Develop Reference

Static ArrayList from a service is empty when accessed from my MainActivity

I am making a basic app that just reads RSS files from google and displays the headlines in a listview. The problem I am having is that the static ArrayList I am using in an IntentService is empty when I access it after I start the intent for the service. There could be something very basic I am missing here but tit used to work before I added more RSS links to the service. I tried commenting them out to see if there was some sort of overloading somewhere but nothing changed, which I guess means that I changed something else without realizing or remembering it.
Here is my relavent code, the ArrayList I am trying to access is the newsList variable in RSSsearcher. In the past I have logged the string values of the arraylist and confirmed that it was being populated in the RSSsearcher class, but empty in the MainActivity class.
Relevant code:
RSSsearcher:
public class RSSsearcher extends IntentService {
public static ArrayList<NewsCard> newsList = new ArrayList<>();
private static String TAG = "RSS";
public RSSsearcher() {
super("RSSsearcher");
}
#Override
protected void onHandleIntent(#Nullable Intent intent) {
parseNewsLists();
Log.i(TAG,"newsList in onHandleIntent" + newsList);
}
public static ArrayList<NewsCard> getNewsCards() {
return newsList;
}
//helper method to create all the RSSfeed objects
private void parseNewsLists() {
Log.i(TAG, "the service has been started");
//Creating the RSS feed objects
RSSfeed topStories = new RSSfeed("https://news.google.com/news?cf=all&hl=en&pz=1&ned=us&output=rss");
RSSfeed worldNews = new RSSfeed("https://news.google.com/news/rss/headlines/section/topic/WORLD?ned=us&hl=en");
RSSfeed usNews = new RSSfeed("https://news.google.com/news/rss/headlines/section/topic/NATION?ned=us&hl=en");
RSSfeed buisnessNews = new RSSfeed("https://news.google.com/news/rss/headlines/section/topic/BUSINESS?ned=us&hl=en");
RSSfeed technologyNews = new RSSfeed("https://news.google.com/news/rss/headlines/section/topic/TECHNOLOGY?ned=us&hl=en");
RSSfeed entertainmentNews = new RSSfeed("https://news.google.com/news/rss/headlines/section/topic/ENTERTAINMENT?ned=us&hl=en");
RSSfeed sportsNews = new RSSfeed("https://news.google.com/news/rss/headlines/section/topic/SPORTS?ned=us&hl=en");
RSSfeed scienceNews = new RSSfeed("https://news.google.com/news/rss/headlines/section/topic/SCIENCE?ned=us&hl=en");
RSSfeed healthNews = new RSSfeed("https://news.google.com/news/rss/headlines/section/topic/HEALTH?ned=us&hl=en");
try {
//getting RSS feeds
topStories.FileReader();
worldNews.FileReader();
usNews.FileReader();
buisnessNews.FileReader();
technologyNews.FileReader();
entertainmentNews.FileReader();
sportsNews.FileReader();
scienceNews.FileReader();
healthNews.FileReader();
} catch (Exception e) {
Log.i(TAG, Log.getStackTraceString(e));
}
//adding stories to main
newsList.addAll(topStories.getNews());
newsList.addAll(worldNews.getNews());
newsList.addAll(usNews.getNews());
newsList.addAll(buisnessNews.getNews());
newsList.addAll(technologyNews.getNews());
newsList.addAll(entertainmentNews.getNews());
newsList.addAll(sportsNews.getNews());
newsList.addAll(scienceNews.getNews());
newsList.addAll(healthNews.getNews());
}
}
MainActivity:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//TODO remove and have actual tags show up
TagCard onecard = new TagCard("TestCard");
TagCard twocard = new TagCard("TestCard2");
dummyTags.add(onecard);
dummyTags.add(twocard);
mainListView = (ListView) findViewById(R.id.main_content_list);
drawerLayout = (DrawerLayout) findViewById(R.id.main_layout);
tagDrawerList = (ListView) findViewById(R.id.tag_drawer);
//setting an intent for the RSSsearcher to fetch the news
//TODO make this happen every 15 minutes or so
Intent intent = new Intent(this, RSSsearcher.class);
startService(intent);
NewsCard card = new NewsCard("Testing", "linkeroni");
//adding all the NewsCard objects to this classes newsList
newsList.addAll(RSSsearcher.getNewsCards());
MainAdapter adapter = new MainAdapter(this, newsList);
mainListView.setAdapter(adapter);
Log.i(TAG, "This is the array from main activity" + newsList.toString());
actionBarDrawerToggle = new ActionBarDrawerToggle(this, drawerLayout, R.string.open_drawer, R.string.close_drawer){
public void onDrawerClosed(View view) {
super.onDrawerClosed(view);
getActionBar().setTitle("Closed");
}
public void onDrawerOpened(View view){
super.onDrawerOpened(view);
getActionBar().setTitle("Open");
}
};
//TODO removed dummytags and add actual tag implementation
tagDrawerList.setAdapter(new TagAdapter(this,dummyTags));
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setHomeButtonEnabled(true);
}
Thank you in advance!

