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Pass the data from activity to Page Adapter

I need to pass the String data to tab layout. i'm already pass the data from adapter to fragments in Tab layout. But my problem is I cannot to pass that data from activity to Adapter java class. I need to pass the data to more than one fragment. how can i do this?
Main Activity Code
package com.example.tablay;
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager.widget.ViewPager;
import android.content.Intent;
import android.os.Bundle;
import android.provider.ContactsContract;
import com.google.android.material.tabs.TabLayout;
import java.util.List;
import java.util.Stack;
public class MainActivity extends AppCompatActivity {
private ViewPager pager;
private TabLayout tabs;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
pager=(ViewPager) findViewById(R.id.pager);
tabs=(TabLayout) findViewById(R.id.tabs);
pager.setAdapter(new TabFragmentPagerAdapter(getSupportFragmentManager()));
tabs.setupWithViewPager(pager);
tabs.setTabGravity(TabLayout.GRAVITY_FILL);
}
}
Page Adapter Code :
package com.example.tablay;
import android.os.Bundle;
import android.provider.ContactsContract;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentPagerAdapter;
import java.util.Date;
import java.util.List;
public class TabFragmentPagerAdapter extends FragmentPagerAdapter {
String[] title = new String[]{
"Tab 1", "Tab 2", "Tab 3"
};
public TabFragmentPagerAdapter(#NonNull FragmentManager fm) {
super(fm);
}
#NonNull
#Override
public Fragment getItem(int position) {
Fragment fragment=null;
switch (position){
case 0:
tab1Fragment tab1Fragment=new tab1Fragment();
Bundle bundle = new Bundle();
bundle.putString("edttext", "data From Activity");
tab1Fragment.setArguments(bundle);
return tab1Fragment;
case 1:
tab2Fragment tab2Fragment=new tab2Fragment();
bundle = new Bundle();
bundle.putString("edttext1", "data From Activity1");
tab2Fragment.setArguments(bundle);
return tab2Fragment;
case 2:
tab3Fragment tab3Fragment=new tab3Fragment();
return tab3Fragment;
default:
fragment=null;
break;
}
return fragment;
}
#Nullable
#Override
public CharSequence getPageTitle(int position) {
return title[position];
}
#Override
public int getCount() {
return title.length;
}
}
Fragment Code:
package com.example.tablay;
import android.os.Bundle;
import androidx.fragment.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class tab1Fragment extends Fragment {
public tab1Fragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_tab1, container, false);
TextView tes=(TextView) view.findViewById(R.id.testtab1);
String strtext = getArguments().getString("edttext");
tes.setText(strtext);
return view;
}
}
I need to pass the String data to tab layout. i'm already pass the data from adapter to fragments in Tab layout. But my problem is I cannot to pass that data from activity to Adapter java class. I need to pass the data to more than one fragment. how can i do this?

You can pass data from activity to the adapter by constructor like this :
public class MainActivity extends AppCompatActivity {
private ViewPager pager;
private TabLayout tabs;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
pager=(ViewPager) findViewById(R.id.pager);
tabs=(TabLayout) findViewById(R.id.tabs);
pager.setAdapter(new TabFragmentPagerAdapter(getSupportFragmentManager(),ActivityStringData));
tabs.setupWithViewPager(pager);
tabs.setTabGravity(TabLayout.GRAVITY_FILL);
}
to
public class TabFragmentPagerAdapter extends FragmentPagerAdapter {
String[] title = new String[]{
"Tab 1", "Tab 2", "Tab 3"
};
String data=null;
public TabFragmentPagerAdapter(#NonNull FragmentManager fm,String activityData) {
super(fm);
this.data=activityData
}
#NonNull
#Override
public Fragment getItem(int position) {
Fragment fragment=null;
switch (position){
case 0:
tab1Fragment tab1Fragment=new tab1Fragment();
Bundle bundle = new Bundle();
bundle.putString("edttext", "data From Activity");
tab1Fragment.setArguments(bundle);
return tab1Fragment;
case 1:
tab2Fragment tab2Fragment=new tab2Fragment();
bundle = new Bundle();
bundle.putString("edttext1", "data From Activity1");
tab2Fragment.setArguments(bundle);
return tab2Fragment;
case 2:
tab3Fragment tab3Fragment=new tab3Fragment();
return tab3Fragment;
default:
fragment=null;
break;
}
return fragment;
}
#Nullable
#Override
public CharSequence getPageTitle(int position) {
return title[position];
}
#Override
public int getCount() {
return title.length;
}
}

