我有这个空指针执行错误
03-10 14:08:27.510 9297-9297/? E/AndroidRuntime: FATAL
EXCEPTION: main
Process: com.anakacara.anakacara, PID: 9297
java.lang.NullPointerException
at com.anakacara.anakacara.Fragment.EventFragment.getDataFromServer(EventFragment.java:163)
at com.anakacara.anakacara.Fragment.EventFragment.getData(EventFragment.java:192)
at com.anakacara.anakacara.Fragment.EventFragment.onCreateView(EventFragment.java:127)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1962)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1248)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738)
这是我的customVolleyRequest代码
public class CustomVolleyRequest {
private static CustomVolleyRequest customVolleyRequest;
private static Context context;
private RequestQueue requestQueue;
private ImageLoader imageLoader;
private CustomVolleyRequest(Context context) {
this.context = context;
this.requestQueue = getRequestQueue();
imageLoader = new ImageLoader(requestQueue,
new ImageLoader.ImageCache() {
private final LruCache<String, Bitmap>
cache = new LruCache<String, Bitmap>(20);
@Override
public Bitmap getBitmap(String url) {
return cache.get(url);
}
@Override
public void putBitmap(String url, Bitmap bitmap) {
cache.put(url, bitmap);
}
});
}
public static synchronized CustomVolleyRequest getInstance(Context context) {
if (customVolleyRequest == null) {
customVolleyRequest = new CustomVolleyRequest(context);
}
return customVolleyRequest;
}
public RequestQueue getRequestQueue() {
if (requestQueue == null) {
Cache cache = new DiskBasedCache(context.getCacheDir(), 10 * 1024 * 1024);
Network network = new BasicNetwork(new HurlStack());
requestQueue = new RequestQueue(cache, network);
requestQueue.start();
}
return requestQueue;
}
public ImageLoader getImageLoader() {
return imageLoader;
}
}
这是我用于存储标记
的appconfig类public class AppConfig {
// Server user login url
public static String URL_LOGIN = "http://192.168.0.13:80/task_manager/v1/login";
// Server user register url
public static String URL_REGISTER = "http://192.168.0.13/task_manager/v1/register";
//URL of my even
public static final String DATA_URL = "http://192.168.0.13/task_manager/v1/even/";
//Tags for my JSON
public static final String TAG_IMAGE_URL = "gambar";
public static final String TAG_JUDUL = "judul";
public static final String TAG_DESKRIPSI = "deskripsi";
public static final String TAG_DUIT = "duit";
public static final String TAG_PERSEN = "persen";
public static final String TAG_SISA_HARI = "sisahari";
}
这是getter和setter
public class Event {
//Data Variables
private String imageUrl;
private String name;
private String rank;
private int realName;
private int createdBy;
private int firstAppearance;
//private ArrayList<String> powers;
//Getters and Setters
public String getImageUrl() {
return imageUrl;
}
public void setImageUrl(String imageUrl) {
this.imageUrl = imageUrl;
}
//GET AND SET JUDUL
public String getJudul() {
return name;
}
public void setJudul(String name) {
this.name = name;
}
//GET AND SET DESKRIPSI
public String getDeskripsi() {
return rank;
}
public void setDeskripsi(String rank) {
this.rank = rank;
}
//GET AND SET DUIT
public int getDuit() {
return realName;
}
public void setDuit(int realName) {
this.realName = realName;
}
//GET AND SET PERSEN
public int getPersen() {
return createdBy;
}
public void setPersen(int createdBy) {
this.createdBy = createdBy;
}
//GET AND SET SISA HARI
public int getSisaHari() {
return firstAppearance;
}
public void setSisaHari(int firstAppearance) {
this.firstAppearance = firstAppearance;
}
}
这是我的主要片段
public class EventFragment extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
//Creating a List of event
private List<Event> listEvent;
//Creating Views
private RecyclerView recyclerView;
private RecyclerView.LayoutManager layoutManager;
private RecyclerView.Adapter adapter;
private int requestCount = 1;
private OnFragmentInteractionListener mListener;
private RequestQueue requestQueue;
public EventFragment() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @param param1 Parameter 1.