I think that when you call
newsList.addAll(RSSsearcher.getNewsCards());
The intent is still in execution

The recyclerview crashes when I update it

Please don't mark it as duplicate, as the solutions provided yesterday did not work.
I have populated a recyclerview, and it is working fine, albeit it loads a bit slowly.
However, say when I add a new name and update the recyclerview it crashes with the NullPointerException.
Below are the classes and code:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mainOnes);
recyclerView = (RecyclerView) findViewById(R.id.recycleOnes);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
recyclerView.setLayoutManager(linearLayoutManager);
recyclerView.setHasFixedSize(true);
adapter = new MusicRecyclerAdapter(list);
recyclerView.setAdapter(adapter);
populateList();
}
public void populateList(){
DisplayUsersList displayUsersList = new DisplayUsersList();
displayUsersList.execute();
}
public class DisplayUsersList extends AsyncTask<String, String, String> {
#Override
protected String doInBackground(String... params) {
...
}
#Override
protected void onPostExecute(String postData) {
try {
list.clear();
JSONArray jsonArray = new JSONArray(postData);
for(int i=0; i < jsonArray.length(); i++){
String forename = jsonArray.getJSONObject(i).getString("forename");
String surname = jsonArray.getJSONObject(i).getString("surname");
UserDetails userDetails = new UserDetails(forename, musicName, surname);
list.add(userDetails);
}
adapter.notifyDataSetChanged();
} catch (JSONException e) {
e.printStackTrace();
}
}
}
public class AddUsers extends AsyncTask<String, String, String> {
#Override
protected String doInBackground(String... params) {
...
}
#Override
protected void onPostExecute(String postData) {
populateList();
}
}
I think it is crashing because of the populateList() method call because I have already initialised everything
My logcat:
java.lang.NullPointerException
at georgezs.userdas.UserDBGUI$DisplayUsersList.onPostExecute(UserDBGUI.java:218)
at android.os.AsyncTask.finish(AsyncTask.java:741)
at android.os.AsyncTask.access$600(AsyncTask.java:197)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:654)
at android.os.Handler.dispatchMessage(Handler.java:100)
Line 218 is adapter.notifyDataSetChanged();
I tried instantiating the recyclerview in onPostExecute but it keeps crashing. My code works in the sense that it actually loads the data and displays it in a recyclerview. It just doesn't redisplay or reload when I call the populateList() method again.
This bug has been bugging me in my sleep literally - so any help and solutions would mean a lot to me
EDIT: I THINK I KNOW EXACTLY WHERE THE ERROR IS - IT IS IN THE POSTEXECUTE METHOD IN ADDUSERS CLASS.
Thanks

Just check if the adapter is not null before calling notifyDataSetChanged():
if (adapter != null) {
adapter.notifyDataSetChanged();
}
This happens because the AsyncTask executes asynchronously and by the time it finishes, the adapter might not be available anymore.

One option you could try is, instead of using
adapter.notifyDataSetChanged();
replace with
recyclerView.getAdapter().notifyDataSetChanged();
This is assuming for whatever reason, you have got your adapter set to null, but not shown in the code clearly above, while your recyclerview is still fully intact.
p/s: I also didn't see you update your latest retrieved data and insert into the adapter. You might want to check that as well.

You're handling variables outside the scope of your main class in a Threaded class which can always be sketchy. Granted AsyncTask is supposed to synchronize operations for you, I'm always cautious
Try passing your list and adapter to your DisplayUsersList class e.g.
DisplayUsersList displayUsersList = new DisplayUsersList(list, adapter);
displayUsersList.execute();
And in your DisplayUsersList make sure the reference of these is explicit e.g.
public class DisplayUsersList extends AsyncTask<String, String, String> {
private final List<UserDetails> list;
private final Adapter adapter;
public DisplayUsersList(List<UserDetails> list, Adapter adapter) {
this.list = list;
this.adapter = adapter;
}
...
Also, try moving the populateList(); to OnStart rather than onCreate
As although the variables are assigned they may still be initialising.
Edit
Could you try moving the call to the top level class e.g.
public void dataSetChangedCallback() {
adapter.notifyDataSetChanged();
}
And in your DisplayUsersList change adapter.notifyDataSetChanged(); to
...
dataSetChangedCallback();
...

