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我試圖用viewpager和兩個選項卡實現一項活動，以便在各部分之間實現輕掃手勢，每個部分都包含帶有自定義適配器的列表視圖它從一個asynctask加載數據。我想在加載數據時顯示加載微調器。如何實現帶有片段，自定義適配器，選項卡和viewpager的listview android
如果我們使用普通的listview和一個簡單的適配器，它就可以工作。當我們爲列表視圖引入一個自定義適配器時，問題就出現了。 Eclipse返回以下錯誤：
FATAL EXCEPTION: main java.lang.NullPointerException at libraries.BoostAdapter.getCount(BoostAdapter.java:58) at android.widget.ListView.setAdapter(ListView.java:466) at kasuga.gamble.roma.LikeAttendList$AppSectionsPagerAdapter$LikeFragmentList.onActivityCreated(LikeAttendList.java:237) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:891) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1080) at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:622) [...]
任何建議將是最受歡迎的！謝謝。
活動（爲了簡單起見，我們只考慮一個ListFragment）
public class LikeAttendList extends FragmentActivity implements ActionBar.TabListener { AppSectionsPagerAdapter mAppSectionsPagerAdapter; //ListView Adapter static BoostAdapter adapterLike; static BoostAdapter adapterAttend; ViewPager mViewPager; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.attendlike); //Retrieve intent extras: event Id Intent i2 = getIntent(); uid = i2.getExtras().getString("eventid"); //Adapter creation Log.e("LikeAttend Report", "Entering LikeAttendList, eventID: " + uid); // Create the adapter that will return a fragment for each of the two sections // of the app. mAppSectionsPagerAdapter = new AppSectionsPagerAdapter(getSupportFragmentManager()); // Set up the action bar. final ActionBar actionBar = getActionBar(); // Specify that the Home/Up button should not be enabled, since there is no hierarchical // parent. actionBar.setHomeButtonEnabled(false); // Specify that we will be displaying tabs in the action bar. actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS); // Set up the ViewPager, attaching the adapter and setting up a listener for when the // user swipes between sections. mViewPager = (ViewPager) findViewById(R.id.pager); mViewPager.setAdapter(mAppSectionsPagerAdapter); mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() { @Override public void onPageSelected(int position) { // When swiping between different app sections, select the corresponding tab. // We can also use ActionBar.Tab#select() to do this if we have a reference to the // Tab. actionBar.setSelectedNavigationItem(position); } }); // For each of the sections in the app, add a tab to the action bar. for (int i = 0; i < mAppSectionsPagerAdapter.getCount(); i++) { // Create a tab with text corresponding to the page title defined by the adapter. // Also specify this Activity object, which implements the TabListener interface, as the // listener for when this tab is selected. actionBar.addTab( actionBar.newTab() .setText(mAppSectionsPagerAdapter.getPageTitle(i)) .setTabListener(this)); } } /** * A FragmentPagerAdapter that returns a fragment corresponding to one of the primary * sections of the app. */ public static class AppSectionsPagerAdapter extends FragmentPagerAdapter { public AppSectionsPagerAdapter(FragmentManager fm) { super(fm); } @Override public Fragment getItem(int i) { switch (i) { case 0: // The first section of the app shows all likes. return new LikeFragmentList(); //The second should show all user who will attend the event default: // The other sections of the app are dummy placeholders. Fragment fragment = new DummySectionFragment(); Bundle args = new Bundle(); args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, i + 1); fragment.setArguments(args); return fragment; } } public static class LikeFragmentList extends ListFragment { private ListView listv; private BoostAdapter adapter; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); //retrieves data from asyncTask LikeAttendList mc = new LikeAttendList(); mc. new EventDataTask().execute(uid); //Sets up the adapter Activity ctx = this.getActivity(); adapterLike = new BoostAdapter(ctx, userList); } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View v1 = inflater.inflate(R.layout.likelist, container, false); listv = (ListView) v1.findViewById(android.R.id.list); return v1; } @Override public void onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); //ArrayAdapter<String> adapter = new ArrayAdapter<String>(inflater.getContext(), android.R.layout.simple_list_item_1,countries); listv.setAdapter(adapterLike); /* Trying to implement a cross fade transition, we should use an xml with the listview and the loading spinner, all advices //Cross Fade transition views // save the content mContentView = getView().findViewById(R.id.likelist); // save the loading spinner mLoadingView = getView().findViewById(R.id.loading_spinner); // remove content mContentView.setVisibility(View.GONE); // save the animation duration mAnimationDuration = getResources().getInteger(android.R.integer.config_longAnimTime); */ } } public String[] titles= { "Likes", "Attends" }; @Override public int getCount() { return titles.length; } @Override public CharSequence getPageTitle(int position) { return titles[position]; } } public static class DummySectionFragment extends Fragment { public static final String ARG_SECTION_NUMBER = "section_number"; @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View rootView = inflater.inflate(R.layout.fragment_section_dummy, container, false); Bundle args = getArguments(); ((TextView) rootView.findViewById(android.R.id.text1)).setText( getString(R.string.dummy_section_text, args.getInt(ARG_SECTION_NUMBER))); return rootView; } } @Override public void onTabReselected(Tab tab, FragmentTransaction ft) { // TODO Auto-generated method stub } @Override public void onTabSelected(Tab tab, FragmentTransaction ft) { // When the given tab is selected, switch to the corresponding page in the ViewPager. mViewPager.setCurrentItem(tab.getPosition()); } @Override public void onTabUnselected(Tab tab, FragmentTransaction ft) { } private class EventDataTask extends AsyncTask<String, Void, JSONObject> { //Returns a ArrayList<HashMap<String, String>> with datas called userlist used to populate listview. cf: onCreate in LikeFragmentList() private View mContent; private View mSpinner; private int mDuration; public EventDataTask() { eventsFunctions = new EventsFunctions(); } protected JSONObject doInBackground(String... uid) { Log.e("Social","List Requested: num item: " + max_item +" page number: " + current_page); // getting JSON string from URL current_page=1; String eventId=uid[0]; return eventsFunctions.eventList(Integer.toString(current_page),Integer.toString(max_item),TAG_ACTIVITY, eventId); } @Override protected void onPostExecute(JSONObject json) { // Check your log cat for JSON reponse //Log.e("All Socials list data Once: ", json.toString()); userList = new ArrayList<HashMap<String, String>>(); try { // Checking for SUCCESS TAG String success = json.getString(TAG_SUCCESS); if (success != null) { if (Integer.parseInt(json.getString(TAG_SUCCESS)) != 0) { JSONArray like = json.getJSONArray("likes"); for (int i = 0; i < like.length(); i++) { JSONObject c = like.getJSONObject(i); String name = c.getString(TAG_NAME); String score = c.getString(TAG_SCORE); String photo = c.getString(TAG_PHOTO); // creating new HashMap HashMap<String, String> firstItemMap = new HashMap<String, String>(); // adding each child node to HashMap key => value firstItemMap.put(TAG_SCORE, score); firstItemMap.put(TAG_NAME, name); firstItemMap.put(TAG_PHOTO, photo); // adding HashList to ArrayList userList.add(firstItemMap); } for (int j=0; j< userList.size(); j++) { //Log.e("AllEvents Reporter", "Torneo numero: "+ j + " Nome: " + tornei.get(j).getName()); Log.e("Social Reporter", "utente numero: "+ j + " Nome: " + userList.get(j).get(TAG_NAME)); } } } } catch (JSONException e) { e.printStackTrace(); } super.onPostExecute(json); } } }
- 自定義BoostAdapter創建：
public class BoostAdapter extends BaseAdapter
{
private static String logo_path = "http://userk.servehttp.com/Gamble/Immagini/Pokeroom/All/";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_PEOPLE = "people";
private static final String TAG_UID = "uid";
private static final String TAG_NAME = "name";
private static final String TAG_RANKING = "ranking";
private static final String TAG_PROFILEPICTURE = "photo";
private static final String TAG_EVENTUID = "eventuid";
