
import java.net.URL; 

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

/** 
* Created by KFB on 8/12/14. 
*/ 
public class MarketUpdatesFragment extends Fragment { 

    ListView listFeed; 
    ProgressBar prgLoading; 
    TextView txtAlert; 

    MarketUpdatesAdapter la; 

    static String[] title; 
    static String[] pubDate; 
    static String[] link; 
    static String[] thumb; 

    String URLFeed; 

    URL Feed; 
    DocumentBuilder db; 
    Document doc; 
    NodeList nodeList; 
    Bundle rssBundle = new Bundle(); 

    public MarketUpdatesFragment(){} 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 

     super.onCreateView(inflater, container, savedInstanceState); 
     View rootView = inflater.inflate(R.layout.fragment_marketupdates, null); 

     URLFeed = "https://www.kyfb.com/index.cfm/_api/feed/v1/KYFB/?feedID=62BDAE63-9862-79EC-82AA7CE0C82E8B26"; 


     Context ctx = rootView.getContext(); 

     la = new MarketUpdatesAdapter(ctx); 

     listFeed = (ListView) rootView.findViewById(R.id.listFeed); 
     prgLoading = (ProgressBar) rootView.findViewById(R.id.prgLoading); 
     txtAlert = (TextView) rootView.findViewById(R.id.txtAlert); 

     ColorDrawable whiteColor = new ColorDrawable(Color.WHITE); 
     ColorDrawable blackColor = new ColorDrawable(Color.BLACK); 
     listFeed.setDivider(whiteColor); 
     listFeed.setDividerHeight(3); 

     new getDataTask().execute(); 

     listFeed.setOnItemClickListener(new OnItemClickListener() { 

      public void onItemClick(AdapterView<?> arg0, View arg1, int position, 
            long arg3) { 
       // TODO Auto-generated method stub 

       Intent web = new Intent(getActivity(), WebBrowser.class); 
       rssBundle.putString("myURL", link[position]); 
       web.putExtras(rssBundle); 
       startActivity(web); 
      } 
     }); 

     return rootView; 
    } 

    /** this class is used to handle thread */ 
    public class getDataTask extends AsyncTask<Void, Void, Void> { 

     @Override 
     protected void onPreExecute() { 
      // TODO Auto-generated method stub 
     } 

     @Override 
     protected Void doInBackground(Void... arg0) { 
      // TODO Auto-generated method stub 
      getDataFromFeed(); 

      return null; 
     } 

     @Override 
     protected void onPostExecute(Void result) { 
      // TODO Auto-generated method stub 
      //dialog.dismiss(); 
      prgLoading.setVisibility(8); 
      if(title != null){ 
       listFeed.setVisibility(0); 
       listFeed.setAdapter(la); 
      }else{ 
       txtAlert.setVisibility(0); 
      } 
     } 
    } 

    /* 
    * This code is used to get data from feed and store them 
    * to array attributes 
    */ 
    public void getDataFromFeed(){ 

     try { 
      Feed = new URL(URLFeed); 
      DocumentBuilderFactory dbf= DocumentBuilderFactory.newInstance(); 
      db = dbf.newDocumentBuilder(); 
      doc = db.parse(new InputSource(Feed.openStream())); 
      doc.getDocumentElement().normalize(); 
      nodeList = doc.getElementsByTagName("item"); 

      title = new String[nodeList.getLength()]; 
      pubDate = new String[nodeList.getLength()]; 
      link = new String[nodeList.getLength()]; 
      thumb = new String[nodeList.getLength()]; 

      for(int i = 0; i < nodeList.getLength(); i++) { 
       Node node = nodeList.item(i); 

       Element fstElmnt = (Element) node; 

       NodeList titleList = fstElmnt.getElementsByTagName("title"); 
       Element titleElement = (Element) titleList.item(0); 
       titleList = titleElement.getChildNodes(); 
       title[i] = ((Node) titleList.item(0)).getNodeValue(); 

       NodeList pubDateList = fstElmnt.getElementsByTagName("pubDate"); 
       Element pubDateElement = (Element) pubDateList.item(0); 
       pubDateList = pubDateElement.getChildNodes(); 
       pubDate[i] = ((Node) pubDateList.item(0)).getNodeValue(); 
       // chops off the " +0000" on date 
       pubDate[i] = pubDate[i].substring(0, pubDate[i].length()-14); 