NumberFormatException in Android

I'm making an application in which the user can add Store departments and for those departments the ability to add the cities of where the departments are located.
I keep on getting a NumberFormatException when I'm trying to add a city for a departement:
Caused by: java.lang.NumberFormatException: Invalid long: "null"
at java.lang.Long.invalidLong(Long.java:124)
at java.lang.Long.parseLong(Long.java:345)
at java.lang.Long.parseLong(Long.java:321)
at org.hello.addgroups.vestiging_list.onCreate(vestiging_list.java:45)
after this the app crashes but when I restart the app the values are added into the list.
these are my classes:
Add_vestiging.java:
public class Add_vestiging extends Activity implements View.OnClickListener{
EditText et,hiddenet;
Button add_bt, cancel_btn;
SQLController dbcon;
Intent i;
Long groupd;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.add_new_vestiging);
et = (EditText)findViewById(R.id.vestigingName);
add_bt = (Button) findViewById(R.id.addBtn);
cancel_btn = (Button) findViewById(R.id.cancelBtn);
dbcon = new SQLController(this);
try {
dbcon.open();
} catch(SQLException e) {
e.printStackTrace();
}
i = getIntent();
String id = i.getStringExtra("groupID");
groupd = Long.parseLong(id);
add_bt.setOnClickListener(this);
cancel_btn.setOnClickListener(this);
}
#Override
public void onClick(View v) {
switch(v.getId()) {
case R.id.addBtn:
String name = et.getText().toString();
try {
dbcon.insertVestiging(groupd, name);
}catch(SQLiteException e) {
e.printStackTrace();
}
Intent main = new Intent(Add_vestiging.this, vestiging_list.class);
startActivity(main);
break;
case R.id.cancelBtn:
super.finish();
break;
}
}
}
vestiging_list.java:
public class vestiging_list extends Activity {
ListView lv;
SQLController dbcon;
TextView title;
Button addves;
Long long_id;
String groupid;
Intent add_ves;
String groupname;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.vestiging_list);
dbcon = new SQLController(this);
title = (TextView) findViewById(R.id.vestitel);
try {
dbcon.open();
} catch (SQLException e) {
e.printStackTrace();
}
add_ves = getIntent();
groupid = add_ves.getStringExtra("groupID");
groupname = add_ves.getStringExtra("groupName");
title.setText(groupname);
long_id = Long.parseLong(groupid);
addves = (Button)findViewById(R.id.addves_bt_id);
lv = (ListView)findViewById(R.id.vestigingList_id);
addves.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
add_ves = new Intent(getApplicationContext(), Add_vestiging.class);
add_ves.putExtra("groupID", groupid);
startActivity(add_ves);
}
});
Cursor cursor = dbcon.readVestigingen(long_id);
String[] from = new String[] { GroupDatabaseHelper.V_ID, GroupDatabaseHelper.VESNAME};
int[] to = new int [] { R.id.vesID, R.id.vesName};
SimpleCursorAdapter adapter = new SimpleCursorAdapter(vestiging_list.this, R.layout.vestiging_single_row_item, cursor, from, to,1);
adapter.notifyDataSetChanged();
lv.setAdapter(adapter);
}
}
Any ideas on how to remove the NumberFormatException?
Any help is greatly appreciated.
Thanks in advance.

Any ideas on how to remove the NumberFormatException?
The exception is caused by Long.parseLong in vestiging_list at line 45. The reason is that groupid, in your case in null. Since you didn't fill up the Intent object you used to start vestiging_list.
E.g.
case R.id.addBtn:
String name = et.getText().toString();
try {
dbcon.insertVestiging(groupd, name);
}catch(SQLiteException e) {
e.printStackTrace();
}
Intent main = new Intent(Add_vestiging.this, vestiging_list.class);
main.putExtra("groupID", String.valueOf(groupd));
startActivity(main);
break;
assuming that groupd is a long.

I think problem is in the following line :
int[] to = new int [] { R.id.vesID, R.id.vesName};
What is the type of "R.id.vesName" ?. It should be integer.

