We Keep Coding

Android - How to pass another activity application context from java class extends fragments to asynctask?

Hi I am trying to make application that has view pager and tablayout. So when I choose 'friends' tab layout it will call java class named FragFriends.java,
In this class I want to inflate layout where recycler view adapter is filled with data from database that I retrieve using asynctask method in class PHPuserlist.java
However my application suddenly stopped
Here is the the FragFriends.java
public class FragmentFriends extends Fragment {
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View rootview = inflater.inflate(R.layout.activity_user_view,container,false);// The activity that contains recyclerview
View dview = inflater.inflate(R.layout.activity_profile,container,false); //This is the activity that contains tablayout
PHPUserList phpUserList = new PHPUserList(dview.getContext());
phpUserList.execute();
return rootview;
}
}
I have implement this recycler view with intent and it work just fine. But I need to use this with fragment
Pleas help me
This is the logcat
05-27 16:55:12.198 14031-14031/com.rumahdosen.www.rumahdosen E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.rumahdosen.www.rumahdosen, PID: 14031
java.lang.NullPointerException
at com.rumahdosen.www.rumahdosen.PHPUserList.onPreExecute(PHPUserList.java:82)
at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:587)
at android.os.AsyncTask.execute(AsyncTask.java:535)
at com.rumahdosen.www.rumahdosen.FragmentFriends.onCreateView(FragmentFriends.java:20)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1974)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1252)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617)
at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:570)
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1177)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1025)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1545)
at android.view.View.measure(View.java:16834)
at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:824)
at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:500)
at android.view.View.measure(View.java:16834)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:340)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
at android.view.View.measure(View.java:16834)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
at android.support.v7.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:391)
at android.view.View.measure(View.java:16834)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:340)
at android.view.View.measure(View.java:16834)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1621)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:742)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:607)
at android.view.View.measure(View.java:16834)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:340)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2332)
at android.view.View.measure(View.java:16834)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2252)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1315)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1513)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1192)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6231)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:788)
at android.view.Choreographer.doCallbacks(Choreographer.java:591)
at android.view.Choreographer.doFrame(Choreographer.java:560)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:774)
at android.os.Handler.handleCallback(Handler.java:808)
at android.os.Handler.dispatchMessage(Handler.java:103)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:5292)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640)
at dalvik.system.NativeStart.main(Native Method)
Below is the PHPUserList.java
public class PHPUserList extends AsyncTask<Void,UserList,Void> {
private Context context;
Activity activity;
RecyclerView recyclerView;
RecyclerView.Adapter adapter;
RecyclerView.LayoutManager layoutManager;
ArrayList<UserList> arrayList = new ArrayList<>();
PHPUserList(Context ctx){
this.context = ctx;
activity = (Activity)ctx;
}
#Override
protected Void doInBackground(Void... params) {
try {
URL url = new URL("http://njtwicomp.pe.hu/listuser.php");
HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
InputStream inputStream = httpURLConnection.getInputStream();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
StringBuilder stringBuilder = new StringBuilder();
String line;
while ((line = bufferedReader.readLine())!=null)
{
stringBuilder.append(line+"\n");
}
httpURLConnection.disconnect();
String json_string = stringBuilder.toString().trim();
JSONObject jsonObject = new JSONObject(json_string);
JSONArray jsonArray = jsonObject.getJSONArray("server_response");
int count = 0;
while(count<jsonArray.length()){
JSONObject JO = jsonArray.getJSONObject(count);
count++;
UserList userList = new UserList(JO.getString("Name"),JO.getString("Username"));
publishProgress(userList);
}
Log.d("JSON STRING", json_string);
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPreExecute() {
recyclerView = (RecyclerView) activity.findViewById(R.id.RVUserList);
layoutManager = new LinearLayoutManager(context);
recyclerView.setLayoutManager(layoutManager);
recyclerView.setHasFixedSize(true);
adapter = new RecyclerAdapter(arrayList);
recyclerView.setAdapter(adapter);
}
#Override
protected void onProgressUpdate(UserList... values) {
arrayList.add(values[0]);
adapter.notifyDataSetChanged();
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
}
}
I try to find the recyclerview by id in another activity while I set the activity as the activity of the passed context. But I don't know how to fix that
So how do I get the activity which is not the context that I passed in asynctask?

