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Listener for custom dialog null

I'm getting a NullPointerException for my listener in my class, even though everything should be working fine. I followed Coding in Flow's tutorial for the custom dialog, rewatched it a few times and checked source code and I didn't miss anything. here's the code
Fragment the dialog is called from
public class FragmentMain extends Fragment implements CustomDialog.DialogListener {
.
.
.
private int timeLimit = 0;
private Button dialogOpen;
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
.
.
.
dialogOpen.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
DialogDashboard dialogDashboard = new DialogDashboard();
dialogDashboard.show(getActivity().getSupportFragmentManager(), "notif_dialog");
}
}); //dialog called here
return view;
}
//getting text from spinner in dialog
#Override
public void applyText(String time) {
switch (time) {
case "30 Minutes":
timeLimit = 30;
case "1 Hour":
timeLimit = 60;
case "2 Hours":
timeLimit = 120;
case "4 Hours":
timeLimit = 240;
case "5 Hours":
timeLimit = 300;
}
}
}
Dialog Code:
public class CustomDialog extends AppCompatDialogFragment {
private Button confirmButton;
private Spinner spinner;
private DialogListener listener;
#NonNull
#Override
public Dialog onCreateDialog(#Nullable Bundle savedInstanceState) {
final AlertDialog.Builder builder = new AlertDialog.Builder(getActivity(),
R.style.NotificationAlertDialog);
LayoutInflater inflater = getActivity().getLayoutInflater();
View view = inflater.inflate(R.layout.custom_dialog_notif, null);
confirmButton = view.findViewById(R.id.dialogButton);
spinner = view.findViewById(R.id.dialogSpinner);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(getActivity(),
R.array.spinner_array, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter);
confirmButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
String time = spinner.getSelectedItem().toString();
listener.applyText(time); // says listener is null when I just do e.printStackTrace();
dismiss();
}
});
builder.setView(view)
.setCancelable(true);
return builder.create();
}
#Override
public void onAttach(#NonNull Context context) {
super.onAttach(context);
try {
listener = (DialogListener) context;
} catch (Exception e) {
e.printStackTrace();
throw new ClassCastException(context.toString() +
"must implement dialog listener"); // this says if the listener is null, but even if it's implemented it returns null...
}
}
public interface DialogListener {
void applyText(String time);
}
}

Root cause
You got NPE because onAttach() callback is called when the fragment is attached to its host/activity. The context param is the activity itseft, not the FragmentMain.
Solution
Step 1: When you click on the open dialog button in FragmentMain.
CustomDialog dialogDashboard = new CustomDialog();
dialogDashboard.show(getChildFragmentManager(), "notif_dialog");
Step 2: Modify the code in CustomDialog
Remove this code
#Override
public void onAttach(#NonNull Context context) {
super.onAttach(context);
try {
listener = (DialogListener) context;
} catch (Exception e) {
e.printStackTrace();
throw new ClassCastException(context.toString() +
"must implement dialog listener");
}
}
When users click on the confirm button.
String time = spinner.getSelectedItem().toString();
Fragment fragment = getParentFragment();
if (fragment instanceof CustomDialog.DialogListener) {
listener = (DialogListener) fragment;
listener.applyText(time);
}
dismiss();

Going from fragment to activity with a button. Android Studio

I'm trying to implent the next code in Android Studio and it does not work.
I want to pass from a Fragment (GalleryFragment) to an Activity (postropa) with a button.
I have linked the botton with the function (BotonPulsado) and I don't know what is wrong (In the design view).
Design View
Code:
import (...)
public class GalleryFragment extends Fragment {
private GalleryViewModel galleryViewModel;
public View onCreateView(#NonNull LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
galleryViewModel =
ViewModelProviders.of(this).get(GalleryViewModel.class);
View root = inflater.inflate(R.layout.fragment_gallery, container, false);
final TextView textView = root.findViewById(R.id.text_gallery);
galleryViewModel.getText().observe(getViewLifecycleOwner(), new Observer<String>() {
#Override
public void onChanged(#Nullable String s) {
textView.setText(s);
}
});
return root;
}
public void BotonPulsado(View view) {
Intent intent = new Intent(getContext(), postropa.class);
startActivity(intent);
}
}