From the stack trace that you have provided I can assume that groupId is null:
groupid = add_ves.getStringExtra("groupID");
...
long_id = Long.parseLong(groupid);
According to the Long's Javadoc Long#parseLong(String) throws an Exception if the argument is not a parsable Long, sth which is the case with null.
Check if groupid can be null else you have a bug. If it can be null then check if it equals null and then set long_id to an appropriate value e.g. 0 or -1.

It looks to me like you're creating an Intent, but you're not passing the info to the intent. The class reference to the current class is just a trace, and doesn't include info.
When you make the Intent in the Add_vestiging class, in onClick, do something like main.putExtra("groupID", id).
Looks like you're putting it in the SQLController, so you could try passing that as well.

Java.lang.NullPointerException at getapplicationContext() Android

I'm getting NPE when I try to instantiate a class, I already tried using NameOftheClass.this, getApplicationContext(), getApplication(). None of those is working, here is the log:
java.lang.NullPointerException
at br.com.FragmentClientes.<init>(FragmentClientes.java:87)
line 87 is: mRepositorio = new Repositorio(FragmentClientes.this);
And here is the snippet:
public class FragmentClientes extends ActionBarActivity {
private boolean searchCheck;
private List<ClienteModel> clientes = new ArrayList<ClienteModel>();
private ProgressBar progressBar;
private ListView lv;
private ClientViewAdapter ad;
private ClientViewAdapter ads;
private SearchView searchView;
private LinearLayout footerLinearLayout;
private boolean shouldExecuteOnResume;
private Repositorio mRepositorio;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// TODO Auto-generated method stub
setContentView(R.layout.fragment_cliente);
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
SecurePreferences mSessao = new SecurePreferences(FragmentClientes.this, "sessao");
mSessao.put("menuAtual", "Clientes");
lv = (ListView) findViewById(R.id.listaClientes);
}
public FragmentClientes(Integer idViagem) {
clientes = new ArrayList<ClienteModel>();
try {
mRepositorio = new Repositorio(FragmentClientes.this);
List lista = mRepositorio.getClientesViagem(idViagem);
clientes = lista;
ad = new ClientViewAdapter(FragmentClientes.this, this, clientes);
lv.setVerticalFadingEdgeEnabled(true);
lv.setVerticalScrollBarEnabled(true);
lv.setAdapter(ad);
} catch (Exception e) {
e.printStackTrace();
}
}
}

Do not use an activity context inside its constructor, it will now work. Please put all the code from the constructor into a method and call it inside the `onCreate method like this:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// TODO Auto-generated method stub
setContentView(R.layout.fragment_cliente);
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
SecurePreferences mSessao = new SecurePreferences(FragmentClientes.this, "sessao");
mSessao.put("menuAtual", "Clientes");
Integer idViagem = getIntent().getIntExtra(TAG, -1);
init(idViagem);
}
public void init(Integer mId) {
clientes = new ArrayList<ClienteModel>();
try {
mRepositorio = new Repositorio(FragmentClientes.this);
List lista = mRepositorio.getClientesViagem(mId);
clientes = lista;
ad = new ClientViewAdapter(FragmentClientes.this, this, clientes);
lv.setVerticalFadingEdgeEnabled(true);
lv.setVerticalScrollBarEnabled(true);
lv.setAdapter(ad);
} catch (Exception e) {
e.printStackTrace();
}
}
Also, you will need to find another way of passing the integer parameter.
For this, use Intent.putExtra(TAG, idViagem) on the intent which starts the activity and then retrieve the value in the constructor with getIntent().getIntExtra(TAG, -1)
For example if you're starting FragmentClientes activity from another activity:
Intent intent = new Intent(this, FragmentClientes.class);
intent.putExtra("idViagem", int_value_of_id_that_you_passed_through_constructor);
startActivity(intent);

Dont create Parameteriged Activity Constructor
just init your data in Activity Call back methods like onCreate(),onResume()
Start your Activity Using Intent
For more read Activity doc Activity Documnetation

FragmentClientes is an Activity. You should not define a custom counstructor, since the method onCreate behaves as constructor and will be called automatically by the system.
so put you code into onCreate method.
Important: you should never, i mean realy never call new FragmentClientes(1);

It might be because yout ListView is not properly instantiated
private ListView lv;
You never asign (in the code you provided) any instantiation for the object.