Change this:
PHPUserList phpUserList = new PHPUserList(dview.getContext());
phpUserList.execute();
to :
new PHPUserList(getActivity()).execute();

In your fragment class just put getActivity(), where Context is needed it will do the job!

just use getContext();
This does the work.
In case you need to use the Activity Context then Have static context of ClassName.this

I keep getting a nullpointer exception with my JSON Object Calls

For some reason I keep getting a nullpointer exception with my double parsing. AFter further inquiry there seems to be some issue with my JSON Objects but I have no clue what the issue is.I am pulling JSON data form openweathermap api. I scuessfully pulled and printed the data into the log.i, however when I try to access with the JSONObject I am getting an error. Please help.
Code:
package com.anuraagy.myweather;
import android.app.Activity;
import android.app.ActionBar;
import android.app.Fragment;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.*;
import android.content.*;
import android.os.Build;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.StatusLine;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
public class MyActivity extends Activity {
private String s;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
if (savedInstanceState == null) {
getFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment())
.commit();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.my, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
private JSONObject myObject,mainObject,nameObject;
private ImageView myImage;
private TextView titleText;
private String hello,weatherName,max_temp,min_temp;
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_my, container, false);
RequestTask task = new RequestTask();
task.execute(new String[]{"http://api.openweathermap.org/data/2.5/weather?q=Ashburn&APPID=970bf0e4978dae293b065f8f2830ba58"});
return rootView;
}
public class RequestTask extends AsyncTask<String, String, String> {
private TextView myView;
private String s;
#Override
protected String doInBackground(String... uri) {
HttpClient httpclient = new DefaultHttpClient();
HttpResponse response;
String responseString = null;
try {
response = httpclient.execute(new HttpGet(uri[0]));
StatusLine statusLine = response.getStatusLine();
if (statusLine.getStatusCode() == HttpStatus.SC_OK) {
ByteArrayOutputStream out = new ByteArrayOutputStream();
response.getEntity().writeTo(out);
out.close();
responseString = out.toString();
} else {
//Closes the connection.
response.getEntity().getContent().close();
throw new IOException(statusLine.getReasonPhrase());
}
} catch (ClientProtocolException e) {
//TODO Handle problems..
} catch (IOException e) {
//TODO Handle problems..
}
Log.i("", responseString);
return responseString;
}
#Override
protected void onPostExecute(String result){
Log.i("","hello");
super.onPostExecute(result);
try {
myObject = new JSONObject(result);
nameObject = myObject.getJSONObject("weather");
weatherName = nameObject.getString("main");
mainObject = myObject.getJSONObject("main");
Log.i("Wather Name",weatherName);
Log.i("mainObject",mainObject.toString());
hello = mainObject.getString("temp");
max_temp = mainObject.getString("temp_max");
min_temp = mainObject.getString("temp_min");
} catch(JSONException jsonException){
}
double f = Double.parseDouble(hello);
double max = Double.parseDouble(max_temp);
double min = Double.parseDouble(min_temp);
double realMax = (max - 273)* 1.8 + 32;
double realMin = (min - 273)* 1.8 + 32;
double realTemp = (max - 273)* 1.8 + 32;
int myMax = (int)realMax;
int myMin = (int)realMin;
int myWeather = (int)realTemp;
titleText = (TextView)getActivity().findViewById(R.id.textView3);
String fe = titleText.getText().toString();
fe.replace("definetly",weatherName);
myView = (TextView)getActivity().findViewById(R.id.textView);
// if()
// {
//
// }
// else
// {
//
// }
myImage = (ImageView)getActivity().findViewById(R.id.imageView);
myImage.setImageResource(R.drawable.clearnight);
String weather = myWeather + "";
myView.setText(weather + (char) 0x00B0 +"F");
// //Do anything with response..
}
}
}
}
Error:
10-16 10:01:26.398 664-664/com.anuraagy.myweather E/Trace﹕ error opening trace file: No such file or directory (2)
10-16 10:01:35.058 664-668/com.anuraagy.myweather D/dalvikvm﹕ GC_CONCURRENT freed 75K, 2% free 11112K/11335K, paused 17ms+3ms, total 312ms
10-16 10:01:35.058 664-664/com.anuraagy.myweather D/dalvikvm﹕ WAIT_FOR_CONCURRENT_GC blocked 282ms
10-16 10:01:35.498 664-664/com.anuraagy.myweather D/gralloc_goldfish﹕ Emulator without GPU emulation detected.
10-16 10:01:38.388 664-680/com.anuraagy.myweather I/﹕ {"coord":{"lon":-77.49,"lat":39.04},"sys":{"type":1,"id":2856,"message":0.0194,"country":"US","sunrise":1413458470,"sunset":1413498574},"weather":[{"id":701,"main":"Mist","description":"mist","icon":"50d"},{"id":721,"main":"Haze","description":"haze","icon":"50d"},{"id":741,"main":"Fog","description":"fog","icon":"50d"}],"base":"cmc stations","main":{"temp":288.03,"pressure":1008,"humidity":100,"temp_min":286.15,"temp_max":290.15},"wind":{"speed":2.86,"deg":261.502},"clouds":{"all":90},"dt":1413468071,"id":4744870,"name":"Ashburn","cod":200}
10-16 10:01:38.398 664-664/com.anuraagy.myweather I/﹕ hello
10-16 10:01:38.438 664-664/com.anuraagy.myweather D/AndroidRuntime﹕ Shutting down VM
10-16 10:01:38.438 664-664/com.anuraagy.myweather W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x40a13300)
10-16 10:01:38.448 664-664/com.anuraagy.myweather E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.NullPointerException
at java.lang.StringToReal.parseDouble(StringToReal.java:244)
at java.lang.Double.parseDouble(Double.java:295)
at com.anuraagy.myweather.MyActivity$PlaceholderFragment$RequestTask.onPostExecute(MyActivity.java:141)
at com.anuraagy.myweather.MyActivity$PlaceholderFragment$RequestTask.onPostExecute(MyActivity.java:91)
at android.os.AsyncTask.finish(AsyncTask.java:631)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4745)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)

