我正在工作json.i创建了viepager（tabhost）我有三个片段和每个片段我解析了json（我使用Asynctask每个片段）我可以在listview中显示json数据（图像和文本）。完美但是当程序启动的时候有三个asynctask开始同一时间和程序是缓慢的，当我去下一个片段时我还有另一个问题然后如果我回到片段Asynctask也运行两次。例如，如果我的json服务器链接包含两个数据当我回到片段然后我有4件物品 如果有人知道解决方案有什么问题请帮助我 谢谢 这是我的代码： MainActivity.java代码
public class MainActivity extends FragmentActivity implements
TabHost.OnTabChangeListener, ViewPager.OnPageChangeListener {
private TabHost mTabHost;
private ViewPager mViewPager;
private HashMap<String, TabInfo> mapTabInfo = new HashMap<String, MainActivity.TabInfo>();
private PagerAdapter mPagerAdapter;
private HorizontalScrollView horizontalScrollView;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_main);
this.initialiseTabHost(savedInstanceState);
if (savedInstanceState != null) {
mTabHost.setCurrentTabByTag(savedInstanceState.getString("tab"));
}
this.intialiseViewPager();
}
protected void onSaveInstanceState(Bundle outState) {
outState.putString("tab", mTabHost.getCurrentTabTag());
super.onSaveInstanceState(outState);
}
private void intialiseViewPager() {
List<Fragment> fragments = new Vector<Fragment>();
fragments.add(Fragment.instantiate(this, Pirveli.class.getName()));
fragments.add(Fragment.instantiate(this, Meore.class.getName()));
fragments.add(Fragment.instantiate(this, Mesame.class.getName()));
this.mPagerAdapter = new PagerAdapter(
super.getSupportFragmentManager(), fragments);
//
this.mViewPager = (ViewPager) super.findViewById(R.id.viewpager);
this.horizontalScrollView = (HorizontalScrollView) super
.findViewById(R.id.horizontalScrollView);
this.mViewPager.setAdapter(this.mPagerAdapter);
this.mViewPager.setOnPageChangeListener(this);
}
public void centerTabItem(int position) {
mTabHost.setCurrentTab(position);
final TabWidget tabWidget = mTabHost.getTabWidget();
final int screenWidth = getWindowManager().getDefaultDisplay()
.getWidth();
final int leftX = tabWidget.getChildAt(position).getLeft();
int newX = 0;
newX = leftX + (tabWidget.getChildAt(position).getWidth() / 2)
- (screenWidth / 2);
if (newX < 0) {
newX = 0;
}
horizontalScrollView.scrollTo(newX, 0);
}
private void initialiseTabHost(Bundle args) {
mTabHost = (TabHost) findViewById(android.R.id.tabhost);
mTabHost.setup();
TabInfo tabInfo = null;
MainActivity.AddTab(this, this.mTabHost,
this.mTabHost.newTabSpec("Send").setIndicator("Send"),
(tabInfo = new TabInfo("Send", Pirveli.class, args)));
this.mapTabInfo.put(tabInfo.tag, tabInfo);
MainActivity.AddTab(this, this.mTabHost,
this.mTabHost.newTabSpec("Recived").setIndicator("Recived"),
(tabInfo = new TabInfo("Recived", Meore.class, args)));
this.mapTabInfo.put(tabInfo.tag, tabInfo);
MainActivity
.AddTab(this,
this.mTabHost,
this.mTabHost.newTabSpec("Favourite").setIndicator(
"Favourite"), (tabInfo = new TabInfo(
"Favourite", Mesame.class, args)));
this.mapTabInfo.put(tabInfo.tag, tabInfo);
mTabHost.setOnTabChangedListener(this);
}
private static void AddTab(MainActivity activity, TabHost tabHost,
TabHost.TabSpec tabSpec, TabInfo tabInfo) {
tabSpec.setContent(activity.new TabFactory(activity));
tabHost.addTab(tabSpec);
}
public void onTabChanged(String tag) {
for (int i = 0; i < mTabHost.getTabWidget().getChildCount(); i++) {
TextView tv = (TextView) mTabHost.getTabWidget().getChildAt(i)
.findViewById(android.R.id.title);
// tv.setTextColor(getResources().getColor(R.color.sa_green));
}
int pos = this.mTabHost.getCurrentTab();
this.mViewPager.setCurrentItem(pos);
}
@Override
public void onPageScrolled(int position, float positionOffset,
int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
centerTabItem(position);
}
@Override
public void onPageScrollStateChanged(int state) {
}
private class TabInfo {
private String tag;
private Class<?> clss;
private Bundle args;
private Fragment fragment;
TabInfo(String tag, Class<?> clazz, Bundle args) {
this.tag = tag;
this.clss = clazz;
this.args = args;
}
}
class TabFactory implements TabContentFactory {
private final Context mContext;
public TabFactory(Context context) {
mContext = context;
}
public View createTabContent(String tag) {
View v = new View(mContext);
v.setMinimumWidth(0);
v.setMinimumHeight(0);
return v;
}
}
} 和第一个片段java代码
public class Pirveli extends Fragment {
private String URL = "*************";
private JSONArray jsonarray;
private ListView list;
private TransparentProgressDialog pd;
private JSONParser jsonparser;
