我在android中使用ExpandableListView，但问题是我的代码在填充HashMap之前就已加载此代码，因此它显示了一个空的ListView。
我加载我的ExpandableListView的片段是这个片段：
package com.example.arno.eventaris.Fragment;
import android.app.Activity;
import android.app.DialogFragment;
import android.net.wifi.WifiConfiguration;
import android.os.Bundle;
import android.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.example.arno.eventaris.Activity.MainActivity;
import com.example.arno.eventaris.Error.ErrorJason;
import com.example.arno.eventaris.Expandable.ExpandableListAdapter;
import com.example.arno.eventaris.R;
import android.widget.ExpandableListView;
import android.widget.ExpandableListView.OnChildClickListener;
import android.widget.ExpandableListView.OnGroupClickListener;
import android.widget.ExpandableListView.OnGroupCollapseListener;
import android.widget.ExpandableListView.OnGroupExpandListener;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import android.widget.Toast;
/**
* A simple {@link Fragment} subclass.
*/
public class HomeFragment extends Fragment {
private OnHomeFragmentInteractionListener mListener;
private View view;
private ExpandableListAdapter listAdapter;
private ExpandableListView expListView;
private List<String> listDataHeader;
private HashMap<String, List<String>> listDataChild;
private HashMap<String,HashMap<String,String>> events;
public HomeFragment() {
// Required empty public constructor
}
@Override
public View onCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
((MainActivity)getActivity()).populateEvents();
events = ((MainActivity)getActivity()).getEvents();
view=inflater.inflate(R.layout.fragment_home, container, false);
// get the listview
expListView = (ExpandableListView) view.findViewById(R.id.lvExp);
// preparing list data
prepareListData();
listAdapter = new ExpandableListAdapter(getActivity(), listDataHeader, listDataChild);
// setting list adapter
expListView.setAdapter(listAdapter);
return view;
}
/*
* Preparing the list data
*/
private void prepareListData() {
listDataHeader = new ArrayList<String>();
listDataChild = new HashMap<String, List<String>>();
// Adding child data
listDataHeader.add("A");
listDataHeader.add("B");
listDataHeader.add("C");
listDataHeader.add("D");
listDataHeader.add("E");
listDataHeader.add("F");
listDataHeader.add("G");
listDataHeader.add("H");
listDataHeader.add("I");
listDataHeader.add("J");
listDataHeader.add("K");
listDataHeader.add("L");
listDataHeader.add("M");
listDataHeader.add("N");
listDataHeader.add("O");
listDataHeader.add("P");
listDataHeader.add("Q");
listDataHeader.add("R");
listDataHeader.add("S");
listDataHeader.add("T");
listDataHeader.add("U");
listDataHeader.add("V");
listDataHeader.add("W");
listDataHeader.add("X");
listDataHeader.add("Y");
listDataHeader.add("Z");
listDataHeader.add("*");
// Adding child data
List<String> A = new ArrayList<String>();
List<String> B = new ArrayList<String>();
List<String> C = new ArrayList<String>();
List<String> D = new ArrayList<String>();
List<String> E = new ArrayList<String>();
List<String> F = new ArrayList<String>();
List<String> G = new ArrayList<String>();
List<String> H = new ArrayList<String>();
List<String> I = new ArrayList<String>();
List<String> J = new ArrayList<String>();
List<String> K = new ArrayList<String>();
List<String> L = new ArrayList<String>();
List<String> M = new ArrayList<String>();
List<String> N = new ArrayList<String>();
List<String> O = new ArrayList<String>();
List<String> P = new ArrayList<String>();
List<String> Q = new ArrayList<String>();
List<String> R = new ArrayList<String>();
List<String> S = new ArrayList<String>();
List<String> T = new ArrayList<String>();
List<String> U = new ArrayList<String>();
List<String> V = new ArrayList<String>();
List<String> W = new ArrayList<String>();
List<String> X = new ArrayList<String>();
List<String> Y = new ArrayList<String>();
List<String> Z = new ArrayList<String>();
List<String> anders = new ArrayList<String>();
for(String key : events.keySet())
{
String eersteLetter = Character.toString(key.charAt(0));
switch(eersteLetter)
{
case "a" : A.add(key);
break;
case "b" : B.add(key);
break;
case "c" : C.add(key);
break;
case "d" : D.add(key);