Be careful - "weather" is a JSONArray, not a JSONObject. The NullPointerException is likely due to that.
Try instead using myObject.getJSONArray("weather"), and from there iterate through the JSONObjects inside.
See here for more information on that last part: Accessing members of items in a JSONArray with Java

It looks like myObject doesn't have item named "temp", so:
- on line 133 you set hello to null
- on line 141 you pass that null to Double.parseDouble()
- get your exception because class Double can't digest null
That's it!
Check it in the debugger, but I'm almost sure - according to your stack trace

NullPointerException on onPostExecute method

I’m having a navigation drawer for my app that contains a menu with which I can navigate between the fragments. The first fragment that i get after the app lunch is the Home which contains a listView and a footer attached in the bottom (is just for the test). The problem is when I lunch the Home fragment for the first time nothing happen and its work very well, but when I change the fragments from the navigation drawer and trying to get back the home fragment the app crash. The error log show me a null pointer Exception. Thes is my code detail
onCreateView method
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
if (v != null) {
ViewGroup parent = (ViewGroup) v.getParent();
if (parent != null)
parent.removeView(v);
}
try {
v = inflater.inflate(R.layout.fragment_homes, container, false);
listView = (ListView) v.findViewById(R.id.homeList);
l = new HomeListAdapter(this, homeList);
if(l == null)
Log.i("tag","null");
listView.setAdapter(l);
} catch (InflateException e) {
}
return v;
}
onPostExecute method
#Override
protected void onPostExecute(final String res) {
/*try {
jObj = new JSONArray(res);
} catch (JSONException e) {
e.printStackTrace();
}*/
/* JSONArray j = null;
try {
j = new JSONArray(res);
} catch (JSONException e) {
e.printStackTrace();
}*/
// Parsing json
for (int i = 0; i < 5; i++) {
//JSONObject obj = j.getJSONObject(i);
Home home = new Home();
//String photoNews = java.net.URLDecoder.decode(obj.getString("photonews"), "UTF-8");
home.setNomC("Karim Ennassiri");
home.setPhotoP("http://i1239.photobucket.com/albums/ff509/FestusMANAFEST/iker-casillas20Wallpaper__yvt2.jpg");
home.setPhotoAr("http://voyage-essaouira-maroc.com/upload/apostrophe_image_(13).jpg");
home.setText("Chlada V2.0 Edition");
home.setNbrSick("5");
home.setNbrComm("8");
home.setNbrShare("0");
homeList.add(home);
}
l.notifyDataSetChanged();
//pDialog.hide();
}
The error log
10-10 09:31:30.884 2447-2447/com.example.user.unchained E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.user.unchained, PID: 2447
java.lang.NullPointerException
at com.example.user.unchained.HomesActivity$PlaceholderFragment$FeedsTask.onPostExecute(HomesActivity.java:375)
at com.example.user.unchained.HomesActivity$PlaceholderFragment$FeedsTask.onPostExecute(HomesActivity.java:277)
at android.os.AsyncTask.finish(AsyncTask.java:632)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
And this is exactly the line that cause the error : l.notifyDataSetChanged();. I notice that the error is just in the case when i'm trying to display the fragment for the secode time.
So any help please ? Thanks !

