Develop Reference

How to implement navigation activity and Recyclerview in MainActivity

I started off with a Navigation drawer activity and I added a recyclerView into the content_main.xml but I have been unable to implement the RecyclerView into the ManiActivity.java file.
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.addDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
}
#Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, 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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
#SuppressWarnings("StatementWithEmptyBody")
#Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_camera) {
// Handle the camera action
} else if (id == R.id.nav_gallery) {
} else if (id == R.id.nav_slideshow) {
} else if (id == R.id.nav_manage) {
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
That is what my MainAcitity.java looks like when I haven't only implemented the NavigationView Activity.
public class MainActivity extends AppCompatActivity implements MyRecyclerViewAdapter.ItemClickListener {
MyRecyclerViewAdapter adapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// data to populate the RecyclerView with
ArrayList<String> animalNames = new ArrayList<>();
animalNames.add("Horse");
animalNames.add("Cow");
animalNames.add("Camel");
animalNames.add("Sheep");
animalNames.add("Goat");
// set up the RecyclerView
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.rvAnimals);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
adapter = new MyRecyclerViewAdapter(this, animalNames);
adapter.setClickListener(this);
recyclerView.setAdapter(adapter);
}
#Override
public void onItemClick(View view, int position) {
Toast.makeText(this, "You clicked " + adapter.getItem(position) + " on row number " + position, Toast.LENGTH_SHORT).show();
}
}
And I also need this(the recyclerview) into my MainActivity.java There isn't room for both
This code below is my adapter class and the whole struggle is to add this to the MainActivity.java
public class MyRecyclerViewAdapter extends RecyclerView.Adapter<MyRecyclerViewAdapter.ViewHolder> {
private List<String> mData = Collections.emptyList();
private LayoutInflater mInflater;
private ItemClickListener mClickListener;
// data is passed into the constructor
public MyRecyclerViewAdapter(Context context, List<String> data) {
this.mInflater = LayoutInflater.from(context);
this.mData = data;
}
// inflates the row layout from xml when needed
#Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = mInflater.inflate(R.layout.recyclerview_row, parent, false);
ViewHolder viewHolder = new ViewHolder(view);
return viewHolder;
}
// binds the data to the textview in each row
#Override
public void onBindViewHolder(ViewHolder holder, int position) {
String animal = mData.get(position);
holder.myTextView.setText(animal);
}
// total number of rows
#Override
public int getItemCount() {
return mData.size();
}
// stores and recycles views as they are scrolled off screen
public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
public TextView myTextView;
public ViewHolder(View itemView) {
super(itemView);
myTextView = (TextView) itemView.findViewById(R.id.tvAnimalName);
itemView.setOnClickListener(this);
}
#Override
public void onClick(View view) {
if (mClickListener != null) mClickListener.onItemClick(view, getAdapterPosition());
}
}
// convenience method for getting data at click position
public String getItem(int id) {
return mData.get(id);
}
// allows clicks events to be caught
public void setClickListener(ItemClickListener itemClickListener) {
this.mClickListener = itemClickListener;
}
// parent activity will implement this method to respond to click events
public interface ItemClickListener {
void onItemClick(View view, int position);
}
}

You need to implement both NavigationView.OnNavigationItemSelectedListener and MyRecyclerViewAdapter.ItemClickListener interfaces on the MainActivity class. This way you would be able to call the adapter class for the Recycler view.Your code should look like this:
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener, MyRecyclerViewAdapter.ItemClickListener {
MyRecyclerViewAdapter adapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.addDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
// data to populate the RecyclerView with
ArrayList<String> animalNames = new ArrayList<>();
animalNames.add("Horse");
animalNames.add("Cow");
animalNames.add("Camel");
animalNames.add("Sheep");
animalNames.add("Goat");
// set up the RecyclerView
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.rvAnimals);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
adapter = new MyRecyclerViewAdapter(this, animalNames);
adapter.setClickListener(this);
recyclerView.setAdapter(adapter);
}
#Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, 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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
#SuppressWarnings("StatementWithEmptyBody")
#Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_camera) {
// Handle the camera action
} else if (id == R.id.nav_gallery) {
} else if (id == R.id.nav_slideshow) {
} else if (id == R.id.nav_manage) {
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
#Override
public void onItemClick(View view, int position) {
Toast.makeText(this, "You clicked " + adapter.getItem(position) + " on row number " + position, Toast.LENGTH_SHORT).show();
}
}
In Java, a class can implement more than one interfaces and a class can only extend from one parent. Implementation of more than one interfaces eliminates multiple inheritance which is not allowed in Java.
For example:
ClassA implements ClassB, ClassC
Your edited code can be found here