* @param param2 Parameter 2.
* @return A new instance of fragment EventFragment.
*/
// TODO: Rename and change types and number of parameters
public static EventFragment newInstance(String param1, String param2) {
EventFragment fragment = new EventFragment();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
private final RecyclerView.OnScrollListener onScrollListener = new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(final RecyclerView recyclerView, final int newState) {
// code
if (isLastItemDisplaying(recyclerView)) {
//Calling the method getdata again
getData();
}
}
@Override
public void onScrolled(final RecyclerView recyclerView, final int dx, final int dy) {
// code
if (isLastItemDisplaying(recyclerView)) {
//Calling the method getdata again
getData();
}
}
};
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View x = inflater.inflate(R.layout.fragment_event,null);;
recyclerView = (RecyclerView) x.findViewById(R.id.recyclerView);
recyclerView.setHasFixedSize(true);
layoutManager = new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(layoutManager);
//Initializing our event list
listEvent = new ArrayList<>();
requestQueue = Volley.newRequestQueue(getActivity().getApplication());
//Calling method to get data
getData();
recyclerView.addOnScrollListener(rVOnScrollListener);
adapter = new CardAdapter(listEvent, getActivity().getApplication());
//Adding adapter to recyclerview
recyclerView.setAdapter(adapter);
// RecyclerView.ItemAnimator itemAnimator = new DefaultItemAnimator();
// itemAnimator.setAddDuration(1000);
// itemAnimator.setRemoveDuration(1000);
// recyclerView.setItemAnimator(itemAnimator);
// recyclerView.addOnItemTouchListener(new RecyclerTouchListener(getActivity(), recyclerView, new ClickListener() {
// @Override
// public void onClick(View view, int position) {
// Intent intent = new Intent(getActivity(), DetailEvent.class);
// intent.putExtra("event_judul", listEvent.get(position).getJudul()); //you can name the keys whatever you like
// intent.putExtra("event_deskripsi", listEvent.get(position).getDeskripsi()); //note that all these values have to be primitive (i.e boolean, int, double, String, etc.)
// intent.putExtra("event_duit", listEvent.get(position).getDuit());
// intent.putExtra("event_persen", listEvent.get(position).getPersen()); //note that all these values have to be primitive (i.e boolean, int, double, String, etc.)
// intent.putExtra("event_sisa_hari", listEvent.get(position).getSisaHari());
// intent.putExtra("event_image", listEvent.get(position).getImageUrl());
// startActivity(intent);
// }
//
// @Override
// public void onLongClick(View view, int position) {
// Toast.makeText(getActivity(), "Kepencet Lama " + position, Toast.LENGTH_LONG).show();
// }
// }));
return x;
}
private JsonArrayRequest getDataFromServer(int requestCount) {
//Initializing ProgressBar
final ProgressBar progressBar = (ProgressBar) getActivity().findViewById(R.id.progressBar1);
//Displaying Progressbar
progressBar.setVisibility(View.VISIBLE);
getActivity().getParent().setProgressBarIndeterminateVisibility(true);
//JsonArrayRequest of volley
JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(AppConfig.DATA_URL + String.valueOf(requestCount),
new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray response) {
//Calling method parseData to parse the json response
parseData(response);
//Hiding the progressbar
progressBar.setVisibility(View.GONE);
}
},
new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
progressBar.setVisibility(View.GONE);
//If an error occurs that means end of the list has reached
Toast.makeText(getActivity(), "No More Items Available", Toast.LENGTH_SHORT).show();
}
});
//Returning the request
return jsonArrayRequest;
}
private void getData(){