EventsFunctions eventsFunctions;
Bitmap bitmapLogo;
Bitmap bit;
private static LayoutInflater inflater=null;
public ImageLoader imageLoader;
private ArrayList<HashMap<String, String>> people;
private Activity context;
public BoostAdapter()
{
super();
}
public BoostAdapter(Activity ctx, ArrayList<HashMap<String, String>> persons)
{
super();
context = ctx;
people = persons;
inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
imageLoader=new ImageLoader(context.getApplicationContext());
}
public int getCount()
{
return people.size();
}
public Object getItem(int position)
{
return people.get(position);
}
public long getItemId(int position)
{
return position;
}
static class ViewHolder
{
public TextView row_name;
public TextView rankinglist;
public ImageView image;
}
public View getView(int position, View convertView, ViewGroup parent)
{
View vi=convertView;
if(convertView==null)
{
LayoutInflater inflater = ((Activity) context).getLayoutInflater();
vi = inflater.inflate(R.layout.list_item, null);
ViewHolder viewholder = new ViewHolder();
viewholder.row_name= (TextView) vi.findViewById(R.id.row_name);
viewholder.rankinglist= (TextView) vi.findViewById(R.id.rankinglist);
viewholder.image = (ImageView) vi.findViewById(R.id.row_icon);
vi.setTag(viewholder);
}
//Log.e("BassAdapter Reporter","Checking infos retrivial: Received event: " + Integer.toString(position) + " of " +Integer.toString(tornei.size()) +
// " Infos:\n Name: "+ tornei.get(position).get(TAG_NAME) + " logo: " + tornei.get(position).get(TAG_LOGO) +" Gtd: " + tornei.get(position).get(TAG_GTD).length() +"Buyin: "+ tornei.get(position).get(TAG_BUYIN) + " partecipanti " + tornei.get(position).get(TAG_PARTECIPANTI));
ViewHolder holder = (ViewHolder) vi.getTag();
holder.row_name.setText(people.get(position).get(TAG_NAME));
holder.row_name.setMaxLines(1);
holder.rankinglist.setText(people.get(position).get(TAG_RANKING));
if (people.get(position).get(TAG_PROFILEPICTURE)!="")
{
String url2 = logo_path + people.get(position).get(TAG_PROFILEPICTURE);
//Log.e(" Adapter report:", tornei.get(position).getName() + " and its image path is " + url2);
Log.e("Adapter report:", "Item " + Integer.toString(position) + " of " +Integer.toString(people.size()));
imageLoader.DisplayImage(url2, holder.image);
}
return vi;
}
}
這些都是所要求的XML：
- likelist
attendlike.xml
<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/pager" android:layout_width="match_parent" android:layout_height="match_parent" />attendlikelistitem
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="50dp" android:orientation="horizontal" android:cacheColorHint="#00000000" > <ImageView android:id="@+id/row_icon" android:layout_width="50dp" android:layout_height="50dp" android:padding="5dp" android:src="@drawable/ic_launcher" /> <LinearLayout android:layout_width="wrap_content" android:layout_height="wrap_content" android:orientation="vertical" android:baselineAligned="false" android:paddingLeft="7dp" android:paddingTop="5dp"> <TextView android:id="@+id/row_name" android:layout_width="wrap_content" android:layout_height="fill_parent" android:text="@string/namelist" android:textColor="#000000" android:textSize="15sp" android:ellipsize="marquee" android:scrollHorizontally="true" android:textStyle="bold"/> <LinearLayout android:layout_width="wrap_content" android:layout_height="fill_parent"> <TextView android:id="@+id/ramkingList" android:layout_width="wrap_content" android:layout_height="fill_parent" android:text="@string/rankinglist" android:textColor="#000000" android:textSize="14sp" /> <TextView android:id="@+id/rankinglist" android:layout_width="wrap_content" android:layout_height="fill_parent" android:text="@string/rankingexample" android:textColor="#000000" android:textSize="14sp" /> </LinearLayout> </LinearLayout> </LinearLayout>
用戶列表爲空.... AsyncTask.execute不要等到任務完成了...... – Selvin
確定這就是問題所在，我已經把的AsyncTask在onCreate（）方法在LikeFragmentList類中，然後調用'adapterLike = new BoostAdapter（ctx，userList）;'以便用某種東西填充listview，但顯然這是不夠的。我試着離開onCreate（）中的asynctask，並在onActivityCreated中移動'adapterLike = new BoostAdapter（ctx，userList）;'。但它返回相同的錯誤。 AsyncTask代碼有問題嗎？ – UserK