Problem seems to be associated with Adapter class. I would like to see your code for adapter.
1. Make sure if count is not equal to zero.
2. Make sure you are inflating a proper view in adapter class.
3. The view you are inflating must have external layout Relative or Linear or Constraint.

public class HomeActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener{
TabLayout tabLayout;
ViewPager viewPager;
NavigationView navigationView;
View navHeaderView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
navHeaderView = navigationView.getHeaderView(0);
viewPager = (ViewPager) findViewById(R.id.viewPagerContainer);
tabLayout = (TabLayout) findViewById(R.id.tabLayout);
textViewNavigationName = (TextView)
navHeaderView.findViewById(R.id.textViewNavigationName);
textViewNavigationEmail = (TextView)
navHeaderView.findViewById(R.id.textViewNavigationEmail);
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction =
fragmentManager.beginTransaction();
Fragment_Home objFragment1 = new Fragment_Home();
fragmentTransaction.add(R.id.viewPagerContainer, objFragment1).addToBackStack("backkkkkkkkkkkkk");
fragmentTransaction.commit();
}
}
public class Fragment_Home extends Fragment
{
private static final String ARG_PAGE_KEY = "arg_page";
String nextPageToken;
String prevPageToken;
String pageToken;
int sizeOfPlaylist;
int sizeOfCurrentList;
int firstItemPosition;
MenuItem nextItem;
MenuItem lastItem;
LinearLayout linearLayoutProgress, linearLayoutNoConnection;
Button buttonReload;
RecyclerView recyclerViewVideos;
AllVideosAdapterR adapter;
TextView textViewProgress;
public static Fragment_Home newInstance(int pageNumber) {
Fragment_Home myFragment = new Fragment_Home();
Bundle arguments = new Bundle();
arguments.putInt(ARG_PAGE_KEY, pageNumber);
myFragment.setArguments(arguments);
return myFragment;
}
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
setHasOptionsMenu(true);
LayoutInflater inflater1 = (LayoutInflater) getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View view = inflater1.inflate(R.layout.fragment_home, container, false);
getActivity().invalidateOptionsMenu();
findControls(view);
gettingList();
buttonReload.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
gettingList();
}
});
return view;
}
public void findControls(View view)
{
recyclerViewVideos = (RecyclerView)view.findViewById(R.id.recyclerViewVideos);
linearLayoutProgress = (LinearLayout)view. findViewById(R.id.linearLayoutProgress);
textViewProgress = (TextView) view.findViewById(R.id.textViewProgress);
linearLayoutProgress.setVisibility(View.INVISIBLE);
linearLayoutNoConnection = (LinearLayout)view.findViewById(R.id.linearLayoutNoConnection);
linearLayoutNoConnection.setVisibility(View.INVISIBLE);
buttonReload = (Button)view.findViewById(R.id.buttonReload);
}
private boolean isDeviceOnline() {
ConnectivityManager connMgr =
(ConnectivityManager)getActivity().getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
return (networkInfo != null && networkInfo.isConnected());
}
public void setAdapter(List<Item> listItems) {
recyclerViewVideos.setLayoutManager(new
LinearLayoutManager(getActivity()));
adapter = new AllVideosAdapterR(getActivity(), listItems);
recyclerViewVideos.setAdapter(adapter);
}
public void showProgress(String message) {
textViewProgress.setText(message);
linearLayoutProgress.setVisibility(View.VISIBLE);
}
public void stopProgress() {
linearLayoutProgress.setVisibility(View.INVISIBLE);
}
public void gettingList() {
if (!isDeviceOnline()) {
linearLayoutNoConnection.setVisibility(View.VISIBLE);
} else {
linearLayoutNoConnection.setVisibility(View.INVISIBLE);
}
showProgress("Loading videos..");
Retrofit retrofit = newRetrofit.Builder().baseUrl(BaseUrls.BASE_URL).addConverterFactory(GsonConverterFactory.create()).build();
WebApis call1 = retrofit.create(WebApis.class);
Call<ListResponse> call = call1.requestList();
call.enqueue(new Callback<ListResponse>() {
#Override
public void onResponse(Call<ListResponse> call, Response<ListResponse> response) {
System.out.println("size....................." + response.body().getItems().size());
setAdapter(response.body().getItems());
sizeOfPlaylist = response.body().getPageInfo().getTotalResults();
try {
nextPageToken = response.body().getNextPageToken();
prevPageToken = response.body().getPrevPageToken();
firstItemPosition = response.body().getItems().get(0).getSnippet().getPosition();
sizeOfCurrentList = response.body().getItems().size();
} catch (Exception e) {
Toast.makeText(getActivity(), "More pages not available", Toast.LENGTH_SHORT).show();
}
stopProgress();
}
#Override
public void onFailure(Call<ListResponse> call, Throwable t) {
stopProgress();
Toast.makeText(getActivity(), "Check your Network connection", Toast.LENGTH_LONG).show();
linearLayoutNoConnection.setVisibility(View.VISIBLE);
}
});
}
public void gettingNextList(String token) {
showProgress("Loading videos..");
Retrofit retrofit = new Retrofit.Builder().baseUrl(BaseUrls.BASE_URL).addConverterFactory(GsonConverterFactory.create()).build();
WebApis call1 = retrofit.create(WebApis.class);
Call<ListResponse> call = call1.requestNextList(token);
call.enqueue(new Callback<ListResponse>() {
#Override
public void onResponse(Call<ListResponse> call, Response<ListResponse> response) {
System.out.println("size....................." + response.body().getItems().size());
setAdapter(response.body().getItems());
try {
nextPageToken = response.body().getNextPageToken();
prevPageToken = response.body().getPrevPageToken();
firstItemPosition = response.body().getItems().get(0).getSnippet().getPosition();
sizeOfCurrentList = response.body().getItems().size();
} catch (Exception e) {
Toast.makeText(getActivity(), "More pages not available", Toast.LENGTH_SHORT).show();
}
stopProgress();
}
#Override
public void onFailure(Call<ListResponse> call, Throwable t) {
stopProgress();
Toast.makeText(getActivity(), "Network Problem", Toast.LENGTH_LONG).show();
}
});
}
public interface WebApis {
#GET(BaseUrls.GETTING_LIST)
Call<ListResponse> requestList();
#GET(BaseUrls.GETTING_LIST)
Call<ListResponse> requestNextList(#Query("pageToken") String pageToken);
}
}

