android - ListView 内部 fragment 错误

Question

我的 fragment :

public class NewsFragment extends ListFragment {

    private ProgressDialog pDialog;

    // URL to get contacts JSON
    private static String url = "url";

    // JSON Node names
    private static final String TAG_NEWS = "news";
    private static final String TAG_ID = "id";
    private static final String TAG_JUDUL = "judul";
    private static final String TAG_TGL = "tanggal";
    private static final String TAG_ISI = "isi";
    private static final String TAG_SUMBER = "sumber";
    private static final String TAG_GAMBAR = "gambar";

    // contacts JSONArray
    JSONArray news = null;

    // Hashmap for ListView
    ArrayList<HashMap<String, String>> newsList;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View newsView = inflater.inflate(R.layout.fragment_news, container, false) ;
        newsList = new ArrayList<HashMap<String, String>>();

        ListView lv = getListView();
        lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view,
                                    int position, long id) {
                // getting values from selected ListItem
                String judul = ((TextView) view.findViewById(R.id.judul))
                        .getText().toString();
                String tanggal = ((TextView) view.findViewById(R.id.tglPublish))
                        .getText().toString();
                String sumber = ((TextView) view.findViewById(R.id.sumber))
                        .getText().toString();

                // Starting single contact activity
                Intent in = new Intent(getActivity().getApplicationContext(),
                        NewsDetailActivity.class);
                in.putExtra(TAG_JUDUL, judul);
                in.putExtra(TAG_TGL, tanggal);
                in.putExtra(TAG_SUMBER, sumber);
                startActivity(in);

            }
        });

        // Calling async task to get json
        new GetNews().execute();

        return newsView ;
    }

    /**
     * Async task class to get json by making HTTP call
     * */
    private class GetNews extends AsyncTask<Void, Void, Void> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            // Showing progress dialog
            pDialog = new ProgressDialog(getActivity());
            pDialog.setMessage("Mohon tunggu...");
            pDialog.setCancelable(false);
            pDialog.show();

        }

        @Override
        protected Void doInBackground(Void... arg0) {
            // Creating service handler class instance
            ServiceHandler sh = new ServiceHandler();

            // Making a request to url and getting response
            String jsonStr = sh.makeServiceCall(url, ServiceHandler.POST);

            Log.d("Response: ", "> " + jsonStr);

            if (jsonStr != null) {
                try {
                    JSONObject jsonObj = new JSONObject(jsonStr);

                    // Getting JSON Array node
                    news = jsonObj.getJSONArray("");

                    // looping through All Contacts
                    for (int i = 0; i < news.length(); i++) {
                        JSONObject c = news.getJSONObject(i);

                        String id = c.getString(TAG_ID);
                        String judul = c.getString(TAG_JUDUL);
                        String tgl = c.getString(TAG_TGL);
                        String sumber = c.getString(TAG_SUMBER);
//                        String gambar = c.getString(TAG_GENDER);


                        // tmp hashmap for single contact
                        HashMap<String, String> news = new HashMap<String, String>();

                        // adding each child node to HashMap key => value
                        news.put(TAG_ID, id);
                        news.put(TAG_JUDUL, judul);
                        news.put(TAG_TGL, tgl);
                        news.put(TAG_SUMBER, sumber);

                        // adding contact to contact list
                        newsList.add(news);
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            } else {
                Log.e("ServiceHandler", "Couldn't get any data from the url");
            }

            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            super.onPostExecute(result);
            // Dismiss the progress dialog
            if (pDialog.isShowing())
                pDialog.dismiss();
            /**
             * Updating parsed JSON data into ListView
             * */
            ListAdapter adapter = new SimpleAdapter(
                    getActivity().getApplicationContext(), newsList,
                    R.layout.list_item, new String[] { TAG_JUDUL, TAG_TGL,
                    TAG_SUMBER }, new int[] { R.id.judul,
                    R.id.tglPublish, R.id.sumber });

            setListAdapter(adapter);
        }

    }

}

我的 xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:layout_marginLeft="12dp"
    android:layout_marginRight="12dp">

    <!-- Main ListView
         Always give id value as list(@android:id/list)
    -->
    <ListView
        android:id="@android:id/list"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"/>

</LinearLayout>

列表项.xml :

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="10dp"
    android:paddingLeft="10dp"
    android:paddingRight="10dp" >

    <!-- Judul -->

    <TextView
        android:id="@+id/judul"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:paddingBottom="2dip"
        android:paddingTop="6dip"
        android:textColor="#43bd00"
        android:textSize="16sp"
        android:textStyle="bold" />

    <!-- Tgl Publish -->
    <TextView
        android:id="@+id/tglPublish"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:paddingBottom="2dip"
        android:textColor="#acacac" />

    <!-- Sumber -->
    <TextView
        android:id="@+id/sumber"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="left"
        android:textColor="#5d5d5d"
        android:textStyle="bold" />
    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

和错误日志:

05-20 00:24:41.091  20376-20376/com.emaszda.nutrisibunda E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.IllegalStateException: Content view not yet created
            at android.support.v4.app.ListFragment.ensureList(ListFragment.java:328)
            at android.support.v4.app.ListFragment.getListView(ListFragment.java:222)
            at com.emaszda.nutrisibunda.NewsFragment.onCreateView(NewsFragment.java:58)
            at android.support.v4.app.Fragment.performCreateView(Fragment.java:1786)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:953)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1136)
            at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
            at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1499)
            at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:488)
            at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
            at android.support.v4.view.ViewPager.populate(ViewPager.java:1073)
            at android.support.v4.view.ViewPager.populate(ViewPager.java:919)
            at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1441)
            at android.view.View.measure(View.java:15891)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5035)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
            at android.view.View.measure(View.java:15891)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5035)
            at android.support.v7.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:453)
            at android.view.View.measure(View.java:15891)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5035)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
            at android.view.View.measure(View.java:15891)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5035)
            at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404)
            at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
            at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
            at android.view.View.measure(View.java:15891)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5035)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
            at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2208)
            at android.view.View.measure(View.java:15891)
            at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1957)
            at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1156)
            at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1336)
            at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1056)
            at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5542)
            at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
            at android.view.Choreographer.doCallbacks(Choreographer.java:562)
            at android.view.Choreographer.doFrame(Choreographer.java:532)
            at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
            at android.os.Handler.handleCallback(Handler.java:730)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:5162)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:525)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:756)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:572)
            at miui.dexspy.DexspyInstaller.main(DexspyInstaller.java:171)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

作为onCreateView :

Creates and returns the view hierarchy associated with the fragment. Since the method does not return the view, you will not able to access the ListView through getListView().

将 getListView() 放入 onViewCreated() 方法中，如下所示:

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    ListView lv = getListView();
    lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View view,
                                int position, long id) {
            // getting values from selected ListItem
            String judul = ((TextView) view.findViewById(R.id.judul))
                    .getText().toString();
            String tanggal = ((TextView) view.findViewById(R.id.tglPublish))
                    .getText().toString();
            String sumber = ((TextView) view.findViewById(R.id.sumber))
                    .getText().toString();

            // Starting single contact activity
            Intent in = new Intent(getActivity().getApplicationContext(),
                    NewsDetailActivity.class);
            in.putExtra(TAG_JUDUL, judul);
            in.putExtra(TAG_TGL, tanggal);
            in.putExtra(TAG_SUMBER, sumber);
            startActivity(in);

        }
    });
}

onViewCreated 是在 api level 13 中添加的，所以如果你的 minSdkVersion 低于 13 则使用 onActivityCreated 来获取 Listview 对象。