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POExpandableListView won't populate
 

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  1. POExpandableListView won't populate
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    <p>I'm trying to inflate an ExpandableListView in a Fragment and use a setAdapter. I succeed properly when I don't use it in a fragment, but in Fragment, I either get errors (NullPointerException) or the ExpandableListView won't be populated.</p> <pre><code>package com.stylingandroid.basicactionbar; import java.util.ArrayList; import java.util.Arrays; import java.util.List; import android.app.Fragment; import android.os.Bundle; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.ExpandableListView; public class Friends extends Fragment { private static List&lt;Country&gt; Countries; private ExpandableListView expandableListView; private CountryAdapter adapter; private View V; @Override public View onCreateView( LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState ) { V = inflater.inflate( R.layout.frag2, container, false ); LoadCountries(); expandableListView = (ExpandableListView) V.findViewById(R.id.expandableListView); expandableListView.setAdapter(adapter); adapter = new CountryAdapter(this, Countries); return V; } private void LoadCountries() { Countries = new ArrayList&lt;Country&gt;(); ArrayList&lt;String&gt; citiesAustralia = new ArrayList&lt;String&gt;( Arrays.asList("Brisbane", "Hobart", "Melbourne", "Sydney")); Countries.add(new Country("Australia", citiesAustralia)); ArrayList&lt;String&gt; citiesChina = new ArrayList&lt;String&gt;( Arrays.asList("Beijing", "Chuzhou", "Dongguan", "Shangzhou")); Countries.add(new Country("China", citiesChina)); } } </code></pre> <p>frag2.xml:</p> <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt; &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"&gt; &lt;ExpandableListView android:id="@+id/expandableListView" android:layout_width="fill_parent" android:layout_height="fill_parent"/&gt; &lt;/LinearLayout&gt; package com.stylingandroid.basicactionbar; import android.app.ActionBar; import android.app.ActionBar.Tab; import android.app.Activity; import android.app.Fragment; import android.app.FragmentTransaction; import android.content.Intent; import android.os.Bundle; import android.view.Menu; import android.view.MenuItem; public class MainActivity extends Activity { private class MyTabListener implements ActionBar.TabListener { private Fragment mFragment; private final Activity mActivity; private final String mFragName; public MyTabListener( Activity activity, String fragName ) { mActivity = activity; mFragName = fragName; } @Override public void onTabReselected( Tab tab, FragmentTransaction ft ) { // TODO Auto-generated method stub } @Override public void onTabSelected( Tab tab, FragmentTransaction ft ) { mFragment = Fragment.instantiate( mActivity, mFragName ); ft.add( android.R.id.content, mFragment ); } @Override public void onTabUnselected( Tab tab, FragmentTransaction ft ) { ft.remove( mFragment ); mFragment = null; } } @Override public void onCreate( Bundle savedInstanceState ) { super.onCreate( savedInstanceState ); Intent intent; ActionBar ab = getActionBar(); ab.setNavigationMode( ActionBar.NAVIGATION_MODE_TABS ); Tab tab = ab.newTab() .setText( R.string.title_param ) .setTabListener( new MyTabListener( this, Param.class.getName() ) ); ab.addTab( tab ); intent = new Intent().setClass(this, Friends.class); tab = ab.newTab() .setText( R.string.title_friends ) .setTabListener( new MyTabListener( this, Friends.class.getName() ) ); ab.addTab( tab ); tab = ab.newTab() .setText( R.string.title_maps ) .setTabListener( new MyTabListener( this, Maps.class.getName() ) ); ab.addTab( tab ); } @Override public boolean onCreateOptionsMenu( Menu menu ) { getMenuInflater().inflate( R.menu.main, menu ); return true; } @Override public boolean onOptionsItemSelected( MenuItem item ) { boolean ret; if (item.getItemId() == R.id.menu_settings) { // Handle Settings ret = true; } else { ret = super.onOptionsItemSelected( item ); } return ret; } } </code></pre> <p>CountryAdapter:</p> <pre><code>package com.stylingandroid.basicactionbar; import android.R; import android.content.Context; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.BaseExpandableListAdapter; import android.widget.TextView; import java.util.List; public class CountryAdapter extends BaseExpandableListAdapter { private List&lt;Country&gt; countries; private LayoutInflater inflater; public CountryAdapter(Context context) { this.countries = countries; inflater = LayoutInflater.from(context); } public CountryAdapter(Friends friends, List&lt;Country&gt; countries2) { // TODO Auto-generated constructor stub } @Override public int getGroupCount() { return countries.size(); } @Override public int getChildrenCount(int groupPosition) { return countries.get(groupPosition).getCities().size(); } @Override public Object getGroup(int groupPosition) { return countries.get(groupPosition).getName(); } @Override public Object getChild(int groupPosition, int childPosition) { return countries.get(groupPosition).getCities().get(childPosition); } @Override public long getGroupId(int groupPosition) { return groupPosition; } @Override public long getChildId(int groupPosition, int childPosition) { return childPosition; } @Override public boolean hasStableIds() { return true; } @Override public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) { if (convertView == null) { convertView = inflater.inflate(R.layout.simple_expandable_list_item_1, parent, false); } ((TextView) convertView).setText(getGroup(groupPosition).toString()); return convertView; } @Override public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) { if(convertView == null) { convertView = inflater.inflate(R.layout.simple_list_item_1, parent, false); } ((TextView)convertView).setText(getChild(groupPosition,childPosition).toString()); return convertView; } @Override public boolean isChildSelectable(int i, int i2) { return false; } } </code></pre> <p>The part, I guess, that is wrong is there:</p> <pre><code>public CountryAdapter(Context context) { this.countries = countries; inflater = LayoutInflater.from(context); } </code></pre> <p>The problem is that I don't understand how to use the (Context, context) for the fragment Friends. Any idea?