Cant open file.txt from raw folder on a fragment

I'm trying to open file.txt from my raw folder through a fragment.
here is my code on KonsumerFragment.java
public class KonsumerFragment extends Fragment implements View.OnClickListener{
public KonsumerFragment() {
// Required empty public constructor
}
float marginValue;
Spinner spinnerProduct;
Spinner spinnerType;
EditText pengajuan;
EditText tenor;
TextView tvAngsuran;
String[] arrayMargin;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_konsumer, container, false);
//Define Variables
spinnerProduct = (Spinner) v.findViewById(R.id.spinnerProduct) ;
spinnerType = (Spinner) v.findViewById(R.id.spinnerType);
pengajuan = (EditText) v.findViewById(R.id.etPengajuan);
tenor = (EditText) v.findViewById(R.id.etTenor);
// Inflate the layout for this fragment
Button hitung = (Button) v.findViewById(R.id.btnHitung);
hitung.setOnClickListener(this);
return v;
}
#Override
public void onClick(View view) {
try {
switch (view.getId()){
case R.id.btnHitung :
//simulate();
readMargin();
break;
}
} catch (Exception e){
e.getCause();
e.printStackTrace();
}
}
public void readMargin() throws FileNotFoundException {
try {
InputStream in = getContext().getResources().openRawResource(R.raw.margingriyafix);
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
String line = reader.readLine();
String result = "";
while(line !=null){
result += line + "\n";
}
arrayMargin = result.split("\\n");
for (int i=0 ; i<arrayMargin.length ; i++){
System.out.println(arrayMargin[i]);
}
System.out.println(arrayMargin);
} catch (Exception e){
System.out.println(e);
e.getCause();
}
}
}
MainActivity.java
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
KonsumerFragment konsFragment = new KonsumerFragment();
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.frameLayout, konsFragment);
transaction.commit();
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
}
#Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, 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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
#SuppressWarnings("StatementWithEmptyBody")
#Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_konsumer) {
KonsumerFragment konsFragment = new KonsumerFragment();
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.frameLayout, konsFragment);
transaction.commit();
} else if (id == R.id.nav_produktif) {
ProduktifFragment prodFragment = new ProduktifFragment();
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.frameLayout, prodFragment);
transaction.commit();
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
the part of the reading file has been in the right way. I tested it running on MainAcivity directly. but it won't run on Fragment. it has been successfully running on an Activity, I believe that the problem comes from the InputStream, but anyway I've tried doing like
getActivity().getResources().openRawResource(R.raw.margingriyafix);
and also
getContext().getResources().openRawResource(R.raw.margingriyafix);
still not working.
please anyone help me.