Android java - making 1 ImageAdapter for 2 or more viewpagers (currently 2 adapters for 2 viewpagers)

I made an ImageAdapter class that contains images and an activity that contains 2 buttons, on click each one opens a new activity with a viewpager. The 2 viewpagers have different images and this is where my inexperience comes in.
I took the easy way and duplicated the ImageAdapter (named it ImageAdapter2) and linked it to the 2nd viewpager. visual representation
It works fine, but what I'm trying to do is clean it up and do it all through 1 adapter and 1 viewpager. I tried to do it through Intent getStringExtra but it didn't recognize Intent method. Here are my classes:
ImageAdapter (ImageAdapter2 is the same, just has different images in sliderImageId):
package hr.cnzd.prepoznajmoenasilje;
import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.LinearLayout;
import androidx.viewpager.widget.PagerAdapter;
import androidx.viewpager.widget.ViewPager;
public class ImageAdapter extends PagerAdapter {
Context mContext;
ImageAdapter(Context context){
this.mContext = context;
}
#Override
public boolean isViewFromObject(View view, Object o){
return view == ((ImageView) o);
}
private int[] sliderImageId = new int[]{
R.drawable.djeca01, R.drawable.djeca02, R.drawable.djeca03, R.drawable.djeca04, R.drawable.djeca05, R.drawable.djeca06, R.drawable.djeca07, R.drawable.djeca08
};
#Override
public Object instantiateItem(ViewGroup viewGroup, int position){
ImageView imageView = new ImageView(mContext);
imageView.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.MATCH_PARENT));
imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
imageView.setImageResource(sliderImageId[position]);
((ViewPager) viewGroup).addView(imageView, 0);
return imageView;
}
#Override
public void destroyItem(ViewGroup viewGroup, int position, Object o){
((ViewPager) viewGroup).removeView((ImageView) o);
}
#Override
public int getCount(){
return sliderImageId.length;
}
}
Activity with buttons:
package hr.cnzd.prepoznajmoenasilje;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ImageButton;
import androidx.appcompat.app.AppCompatActivity;
public class MA_Savjeti extends AppCompatActivity {
private ImageButton imageButtonDjeca;
private ImageButton imageButtonOdrasli;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_ma__savjeti);
imageButtonDjeca = findViewById(R.id.imgBtnDjeca);
imageButtonDjeca.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
openActivitySavjetiDjeca();
}
});
imageButtonOdrasli = findViewById(R.id.imgBtnOdrasli);
imageButtonOdrasli.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
openActivitySavjetiOdrasli();
}
});
}
public void openActivitySavjetiDjeca() {
Intent intent = new Intent(this, Savjeti_Djeca.class);
intent.putExtra("savjeti", "djeca");
startActivity(intent);
}
public void openActivitySavjetiOdrasli() {
Intent intent = new Intent(this, Savjeti_Odrasli.class);
intent.putExtra("savjeti", "odrasli");
startActivity(intent);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
finish();
return true;
}
return super.onOptionsItemSelected(item);
}
public boolean onCreateOptionsMenu(Menu menu) {
return true;
}
}
Activity with viewpager (other activity with viewpager has the same code, just calls ImageAdapter2)
package hr.cnzd.prepoznajmoenasilje;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager.widget.ViewPager;
public class Savjeti_Djeca extends AppCompatActivity {
ViewPager viewPager;
ImageAdapter imageAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
this.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.savjeti_djeca);
viewPager = findViewById(R.id.viewpager);
imageAdapter = new ImageAdapter(this);
viewPager.setAdapter(imageAdapter);
}
}
TLDR: I have 2 ImageAdapters and 2 Viewpagers, but I wanna do it through 1 ImageAdapter and 1 Viewpager (2 buttons on a previous activity decide which set of images is shown on the viewpager)

Solved it using ViewPager2 instead of this way.