break;
case "e" : E.add(key);
break;
case "f" : F.add(key);
break;
case "g" : G.add(key);
break;
case "h" : H.add(key);
break;
case "i" : I.add(key);
break;
case "j" : J.add(key);
break;
case "k" : K.add(key);
break;
case "l" : L.add(key);
break;
case "m" : M.add(key);
break;
case "n" : N.add(key);
break;
case "o" : O.add(key);
break;
case "p" : P.add(key);
break;
case "q" : Q.add(key);
break;
case "r" : R.add(key);
break;
case "s" : S.add(key);
break;
case "t" : T.add(key);
break;
case "u" : U.add(key);
break;
case "v" : V.add(key);
break;
case "w" : W.add(key);
break;
case "x" : X.add(key);
break;
case "y" : Y.add(key);
break;
case "z" : Z.add(key);
break;
default : anders.add(key);
break;
}
}
listDataChild.put(listDataHeader.get(0), A); // Header, Child data
listDataChild.put(listDataHeader.get(1), B);
listDataChild.put(listDataHeader.get(2), C);
listDataChild.put(listDataHeader.get(3), D);
listDataChild.put(listDataHeader.get(4), E);
listDataChild.put(listDataHeader.get(5), F);
listDataChild.put(listDataHeader.get(6), G);
listDataChild.put(listDataHeader.get(7), H);
listDataChild.put(listDataHeader.get(8), I);
listDataChild.put(listDataHeader.get(9), J);
listDataChild.put(listDataHeader.get(10), K);
listDataChild.put(listDataHeader.get(11), L);
listDataChild.put(listDataHeader.get(12), M);
listDataChild.put(listDataHeader.get(13), N);
listDataChild.put(listDataHeader.get(14), O);
listDataChild.put(listDataHeader.get(15), P);
listDataChild.put(listDataHeader.get(16), Q);
listDataChild.put(listDataHeader.get(17), R);
listDataChild.put(listDataHeader.get(18), S);
listDataChild.put(listDataHeader.get(19), T);
listDataChild.put(listDataHeader.get(20), U);
listDataChild.put(listDataHeader.get(21), V);
listDataChild.put(listDataHeader.get(22), W);
listDataChild.put(listDataHeader.get(23), X);
listDataChild.put(listDataHeader.get(24), Y);
listDataChild.put(listDataHeader.get(25), Z);
listDataChild.put(listDataHeader.get(26), anders);
}
@Override
public void onAttach(Activity activity)
{
super.onAttach(activity);
try{
mListener = (OnHomeFragmentInteractionListener) activity;
}
catch (ClassCastException e)
{
throw new ClassCastException(activity.toString() + "must implement OnFragmentInteractionListener");
}
}
@Override
public void onDetach()
{
super.onDetach();
mListener = null;
}
public interface OnHomeFragmentInteractionListener
{
}
}
问题是，我用于ExpandableListView的数据来自我在MaintActivity.Java中的HashMap中放入的JSON文件。
现在，它将遍历我的整个HomeFragment.java代码，直到最后，只有在这种情况发生时，它才开始执行以下代码行：
((MainActivity)getActivity()).populateEvents();
我已将其放在onCreateView方法的开头。我跟随调试器，所以我知道他遵循的顺序不是我想要的顺序。有没有办法确保他在创建ExpendableListView之前执行这一行代码？
我建议您使用AsyncTask来填充数据。您将在doInBackground()方法中加载数据，然后在中创建适配器onPostExecute()。
1）创建您的AsyncTask类：
private class PopulatingTask extends AsyncTask<Void, Void, Boolean> {
private ProgressDialog dialog;
private MainActivity activity;
public PopulatingTask (MainActivity activity) {
this.activity = activity;
dialog = new ProgressDialog(activity);
}
@Override
protected void onPreExecute() {
this.dialog.setMessage("Loading data...");
this.dialog.show();
}
@Override
protected Boolean doInBackground(Void... args) {
try{
activity.populateEvents();
events = activity.getEvents();
// preparing list data
prepareListData();
return true;
} catch (Exception e){
Log.e("tag", "error", e);
return false;
}
}
@Override
protected void onPostExecute(Boolean success) {
listAdapter = new ExpandableListAdapter(activity, listDataHeader, listDataChild);
// setting list adapter
expListView.setAdapter(listAdapter);
// dismiss the dialog
if (dialog.isShowing()) {
dialog.dismiss();
}
if (success) {
Toast.makeText(activity, "OK", Toast.LENGTH_LONG).show();
} else {
Toast.makeText(activity, "Error", Toast.LENGTH_LONG).show();
}
}
}
2）将您的onCreateView()方法更改为：
@Override
public View onCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
view=inflater.inflate(R.layout.fragment_home, container, false);
// get the listview
expListView = (ExpandableListView) view.findViewById(R.id.lvExp);
// start the asyncTask
new PopulatingTask((MainActivity)getActivity()).execute();
return view;
}
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