Fragment doesn't execute AsyncTask on startup

When my app starts up, it replaces layout with fragment, that needs AsyncTask to load correctly. When I load this fragment from navigation drawer, everything works fine, but wen it loads on app startup, AsyncTask doesn't execute. How can i fix this?
MainActivity:
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
Fragment fragment = null;
Class fragmentClass = null;
fragmentClass = NewsFragment.class;
try {
fragment = (Fragment) fragmentClass.newInstance();
} catch (Exception e) {
e.printStackTrace();
}
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.frameLayoutForFragments, fragment);
fragmentTransaction.commit();
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
navigationView.getMenu().getItem(0).setChecked(true);
}
#Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, 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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
#SuppressWarnings("StatementWithEmptyBody")
#Override
public boolean onNavigationItemSelected(MenuItem item) {
//Wybory elementów w navigationdrawer
Fragment fragment = null;
Class fragmentClass = null;
int id = item.getItemId();
if (id == R.id.nav_news) {
fragmentClass = NewsFragment.class;
} else if (id == R.id.nav_map) {
fragmentClass = MapFragment.class;
} else if (id == R.id.nav_buildings) {
fragmentClass = BuildingsFragment.class;
} else if (id == R.id.nav_manage) {
fragmentClass = MapFragment.class;
} else if (id == R.id.nav_info) {
fragmentClass = AppInfoFragment.class;
} else if (id == R.id.nav_bugreport) {
fragmentClass = ContactFragment.class;
}
try {
fragment = (Fragment) fragmentClass.newInstance();
} catch (Exception e) {
e.printStackTrace();
}
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction().replace(R.id.frameLayoutForFragments, fragment).commit();
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
Fragment that loads on startup:
public class NewsFragment extends Fragment {
public static ArrayList <ParsedWebData> list = new ArrayList<ParsedWebData>();
public NewsFragment() {
// Required empty public constructor
}
public static NewsFragment newInstance(Context context) {
NewsFragment fragment = new NewsFragment();
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//Start AsyncTask w momencie ładowania fragmentu
AsyncXMLParser parser = new AsyncXMLParser();
parser.execute();
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_news, container, false);
ListView listView = (ListView) view.findViewById(R.id.listViewNews);
CustomListViewAdapter customListViewAdapter = new CustomListViewAdapter(getContext(), R.id.listViewNews, list);
listView.setAdapter(customListViewAdapter);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> a, View v, int position, long id) {
ParsedWebData singleData = list.get(position);
String url = singleData.getUrl();
Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
startActivity(browserIntent);
}
});
return view;
}
}
AsyncTask:
public class AsyncXMLParser extends AsyncTask <Void, Integer, ArrayList<ParsedWebData>> {
#Override
protected void onPreExecute() {
}
#Override
protected ArrayList<ParsedWebData> doInBackground(Void... params) {
ArrayList<ParsedWebData> list = new ArrayList<ParsedWebData>();
try {
XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
factory.setNamespaceAware(false);
XmlPullParser xpp = factory.newPullParser();
// We will get the XML from an input stream
InputStream input = new URL("linkhere").openStream();
xpp.setInput(input, "UTF_8");
int eventType = xpp.getEventType();
String text = null;
ParsedWebData data = new ParsedWebData();
while (eventType != XmlPullParser.END_DOCUMENT) {
String tagname = xpp.getName();
switch (eventType) {
case XmlPullParser.START_TAG:
if (tagname.equalsIgnoreCase("item")) {
data = new ParsedWebData();
}
break;
case XmlPullParser.TEXT:
text = xpp.getText();
break;
case XmlPullParser.END_TAG:
if (tagname.equalsIgnoreCase("item")) {
// add employee object to list
list.add(data);
} else if (tagname.equalsIgnoreCase("title")) {
data.title = text;
} else if (tagname.equalsIgnoreCase("link")) {
data.url = text;
} else if (tagname.equalsIgnoreCase("description")) {
text = Jsoup.parse(text).text();
data.description = text;
}
break;
default:
break;
}
eventType = xpp.next();
}
} catch (XmlPullParserException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
NewsFragment.list = list;
return list;
}
#Override
protected void onPostExecute(ArrayList <ParsedWebData> result) {
}
}
I tried to find the reason myself, and tried to execute AsyncTask manually in MainActivity, but it didn't help. Any ideas what's wrong?