Android: E/RecyclerView: No adapter attached; skipping layout

so i have a tabbed activity that contains 3 tabs as fragments, each tab has a RecyclerView.
I checked all the answered questions on here and on other sites, everything seems fine, yet it doesn't work!
here's my Code:
MainActivity.java:
package esprit.tn.mywaterproject;
import android.support.design.widget.TabLayout;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;
import java.time.Duration;
import java.util.zip.Inflater;
public class MainActivity extends AppCompatActivity {
/**
* The {#link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {#link FragmentPagerAdapter} derivative, which will keep every
* loaded fragment in memory. If this becomes too memory intensive, it
* may be best to switch to a
* {#link android.support.v4.app.FragmentStatePagerAdapter}.
*/
private SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {#link ViewPager} that will host the section contents.
*/
private ViewPager mViewPager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.e("test","test log");
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new
SectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
mViewPager.addOnPageChangeListener(new
TabLayout.TabLayoutOnPageChangeListener(tabLayout));
tabLayout.addOnTabSelectedListener(new
TabLayout.ViewPagerOnTabSelectedListener(mViewPager));
FloatingActionButton fab = findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Toast.makeText(getApplicationContext(), "Chat avec un
résponsable", Toast.LENGTH_SHORT).show();
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.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);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
private static final String ARG_SECTION_NUMBER = "section_number";
public PlaceholderFragment() {
}
/**
* Returns a new instance of this fragment for the given section
* number.
*/
public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Log.e("frag number", "frag test number
:"+getArguments().getInt(ARG_SECTION_NUMBER));
if (getArguments().getInt(ARG_SECTION_NUMBER)==1){
Log.e("frag test1", "frag test TEST1");
new Eaux_Fragment();
return inflater.inflate(R.layout.fragment_eaux,
container,false);
}
if (getArguments().getInt(ARG_SECTION_NUMBER)==2){
Log.e("frag test2", "frag test TEST2");
return inflater.inflate(R.layout.fragment_piscine,
container,false);
}
if (getArguments().getInt(ARG_SECTION_NUMBER)==3){
Log.e("frag test3", "frag test TEST3");
return inflater.inflate(R.layout.fragment_electricite, container,false);
}
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
TextView textView = (TextView) rootView.findViewById(R.id.section_label);
textView.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER)));
return rootView;
}
}
/**
* A {#link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class below).
return PlaceholderFragment.newInstance(position + 1);
}
#Override
public int getCount() {
// Show 3 total pages.
return 3;
}
}
}
Here's my Adapter
ProduitAdapter.java :
package esprit.tn.mywaterproject;
import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
import esprit.tn.mywaterproject.Entities.Produit_Eau;
public class ProduitAdapter extends
RecyclerView.Adapter<ProduitAdapter.ViewHolder> {
private Context context;
private List<Produit_Eau> list;
public ProduitAdapter( Context context, ArrayList<Produit_Eau> list) {
this.context=context;
this.list = list;
}
#Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