You need to use this in doInBackground.
#Override
protected Void doInBackground(void... ) {
try {
for (int i = 0; i < 5; i++) {
//JSONObject obj = j.getJSONObject(i);
Home home = new Home();
//String photoNews = java.net.URLDecoder.decode(obj.getString("photonews"), "UTF-8");
home.setNomC("Karim Ennassiri");
home.setPhotoP("http://i1239.photobucket.com/albums/ff509/FestusMANAFEST/iker-casillas20Wallpaper__yvt2.jpg");
home.setPhotoAr("http://voyage-essaouira-maroc.com/upload/apostrophe_image_(13).jpg");
home.setText("Chlada V2.0 Edition"); //give some other name in getter setter for setText in Home.java. It makes not to understand whether you are using setText for textview assigning.
home.setNbrSick("5");
home.setNbrComm("8");
home.setNbrShare("0");
homeList.add(home);
}
postExecute is used to display UI. don't perform heavy operation like parsing in PostExecute.

Updating Listview ( SharedPreferences -> ArrayList) from separate Class

I would like to update my Listview in a fragmen in a onPostExecute() separate class.
The first initialization of the the Listview doas work, but wehe I call createList() again, the App crashes (NullPointerException)
Any Idea?
Main_Fragment:
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
View fragmentView = inflater.inflate(R.layout.main_fragment, container, false);
StartSocketService = (Button) fragmentView.findViewById(R.id.start_socketservice);
StartSocketService.setOnClickListener(this);
StopSocketService = (Button) fragmentView.findViewById(R.id.stop_socketservice);
StopSocketService.setOnClickListener(this);
listview = (ListView) fragmentView.findViewById(R.id.listView1);
createList();
return fragmentView;
}
public void createList(){
//Reading Server IPs from SharedPreferences and put them to ListView
SharedPreferences settings = getActivity().getSharedPreferences("Found_Devices", 0);
for (int i = 0; i < 255; i++) {
if ((settings.getString("Server"+i,null)) != null) {
serverList.add(settings.getString("Server"+i, null));
Log.v("Reading IP: " +settings.getString("Server"+i, null), " from SraredPreferrences at pos.: "+i );
}
}
//Initializing listView
final StableArrayAdapter adapter = new StableArrayAdapter(getActivity(),android.R.layout.simple_list_item_1, serverList);
listview.setAdapter(adapter);
listview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#TargetApi(Build.VERSION_CODES.JELLY_BEAN)
#Override
public void onItemClick(AdapterView<?> parent, final View view, int position, long id) {
final String item = (String) parent.getItemAtPosition(position);
view.animate().setDuration(2000).alpha(0).withEndAction(new Runnable() {
#Override
public void run() {
serverList.remove(item);
adapter.notifyDataSetChanged();
view.setAlpha(1);
}
});
}
});
}
Some class:
async_cient = new AsyncTask<Void, Void, Void>() {
...
protected void onPostExecute(Void result) {
Toast.makeText(mContext, "Scan Finished", Toast.LENGTH_SHORT).show();
Main_Fragment cList = new Main_Fragment();
cList.createList();
super.onPostExecute(result);
}
};
Log:
07-29 14:42:46.428 3382-3382/de.liquidbeam.LED.control D/AndroidRuntime﹕ Shutting down VM
07-29 14:42:46.428 3382-3382/de.liquidbeam.LED.control W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x41549ba8)
07-29 14:42:46.438 3382-3382/de.liquidbeam.LED.control E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: de.liquidbeam.LED.control, PID: 3382
java.lang.NullPointerException
at de.liquidbeam.LED.control.fragments.Main_Fragment.createList(Main_Fragment.java:56)
at de.liquidbeam.LED.control.background.UDP_Discover$1.onPostExecute(UDP_Discover.java:94)
at de.liquidbeam.LED.control.background.UDP_Discover$1.onPostExecute(UDP_Discover.java:57)
at android.os.AsyncTask.finish(AsyncTask.java:632)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
07-29 14:47:46.591 3382-3382/de.liquidbeam.LED.control I/Process﹕ Sending signal. PID: 3382 SIG: 9
Lines:
56 : SharedPreferences settings = getActivity().getSharedPreferences("Found_Devices", 0);
94 : cList.createList();
57: async_cient = new AsyncTask<Void, Void, Void>() {