Is there a better way to link up XML elements with java classes in Android than findViewById()

While I would like to make everything programatically whenever I can, and leave XML blank, that is not possible where I work (designers will not work with raw program code...)
So, to that extend, almost every one of my activity that I work with or built contains a large block of findViewById at the start somewhere.
This is especially painful if I had to create it from scratch and I am now allowed to programatically create an array of buttons and add it to the layout... Thankfully they will let me do that if it gets to 10+ elements and they are all the same type.
Is there a way to avoid this? Or a way to make it automatically cast it into what I am assigning it to? So I don't need to type Button mButton = (Button) findview...
If there is some way to automagically generate java instances of buttons and what nots from the XML given the layout that would be great (esp if the names were nice and autocompleteable).

Try to use Android annotations
AndroidAnnotations is an Open Source framework that speeds up Android development. It takes care of the plumbing, and lets you concentrate on what's really important. By simplifying your code, it facilitates its maintenance.
Here is a simple example of how your code can dramatically shrink, and become much easier to understand:
Before Android Annotations
public class BookmarksToClipboardActivity extends Activity {
BookmarkAdapter adapter;
ListView bookmarkList;
EditText search;
BookmarkApplication application;
Animation fadeIn;
ClipboardManager clipboardManager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(FLAG_FULLSCREEN, FLAG_FULLSCREEN);
setContentView(R.layout.bookmarks);
bookmarkList = (ListView) findViewById(R.id.bookmarkList);
search = (EditText) findViewById(R.id.search);
application = (BookmarkApplication) getApplication();
fadeIn = AnimationUtils.loadAnimation(this, anim.fade_in);
clipboardManager = (ClipboardManager) getSystemService(CLIPBOARD_SERVICE);
View updateBookmarksButton1 = findViewById(R.id.updateBookmarksButton1);
updateBookmarksButton1.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
updateBookmarksClicked();
}
});
View updateBookmarksButton2 = findViewById(R.id.updateBookmarksButton2);
updateBookmarksButton2.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
updateBookmarksClicked();
}
});
bookmarkList.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView p, View v, int pos, long id) {
Bookmark selectedBookmark = (Bookmark) p.getAdapter().getItem(pos);
bookmarkListItemClicked(selectedBookmark);
}
});
initBookmarkList();
}
void initBookmarkList() {
adapter = new BookmarkAdapter(this);
bookmarkList.setAdapter(adapter);
}
void updateBookmarksClicked() {
UpdateBookmarksTask task = new UpdateBookmarksTask();
task.execute(search.getText().toString(), application.getUserId());
}
private static final String BOOKMARK_URL = //
"http://www.bookmarks.com/bookmarks/{userId}?search={search}";
class UpdateBookmarksTask extends AsyncTask {
#Override
protected Bookmarks doInBackground(String... params) {
String searchString = params[0];
String userId = params[1];
RestTemplate client = new RestTemplate();
HashMap args = new HashMap();
args.put("search", searchString);
args.put("userId", userId);
HttpHeaders httpHeaders = new HttpHeaders();
HttpEntity request = new HttpEntity(httpHeaders);
ResponseEntity response = client.exchange( //
BOOKMARK_URL, HttpMethod.GET, request, Bookmarks.class, args);
Bookmarks bookmarks = response.getBody();
return bookmarks;
}
#Override
protected void onPostExecute(Bookmarks result) {
adapter.updateBookmarks(result);
bookmarkList.startAnimation(fadeIn);
}
}
void bookmarkListItemClicked(Bookmark selectedBookmark) {
clipboardManager.setText(selectedBookmark.getUrl());
}
}
After:
#NoTitle
#Fullscreen
#EActivity(R.layout.bookmarks)
public class BookmarksToClipboardActivity extends Activity {
BookmarkAdapter adapter;
#ViewById
ListView bookmarkList;
#ViewById
EditText search;
#App
BookmarkApplication application;
#RestService
BookmarkClient restClient;
#AnimationRes
Animation fadeIn;
#SystemService
ClipboardManager clipboardManager;
#AfterViews
void initBookmarkList() {
adapter = new BookmarkAdapter(this);
bookmarkList.setAdapter(adapter);
}
#Click({R.id.updateBookmarksButton1, R.id.updateBookmarksButton2})
void updateBookmarksClicked() {
searchAsync(search.getText().toString(), application.getUserId());
}
#Background
void searchAsync(String searchString, String userId) {
Bookmarks bookmarks = restClient.getBookmarks(searchString, userId);
updateBookmarks(bookmarks);
}
#UiThread
void updateBookmarks(Bookmarks bookmarks) {
adapter.updateBookmarks(bookmarks);
bookmarkList.startAnimation(fadeIn);
}
#ItemClick
void bookmarkListItemClicked(Bookmark selectedBookmark) {
clipboardManager.setText(selectedBookmark.getUrl());
}
}