Log.e("LOG IN ADAPTER","TEST ADAPTER");
View v =
LayoutInflater.from(context).inflate(R.layout.single_produit_eau, parent,
false);
return new ViewHolder(v);
}
#Override
public void onBindViewHolder(ViewHolder holder, int position) {
Produit_Eau prod_eau = list.get(position);
holder.text_single_prod_nom.setText(prod_eau.getNom());
holder.text_single_prod_description.setText(prod_eau.getDescription());
}
#Override
public int getItemCount() {
return list.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
public TextView text_single_prod_nom, text_single_prod_description;
public ViewHolder(View itemView) {
super(itemView);
text_single_prod_nom = itemView.findViewById(R.id.single_prod_nom);
text_single_prod_description =
itemView.findViewById(R.id.single_prod_description);
}
}
}
And Here's one of the fragments
Eau_Fragment.java
package esprit.tn.mywaterproject.Fragments;
import android.app.ProgressDialog;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.widget.DividerItemDecoration;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonArrayRequest;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.List;
import esprit.tn.mywaterproject.Entities.Produit_Eau;
import esprit.tn.mywaterproject.ProduitAdapter;
import esprit.tn.mywaterproject.R;
/**
* A simple {#link Fragment} subclass.
*/
public class Eaux_Fragment extends Fragment {
private RecyclerView recyclerList;
private LinearLayoutManager linearLayoutManager;
private ArrayList<Produit_Eau> produit_eauList;
private ProduitAdapter adapter;
private String UrlShowProducts = "http://192.168.1.7:3003/prodeau";
private LinearLayout linearLayout;
public Eaux_Fragment() {
Log.e("Test Eau Fragment","EAU FRAG TEST");
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragmentd
View view = inflater.inflate(R.layout.fragment_eaux, container, false);
linearLayoutManager = new
LinearLayoutManager(getActivity().getApplicationContext());
linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
DividerItemDecoration(recyclerList.getContext(),
linearLayoutManager.getOrientation());
adapter = new ProduitAdapter(getActivity().getApplicationContext(),
produit_eauList);
recyclerList = getActivity().findViewById(R.id.eau_prod_list);
recyclerList.setHasFixedSize(true);
recyclerList.setLayoutManager(linearLayoutManager);
produit_eauList = new ArrayList<>();
getData();
recyclerList.setAdapter(adapter);
adapter.notifyDataSetChanged();
return view;
}
private void getData() {
JsonArrayRequest jsonArrayRequest = new
JsonArrayRequest(UrlShowProducts, new Response.Listener<JSONArray>() {
#Override
public void onResponse(JSONArray response) {
for (int i = 0; i < response.length(); i++) {
try {
JSONObject jsonObject = response.getJSONObject(i);
Produit_Eau produit_eau = new Produit_Eau();
produit_eau.setNom(jsonObject.getString("name"));
produit_eau.setDescription(jsonObject.getString("description"));
produit_eauList.add(produit_eau);
} catch (JSONException e) {
e.printStackTrace();
}
}
adapter.notifyDataSetChanged();
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
Log.e("Volley", error.toString());
}
});
RequestQueue requestQueue =
Volley.newRequestQueue(getActivity().getApplicationContext());
requestQueue.add(jsonArrayRequest);
}
}
Edit:
The problem i'm facing here is that Eau_Fragment is not showing in the application. i've deleted every other fragment and kept only this one to test it, the fragment is displayed empty, and the only error i got is the one mentionned above.

