在AsyncTask中的HTTP请求
我有一个解析XML文件的HTTP请求。 我试图从asyntask连接到互联网,但我一直没能在AsyncTask中的HTTP请求
我通过把代码中的线程内做到这一点和作品,而不是内部的AsycTask 我的问题是,HTTP请求是一个字符串内调用这行代码:
String xml = parser.getXmlFromUrl(URL);
运行此
public String getXmlFromUrl(String url) {
Thread t= new Thread(){
public void run() {
xml = null;
try {
Log.i("Log1","Parse");
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost("http://api.androidhive.info/music/music.xml");
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
xml = EntityUtils.toString(httpEntity);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
mHandler.post(mUpdateResults);
}
};
t.start();
return xml;
}
final Runnable mUpdateResults =new Runnable(){
public void run(){//2
}
};
正如我提到的那样,HTTP请求是在一个线程中,但我总能找到错误,当我试图把它在一个AsycTa里面sk ...我不知道该怎么做。
我已经被引用到AsycTask的文档并阅读了很多次,我已经搜索了教程,但是我无法正确构建它。
经过两次天,我开始有点绝望
我把完整的代码对我的工作,如果有人能告诉我如何更换的AsyncTask线程,我将非常感激。
非常感谢你,并认为
充分的活动:
public class PruebasActivity extends Activity {
static final String URL = "http://api.androidhive.info/music/music.xml";
// XML node keys
static final String KEY_SONG = "song"; // parent node
static final String KEY_ID = "id";
static final String KEY_TITLE = "title";
static final String KEY_ARTIST = "artist";
static final String KEY_DURATION = "duration";
static final String KEY_THUMB_URL = "thumb_url";
private ArrayList<HashMap<String, String>> data;
ArrayList<HashMap<String, String>> songsList;
ListView list;
LazyAdapter adapter;
String xml;
final Handler mHandler=new Handler();
// constructor
public void XMLParser() {
}
/**
* Cogiendo el XML de la URL mediante HTTP request
* @param url string
* */
public String getXmlFromUrl(String url) {
Thread t= new Thread(){
public void run() {
xml = null;
try {
Log.i("Log1","Parse");
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost("http://api.androidhive.info/music/music.xml");
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
xml = EntityUtils.toString(httpEntity);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
mHandler.post(mUpdateResults);
}
};
t.start();
return xml;
}
final Runnable mUpdateResults =new Runnable(){
public void run(){//2
}
};
/*
* @param XML string
* */
public Document getDomElement(String xml){
Document doc = null;
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder db = dbf.newDocumentBuilder();
InputSource is = new InputSource();
is.setCharacterStream(new StringReader(xml));
doc = db.parse(is);
} catch (ParserConfigurationException e) {
Log.e("Error: ", e.getMessage());
return null;
} catch (SAXException e) {
Log.e("Error: ", e.getMessage());
return null;
} catch (IOException e) {
Log.e("Error: ", e.getMessage());
return null;
}
return doc;
}
/*
* @param elem element
*/
public final String getElementValue(Node elem) {
Node child;
if(elem != null){
if (elem.hasChildNodes()){
for(child = elem.getFirstChild(); child != null; child = child.getNextSibling()){
if(child.getNodeType() == Node.TEXT_NODE ){
return child.getNodeValue();
}
}
}
}
return "";
}
/*
* @param Element node
* @param key string
* */
public String getValue(Element item, String str) {
NodeList n = item.getElementsByTagName(str);
return this.getElementValue(n.item(0));
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
list=(ListView)findViewById(R.id.list);
songsList = new ArrayList<HashMap<String, String>>();
XMLParser parser = new XMLParser();
String xml = parser.getXmlFromUrl(URL); // Cogiendo XML de la URL
Document doc = parser.getDomElement(xml); // Cogiendo DOM de los elementos
NodeList nl = doc.getElementsByTagName(KEY_SONG);
// looping through all song nodes <song>
for (int i = 0; i < nl.getLength(); i++) {
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
Element e = (Element) nl.item(i);
// adding each child node to HashMap key => value
map.put(KEY_ID, parser.getValue(e, KEY_ID));
map.put(KEY_TITLE, parser.getValue(e, KEY_TITLE));
map.put(KEY_ARTIST, parser.getValue(e, KEY_ARTIST));
map.put(KEY_DURATION, parser.getValue(e, KEY_DURATION));
map.put(KEY_THUMB_URL, parser.getValue(e, KEY_THUMB_URL));
// adding HashList to ArrayList
songsList.add(map);
}
// Pasando datos parseados del adaptador al arrayList
adapter=new MinAdapter(this, songsList);
list.setAdapter(adapter);
}
}
HTTP请求可以的AsyncTask的doInBackground功能运行,可运行的是onPostExecute功能。 结果是这样的:
public class XmlTask extends AsyncTask<String, Void, String>{
public String doInBackground(String... urls){
String url = urls[0];
// Place your getXmlFromUrl content here
return xml;
}
public void onPostExecute(String xml){
// Your XML parsing staement here
}
}
在该代码中,线程和可运行是不必要的。
而在你活动只需轻按:
new XmlTask().execute("http://yoururl");
hi 当我将适配器连接到OnPostExecute的列表视图时出现错误 songsList = new ArrayList
你可以发布你的stacktrace吗? – throrin19 2012-07-11 07:07:15
解决了!非常感谢:) – Sergio76 2012-07-11 08:57:14
下面的代码应该为你工作。试试看:
public class PruebasActivity extends Activity {
static final String URL = "http://api.androidhive.info/music/music.xml";
// XML node keys
static final String KEY_SONG = "song"; // parent node
static final String KEY_ID = "id";
static final String KEY_TITLE = "title";
static final String KEY_ARTIST = "artist";
static final String KEY_DURATION = "duration";
static final String KEY_THUMB_URL = "thumb_url";
private ArrayList<HashMap<String, String>> data;
ArrayList<HashMap<String, String>> songsList;
ListView list;
LazyAdapter adapter;
String xml;
// constructor
public void XMLParser() {
}
/**
* Cogiendo el XML de la URL mediante HTTP request
* @param url string
* */
public String getXmlFromUrl(String url) {
xml = null;
try {
Log.i("Log1","Parse");
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost("http://api.androidhive.info/music/music.xml");
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
xml = EntityUtils.toString(httpEntity);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return xml;
}
/*
* @param XML string
* */
public Document getDomElement(String xml){
Document doc = null;
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder db = dbf.newDocumentBuilder();
InputSource is = new InputSource();
is.setCharacterStream(new StringReader(xml));
doc = db.parse(is);
} catch (ParserConfigurationException e) {
Log.e("Error: ", e.getMessage());
return null;
} catch (SAXException e) {
Log.e("Error: ", e.getMessage());
return null;
} catch (IOException e) {
Log.e("Error: ", e.getMessage());
return null;
}
return doc;
}
/*
* @param elem element
*/
public final String getElementValue(Node elem) {
Node child;
if(elem != null){
if (elem.hasChildNodes()){
for(child = elem.getFirstChild(); child != null; child = child.getNextSibling()){
if(child.getNodeType() == Node.TEXT_NODE ){
return child.getNodeValue();
}
}
}
}
return "";
}
/*
* @param Element node
* @param key string
* */
public String getValue(Element item, String str) {
NodeList n = item.getElementsByTagName(str);
return this.getElementValue(n.item(0));
}
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
list=(ListView)findViewById(R.id.list);
AsyncTask<Void, Void, Void> ast = new AsyncTask<Void, Void, Void>(){
ProgressDialog p;
@Override
protected void onPreExecute() {
// TODO Auto-generated method stub
p = new ProgressDialog(EditTextDemoActivity.this);
//write code to start the progress dialog
}
@Override
protected Void doInBackground(Void... params) {
// TODO Auto-generated method stub
songsList = new ArrayList<HashMap<String, String>>();
XMLParser parser = new XMLParser();
String xml = parser.getXmlFromUrl(URL); // Cogiendo XML de la URL
Document doc = parser.getDomElement(xml); // Cogiendo DOM de los elementos
NodeList nl = doc.getElementsByTagName(KEY_SONG);
// looping through all song nodes <song>
for (int i = 0; i < nl.getLength(); i++) {
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
Element e = (Element) nl.item(i);
// adding each child node to HashMap key => value
map.put(KEY_ID, parser.getValue(e, KEY_ID));
map.put(KEY_TITLE, parser.getValue(e, KEY_TITLE));
map.put(KEY_ARTIST, parser.getValue(e, KEY_ARTIST));
map.put(KEY_DURATION, parser.getValue(e, KEY_DURATION));
map.put(KEY_THUMB_URL, parser.getValue(e, KEY_THUMB_URL));
// adding HashList to ArrayList
songsList.add(map);
}
}
@Override
protected void onPostExecute(Void result) {
// TODO Auto-generated method stub
p.dismiss();
adapter=new MinAdapter(this, songsList);
lst.setAdapter(adapter);
}
};
ast.execute();
}
}
我已经使用AsyncTask
实施了代码。当您使用AsyncTask
时,您不需要任何其他Thread
来实施后台活动。我已经留下了一小部分编码(创建并显示进度对话框)作为练习。
希望这会有所帮助。
谢谢你太朋友:) – Sergio76 2012-07-11 09:00:19
我认为如果您在AsyncTask中尝试使用代码以及堆栈跟踪时发布代码会更有帮助。 – bytebender 2012-07-10 17:45:40