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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);
}
}

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();
}
}
}
}

Buttons all open the same activity from an Android fragment

Currently I have a fragment_one.xml which has 5 CardViews on it and and each card has a Button on it that is meant to go to separate XML pages (Lesson_One,Lesson_Two etc...) but with the code I have in OneFragment.java, both buttons are opening Lesson_Two
How I can I fix this? Here is my code
FragmentOne.java
public class OneFragment extends Fragment{
Intent intent;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.fragment_one, container, false);
intent = new Intent(getActivity(), LessonOne.class);
final Button button = (Button) root.findViewById(R.id.button1);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
startActivity(intent);
}
});
intent = new Intent(getActivity(), LessonTwo.class);
final Button button2 = (Button) root.findViewById(R.id.button2);
button2.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
startActivity(intent);
}
});
return root;
}
}

You're assigning intent twice, effectively overwriting the first intent with the second.
So no matter which click event is triggered LessonTwo.class is the activity that is started.
A simple fix would be to create the intents inside the click handlers like
public class OneFragment extends Fragment{
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.fragment_one, container, false);
final Button button = (Button) root.findViewById(R.id.button1);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
startActivity(new Intent(getActivity(), LessonOne.class));
}
});
final Button button2 = (Button) root.findViewById(R.id.button2);
button2.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
startActivity(new Intent(getActivity(), LessonTwo.class););
}
});
return root;
}
}
This makes it explicit which click handler starts what activity

Alternative answer - implement the click listener on the class itself.
This cleans up the onCreateView method. You also don't need to "capture" the buttons to set their listeners.
public class OneFragment extends Fragment implements View.OnClickListener {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.fragment_one, container, false);
root.findViewById(R.id.button1).setOnClickListener(this);
root.findViewById(R.id.button2).setOnClickListener(this);
return root;
}
#Override
public void onClick(View v) {
Class clz = null;
switch (v.getId()) {
case R.id.button1:
clz = LessonOne.class;
case R.id.button2;
clz = LessonTwo.class;
}
if (clz != null) startActivity(new Intent(getActivity(), clz));
}
}

Handling Multiple Fragments when orientation changes

I have a MainActivity, and I want to attach a fragment with 3 buttons in it to that activity. On clicking button 1 it should replace this fragment with another fragment. But when I change orientation the current fragment and the old fragment are both getting attached. Can someone help me solve this ?
Following is my MainActivity.java:
public class MainActivity extends AppCompatActivity implements OnButtonsClickListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
getSupportFragmentManager().beginTransaction()
.add(R.id.mainactivity, new FragmentHomepage(), "aboutMe")
.commit();
}
#Override
public void button1Action() {
FragmentAboutMe fragmentAboutMe=new FragmentAboutMe();
getSupportFragmentManager().beginTransaction()
.add(R.id.mainactivity,fragmentAboutMe)
.commit();
}
#Override
public void button2Action() {
Intent intent =new Intent(this,ActivityMasterDetail.class);
startActivity(intent);
}
#Override
public void button3Action() {
Intent intent =new Intent(this,ActivityViewPager.class);
startActivity(intent);
}
}
This is my FragmentHomepage.java:
public class FragmentHomepage extends Fragment {
private static final String ARG_SECTION_NUMBER ="section number";
OnButtonsClickListener onButtonsClickListener;
public static FragmentHomepage newInstance(int sectionNumber){
FragmentHomepage fragmentHomepage=new FragmentHomepage();
Bundle args=new Bundle();
args.putInt(ARG_SECTION_NUMBER,sectionNumber);
fragmentHomepage.setArguments(args);
return fragmentHomepage;
}
public FragmentHomepage(){}
#Override
public void onAttach(Context context) {
super.onAttach(context);
try {
onButtonsClickListener= (OnButtonsClickListener) context;
} catch (Exception e) {
e.printStackTrace();
}
}
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
final Button button1= (Button) getActivity().findViewById(R.id.aboutMe);
final Button button2= (Button) getActivity().findViewById(R.id.task2);
final Button button3= (Button) getActivity().findViewById(R.id.task3);
button1.setOnClickListener(new Button.OnClickListener() {
#Override
public void onClick(View v) {
onButtonsClickListener.button1Action();
}
});
button2.setOnClickListener(new Button.OnClickListener() {
#Override
public void onClick(View v) {
onButtonsClickListener.button2Action();
}
});
button3.setOnClickListener(new Button.OnClickListener() {
#Override
public void onClick(View v) {
onButtonsClickListener.button3Action();
}
});
}
#Nullable
#Override
public View onCreateView(final LayoutInflater inflater,
ViewGroup container,
Bundle savedInstanceState) {
View rootView=null;
rootView =inflater.inflate(R.layout.fragment_homepage,container,false);
return rootView;
}
}
and my second activity is as follows
(in FragmentAboutMe.java):
public class FragmentAboutMe extends Fragment {
int counters=0;
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if(savedInstanceState==null)counters=0;
else counters=savedInstanceState.getInt("count");
}
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt("count",13);
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater,
ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_aboutme,container,false);
}
}

