我正在开发Android应用程序并创建幻灯片菜单。在幻灯片菜单中，我有“搜索”项。这是一个调用json的片段（使用volley）并将结果输入到自定义列表视图中。
现在，当我调用片段（使用调试模式）时，片段开始下载一些数据，但在json的一些记录下载应用程序崩溃后，我收到此错误：
E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.NullPointerException
at com.firstproject.fragment.SearchFragment.loadListView(SearchFragment.java:175)
at com.firstproject.fragment.SearchFragment.access$000(SearchFragment.java:46)
at com.firstproject.fragment.SearchFragment$1.onResponse(SearchFragment.java:105)
at com.firstproject.fragment.SearchFragment$1.onResponse(SearchFragment.java:98)
at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:60)
at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:30)
at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:99)
at android.os.Handler.handleCallback(Handler.java:730)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:213)
at android.app.ActivityThread.main(ActivityThread.java:5225)
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:741)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
at dalvik.system.NativeStart.main(Native Method)
我在我调用json文件的地方附上我的代码（隐私删除url json）
请帮忙吗？ 感谢
public class SearchFragment extends Fragment {
public SearchFragment(){}
private static final String url = "http://<server_name>/<folder>/data.json";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_search, container, false);
}
ListView geoJSON;
String globalResponse="";
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
String tag_string_req = "string_req";
final ProgressDialog pDialog = new ProgressDialog(getActivity());
// Showing progress dialog before making http request
pDialog.setMessage("Loading...");
pDialog.show();
RequestQueue mRequestQueue;
Network network = new BasicNetwork(new HurlStack());
//Cache cache = new DiskBasedCache(getCacheDir(), 1024 * 1024); // 1MB cap
// Instantiate the RequestQueue with the cache and network.
Cache cache = AppController.getInstance().getRequestQueue().getCache();
mRequestQueue = new RequestQueue(cache, network);
// Start the queue
mRequestQueue.start();
Cache.Entry entry = cache.get(url);
if(entry != null){
try {
String data = new String(entry.data, "UTF-8");
//loadListView(gobalResponse,0,1000);
//Toast.makeText(getActivity(), "Cache utilized!", 0).show();
// handle data, like converting it to xml, json, bitmap etc.,
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}else{
// Cached response doesn't exists. Make network call here
StringRequest strReq = new StringRequest(Request.Method.GET,
url, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
globalResponse=response;
Globals.GlobalResponse=globalResponse;
Log.d("", response.toString());
loadListView(globalResponse,0,1000);
//loadListView(response,0,1000);
pDialog.hide();
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
VolleyLog.d("", "Error: " + error.getMessage());
//Toast.makeText(getApplicationContext(), error.getMessage()+"", 0).show();
pDialog.hide();
}
});
strReq.setShouldCache(true);
//strReq.
// Adding request to request queue
AppController.getInstance().addToRequestQueue(strReq, tag_string_req);
}
}
private ArrayList<GeoJsonResponse> globalResponseObject;//=new ArrayList<GeoJsonResposne>();
private void loadListView(String response,float lowerLimit,float upperLimit)
{
try {
JSONObject featureCollection=new JSONObject(response);
globalResponseObject=new ArrayList<GeoJsonResponse>();
JSONArray features=featureCollection.getJSONArray("features");
for (int i = 0; i < features.length(); i++) {
JSONObject properties=features.getJSONObject(i);
float mag=Float.parseFloat(properties.getJSONObject("properties").getString("mag"));
if(!(mag>=lowerLimit&&mag<upperLimit)) continue;
Log.d("",properties.getJSONObject("properties").getString("author")
+ properties.getJSONObject("properties").getString("mag")
+ properties.getJSONObject("properties").getString("place")
+ properties.getJSONObject("geometry").getJSONArray("coordinates").getString(0)
+ properties.getJSONObject("geometry").getJSONArray("coordinates").getString(1)
+ properties.getJSONObject("geometry").getJSONArray("coordinates").getString(2)
);
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss");
Date date1 = format.parse(properties.getJSONObject("properties").getString("time"));
GeoJsonResponse obj=new GeoJsonResponse(
properties.getJSONObject("properties").getString("eventId"),
properties.getJSONObject("properties").getString("author"),
properties.getJSONObject("properties").getString("place"),
Double.parseDouble(properties.getJSONObject("properties").getString("mag")),
Double.parseDouble(properties.getJSONObject("geometry").getJSONArray("coordinates").getString(2)),
properties.getJSONObject("properties").getString("time"),date1,
Double.parseDouble(properties.getJSONObject("geometry").getJSONArray("coordinates").getString(0)),
Double.parseDouble(properties.getJSONObject("geometry").getJSONArray("coordinates").getString(1))
);
globalResponseObject.add(obj);}
if(lowerLimit==0)
Globals.geoJsonResponse=globalResponseObject;
// Collections.sort(globalResponseObject, new DateSorter());
CustomListAdapter adpater=new CustomListAdapter(getActivity()
, globalResponseObject);
adpater.notifyDataSetChanged();
geoJSON.setAdapter(adpater);
geoJSON.invalidate();
geoJSON.invalidateViews();
//, author, place, magnitude, distance, date)
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}