It's only a warning but if you're concerned about it, then set the adapter before the layout manager:
recyclerList = getActivity().findViewById(R.id.eau_prod_list);
recyclerList.setAdapter(adapter);
recyclerList.setHasFixedSize(true);
recyclerList.setLayoutManager(linearLayoutManager);
Because it triggers layout update immediately when you set layout manager, which looks for the adapter eventually.

I am not sure what is the problem you are facing, but one thing I noticed, is that you are not using Eaux_Fragment in your SectionsPagerAdapter so you need change :
return PlaceholderFragment.newInstance(position + 1);
to
return Eaux_Fragment(position + 1);
and do not forget to add the newInstance method to Eaux_Fragment
public static Eaux_Fragment newInstance(int position) {
Eaux_Fragment fragment = new Eaux_Fragment();
Bundle args = new Bundle();
args.putString(ARG_POSITION, position);
fragment.setArguments(args);
return fragment;
}

Unable to retrieve context in Fragment [duplicate]

This question already has answers here:
Why is my context in my Fragment null?
(4 answers)
Closed 5 years ago.
I tried to find the solution with several resources:
Retrieve Context from a fragment
Using context in a fragment
But I still got the following error:
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.support.v4.app.FragmentActivity.getApplicationContext()' on a null object reference
Any help will be appreciated. Thanks!
My current codes:
AnalysisActivity.java:
package com.app.component.fragment;
import android.os.Bundle;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import com.material.components.R;
import com.material.components.fragment.FragmentTabsEvents;
import com.material.components.fragment.FragmentTabsPerformance;
import com.material.components.fragment.FragmentTabsRecommendation;
import com.material.components.utils.Tools;
import java.util.ArrayList;
import java.util.List;
public class AnalysisActivity extends AppCompatActivity {
private ViewPager view_pager;
private TabLayout tab_layout;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_analysis);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setHomeButtonEnabled(true);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
Tools.setSystemBarColor(this,R.color.black);
view_pager = findViewById(R.id.view_pager);
setupViewPager(view_pager);
tab_layout = findViewById(R.id.tab_layout);
tab_layout.setupWithViewPager(view_pager);
}
private void setupViewPager(ViewPager viewPager) {
SectionsPagerAdapter adapter = new SectionsPagerAdapter(getSupportFragmentManager());
adapter.addFragment(FragmentTabsPerformance.newInstance(), "PERFORMANCE");
adapter.addFragment(FragmentTabsRecommendation.newInstance(), "RECOMMENDATION");
adapter.addFragment(FragmentTabsEvents.newInstance(), "EVENTS RELATED TO YOU");
viewPager.setAdapter(adapter);
}
private class SectionsPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public SectionsPagerAdapter(FragmentManager manager) {
super(manager);
}
#Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
#Override
public int getCount() {
return mFragmentList.size();
}
public void addFragment(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
#Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
}
#Override
public boolean onSupportNavigateUp() {
onBackPressed();
return true;
}
}
FragmentTabsPerformance.java:
package com.app.component.fragment;
import android.content.Context;
import android.graphics.Color;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import com.material.components.R;
import com.material.components.utils.Tools;
import java.util.ArrayList;
import java.util.List;
import lecho.lib.hellocharts.model.Line;
import lecho.lib.hellocharts.model.LineChartData;
import lecho.lib.hellocharts.model.PointValue;
import lecho.lib.hellocharts.view.LineChartView;
public class FragmentTabsPerformance extends Fragment {
private Context context;
public FragmentTabsPerformance() {
this.context = getActivity().getApplicationContext();
List<PointValue> values = new ArrayList<>();
values.add(new PointValue(0, 2));
values.add(new PointValue(1, 4));
values.add(new PointValue(2, 3));
values.add(new PointValue(3, 4));
//In most cased you can call data model methods in builder-pattern-like manner.
Line line = new Line(values).setColor(Color.BLUE).setCubic(true);
List<Line> lines = new ArrayList<>();
lines.add(line);
LineChartData data = new LineChartData();
data.setLines(lines);
LineChartView chart = new LineChartView(this.getContext());
chart.setLineChartData(data);
}
public static FragmentTabsPerformance newInstance() {
FragmentTabsPerformance fragment = new FragmentTabsPerformance();
return fragment;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.fragment_tabs_performance, container, false);
Tools.displayImageOriginal(getActivity(), (ImageView) root.findViewById(R.id.image_1), R.drawable.image_8);
Tools.displayImageOriginal(getActivity(), (ImageView) root.findViewById(R.id.image_2), R.drawable.image_9);
Tools.displayImageOriginal(getActivity(), (ImageView) root.findViewById(R.id.image_3), R.drawable.image_15);
Tools.displayImageOriginal(getActivity(), (ImageView) root.findViewById(R.id.image_4), R.drawable.image_14);
Tools.displayImageOriginal(getActivity(), (ImageView) root.findViewById(R.id.image_5), R.drawable.image_12);
Tools.displayImageOriginal(getActivity(), (ImageView) root.findViewById(R.id.image_6), R.drawable.image_2);
Tools.displayImageOriginal(getActivity(), (ImageView) root.findViewById(R.id.image_7), R.drawable.image_5);
return root;
}
}

This exception occurred since you called the getActivity() in the construction method when the fragment is not attached to an activity. You may refer to the API guides about the lifecycle methods about fragment with activity. In your case, you may use getContext() instead of getActivity() method to get the context of fragment.

getActivity() only available after Fragment is attached to activity. So, getActivity() in Fragment constructor will return null. Check fragment life cycle for more detail