You creating a new instance of your fragment with no context (activity) to run in. So
the line
SharedPreferences settings = getActivity().getSharedPreferences("Found_Devices", 0);
Tries to get his activity but there is no activity where the fragment lives in ;)

How to avoid app crash when using Async-task in Fragments?

I am trying to show images in grid-view using tab-swipe. But when include async-task to fetch images from json URL the app does not even starting. It just crashes and closed. Here is my code.
import android.support.v4.app.Fragment;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.GridView;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
public class GamesFragment extends Fragment {
public GamesFragment(){}
// Declare Variables
JSONObject jsonobject;
JSONArray jsonarray;
GridView gridview;
GridViewAdapter adapter;
ProgressDialog mProgressDialog;
ArrayList<HashMap<String, String>> arraylist;
ArrayList<HashMap<String, String>> items;
private Button button;
static String CATEGORY = "category";
int setlimit = 6;
int tolimit = 5;
static String IMAGE = "image";
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.gridview_main, container, false);
new DownloadJSON().execute();
return rootView;
}
// DownloadJSON AsyncTask
private class DownloadJSON extends AsyncTask<Void, Void, Void> {
#Override
protected void onPreExecute() {
super.onPreExecute();
// Create a progressdialog
mProgressDialog = new ProgressDialog(getActivity());
// Set progressdialog title
mProgressDialog.setTitle("Student Government App");
// Set progressdialog message
mProgressDialog.setMessage("Loading...");
mProgressDialog.setIndeterminate(false);
// Show progressdialog
mProgressDialog.show();
}
#Override
protected Void doInBackground(Void... params) {
// Create an array
arraylist = new ArrayList<HashMap<String, String>>();
// Retrieve JSON Objects from the given URL address
jsonobject = JSONfunctions
.getJSONfromURL
("http://jsonurl.com");
try {
// Locate the array name in JSON
jsonarray = jsonobject.getJSONArray("wallpaper");
for (int i = 0; i < jsonarray.length(); i++) {
HashMap<String, String> map = new HashMap<String, String>();
jsonobject = jsonarray.getJSONObject(i);
// Retrive JSON Objects
map.put("category", jsonobject.getString("category"));
map.put("image", jsonobject.getString("image"));
// Set the JSON Objects into the array
arraylist.add(map);
}
} catch (JSONException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(Void args) {
gridview = (GridView) getView().findViewById(R.id.gridViewCustom);
// Pass the results into ListViewAdapter.java
adapter = new GridViewAdapter(getActivity(), arraylist);
gridview.setAdapter(adapter);
mProgressDialog.dismiss();
}
}
}
How can i prevent it from app crash? Any help would be be great.
Logcat:
07-03 15:22:36.692 838-838/info.androidhive.tabsswipe D/ActivityThread﹕ ACT- AM_ON_PAUSE_CALLED ActivityRecord{41353570 token=android.os.BinderProxy#41352cb0 {info.androidhive.tabsswipe/info.androidhive.tabsswipe.MainActivity}}
07-03 15:22:36.707 838-838/info.androidhive.tabsswipe D/ActivityThread﹕ ACT-PAUSE_ACTIVITY_FINISHING handled : 0 / android.os.BinderProxy#41352cb0
07-03 15:22:36.904 838-838/info.androidhive.tabsswipe D/OpenGLRenderer﹕ Flushing caches (mode 0)
07-03 15:22:36.944 838-838/info.androidhive.tabsswipe D/OpenGLRenderer﹕ Flushing caches (mode 0)
07-03 15:22:36.989 838-838/info.androidhive.tabsswipe D/OpenGLRenderer﹕ Flushing caches (mode 0)
07-03 15:22:37.003 838-838/info.androidhive.tabsswipe E/WindowManager﹕ Activity info.androidhive.tabsswipe.MainActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView#4136f300 that was originally added here
android.view.WindowLeaked: Activity info.androidhive.tabsswipe.MainActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView#4136f300 that was originally added here
at android.view.ViewRootImpl.<init>(ViewRootImpl.java:418)
at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:294)
at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:226)
