在我的android应用程序中，我有3个片段.AB和CI正在做一些XML解析和填充listviews。从A到B和B到C的擦除非常流畅。但是当我尝试从C刷到B和B到A，它被卡住了大约10秒。但是，A-> B-> C是平滑的。而且C-> B-> A有问题。它真的很烦人。任何人都可以帮我摆脱这个问题？...提前致谢....
这是我的MainActivity =＆gt;
public class MainActivity extends FragmentActivity {
private ViewPager mViewPager;
private ProgressDialog pd;
Button settings;
static TextView flashnews;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
SharedPreferences mlmprf = getSharedPreferences("malayalam", MODE_PRIVATE);
final SharedPreferences.Editor mlmedit = mlmprf.edit();
if(mlmprf.getBoolean("enable", true))
{
A.headflag="malayalam";
}
else
{
A.headflag="english";
}
flashnews=(TextView)findViewById(R.id.flashs);
flashnews.setSelected(true);
flashnews.setEllipsize(TruncateAt.MARQUEE);
flashnews.setHorizontallyScrolling(true);
flashnews.setSingleLine(true);
flashnews.setLines(1);
PagerTabStrip pagerTabStrip = (PagerTabStrip) findViewById(R.id.pager_title_strip);
pagerTabStrip.setDrawFullUnderline(true);
pagerTabStrip.setTabIndicatorColor(Color.rgb(174, 1, 34));
mViewPager = (ViewPager) findViewById(R.id.viewpager);
mViewPager.setAdapter(new MyAdapter(this));
}
private class MyAdapter extends FragmentPagerAdapter{
private Context mContext;
private String[] frags = {A.class.getName(), B.class.getName(),C.class.getName()};
public MyAdapter(FragmentActivity activity) {
super(activity.getSupportFragmentManager());
mContext = activity;
}
@Override
public Fragment getItem(int pos) {
return Fragment.instantiate(mContext, frags[pos]);
}
@Override
public int getCount() {
return frags.length;
}
@Override
public CharSequence getPageTitle(int pos) {
if(pos==0)
return "A";
if(pos==1)
return "B";
if(pos==2)
return "C";
else
return null;
}
}
}
FragmentA =＆GT;
public class A extends Fragment{
public static String urls;
// XML node keys
static final String KEY_HEAD = "item"; // parent node
//static final String KEY_TITLE = "title";
static final String KEY_DATE = "pubDate";
public static String headflag="english";
public static String[] Title;
public static String[] Description;
public static String[] Tit;
public static String[] Tit2;
public static String[] Desc;
public static String[] Desc2;
public static String[] image;
int f=0;
GridView list;
HeadlinesAdapter adapter;
private TextView mMessageView;
private Button mClearButton;
public ArrayList<HashMap<String, String>> newsList;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflating layout
View v = inflater.inflate(R.layout.headlines_fragment, container, false);
// We obtain layout references
return v;
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
// We set clear listener
if(Headlines.headflag=="malayalam")
{
urls="http://www.abc.com/rssfeeds/19_18_17_25/1/rss.xml";
}
if(Headlines.headflag=="english")
{
urls="http://www.abc.com/en/rssfeeds/1_2_3_5/latest/rss.xml";
}
parse();
populate_listview();
}
public void populate_listview()
{
newsList = new ArrayList<HashMap<String, String>>();
XMLParser parser = new XMLParser();
String xml = parser.getXmlFromUrl(urls); // getting XML from URL
Document doc = parser.getDomElement(xml); // getting DOM element
NodeList nl = doc.getElementsByTagName(KEY_HEAD);
// looping through all song nodes <song>
NodeList itemLst = doc.getElementsByTagName("item");
String MarqueeStr="";
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);
newsList.add(map);
//MarqueeStr = MarqueeStr +" *** "+ Title[i];
}
list=(GridView)getActivity().findViewById(R.id.grid);
// Getting adapter by passing xml data ArrayList
adapter=new HeadlinesAdapter(getActivity(), newsList);
list.setAdapter(adapter);
}
public void parse()
{
URL url;
try {
url = new URL(urls);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
if((conn.getResponseCode() == HttpURLConnection.HTTP_OK)){
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document doc;
doc = db.parse(url.openStream());
doc.getDocumentElement().normalize();
NodeList itemLst = doc.getElementsByTagName("item");
Description = new String[itemLst.getLength()];//........