You should create Button variаble as a class field.
private GalleryViewModel galleryViewModel;
Button button; <<-------
After that you need to define it in method onCreateView()
button = (Button) findViewById(R.id.button2);
And set onClickListener() on this button to handle the call.
There you must call the method that starts the activity.
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
BotonPulsado();
}
});
Your final code:
import (...)
public class GalleryFragment extends Fragment {
private GalleryViewModel galleryViewModel;
Button button;
public View onCreateView(#NonNull LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
galleryViewModel =
ViewModelProviders.of(this).get(GalleryViewModel.class);
View root = inflater.inflate(R.layout.fragment_gallery, container, false);
final TextView textView = root.findViewById(R.id.text_gallery);
galleryViewModel.getText().observe(getViewLifecycleOwner(), new Observer<String>() {
#Override
public void onChanged(#Nullable String s) {
textView.setText(s);
}
});
button = (Button) findViewById(R.id.button2);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
BotonPulsado();
}
});
return root;
}
public void BotonPulsado() {
Intent intent = new Intent(getContext(), postropa.class);
startActivity(intent);
}
}

Communication Between DialogFragment and Fragment

I am trying to pass information from my alert dialog to my second fragment (I am using tabbed activity layout).
I want to pass information from alert dialog to fragment when I click on my ImageView, but my app keep crashing until I implement my interface inside MainActivity.java. My main mission here is to open alert dialog which contains several buttons. When I click first button I want to print "Test br 3" but it does not work inside my Fragment, it only works inside my MainActivity.java where method prints "Test br 2".
My Main Activity
public class MainActivity extends AppCompatActivity implements ExercisesAlertDialog.DataTransfer {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
SectionsPagerAdapter sectionsPagerAdapter = new SectionsPagerAdapter(this, getSupportFragmentManager());
ViewPager viewPager = findViewById(R.id.view_pager);
viewPager.setAdapter(sectionsPagerAdapter);
TabLayout tabs = findViewById(R.id.tabs);
tabs.setupWithViewPager(viewPager);
}
#Override
public void ApplyData() {
System.out.println("Test br 2");
}
My Fragment
public class Frag2 extends Fragment implements ExercisesAlertDialog.DataTransfer {
ImageView plusbtn;
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.frag2, container, false);
plusbtn = (ImageView) v.findViewById(R.id.plusbtn);
plusbtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
ExercisesDialog();
}
});
return v;
}
public void ExercisesDialog()
{
ExercisesAlertDialog exercisesAlertDialog = new ExercisesAlertDialog();
exercisesAlertDialog.show(getFragmentManager(), "Exercises Dialog");
}
#Override
public void ApplyData() {
System.out.println("Test br 3");
}
My Alert Dialog
public class ExercisesAlertDialog extends AppCompatDialogFragment {
ImageButton one, two;
private DataTransfer listener;
public int first;
#Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
final AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
LayoutInflater inflater = getActivity().getLayoutInflater();
View v = inflater.inflate(R.layout.workout_custom_menu, null);
builder.setView(v);
builder.setTitle("Choose your Workout");
builder.setPositiveButton("Cancel", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
dismiss();
}
});
one = (ImageButton) v.findViewById(R.id.first);
two = (ImageButton) v.findViewById(R.id.second);
one.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
first = 1;
if(first ==1)
{
listener.ApplyData();
}
}
});
return builder.create();
}
public interface DataTransfer
{
void ApplyData();
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
try {
listener = (DataTransfer) context;
}
catch (ClassCastException e)
{
throw new ClassCastException(toString() + "Must implement DataTransfer");
}
}
}

I changed getChildFragmentManager() instead of getFragmentManager() in the show() call. Second thing is onAttach() to listener = (DataTransfer) getParentFragment(); instead of context.

How to Access Activity(except mainactivity) from Fragment?