//Adding the method to the queue by calling the method getDataFromServer
requestQueue.add(getDataFromServer(requestCount));
//Incrementing the request counter
requestCount++;
}
//This method will parse json data
private void parseData(JSONArray array){
for(int i = 0; i<array.length(); i++) {
Event event = new Event();
JSONObject json = null;
try {
json = array.getJSONObject(i);
event.setJudul(json.getString(AppConfig.TAG_JUDUL));
event.setDeskripsi(json.getString(AppConfig.TAG_DESKRIPSI));
event.setDuit(json.getInt(AppConfig.TAG_DUIT));
event.setPersen(json.getInt(AppConfig.TAG_PERSEN));
event.setSisaHari(json.getInt(AppConfig.TAG_SISA_HARI));
event.setImageUrl(json.getString(AppConfig.TAG_IMAGE_URL));
} catch (JSONException e) {
e.printStackTrace();
}
listEvent.add(event);
}
adapter.notifyDataSetChanged();
//Finally initializing our adapter
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement OnFragmentInteractionListener");
}
}
@Override
public void onDetach() {
super.onDetach();
mListener = null;
}
class RecyclerTouchListener implements RecyclerView.OnItemTouchListener{
private GestureDetector mGestureDetector;
private ClickListener mClickListener;
public RecyclerTouchListener(final Context context, final RecyclerView recyclerView, final ClickListener clickListener) {
this.mClickListener = clickListener;
mGestureDetector = new GestureDetector(context,new GestureDetector.SimpleOnGestureListener(){
@Override
public boolean onSingleTapUp(MotionEvent e) {
return true;
}
@Override
public void onLongPress(MotionEvent e) {
View child = recyclerView.findChildViewUnder(e.getX(),e.getY());
if (child!=null && clickListener!=null){
clickListener.onLongClick(child, recyclerView.getChildAdapterPosition(child));
}
super.onLongPress(e);
}
});
}
@Override
public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e) {
View child = rv.findChildViewUnder(e.getX(), e.getY());
if (child!=null && mClickListener!=null && mGestureDetector.onTouchEvent(e)){
mClickListener.onClick(child, rv.getChildAdapterPosition(child));
}
return false;
}
@Override
public void onTouchEvent(RecyclerView rv, MotionEvent e) {
}
@Override
public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
}
}
private boolean isLastItemDisplaying(RecyclerView recyclerView) {
if (recyclerView.getAdapter().getItemCount() != 0) {
int lastVisibleItemPosition = ((LinearLayoutManager) recyclerView.getLayoutManager()).findLastCompletelyVisibleItemPosition();
if (lastVisibleItemPosition != RecyclerView.NO_POSITION && lastVisibleItemPosition == recyclerView.getAdapter().getItemCount() - 1)
return true;
}
return false;
}
private RecyclerView.OnScrollListener rVOnScrollListener = new RecyclerView.OnScrollListener(){
@Override
public void onScrollStateChanged(RecyclerView recyclerView,
int newState) {
super.onScrollStateChanged(recyclerView, newState);
// Toast.makeText(getApplicationContext(),
// Config.DATA_URL+String.valueOf(requestCount), Toast.LENGTH_LONG).show();
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if (isLastItemDisplaying(recyclerView)) {
//Calling the method getdata again
getData();
}
}
};
public static interface ClickListener{
public void onClick(View view, int position);
public void onLongClick(View view, int position);
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
}
如果我不使用滚动更改侦听器并且只获取所有json数据，我不知道错误的原因在哪里。 我使用此链接中的教程https://www.simplifiedcoding.net/android-feed-example-using-php-mysql-volley/ 我想把它改成片段
答案 0 :(得分：1)
将ProgressBar绑定行移至 onCreateView（）：
private ProgressBar progressBar;
代码应该：
View x = inflater.inflate(R.layout.fragment_event,null);
progressBar = (ProgressBar) x.findViewById(R.id.progressBar1);
原因： 片段的每个小部件都会与片段的rootView绑定。
修改1：
删除以下行：
getActivity().getParent().setProgressBarIndeterminateVisibility(true);
希望这会对你有所帮助。