What's wrong is, that the AsyncTask (thread) finishes after your OnCreateView runs, so you don't see your data.
What you could do, is move the line of code NewsFragment.list = list; from doInBackground(), to onPostExecute(), and call adapter.notifyDataSetChanged() after that. But the issue is that in your design you have no access to listView adapter in AsyncTask
In addition, having the list as a static variable in the Fragment, so that you can access it from the AsyncTask is very bad programming design.
You should remove the static list variable, and should redesign your AsyncTask, that you pass the listView to the constructor (you will have to move it from onCreate to onCreateView), and assign the listView to a member in the AsyncTask. Then in onPostExecute set the adapter (not in onCreateView)
public class AsyncXMLParser extends AsyncTask <Void, Integer, ArrayList<ParsedWebData>> {
CustomListViewAdapter _adapter;
Public AsyncXMLParser(CustomListViewAdapter adapter) {
_adapter = adapter;
}
...
#Override
protected void onPostExecute(ArrayList <ParsedWebData> result) {
CustomListViewAdapter customListViewAdapter = new CustomListViewAdapter(getContext(), R.id.listViewNews, result);
listView.setAdapter(customListViewAdapter);
// Or, depending on design
_adapter.notifyDataSetChanged();
}
}
This way, the list is not static variable (you can remove code from the fragment), and the listView is filled only after the AsyncTask is finished. If you later need access to the actual list data, you can get it from the Adapter.

I couldn't find the reason to why Asynctask isnt being executed but depending on how much background work you want to do, you might not want to use
Asynctask. Asynctask should only be used to do operations that take a small amount of time(at most seconds) since its lifetime is tied to the lifetime of a ui compoment. The issue here could very well be that you're killing the asynctask because its connected to the ui.
I would recommend you to use an intentservice. They are really easy to use and can run as long as you like in the background. Since u can't seem to find the issue with Asynctask in this case you would probably save time by using intentservices instead. https://developer.android.com/reference/android/app/IntentService.html

