我在我的片段中使用AsyncTask来加载Json的数据列表。单击每个列表项后，此列表片段将被包含详细信息的详细信息片段替换。然后在新片段（细节片段）中，用户按下后退按钮。然后再次列出片段开始
问题是Asynctask再次重新加载以获取列表项。我不想要这个。我想显示以前加载的列表。这是代码：
public class MainList extends Fragment {
public MainList(){}
ArrayList<Country> countryList = new ArrayList<Country>();
Country country;
Button btnLoadMore;
ListView listView;
JSONParser jsonParser = new JSONParser();
public static String received_id;
// Creating JSON Parser object
JSONParser jParser = new JSONParser();
int current_page = 0;
int last_item;
int total_items = 32;
boolean continue_loading = true;
boolean loadingMore = false;
View footerView;
public ImageLoader_Json imageLoader;
int currentPosition = 0;
MyCustomAdapter dataAdapter = null;
private static String url_all_products_LoadMore = "http://www.hitel.ir/FarsiPlanet/Apps.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_PRODUCTS = "products";
private static final String TAG_PID = "pid";
private static final String TAG_NAME = "name";
private static final String TAG_RATE = "rate";
private static final String TAG_RATINGCOUNT = "ratingcount";
private static final String TAG_SHORT_DESCRIPTION = "short_description";
// products JSONArray
JSONArray products = null;
String Category;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.items_list, container, false);
Category = getArguments().getString("category");
footerView= ((LayoutInflater)getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.loading_footer, null,false);
listView = (ListView) rootView.findViewById(R.id.listView1);
listView.addFooterView(footerView);
imageLoader = new ImageLoader_Json(getActivity().getApplicationContext());
displayListView();
return rootView;
}
private void displayListView() {
//create an ArrayAdaptar from the String Array
dataAdapter = new MyCustomAdapter(getActivity(),
R.layout.country_info, countryList);
listView.setOnScrollListener(new OnScrollListener() {
public void onScrollStateChanged(AbsListView view, int scrollState) {
// TODO Auto-generated method stub
}
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
int lastInScreen = firstVisibleItem + visibleItemCount;
if((lastInScreen == totalItemCount) && !(loadingMore)){
new loadMoreListView().execute();
}
}
});
listView.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
final String pid = ((TextView) view.findViewById(R.id.pid)).getText().toString();
Bundle data = new Bundle();
data.putString(TAG_PID, pid);
data.putString("TAG_Category", Category);
Fragment fragment = new Details_Restaurant();
FragmentManager fm = getFragmentManager();
fragment.setArguments(data);
fm.beginTransaction().replace(R.id.frame_container, fragment).addToBackStack("f_02").commit();
}
});
listView.setAdapter(dataAdapter);
listView.setSelectionFromTop(currentPosition, 0);
}
private class MyCustomAdapter extends ArrayAdapter<Country> {
private ArrayList<Country> countryList;
public MyCustomAdapter(Context context, int textViewResourceId,
ArrayList<Country> countryList) {
super(context, textViewResourceId, countryList);
this.countryList = new ArrayList<Country>();
this.countryList.addAll(countryList);
}
private class ViewHolder {
TextView code;
TextView name;
RatingBar rate;
TextView ratingcount;
TextView short_description;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
Log.v("ConvertView", String.valueOf(position));
if (convertView == null) {
LayoutInflater vi = (LayoutInflater)getActivity().getSystemService(
Context.LAYOUT_INFLATER_SERVICE);
convertView = vi.inflate(R.layout.country_info, null);
holder = new ViewHolder();
holder.name = (TextView) convertView.findViewById(R.id.name);
holder.ratingcount = (TextView) convertView.findViewById(R.id.ratingCount);
holder.short_description = (TextView) convertView.findViewById(R.id.short_description);
holder.rate = (RatingBar) convertView.findViewById(R.id.ratingBar1);
holder.code = (TextView) convertView.findViewById(R.id.pid);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
final Country country = countryList.get(position);
holder.name.setText(country.getName());
holder.ratingcount.setText(country.getRatingCount());
holder.short_description.setText(country.getShort_description());
holder.rate.setRating(country.getRate());
holder.code.setText(country.getCode());
return convertView;
}
}
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getActivity().getMenuInflater();
inflater.inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
return super.onOptionsItemSelected(item);
}
class loadMoreListView extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
/*
pDialog = new ProgressDialog(AllProductsActivity.this);
pDialog.setMessage("درحال دريافت اطلاعات...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show(); */
}
/**
* getting All products from url
* */
protected String doInBackground(String... args) {
String firts_item = Integer.toString(current_page*10);
int success;
try {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("pid", firts_item));
params.add(new BasicNameValuePair("category", Category));
// getting product details by making HTTP request
// Note that product details url will use GET request
JSONObject json = jsonParser.makeHttpRequest(
url_all_products_LoadMore, "GET", params);
// json success tag
success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// products found
// Getting Array of Products
products = json.getJSONArray(TAG_PRODUCTS);
// looping through All Products
for (int i = 0; i < products.length(); i++) {
JSONObject c = products.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(TAG_PID);
String name = c.getString(TAG_NAME);
Float rate = (float) c.getInt(TAG_RATE);
String ratingcount = c.getString(TAG_RATINGCOUNT);
String short_description = c.getString(TAG_SHORT_DESCRIPTION);
country = new Country(id,name,rate,ratingcount,short_description,"","");
countryList.add(country);
}
}
else{
continue_loading = false;
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(String file_url) {
current_page += 1;
if (continue_loading) {
currentPosition = listView.getFirstVisiblePosition();
dataAdapter.notifyDataSetChanged();
displayListView();
loadingMore = false;
} else {
listView.removeFooterView(footerView);
}
}
}
}
答案 0 :(得分：1)
在调用onScrollStateChanged和onScroll之前，你需要包含@Override
listView.setOnScrollListener(new OnScrollListener() {
public void onScrollStateChanged(AbsListView view, int scrollState) {
// TODO Auto-generated method stub
}
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
int lastInScreen = firstVisibleItem + visibleItemCount;
if((lastInScreen == totalItemCount) && !(loadingMore)){
new loadMoreListView().execute();
}
}
});
答案 1 :(得分：0)
当您对片段执行replace（）操作时，您将删除列表片段，因此在回击时，您将使用listfragment替换详细信息片段，该片段调用onCreateView（）作为片段生命周期的一部分。
当asynctask的onPostExecute（）结束时，我会尝试将静态booelan设置为true，因此下次调用列表片段的onCreateView（）时，您将检查该标志的值，如果设置为true不会执行任务，只需使用旧的静态数据设置适配器。