In your onCreate() method put a check whether the fragment is already present. Android automatically restores the fragment manager state upon orientation change and hence upon orientation change, the fragment which you added on button click would automatically be added. Thus if you will add new fragment in onCreate() without check, this would result in adding the 2 fragments. This is causing the issue.
FragmentManager fm = getSupportFragmentManager();
if (fm.findfragmentById(R.id.mainactivity) == null) {
FragmentHomepage fragment = new FragmentHomepage ();
fm.beginTransaction().add (R.id.mainactivity, fragment).commit();
}

You would want to save the state. You would need to extend Fragment to store the objects that need saving.
Override the onConfigurationChanged(..) and it should work out.
When I had to handle screen orientation changes, I recall having used this reference [link].

There are two ways.
Either you need to save the state in the bundle in onSaveInstanceState() method. Also save the states of fragment.
When activity recreate itself then check the value of bundle inside onCreate() or onRestoreInstanceState() method. Now initialize all the objects as before.
Else
set the value of activity inside manifest file as
android:configChanges="layoutDirection|orientation|screenLayout|screenSize"
and override the method.
#Override
public void onConfigurationChanged(Configuration newConfig) {
}
Second technique will not allow the activity to restart on orientation change.

onclicklistener in fragment with intent

I have an an Android app with an Intro class.
This Intro class has got three fragments.
in fragment 3 (IntroPage3) i would like to set an onclicklistener with an intent form the IntroPage3 to Overview.class like this:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
FragementView = inflater.inflate(R.layout.intro_page1, container, false);
Button FinishIntroButton = (Button) FragementView.findViewById(R.id.FinishIntroButton);
FinishIntroButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
intent = new Intent(IntroPage3.this, Overview.class);
startActivityForResult(intent, 0);
}
});
return FragementView;
}
Problem: is this line:
intent = new Intent(IntroPage3.this, Intro.class);
Error message:

use intent = new Intent(getActivity(), Overview.class);

public class Fragment3 extends Fragment{
#Nullable
#Override
public View onCreateView(#NonNull final LayoutInflater inflater, #Nullable final ViewGroup container, #Nullable Bundle savedInstanceState) {
View view;
view = inflater.inflate(R.layout.page_4, container, false);
Button button=view.findViewById(R.id.exit);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent;
intent=new Intent(getActivity(),FragmentLogin.class);
startActivity(intent);
}
});
return view;
}
}

You must use getActivity() instead of IntroPage3.this
WHY
getActivity() in a Fragment returns the Activity the Fragment is currently associated with.
Button FinishIntroButton = (Button) FragementView.findViewById(R.id.FinishIntroButton);
FinishIntroButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
intent = new Intent(getActivity(), Overview.class);
startActivityForResult(intent, 0);
}
});