I created my test project where i code to communicate between two fragments but actully I want to access activity from fragment.
Here is code to connect fragment to fragment, its working absolutely right without any error but now i want to change this code to connect activity from fragment instead of fragment to fragment communication.
So Please change this code to access activities from fragment. I stuck on this issue for than a week.So Guys please resolve this.
here is my mainaactivity:
public class MainActivity extends AppCompatActivity implements FragmentA.FragmentAListener, FragmentB.FragmentBListener {
private FragmentA fragmentA;
private FragmentB fragmentB;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
fragmentA = new FragmentA();
fragmentB = new FragmentB();
getSupportFragmentManager().beginTransaction()
.replace(R.id.container_a, fragmentA)
.replace(R.id.container_b, fragmentB)
.commit();
}
#Override
public void onInputASent(CharSequence input) {
fragmentB.updateEditText(input);
}
#Override
public void onInputBSent(CharSequence input) {
fragmentA.updateEditText(input);
}
Here is my FragmentA.java:
public class FragmentA extends Fragment {
private FragmentAListener listener;
private EditText editText;
private Button buttonOk;
public interface FragmentAListener {
void onInputASent(CharSequence input);
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_a, container, false);
editText = v.findViewById(R.id.edit_text);
buttonOk = v.findViewById(R.id.button_ok);
buttonOk.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
CharSequence input = editText.getText();
listener.onInputASent(input);
}
});
return v;
}
public void updateEditText(CharSequence newText) {
editText.setText(newText);
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof FragmentAListener) {
listener = (FragmentAListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement FragmentAListener");
}
}
#Override
public void onDetach() {
super.onDetach();
listener = null;
}
}
Here is my FragmentB.java:
public class FragmentB extends Fragment {
private FragmentBListener listener;
private EditText editText;
private Button buttonOk;
public interface FragmentBListener {
void onInputBSent(CharSequence input);
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_b, container, false);
editText = v.findViewById(R.id.edit_text);
buttonOk = v.findViewById(R.id.button_ok);
buttonOk.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
CharSequence input = editText.getText();
listener.onInputBSent(input);
}
});
return v;
}
public void updateEditText(CharSequence newText) {
editText.setText(newText);
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof FragmentBListener) {
listener = (FragmentBListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement FragmentBListener");
}
}
#Override
public void onDetach() {
super.onDetach();
listener = null;
}
}
Here is my Fertilizers.java file which i want to access from FragmentA.:
public class Fertilizers extends AppCompatActivity {
RecyclerView mRecyclerView;
List<FertilizerData> myFertilizersList;
FertilizerData mFertilizersData;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fertilizers);
mRecyclerView = (RecyclerView)findViewById(R.id.recyclerView);
GridLayoutManager gridLayoutManager;
gridLayoutManager = new GridLayoutManager(Fertilizers.this, 1);
mRecyclerView.setLayoutManager(gridLayoutManager);
myFertilizersList = new ArrayList<>();
mFertilizersData = new FertilizerData("Urea Fertilizer","Urea is a concent","Rs.1900",R.drawable.urea);
myFertilizersList.add(mFertilizersData);
myFertilizersList.add(mFertilizersData); }
}
please write here a block of code to call Fertilzers Activity from FragmentA, I,ll be very thankful to you.

Calling getActivity() in your fragment gives you the calling activity so if MainActivity started your fragment then you would do
(MainActivity(getActivity())).something_from_your_main_activity

Solution found by itself regarding this issue.
FragmentHome.java class should look like this:
public class FragmentHome extends Fragment {
private Button button;
public FragmentHome(){
}
public interface OnMessageReadListener
{
public void onMessageRead(String message);
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_home, container, false);
button = (Button)v.findViewById(R.id.bn);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent intent = new Intent(getActivity(), Fertilizers.class);
intent.putExtra("some"," some data");
startActivity(intent);
}
});
return v;
}
}
FertilizersActivity.java should look like this:
public class Fertilizers extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fertilizers);
Bundle bundle = getIntent().getExtras();
if (bundle != null){
if(bundle.getStringArrayList("some") !=null){
Toast.makeText(getApplicationContext(),"data:" + bundle.getStringArrayList("some"),Toast.LENGTH_LONG).show();
}
}
}
}