NullPointerException when setting text in fragment

I am getting the error:
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
when trying to set the text of a textView within a fragment (in the method changeText)
Here is my fragment code
public class MainFragment extends Fragment {
String date;
TextView infoText2;
public MainFragment() {
// Required empty public constructor
}
public Boolean daily;
//instantiate variables
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
// Inflate the layout for this fragment
View rootview = inflater.inflate(R.layout.fragment_main, container, false);
infoText2 = (TextView) rootview.findViewById(R.id.infoText2);
//TODO THIS COULD POSSIBLY BE A PROBLEM TOO
//calls setdate function
startup(rootview);
btnClick(rootview);
return rootview;
}
public void startup(View v) {
date = new SimpleDateFormat("dd/MM/yyyy").format(new Date());
//gets the current date
TextView textView = (TextView) v.findViewById(R.id.infoText);
textView.setText(date);
//finds and replaces text in textView
SeekBar seekBar = (SeekBar) v.findViewById(R.id.seekBar2);
seekBar.setProgress(5);
seekBar.setMax(10);
//sets the seekbar progress
//BEGIN CHECKING IF USER HAS ADDED ENTRY
//TODO ADD IF ENTRY NOT COMPLETED STATEMENT
}
public void changeText(String mText) {
//TODO FIX THIS PROBLEM
infoText2.setText(mText);
//runs getTheData method
}
public void btnClick(View v) {
Button clickButton = (Button) v.findViewById(R.id.btnRate);
clickButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Toast.makeText(MainFragment.this.getActivity(), "Rating successful", Toast.LENGTH_SHORT).show();
//conformation toast
SeekBar seekBar = (SeekBar) MainFragment.this.getActivity().findViewById(R.id.seekBar2);
seekBar.setEnabled(false);
Button btnRate = (Button) MainFragment.this.getActivity().findViewById(R.id.btnRate);
btnRate.setEnabled(false);
//disable seekbar and button
daily = true;
//marks rating complete for the day
//TODO reset complete back to false the next day
int value = seekBar.getProgress();
TextView ratingDisplay = (TextView) MainFragment.this.getActivity().findViewById(R.id.ratingText);
ratingDisplay.setText("Rating: " + Integer.toString(value) + " out of 10");
//sets the rating display to the value of the seekbar
((MainActivity) getActivity()).writeText(date, Integer.toString(value));
//Runs writeText method
((MainActivity) getActivity()).getTheData();
}
});
and also here is the code from my MainActivity
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
NavigationView navigationView = null;
Toolbar toolbar = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
//sets the initial fragment
MainFragment fragment = new MainFragment();
android.support.v4.app.FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragment);
fragmentTransaction.commit();
//sets up the navigation drawer
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
}
/*public void rateOnClickListener(){
Button btnNavigator = (Button)findViewById(R.id.btnRate);
btnNavigator.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
MainFragment fragment = new MainFragment();
MainFragment.rate(v);
Toast.makeText(MainActivity.this, "yes", Toast.LENGTH_LONG);
}
});
}*/
//if the user presses the back button when the navdrawer is open
#Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, 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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
#SuppressWarnings("StatementWithEmptyBody")#Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_camera) {
MainFragment fragment = new MainFragment();
android.support.v4.app.FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragment);
fragmentTransaction.commit();
} else if (id == R.id.nav_gallery) {
SecondFragment fragment = new SecondFragment();
android.support.v4.app.FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragment);
fragmentTransaction.commit();
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
public void writeText(String timestamp, String rating) {
String my_results = rating + ", " + timestamp + "\n";
// String my results contains the date/time and the my_total score
String file_name = "fresh_3";
try {
FileOutputStream fileOutputStream = openFileOutput(file_name, MODE_APPEND | MODE_PRIVATE);
fileOutputStream.write(my_results.getBytes());
fileOutputStream.close();
Toast.makeText(getApplicationContext(), my_results + " success", Toast.LENGTH_LONG).show();
} catch(FileNotFoundException e) {
e.printStackTrace();
} catch(IOException e) {
e.printStackTrace();
}
//saves values to file
}
public void getTheData() {
try {
String Message;
String myData;
int i = 0;
FileInputStream fileInputStream = openFileInput("fresh_3");
InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream);
BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
StringBuilder stringBuilder = new StringBuilder();
while ((Message = bufferedReader.readLine()) != null) {
stringBuilder.append(Message + "\n");
i++; //counter for the array to sort the data
}
//put data in a string with lines
fileInputStream.close();
myData = stringBuilder.toString(); // old successful method to output - need to count the lines
//instantiate the array
String mylines[] = new String[i]; //assigning number of lines to new array as Java cannot make a indeterminate array
mylines = myData.split("\\n");
Arrays.sort(mylines, Collections.reverseOrder()); //sort the array in order of first character - reverse order - descending
//remove the dodgy brackets and print the sorted data
MainFragment mainFragment = new MainFragment();
mainFragment.changeText(Arrays.toString(mylines).replaceAll("\\[|\\]", "")); //write the sorted data using regex (regular expression)
//infoText2.setVisibility(View.VISIBLE);
Toast.makeText(getApplicationContext(), "Number of records " + i, Toast.LENGTH_LONG).show(); //shows line number
} catch(FileNotFoundException e) {
e.printStackTrace();
} catch(IOException e) {
e.printStackTrace();
}
}
}
I have tried all sorts of things to fix this including getActivity() in front of the findViewById and also rootview.. I have re-arranged them in different positions but nothing has worked.
It appears that everything apart from the .setText is working but I would very much appreciate it if somebody could tell me why it refuses to cooperate.