Title = new String[itemLst.getLength()];
Tit=new String[itemLst.getLength()];
Tit2=new String[itemLst.getLength()];
Desc=new String[itemLst.getLength()];
Desc2=new String[itemLst.getLength()];
image= new String[itemLst.getLength()];
for(int i=0; i < itemLst.getLength(); i++){
Node item = itemLst.item(i);
if(item.getNodeType() == Node.ELEMENT_NODE){
Element ielem = (Element)item;
NodeList title = ielem.getElementsByTagName("title");
NodeList date = ielem.getElementsByTagName("pubDate");
NodeList description = ielem.getElementsByTagName("description");
Tit[i]= title.item(0).getChildNodes().item(0).getNodeValue();
Desc[i]= description.item(0).getChildNodes().item(0).getNodeValue();
Tit2[i]=Translate.title(Tit[i]);
Desc2[i]=Translate.description(Desc[i]);
if(Headlines.headflag=="malayalam")
{
Desc2[i]=Desc2[i].replace("read more","IqSpXÂ");
}
Title[i] =Tit2[i];
if (Desc2[i].contains("<img ")){
String img = Desc2[i].substring(Desc2[i].indexOf("<img "));
String cleanUp = img.substring(0, img.indexOf(">")+1);
img = img.substring(img.indexOf("src=") + 5);
int indexOf = img.indexOf("'");
if (indexOf==-1){
indexOf = img.indexOf("\"");
}
img = img.substring(0, indexOf);
//setImgLink(img);
if(Headlines.headflag=="malayalam")
{
String img2=img.replace("files","files/imagecache/android_320");
Description[i]=Desc2[i].replace(img,img2);
image[i]=img2;
}
else
{
String img2=img.replace("files","files/imagecache/android_1_img");
Description[i]=Desc2[i].replace(img,img2);
image[i]=img2;
}
}
else
{
Description[i] =Desc2[i];
}
}
}
}
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (DOMException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException 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();
}
}
}
片段B =＆gt;
public class B Fragment{
static String urls;
// XML node keys
static final String KEY_HEAD = "item"; // parent node
//static final String KEY_TITLE = "title";
static final String KEY_DATE = "pubDate";
public static String headflag="";
int f=0;
GridView list;
KeralaAdapter adapter;
ProgressBar loading;
ArrayList<HashMap<String, String>> newsList;
public static Kerala classnam;
public static String[] Title;
public static String[] Description;
public static String[] Tit;
public static String[] Tit2;
public static String[] Desc;
public static String[] Desc2;
public static String[] image;
public static String[] Date;
public static String[] Flash;
public static String[] Fl;
public static String[] Fl2;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflating layout
View v = inflater.inflate(R.layout.kerala_fragment, container, false);
// We obtain layout references
return v;
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
// We set clear listener
if(Headlines.headflag=="malayalam")
{
urls="http://www.abc.com/rssfeeds/17/1/rss.xml";
}
if(Headlines.headflag=="english")
{
urls="http://www.abc.com/en/rssfeeds/1/latest/rss.xml";
}
loading=(ProgressBar)getActivity().findViewById(R.id.loading);
new ProgressAsyncTask().execute();
}
public void populate_listview()
{
newsList = new ArrayList<HashMap<String, String>>();
XMLParser parser = new XMLParser();
String xml = parser.getXmlFromUrl(urls); // getting XML from URL
Document doc = parser.getDomElement(xml); // getting DOM element
NodeList nl = doc.getElementsByTagName(KEY_HEAD);
// looping through all song nodes <song>
NodeList itemLst = doc.getElementsByTagName("item");
String MarqueeStr="";
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);
//map.put(KEY_DATE, parser.getValue(e, KEY_DATE));
newsList.add(map);
}
list=(GridView)getActivity().findViewById(R.id.grid2);
}
public class ProgressAsyncTask extends
AsyncTask<Void, Integer, Void> {
int myProgress;
@Override
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
myProgress = 0;
}
@Override
protected void onPostExecute(Void result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
adapter=new NationalAdapter(getActivity(), newsList);
list.setAdapter(adapter);
}
@Override
protected Void doInBackground(Void... arg0) {
// TODO Auto-generated method stub
parse();
populate_listview();
return null;
}
@Override
protected void onProgressUpdate(Integer... values) {
// TODO Auto-generated method stub
}
}
public void parse()
{
URL url;
try {
url = new URL(urls);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
if((conn.getResponseCode() == HttpURLConnection.HTTP_OK)){
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document doc;
doc = db.parse(url.openStream());
doc.getDocumentElement().normalize();
NodeList itemLst = doc.getElementsByTagName("item");
Description = new String[itemLst.getLength()];//........