at android.view.WindowManagerImpl$CompatModeWrapper.addView(WindowManagerImpl.java:151)
at android.view.Window$LocalWindowManager.addView(Window.java:547)
at android.app.Dialog.show(Dialog.java:277)
at info.androidhive.tabsswipe.GamesFragment$DownloadJSON.onPreExecute(GamesFragment.java:65)
at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
at android.os.AsyncTask.execute(AsyncTask.java:534)
at info.androidhive.tabsswipe.GamesFragment.onCreateView(GamesFragment.java:48)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1500)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:938)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1115)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1478)
at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:478)
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1068)
at android.support.v4.view.ViewPager.populate(ViewPager.java:914)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1436)
at android.view.View.measure(View.java:15264)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4918)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at android.view.View.measure(View.java:15264)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:833)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:574)
at android.view.View.measure(View.java:15264)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4918)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2161)
at android.view.View.measure(View.java:15264)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2131)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1242)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1435)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1127)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4609)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:747)
at android.view.Choreographer.doCallbacks(Choreographer.java:567)
at android.view.Choreographer.doFrame(Choreographer.java:536)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:733)
at android.os.Handler.handleCallback(Handler.java:615)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:153)
at android.app.ActivityThread.main(ActivityThread.java:4987)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:821)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:584)
at dalvik.system.NativeStart.main(Native Method)
07-03 15:22:37.004 838-838/info.androidhive.tabsswipe D/OpenGLRenderer﹕ Flushing caches (mode 0)
07-03 15:22:37.004 838-838/info.androidhive.tabsswipe D/ActivityThread﹕ ACT-DESTROY_ACTIVITY handled : 1 / android.os.BinderProxy#41352cb0
07-03 15:22:37.004 838-838/info.androidhive.tabsswipe D/OpenGLRenderer﹕ Flushing caches (mode 1)

You should move gridview initialized in your onCreateView(...) before new DownloadJSON().execute();
gridview = (GridView) rootview.findViewById(R.id.gridViewCustom);

Change you oncreateview like this
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.gridview_main, container, false);
gridview = (GridView) rootView.findViewById(R.id.gridViewCustom);
new DownloadJSON().execute();
return rootView;
}
private class DownloadJSON extends AsyncTask<Void, Void, Void> {
ProgressDialog progressDialog = null;
#Override
protected void onPreExecute() {
progressDialog = new ProgressDialog(getActivity());
progressDialog.setMessage("Loading , Please wait...");
progressDialog.setIndeterminate(true);
progressDialog.setCancelable(false);
progressDialog.setCanceledOnTouchOutside(false);
progressDialog.show();
super.onPreExecute();
}
change your onPostExecute this way
#Override
protected void onPostExecute(Void args) {
mProgressDialog.dismiss();
gridview = (GridView) getView().findViewById(R.id.gridViewCustom);
// Pass the results into ListViewAdapter.java
adapter = new GridViewAdapter(getActivity(), arraylist);
gridview.setAdapter(adapter);
super.onPostExecute(arg);
}
}

You open That app in Debugging mode
and see the error in console (choose warning) and find the error and clear it