How to pass same value to two fragment using single interface

I have two fragment (AddAddressFragment,AddressFragment) and one DialogFragment. In my app i show alert box with radio button. If user choose anyone option, i want to pass that item to two fragment(AddressFragment and also AddAddressFragment). I can passed only one fragment(AddressFragment). How to pass the same value to another fragment(AddAddressFragment). I want to make list view in that AddAddressFragment
My code here:
RadioListAlert.java:
public class RadioListAlert extends DialogFragment {
CharSequence[] tag = { "Home", "Office", "Pg", "Others" };
private AddressListener addressListener;
private String itemClicked;
#Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setCancelable(true);
builder.setTitle("Please Tag Your Address").setSingleChoiceItems(tag, -1,
new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which)
{
Toast.makeText(getActivity(), tag[which],Toast.LENGTH_SHORT).show();
itemClicked = (String) tag[which];
}
}).setPositiveButton("Ok", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialogInterface, int i) {
if (addressListener != null)
addressListener.itemClicked(itemClicked);
//to dismiss the dialog after user choose an item and click ok, you can also add some validation before dismissing the dialog
dismiss();
}
}).setNegativeButton("Cancel",new DialogInterface.OnClickListener(){
#Override
public void onClick(DialogInterface dialog, int which) {
dismiss();
}
});
return builder.create();
}
public void setListener(AddressListener addressListener)
{
this.addressListener = addressListener;
}
public interface AddressListener
{
void itemClicked(String text);
}
}
AddressFragment.java:
public class AddressFragment extends Fragment implements RadioListAlert.AddressListener {
int position = 0;
EditText line1;
EditText line2;
EditText landmark;
AutoCompleteTextView cityText;
EditText zipcode;
Spinner country;
Spinner state;
RadioGroup tag;
Button savaddr;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_layout_address, container, false);
savaddr = (Button) view.findViewById(R.id.addrsave);
tag = (RadioGroup) view.findViewById(R.id.radioGroup);
line1 = (EditText) view.findViewById(R.id.line1);
line2 = (EditText) view.findViewById(R.id.line2);
cityText = (AutoCompleteTextView) view.findViewById(R.id.city_autoCompleteTextView);
zipcode = (EditText) view.findViewById(R.id.zipcode);
country = (Spinner) view.findViewById(R.id.countrySpinner);
state = (Spinner) view.findViewById(R.id.stateSpinner);
landmark = (EditText) view.findViewById(R.id.landmark);
// Get a reference to the AutoCompleteTextView in the layout
AutoCompleteTextView textView = (AutoCompleteTextView) view.findViewById(R.id.city_autoCompleteTextView);
// Get the string array
String[] city = getResources().getStringArray(R.array.city);
// Create the adapter and set it to the AutoCompleteTextView
ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, city);
textView.setAdapter(adapter);
savaddr.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String addr1 = line1.getText().toString();
String addr2 = line2.getText().toString();
String addr_city = cityText.getText().toString();
String addr_zipcode = zipcode.getText().toString();
String addr_country = country.getSelectedItem().toString();
String addr_state = state.getSelectedItem().toString();
//Field Validation
if (Utility.isNotNull(addr1) && Utility.isNotNull(addr2) && Utility.isNotNull(addr_city) && Utility.isNotNull(addr_zipcode) && Utility.isNotNull(addr_country) && Utility.isNotNull(addr_state)) {
if (Utility.line2_validate(addr2)) {
if (Utility.line2_validate(addr_city)) {
//Show alert box with radio button option
RadioListAlert objRadioListAlert=new RadioListAlert();
objRadioListAlert.setListener(AddressFragment .this);
objRadioListAlert.show(getActivity().getFragmentManager(), "Radio Alert");
Toast.makeText(getActivity().getApplicationContext(), "Success.", Toast.LENGTH_SHORT).show();
} else {
cityText.setError("Enter valid City");
}
} else {
line2.setError("Enter valid Address");
}
} else {
Toast.makeText(getActivity().getApplicationContext(), "Please fill the form, don't leave any field blank", Toast.LENGTH_SHORT).show();
}
}
});
return view;
}
#Override
public void itemClicked(String text) {
((AccountActivity) getActivity()).navigatetoAddAddressActivity(text);
}
}
AddAddressFragment.java:
public class AddAddressFragment extends Fragment implements RadioListAlert.AddressListener {
ImageView add;
ListView addressListView;
private ArrayList<String> strArr;
private ArrayAdapter<String> adapter;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_layout_add_address, container,
false);
addressListView = (ListView) view.findViewById(R.id.address_list);
add = (ImageView)view.findViewById(R.id.add_address);
add.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View v) {
//((AccountActivity) getActivity()).navigatetoAddAddressActivity();
FragmentTransaction transaction = getFragmentManager().beginTransaction();
AddressFragment fragment = new AddressFragment();
transaction.replace(R.id.account_frame, fragment);
transaction.commit();
}
});
return view;
}
#Override
public void itemClicked(String text) {
Log.d("Welcome","Its worked");
Toast.makeText(getActivity().getApplicationContext(), "Item Clicked:" + text, Toast.LENGTH_SHORT).show();
strArr = new ArrayList<String>();
for (int i = 0; i < 2; i++) {
strArr.add(text + i);
adapter = new ArrayAdapter<String>(getActivity().getApplicationContext(),
android.R.layout.simple_list_item_1, strArr);
addressListView.setAdapter(adapter);
}
}
}
Please anyone help me!!
Thanks in advance!!!

You can use localbroadcast to send data between fragments
this is also handy when you want to send data from service to fragment or activity
how to use LocalBroadcastManager?