Title = new String[itemLst.getLength()];
Tit=new String[itemLst.getLength()];
Tit2=new String[itemLst.getLength()];
Desc=new String[itemLst.getLength()];
Desc2=new String[itemLst.getLength()];
image= new String[itemLst.getLength()];
for(int i=0; i < itemLst.getLength(); i++){
Node item = itemLst.item(i);
if(item.getNodeType() == Node.ELEMENT_NODE){
Element ielem = (Element)item;
NodeList title = ielem.getElementsByTagName("title");
NodeList date = ielem.getElementsByTagName("pubDate");
NodeList description = ielem.getElementsByTagName("description");
Tit[i]= title.item(0).getChildNodes().item(0).getNodeValue();
Desc[i]= description.item(0).getChildNodes().item(0).getNodeValue();
Tit2[i]=Translate.title(Tit[i]);
Desc2[i]=Translate.description(Desc[i]);
if(Headlines.headflag=="malayalam")
{
Desc2[i]=Desc2[i].replace("read more","IqSpXÂ");
}
Title[i] =Tit2[i];
if (Desc2[i].contains("<img ")){
String img = Desc2[i].substring(Desc2[i].indexOf("<img "));
String cleanUp = img.substring(0, img.indexOf(">")+1);
img = img.substring(img.indexOf("src=") + 5);
int indexOf = img.indexOf("'");
if (indexOf==-1){
indexOf = img.indexOf("\"");
}
img = img.substring(0, indexOf);
//setImgLink(img);
if(Headlines.headflag=="malayalam")
{
String img2=img.replace("files","files/imagecache/android_320");
Description[i]=Desc2[i].replace(img,img2);
image[i]=img2;
}
else
{
String img2=img.replace("files","files/imagecache/android_1_img");
Description[i]=Desc2[i].replace(img,img2);
image[i]=img2;
}
}
else
{
Description[i] =Desc2[i];
}
}
}
}
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (DOMException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException 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();
}
}
}
片段C实际上是一个空白片段。
答案 0 :(得分：5)
一些可以帮助您的解决方案：
1 - 在代码中添加日志记录，以查看是否多次调用onCreateView和onViewCreated。
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.kerala_fragment, container, false);
**Log.i("Tag", "onCreateView");**
return v;
}
2-不要在主UI线程上进行网络调用或任何长时间运行的代码。例如，您正在调用在您的UI线程上进行网络调用的parse（）。这就是为什么你的应用程序有延迟，特别是在片段A中。使用AsyncTask / Thread / Future
3 - 如果你有3个片段，只为viewPager设置此选项：viewPager.setOffscreenPageLimit（3）。看起来你的片段每次都在被重建。这会导致调用viewCreated，从而调用您的parse（）。
4 - 您可以将数据从doInBackground（）传递到onPostExecute。你不需要populate_listview。
如果您需要更多解释，请与我们联系。
答案 1 :(得分：1)
您需要获取数据并在后台线程中解析它，否则您的Fragment的生命周期方法将暂停一段时间，因此您会看到它被卡住了。
使用Aysnctasks或后台线程执行需要很长时间才能完成的操作。
答案 2 :(得分：1)
作为一般规则，您应该始终执行长期任务，例如后台线程中的网络连接。在活动中，您始终可以使用AsyncTask。第二件事为什么每次用户更改视图寻呼机页面时都会加载Feed。你最初应该这样做，并在后台修复间隔后刷新它......
EDIT1：
实现保持可从每个片段访问的全局数据结构的一种方法，您可以使用自定义Application对象，并将每种语言的数据存储在该数据结构中。
每次用户转到您页面检查数据是否在全局对象中可用（如果可用），则显示数据或显示加载。
从您的活动中启动AsyncTask，为每种语言从服务器加载数据，解析并将其存储在全局数据结构中。每次成功下载后，通知片段数据已更新在全局对象中，并相应地更新其视图..
答案 3 :(得分：1)
populateListView必须在异步任务的onPostExecute（）方法中完成....