</p> <p>Thank you in advance! :)</p> <p>EDIT:</p> <p>I used the code of Gaurav Vashisth and I can a NullPointerException. Here is the stack trace.</p> <pre><code>10-12 19:11:52.105: D/dalvikvm(2203): GC_FOR_ALLOC freed 41K, 6% free 2553K/2716K, paused 62ms, total 66ms 10-12 19:11:52.116: I/dalvikvm-heap(2203): Grow heap (frag case) to 3.215MB for 635812-byte allocation 10-12 19:11:52.265: D/dalvikvm(2203): GC_FOR_ALLOC freed 1K, 6% free 3172K/3340K, paused 141ms, total 141ms 10-12 19:11:52.525: D/dalvikvm(2203): GC_CONCURRENT freed &lt;1K, 5% free 3178K/3340K, paused 8ms+176ms, total 264ms 10-12 19:11:53.405: D/libEGL(2203): loaded /system/lib/egl/libEGL_emulation.so 10-12 19:11:53.495: D/(2203): HostConnection::get() New Host Connection established 0x2a155620, tid 2203 10-12 19:11:53.616: D/libEGL(2203): loaded /system/lib/egl/libGLESv1_CM_emulation.so 10-12 19:11:53.625: D/libEGL(2203): loaded /system/lib/egl/libGLESv2_emulation.so 10-12 19:11:53.725: W/EGL_emulation(2203): eglSurfaceAttrib not implemented 10-12 19:11:53.766: D/OpenGLRenderer(2203): Enabling debug mode 0 10-12 19:12:11.858: D/AndroidRuntime(2203): Shutting down VM 10-12 19:12:11.858: W/dalvikvm(2203): threadid=1: thread exiting with uncaught exception (group=0x40a71930) 10-12 19:12:11.906: E/AndroidRuntime(2203): FATAL EXCEPTION: main 10-12 19:12:11.906: E/AndroidRuntime(2203): java.lang.NullPointerException 10-12 19:12:11.906: E/AndroidRuntime(2203): at com.stylingandroid.basicactionbar.CountryAdapter.getGroupCount(CountryAdapter.java:26) 10-12 19:12:11.906: E/AndroidRuntime(2203): at android.widget.ExpandableListConnector.getCount(ExpandableListConnector.java:397) 10-12 19:12:11.906: E/AndroidRuntime(2203): at android.widget.ListView.setAdapter(ListView.java:462) 10-12 19:12:11.906: E/AndroidRuntime(2203): at android.widget.ExpandableListView.setAdapter(ExpandableListView.java:470) 10-12 19:12:11.906: E/AndroidRuntime(2203): at com.stylingandroid.basicactionbar.Friends.onCreateView(Friends.java:32) 10-12 19:12:11.906: E/AndroidRuntime(2203): at android.app.Fragment.performCreateView(Fragment.java:1695) 10-12 19:12:11.906: E/AndroidRuntime(2203): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:885) 10-12 19:12:11.906: E/AndroidRuntime(2203): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1057) 10-12 19:12:11.906: E/AndroidRuntime(2203): at android.app.BackStackRecord.run(BackStackRecord.java:682) 10-12 19:12:11.906: E/AndroidRuntime(2203): at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1435) 10-12 19:12:11.906: E/AndroidRuntime(2203): at android.app.FragmentManagerImpl$1.run(FragmentManager.java:441) 10-12 19:12:11.906: E/AndroidRuntime(2203): at android.os.Handler.handleCallback(Handler.java:725) 10-12 19:12:11.906: E/AndroidRuntime(2203): at android.os.Handler.dispatchMessage(Handler.java:92) 10-12 19:12:11.906: E/AndroidRuntime(2203): at android.os.Looper.loop(Looper.java:137) 10-12 19:12:11.906: E/AndroidRuntime(2203): at android.app.ActivityThread.main(ActivityThread.java:5041) 10-12 19:12:11.906: E/AndroidRuntime(2203): at java.lang.reflect.Method.invokeNative(Native Method) 10-12 19:12:11.906: E/AndroidRuntime(2203): at java.lang.reflect.Method.invoke(Method.java:511) 10-12 19:12:11.906: E/AndroidRuntime(2203): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 10-12 19:12:11.906: E/AndroidRuntime(2203): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 10-12 19:12:11.906: E/AndroidRuntime(2203): at dalvik.system.NativeStart.main(Native Method) 10-12 19:17:12.528: I/Process(2203): Sending signal. PID: 2203 SIG: 9 </code></pre> <p>EDIT 2: With the following code, I get the NullPointerException, stack trace above modified.</p> <pre><code>@Override public View onCreateView( LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState ) { LoadCountries(); V = inflater.inflate( R.layout.frag2, container, false ); expandableListView = (ExpandableListView) V.findViewById(R.id.expandableListView); adapter = new CountryAdapter(getActivity(), Countries); expandableListView.setAdapter(adapter); return V; } </code></pre> <p>CountryAdapter:</p> <pre><code>private List&lt;Country&gt; countries; private LayoutInflater inflater; public CountryAdapter(Context context, List&lt;Country&gt; contries) { this.countries = countries; inflater = LayoutInflater.from(context); } </code></pre>
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    1. COpls post the stack trace
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    2. COwhat is line 27 `CountryAdapter.java` and do you get the exception after making the corrections suggested
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    3. COFrom the logs I guess countries arraylist was null at that moment.
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