Xml parsing with AsyncTask slower than parsing in

2019-09-16 17:19发布

站内问答 / Android
1440 2 5

This question already has an answer here:

I'm having a strange behaviour in my code: parsing a local xml file on simulator with asyncTask takes longer than parsing it on main thread.

Here is my code with AsyncTask:

public class MostraTutti extends SherlockActivity {
ListView lv;
final List<ListViewItem> items = new ArrayList<MostraTutti.ListViewItem>();
final ArrayList<String> nome = new ArrayList<String>();
final ArrayList<String> immagine = new ArrayList<String>();
...

final   int array_image2[] ={R.drawable.iodocloroidrossichinolina,R.drawable.acidoacetilsalicilico,
        ...};

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.mostra_tutti);
    lv = (ListView) findViewById(R.id.listView);
    getSupportActionBar().setDisplayShowHomeEnabled(false);

    RssFeedTask rssTask = new RssFeedTask();
       rssTask.execute();

}

private class RssFeedTask extends AsyncTask<String, Void, String> {
    private ProgressDialog Dialog;
    String response = "";

    @Override
    protected void onPreExecute() {
        Dialog = new ProgressDialog(MostraTutti.this);
        Dialog.setMessage("Leggo le sostanze...");
        Dialog.show();
    }

        @Override
        protected String doInBackground(String... urls) {
            InputStream xmlFile = getResources().openRawResource(R.raw.sostanze);
            try {

            DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
            DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
            final Document document = documentBuilder.parse(xmlFile);
            document.getDocumentElement().normalize();
            NodeList nodeList = document.getElementsByTagName("sostanza");

            for (int i = 0; i < nodeList.getLength(); i++) {
            final int   indice = i;

            nome.add(document.getElementsByTagName("nome").item(indice).getTextContent());
            iupac.add(document.getElementsByTagName("iupac").item(indice).getTextContent());
            aspetto.add(document.getElementsByTagName("aspetto").item(indice).getTextContent());
            formula.add(document.getElementsByTagName("formula").item(indice).getTextContent());
            immagine.add(document.getElementsByTagName("immagine").item(indice).getTextContent());
            appartenenza.add(document.getElementsByTagName("appartenenza").item(indice).getTextContent());
            spiegazione.add(document.getElementsByTagName("spiegazione").item(indice).getTextContent());
            tempFus.add(document.getElementsByTagName("temperaturaFusione").item(indice).getTextContent());
            tempEboll.add(document.getElementsByTagName("temperaturaEbollizione").item(indice).getTextContent());
            solubilita.add(document.getElementsByTagName("solubilita").item(indice).getTextContent());
            note.add(document.getElementsByTagName("eccezioni").item(indice).getTextContent());

            String str = document.getElementsByTagName("formula").item(indice).getTextContent();

            str = str.replaceAll("0", "\u2080");
            str = str.replaceAll("1", "\u2081");
            str = str.replaceAll("2", "\u2082");
            str = str.replaceAll("3", "\u2083");
            str = str.replaceAll("4", "\u2084");
            str = str.replaceAll("5", "\u2085");
            str = str.replaceAll("6", "\u2086");
            str = str.replaceAll("7", "\u2087");
            str = str.replaceAll("8", "\u2088");
            str = str.replaceAll("9", "\u2089");

            final String stringa = str;
            formulaConvertita.add(stringa);

                    //CustomListViewAdapter adapter = new CustomListViewAdapter(MostraTutti.this,items);
                    //lv.setAdapter(adapter);
                    items.add(new ListViewItem()
                    {{
                        ThumbnailResource = array_image2[indice];
                        Title = document.getElementsByTagName("nome").item(indice).getTextContent();
                        SubTitle = stringa;
                    }});   
            };

        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        } catch (ParserConfigurationException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SAXException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }   

        return response;
}
        @Override
        protected void onPostExecute(String result) {
            Dialog.dismiss();
            CustomListViewAdapter adapter = new CustomListViewAdapter(MostraTutti.this,items);
            lv.setAdapter(adapter);

            lv.setOnItemClickListener(
                    new OnItemClickListener()
                    {
                        public void onItemClick(AdapterView<?> arg0, View v, int position, long id)
                        {                           
                            Context context = getBaseContext();
                           Intent myIntent = new Intent(context, Dettagli.class);

                           myIntent.putExtra("nome_sostanza",nome.get(position));
                         //  myIntent.putExtra("formula",formula.get(position));
                           myIntent.putExtra("iupac",iupac.get(position));                  
                           myIntent.putExtra("aspetto",aspetto.get(position));                 
                           myIntent.putExtra("appartenenza",appartenenza.get(position));
                           myIntent.putExtra("solubilita",solubilita.get(position));
                           myIntent.putExtra("tempFus",tempFus.get(position));
                           myIntent.putExtra("tempEboll",tempEboll.get(position));
                           myIntent.putExtra("spiegazione",spiegazione.get(position));
                           myIntent.putExtra("immagine", array_image2[position]);
                           myIntent.putExtra("formulaConvertita", formulaConvertita.get(position));
                           myIntent.putExtra("note", note.get(position));
                           startActivityForResult(myIntent, 0);
                        }

                        }
                 );
        }
        }

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getSupportMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}

class ListViewItem {
public int ThumbnailResource;
public String Title;
public String SubTitle;
}
}

