使用AsyncTask进行Xml解析比在主线程中解析慢 [英] Xml parsing with AsyncTask slower than parsing in main Thread
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问题描述
这是我的代码与AsyncTask：
public class MostraTutti扩展了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）; （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（dissolve）。item（indice）.getTextContent（））;
note.add（document.getElementsByTagName（eccezioni）。item（indice）.getTextContent（））;
String str = document.getElementsByTagName（formula）。item（indice）.getTextContent（）;
str = str.replaceAll（0，\\\₀）;
str = str.replaceAll（1，\\\₁）;
str = str.replaceAll（2，\\\₂）;
str = str.replaceAll（3，\\\₃）;
str = str.replaceAll（4，\\\₄）;
str = str.replaceAll（5，\\\₅）;
str = str.replaceAll（6，\\\₆）;
str = str.replaceAll（7，\\\₇）;
str = str.replaceAll（8，\\\₈）;
str = str.replaceAll（9，\\\₉）;
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];
标题= document.getElementsByTagName（nome）。item（indice）.getTextContent （）;
SubTitle = stringa;
}}）;
};
} catch（IOException e1）{
// TODO自动生成的catch块
e1.printStackTrace（）;
} catch（ParserConfigurationException e）{
// TODO自动生成的catch块
e.printStackTrace（）;
} catch（SAXException e）{
// TODO自动生成的catch块
e.printStackTrace（）;
}
返回响应;
}
@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（dissolve solubilita.g等（位置））;
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（菜单菜单）{
//充满菜单;如果存在，则会将项目添加到操作栏。
getSupportMenuInflater（）。inflate（R.menu.activity_main，menu）;
返回true;
}
class ListViewItem {
public int ThumbnailResource;
public String Title;
public String SubTitle;
}
}
这里是没有AsyncTask的代码：
public class MostraTutti扩展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）; （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（dissolve）。item（indice）.getTextContent（））;
note.add（document.getElementsByTagName（eccezioni）。item（indice）.getTextContent（））;
String str = document.getElementsByTagName（formula）。item（indice）.getTextContent（）;
str = str.replaceAll（0，\\\₀）;
str = str.replaceAll（1，\\\₁）;
str = str.replaceAll（2，\\\₂）;
str = str.replaceAll（3，\\\₃）;
str = str.replaceAll（4，\\\₄）;
str = str.replaceAll（5，\\\₅）;
str = str.replaceAll（6，\\\₆）;
str = str.replaceAll（7，\\\₇）;
str = str.replaceAll（8，\\\₈）;
str = str.replaceAll（9，\\\₉）;
final String stringa = str;
formulaConvertita.add（stringa）;
items.add（new ListViewItem（）
{{
ThumbnailResource = array_image2 [indice];
标题= document.getElementsByTagName（nome）。item indice）.getTextContent（）;
SubTitle = stringa;
}}）;
}
} catch（IOException e1）{
// TODO自动生成的catch块
e1.printStackTrace（）;
} catch（ParserConfigurationException e）{
// TODO自动生成的catch块
e.printStackTrace（）;
} catch（SAXException e）{
// TODO自动生成的catch块
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（dissolve （）;
myIntent.putExtra（tempFus，tempFus.get（position））;
myIntent.putExtra（ tempEboll，tempEboll.get（位置））;
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（菜单菜单）{
getSupportMenuInflater（）。inflate（R.menu.activity_main，menu）;
返回true;
}
class ListViewItem {
public int ThumbnailResource;
public String Title;
public String SubTitle;
}
}
模拟器上的差异是16秒一分钟和一分钟的AsyncTask一个！
解决方案
我把这个问题标记为重复，但是上次我这样做，评论者投票反对。
无论哪种方式，原因是 AsyncTask 的 doInBackground（）运行在背景优先级类中，并且必须与所有其他后台任务（如RSS阅读器等）共享最多10％的CPU时间，无论系统真正处于空闲状态。
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!
解决方案
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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