private static DealBoxAdapter adapter;
private ArrayList<HashMap<String, String>> itemList = new ArrayList<HashMap<String, String>>();
private int screenSize;
private LoadDataAllChanelsToServer loader;
private static String dateTime;
private ArrayList<Content> contents = new ArrayList<Content>();
private static boolean oneTime = false;
private TextView journal, tittle, description, smalllink, DateTime,
smallstatID;
private boolean scrollDetected = false;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.send_items, container, false);
list = (ListView) rootView.findViewById(R.id.pirvelilistview);
pd = new TransparentProgressDialog(getActivity(), R.drawable.loader);
screenSize = getResources().getConfiguration().screenLayout
& Configuration.SCREENLAYOUT_SIZE_MASK;
loader = new LoadDataAllChanelsToServer();
// loader.execute();
list.setOnItemClickListener(new android.widget.AdapterView.OnItemClickListener() {
@Override
public void onItemClick(android.widget.AdapterView<?> parent,
View view, int position, long id) {
journal = (TextView) view.findViewById(R.id.smalljournal1);
tittle = (TextView) view.findViewById(R.id.smalltitle1);
description = (TextView) view
.findViewById(R.id.smallDescription1);
smalllink = (TextView) view.findViewById(R.id.smalllink1);
DateTime = (TextView) view.findViewById(R.id.smallDateTime1);
smallstatID = (TextView) view.findViewById(R.id.smallstatID1);
String Stringjournal = journal.getText().toString();
String Stringtittle = tittle.getText().toString();
String Stringdescription = description.getText().toString();
String Stringlink = smalllink.getText().toString();
String StringdateTime = DateTime.getText().toString();
String StringstatID = smallstatID.getText().toString();
Intent in = new Intent(getActivity(),
com.leavingstone.dealbox.Result.class);
in.putExtra("KEY_journal", Stringjournal);
in.putExtra("KEY_title", Stringtittle);
in.putExtra("KEY_description", Stringdescription);
in.putExtra("KEY_link", Stringlink);
in.putExtra("KEY_pubDate", StringdateTime);
in.putExtra("KEY_statID", StringstatID);
String url = itemList.get(position).get(DealBoxComponents.KEY_image);
if (url.endsWith("-c.jpg"))
url = url.replace("-c.jpg", ".jpg");
in.putExtra("Bitmap", url);
in.putExtra("Bitmap", url);
startActivity(in);
// overridePendingTransition(R.anim.trans_left_in,
// R.anim.trans_left_out);
}
});
return rootView;
}
private class LoadDataAllChanelsToServer extends
AsyncTask<String, Integer, String> {
@Override
protected void onPreExecute() {
pd.show();
}
@Override
protected String doInBackground(String... urls) {
jsonparser = new JSONParser();
JSONObject jsonobject = jsonparser.getJSONfromURL(URL);
try {
jsonarray = jsonobject.getJSONArray("data");
for (int i = 0; i < jsonarray.length(); i++) {
jsonobject = jsonarray.getJSONObject(i);
HashMap<String, String> map = new HashMap<String, String>();
map.put("journal", jsonobject.getString(DealBoxComponents.KEY_journal));
map.put("image", jsonobject.getString(DealBoxComponents.KEY_image));
map.put("title", jsonobject.getString(DealBoxComponents.KEY_title));
map.put("description",
jsonobject.getString(DealBoxComponents.KEY_description));
map.put("JournalID", jsonobject.getString(DealBoxComponents.KEY_JournalID));
map.put("pubDate", jsonobject.getString(DealBoxComponents.KEY_pubDate));
map.put("statID", jsonobject.getString(DealBoxComponents.KEY_statID));
itemList.add(map);
dateTime = itemList.get(itemList.size() - 1).get(
DealBoxComponents.KEY_pubDate);
}
} catch (JSONException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return itemList.toString();
}
@Override
protected void onPostExecute(String result) {
try {
if (pd != null) {
pd.dismiss();
}
} catch (Exception e) {
}
try {
adapter = new DealBoxAdapter(getActivity(), itemList,
screenSize);
list.setAdapter(adapter);
} catch (NullPointerException e) {
e.printStackTrace();
}
}
}
public void Notify() {
adapter.notifyDataSetChanged();
oneTime = false;
}
// @Override
// public void onDestroy() {
// super.onDestroy();
// try {
// if (loader != null) {
// loader.cancel(true);
// loader = null;
// }
// } catch (Exception e) {
// // TODO: handle exception
// }
//
// }
@Override
public void onPause() {
super.onPause();
try {
if (loader != null) {
loader.cancel(true);
loader = null;
}
} catch (Exception e) {
}
}
} 另外两个类（片段）代码与此类似，但differenc仅为URl