And here's my code with no AsyncTask:

public class MostraTutti extends SherlockActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.mostra_tutti);
    getSupportActionBar().setDisplayShowHomeEnabled(false);

    final ListView lv = (ListView) findViewById(R.id.listView);
    final List<ListViewItem> items = new ArrayList<MostraTutti.ListViewItem>();
    final ArrayList<String> nome = new ArrayList<String>();
    final ArrayList<String> immagine = new ArrayList<String>();
    ...

    final   int array_image2[] ={R.drawable.iodocloroidrossichinolina,R.drawable.acidoacetilsalicilico,
            ...};

InputStream xmlFile = getResources().openRawResource(R.raw.sostanze);

    try {

        DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
        final Document document = documentBuilder.parse(xmlFile);
        document.getDocumentElement().normalize();
        //tagHandler.handleChannelTag(document);
        NodeList nodeList = document.getElementsByTagName("sostanza");

        for (int i = 0; i < nodeList.getLength(); i++) {
        final int   indice = i;

        nome.add(document.getElementsByTagName("nome").item(indice).getTextContent());
        iupac.add(document.getElementsByTagName("iupac").item(indice).getTextContent());
        aspetto.add(document.getElementsByTagName("aspetto").item(indice).getTextContent());
        formula.add(document.getElementsByTagName("formula").item(indice).getTextContent());
        immagine.add(document.getElementsByTagName("immagine").item(indice).getTextContent());
        appartenenza.add(document.getElementsByTagName("appartenenza").item(indice).getTextContent());
        spiegazione.add(document.getElementsByTagName("spiegazione").item(indice).getTextContent());
        tempFus.add(document.getElementsByTagName("temperaturaFusione").item(indice).getTextContent());
        tempEboll.add(document.getElementsByTagName("temperaturaEbollizione").item(indice).getTextContent());
        solubilita.add(document.getElementsByTagName("solubilita").item(indice).getTextContent());
        note.add(document.getElementsByTagName("eccezioni").item(indice).getTextContent());

        String str = document.getElementsByTagName("formula").item(indice).getTextContent();

        str = str.replaceAll("0", "\u2080");
        str = str.replaceAll("1", "\u2081");
        str = str.replaceAll("2", "\u2082");
        str = str.replaceAll("3", "\u2083");
        str = str.replaceAll("4", "\u2084");
        str = str.replaceAll("5", "\u2085");
        str = str.replaceAll("6", "\u2086");
        str = str.replaceAll("7", "\u2087");
        str = str.replaceAll("8", "\u2088");
        str = str.replaceAll("9", "\u2089");

        final String stringa = str;
        formulaConvertita.add(stringa);

        items.add(new ListViewItem()
            {{
                ThumbnailResource = array_image2[indice];
                Title = document.getElementsByTagName("nome").item(indice).getTextContent();
                SubTitle = stringa;
            }});
        }
    } catch (IOException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    } catch (ParserConfigurationException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (SAXException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }       
    CustomListViewAdapter adapter = new CustomListViewAdapter(this,items);
    lv.setAdapter(adapter);

    lv.setOnItemClickListener(
            new OnItemClickListener()
            {
                public void onItemClick(AdapterView<?> arg0, View v, int position, long id)
                {                           
                    Context context = getBaseContext();
                   Intent myIntent = new Intent(context, Dettagli.class);

                   myIntent.putExtra("nome_sostanza",nome.get(position));
                 //  myIntent.putExtra("formula",formula.get(position));
                   myIntent.putExtra("iupac",iupac.get(position));                  
                   myIntent.putExtra("aspetto",aspetto.get(position));                 
                   myIntent.putExtra("appartenenza",appartenenza.get(position));
                   myIntent.putExtra("solubilita",solubilita.get(position));
                   myIntent.putExtra("tempFus",tempFus.get(position));
                   myIntent.putExtra("tempEboll",tempEboll.get(position));
                   myIntent.putExtra("spiegazione",spiegazione.get(position));
                   myIntent.putExtra("immagine", array_image2[position]);
                   myIntent.putExtra("formulaConvertita", formulaConvertita.get(position));
                   myIntent.putExtra("note", note.get(position));
                   startActivityForResult(myIntent, 0);
                }

                }
         );
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getSupportMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}

class ListViewItem {
public int ThumbnailResource;
public String Title;
public String SubTitle;
}
}

The difference on simulator is 16 seconds for the main thread one and 1 minute for the AsyncTask one!

2条回答
放我归山
2楼-- · 2019-09-16 17:41

I've marked this question as a duplicate but last time I did this, the reviewers voted against it.

Either way, the reason is that AsyncTask's doInBackground() runs in a backgroud priority class and has to share at most 10% of CPU time with all other background tasks, such as your RSS reader's etc -- no matter how idle the system really is.

For a detailed discussion and solution, see here.

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三岁会撩人
3楼-- · 2019-09-16 18:05

16 seconds on UI thread is still too much and it's not a solution - your users will get hit by an ANR dialog every time. So a few recommendations are:

  1. Optimize the code inside the doInBackground().
  2. Consider using another XML parser, it may improve performance.
  3. If appropriate to your application logic, move this code to a background Service to make it process data while the user isn't interacting with your application. Store the information in a database and load it when an Activity is opened.
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