我正在尝试在片段中膨胀ExpandableListView并使用setAdapter。当我不在片段中使用它时，我成功了，但在Fragment中，我要么得到错误（NullPointerException），要么不会填充ExpandableListView。
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<Country> 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<Country>();
ArrayList<String> citiesAustralia = new ArrayList<String>(
Arrays.asList("Brisbane", "Hobart", "Melbourne", "Sydney"));
Countries.add(new Country("Australia", citiesAustralia));
ArrayList<String> citiesChina = new ArrayList<String>(
Arrays.asList("Beijing", "Chuzhou", "Dongguan", "Shangzhou"));
Countries.add(new Country("China", citiesChina));
}
}
frag2.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<ExpandableListView
android:id="@+id/expandableListView"
android:layout_width="fill_parent"
android:layout_height="fill_parent"/>
</LinearLayout>
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;
}
}
CountryAdapter：
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<Country> countries;
private LayoutInflater inflater;
public CountryAdapter(Context context) {
this.countries = countries;
inflater = LayoutInflater.from(context);
}
public CountryAdapter(Friends friends, List<Country> 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;
}
}
这个部分，我想，那是错误的：
public CountryAdapter(Context context) {
this.countries = countries;
inflater = LayoutInflater.from(context);
}
问题是我不明白如何使用片段Friends的（上下文，上下文）。有什么想法吗？
提前谢谢！ ：）
编辑：
我使用了Gaurav Vashisth的代码，我可以使用NullPointerException。这是堆栈跟踪。
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 <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
编辑2：使用以下代码，我得到NullPointerException，堆栈跟踪已修改。
@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;
}
CountryAdapter：
private List<Country> countries;
private LayoutInflater inflater;
public CountryAdapter(Context context, List<Country> contries) {
this.countries = countries;
inflater = LayoutInflater.from(context);
}
答案 0 :(得分：0)
使用getActivity()
public final Activity getActivity ()
Added in API level 11
Return the Activity this fragment is currently associated with.
替换
adapter = new CountryAdapter(this, Countries);
通过
adapter = new CountryAdapter(getActivity(), Countries);
您还需要撤消
expandableListView.setAdapter(adapter);
adapter = new CountryAdapter(this, Countries);
到
adapter = new CountryAdapter(getActivity(), Countries);
expandableListView.setAdapter(adapter);
编辑：
也可以更改为
private void LoadCountries() {
Countries = new ArrayList<Country>();
ArrayList<String> citiesAustralia = new ArrayList<String>(
Arrays.asList("Brisbane", "Hobart", "Melbourne", "Sydney"));
Countries.add(new Country("Australia", citiesAustralia));
ArrayList<String> citiesChina = new ArrayList<String>(
Arrays.asList("Beijing", "Chuzhou", "Dongguan", "Shangzhou"));
Countries.add(new Country("China", citiesChina));
adapter = new CountryAdapter(getActivity(), Countries);
expandableListView.setAdapter(adapter);
}
答案 1 :(得分：0)
我在你的onCreateView方法中看到你在初始化它之前使用的是适配器方法。以这种方式使用
@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);
adapter = new CountryAdapter(getActivity(), Countries);
expandableListView.setAdapter(adapter);
return V;
}
要获取片段中活动的参考，请使用getActivity（）
除此之外
使适配器的构造函数变为
public CountryAdapter(Context context, List<Country> countries) {
this.countries = countries;
inflater = LayoutInflater.from(context);
}
我还想指出，根据java约定，方法名称以小写字母开头。因此，如果您将LoadCountries()重命名为loadCountries()