The fragment is not attached to the activity when onCreateView runs. To make sure it works, call the needed functions in the OnResume() of the fragment.
For example:
gridview_left = (GridView)getView().findViewById(R.id.gridview_left);

Make sure that TextView with #+id/infoText2 exists in fragment_main layout file.

Try shifting the btnClick(rootview) call inside the onActivityCreated()...
I think the fragment is not yet attached to the activity

MainFragment mainFragment = new MainFragment();
mainFragment.changeText(Arrays.toString(mylines).replaceAll("\\[|\\]", ""));
None of the fragment lifecycle methods such as onCreateView() have been run when you're invoking a method on the fragment here. You'd need to wait for your fragment transaction to be executed.
A better idea would be to use the arguments Bundle to pass parameters to your fragment, and read the arguments in the fragment itself in a lifecycle method.

how to perform an action by selecting an item from the recyclerView on the fragment

I am using the navigation drawer template in the Android Studio
I use one activity only ... fragments are replaced over that one activity
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.addDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
// here I call the fragment
FragmentManager fm=getFragmentManager();
fm.beginTransaction().replace(R.id.content_main_frame, new homeFragment()).commit();
}
#Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, 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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
#SuppressWarnings("StatementWithEmptyBody")
#Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_camera) {
// Handle the camera action
} else if (id == R.id.nav_gallery) {
} else if (id == R.id.nav_slideshow) {
} else if (id == R.id.nav_manage) {
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
public class homeFragment extends Fragment{
RecyclerView recyclerView;
String[] fields={"ALV","NIJU","AJITH","ASWIN"};
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_home, container, false);
//for getting recyclerview id
recyclerView= (RecyclerView) rootView.findViewById(R.id.recyclerView_home);
// for specifying layout manager
LinearLayoutManager manager=new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(manager);
homeListAdapter adapter = new homeListAdapter(this.getActivity(), fields);
recyclerView.setAdapter(adapter);
recyclerView.setHasFixedSize(true);
return rootView;
}
}
public class homeListAdapter extends RecyclerView.Adapter<homeListAdapter.homeViewHolder> {
private Context context;
private String[] field;
public homeListAdapter(Context context, String[] field){
this.context=context;
this.field=field;
}
#Override
public homeViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
LayoutInflater inflater=LayoutInflater.from(parent.getContext());
View view = inflater.from(parent.getContext()).inflate(R.layout.item_home,parent,false);
homeViewHolder viewHolder= new homeViewHolder(view);
return viewHolder;
}
#Override
public void onBindViewHolder(homeViewHolder holder, int position) {
holder.card_home_title.setText(field[position]);
}
#Override
public int getItemCount() {
return field.length;
}
// View holder
public static class homeViewHolder extends RecyclerView.ViewHolder{
public CardView card_view;
public TextView card_home_title;
public homeViewHolder(View itemView) {
super(itemView);
card_view = (CardView) itemView.findViewById(R.id.card_view);
card_home_title = (TextView) itemView.findViewById(R.id.card_text);
}
}
}
public class ItemHome implements Serializable {
public int id;
public String title;
}
When I press ALV I want to replace by this alvfragment, and when I press the Niju I want to display this Nijufragment.
Screenshot:

If i understand you correctly you want to replace fragments from the navigation drawer, For that you need to go to MainActivty and this is an example for how to do that:
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_camera) {
// Handle the camera action
//use here the desired nav
} else if (id == R.id.nav_ALV) {
FragmentManager fm=getFragmentManager();
fm.beginTransaction().replace(R.id.content_main_frame, new ALVFragment).commit();