       NodeList linkList = fstElmnt.getElementsByTagName("link"); 
       Element linkElement = (Element) linkList.item(0); 
       linkList = linkElement.getChildNodes(); 
       link[i] = ((Node) linkList.item(0)).getNodeValue(); 
      } 

      NodeList nodes = doc.getElementsByTagName("enclosure"); 
      for (int i = 0; i < nodes.getLength(); i++) { 
       Element thumbElement = (Element)nodes.item(i); 
       String thumbURL = thumbElement.getAttribute("url"); 
       if (thumbURL.equals("")) { 
        thumb[i] = "null"; 
       } else { 
        String httpURL = thumbURL; 
        String httpsURL = httpURL.toString().replace("http", "https"); 
        thumb[i] = httpsURL; 
       } 

       // System.out.println(thumb[i]); 
      } 

     } catch (MalformedURLException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     }catch (ParserConfigurationException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } catch (SAXException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } catch (IOException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } 
    } 

    @Override 
    public void onConfigurationChanged(final Configuration newConfig) 
    { 
     // Ignore orientation change to keep activity from restarting 
     super.onConfigurationChanged(newConfig); 
    } 
} 

アダプタ：

package kyfb.android.kyfb.com.kyfb; 

import android.content.Context; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.graphics.Canvas; 
import android.graphics.Color; 
import android.graphics.Path; 
import android.graphics.Rect; 
import android.media.Image; 
import android.util.Log; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.BaseAdapter; 
import android.widget.ImageView; 
import android.widget.RelativeLayout; 
import android.widget.TextView; 

import com.squareup.picasso.Picasso; 

import java.io.IOException; 
import java.io.InputStream; 
import java.net.HttpURLConnection; 
import java.net.URL; 

/** 
* Created by KFB on 8/12/14. 
*/ 
class MarketUpdatesAdapter extends BaseAdapter { 
    private LayoutInflater inflater; 

    public MarketUpdatesAdapter(Context context) { 

     inflater = LayoutInflater.from(context); 
    } 

    public int getCount() { 
     // TODO Auto-generated method stub 

     return MarketUpdatesFragment.title.length; 
    } 

    public Object getItem(int position) { 
     // TODO Auto-generated method stub 
     return position; 
    } 

    public long getItemId(int position) { 
     // TODO Auto-generated method stub 
     return position; 
    } 

    public View getView(int position, View convertView, ViewGroup parent) { 
     // TODO Auto-generated method stub 
     ViewHolder holder; 

     if(convertView == null){ 
      convertView = inflater.inflate(R.layout.item_feed, null); 
      holder = new ViewHolder(); 
      holder.lytItemFeed = (RelativeLayout) convertView.findViewById(R.id.lytItemFeed); 
      holder.txtTitle= (TextView) convertView.findViewById(R.id.txtTitle); 
      holder.txtPubDate = (TextView) convertView.findViewById(R.id.txtPubDate); 
      holder.thumbnail = (ImageView) convertView.findViewById(R.id.thumbnail); 

      convertView.setTag(holder); 
     }else{ 
      holder = (ViewHolder) convertView.getTag(); 
     } 

     holder.lytItemFeed.setBackgroundColor(Color.TRANSPARENT); 

     holder.txtTitle.setText(MarketUpdatesFragment.title[position]); 
     holder.txtPubDate.setText(MarketUpdatesFragment.pubDate[position]); 

     Context context = parent.getContext(); 
     if (MarketUpdatesFragment.thumb[position] != "null") { 

      Picasso.with(context) 
        .load(MarketUpdatesFragment.thumb[position]) 
        .placeholder(R.drawable.placeholder) 
        .error(R.drawable.placeholder) 
        .into(holder.thumbnail); 
     } else { 
      holder.thumbnail.setImageResource(R.drawable.placeholder); 
     } 

     holder.txtTitle.setTextColor(Color.WHITE); 
     holder.txtPubDate.setTextColor(Color.WHITE); 

     return convertView; 
    } 

    static class ViewHolder { 
     TextView txtTitle, txtPubDate; 
     ImageView thumbnail; 
     RelativeLayout lytItemFeed; 
    } 
} 

Answer 1

これはピカソの問題として提起されてきました。説明はthisリンクを参照してください。

スクロールするときにピカソの画像の読み込みを停止する必要があります。私はこの機能がPicassoライブラリに統合されていると思います。このコードは、また

listFeed.setOnScrollListener(new PicassoScrollListener(context)); 

thisはSO詳細はスレッドを参照できます場合

は試してみてください。