FragmentViewPagerAdapter not calling getItem after screen rotation

I have a custom viewPagerAdapter in this activity, when the first launch of the activity (When the main activity starts it with the intent) the pager displays the fragments correctly, but when I rotate the device, the recipe is got from the savedInstantState, and the adapter is started, but the fragments are not displayed and the getItem method doesn't get callled!
Here's the code for the Activity:
package com.ameer.bake.activities;
import android.content.Intent;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.NavUtils;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MenuItem;
import android.view.ViewGroup;
import com.ameer.bake.Constants;
import com.ameer.bake.fragments.IngredientsFragment;
import com.ameer.bake.fragments.StepDetailsFragment;
import com.ameer.bake.fragments.StepsFragment;
import com.ameer.bake.R;
import com.ameer.bake.models.Recipe;
import com.ameer.bake.models.Step;
import com.google.gson.Gson;
import com.ogaclejapan.smarttablayout.SmartTabLayout;
public class DetailsActivity extends AppCompatActivity implements StepsFragment.StepCallback{
private Recipe recipe;
private IngredientsFragment ingredientsFragment;
private StepsFragment stepsFragment;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_details);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
if (savedInstanceState != null){
recipe = new Gson().fromJson(savedInstanceState.getString(Constants.RECIPE), Recipe.class);
setupViewPager();
} else if (getIntent().hasExtra(Constants.CURRENT_RECIPE_KEY) ) {
Gson gson = new Gson();
recipe = gson.fromJson(getIntent().getStringExtra(Constants.CURRENT_RECIPE_KEY), Recipe.class);
setTitle(recipe.getName());
setupViewPager();
}
}
#Override
public void onStepClicked(Step step) {
Intent intent = new Intent(DetailsActivity.this, StepActivity.class);
intent.putExtra(Constants.STEP_KEY, new Gson().toJson(step));
startActivity(intent);
}
private class RecipePagerAdapter extends FragmentPagerAdapter {
private static final int NUM_ITEMS = 2;
private final String[] titles = new String[]{
getString(R.string.ingredients), getString(R.string.steps)};
private RecipePagerAdapter(FragmentManager fragmentManager) {
super(fragmentManager);
if (ingredientsFragment == null && stepsFragment == null) {
ingredientsFragment = new IngredientsFragment();
ingredientsFragment.setIngredients(recipe.getIngredients());
stepsFragment = new StepsFragment();
stepsFragment.setSteps(recipe.getSteps());
stepsFragment.setCallback(DetailsActivity.this);
}
}
// Returns total number of pages
#Override
public int getCount() {
return NUM_ITEMS;
}
// Returns the fragment to display for that page
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return ingredientsFragment;
case 1:
return stepsFragment;
default:
return null;
}
}
// Returns the page title for the top indicator
#Override
public CharSequence getPageTitle(int position) {
return titles[position];
}
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
if (item.getItemId() == android.R.id.home){
NavUtils.navigateUpFromSameTask(this);
}
return super.onOptionsItemSelected(item);
}
#Override
public void onSaveInstanceState(Bundle savedInstanceState) {
savedInstanceState.putString(Constants.RECIPE, new Gson().toJson(recipe));
super.onSaveInstanceState(savedInstanceState);
}
private void setupViewPager(){
ViewPager vpPager = (ViewPager) findViewById(R.id.vpPager);
FragmentPagerAdapter pagerAdapter = new RecipePagerAdapter(getSupportFragmentManager());
vpPager.setAdapter(pagerAdapter);
SmartTabLayout viewPagerTab = (SmartTabLayout) findViewById(R.id.viewpager_tab);
viewPagerTab.setViewPager(vpPager);
}
}

Switch to a FragmentStatePagerAdapter rather than using FragmentPagerAdapter. Also use getChildFragmentManager() instead of getSupportFragmentManager()

The solution was as Pedro Varela mentioned in the comments:
"Hope this works. Add setRetainInstance(true); in onCreate of your internal fragments of the view pager "Control whether a fragment instance is retained across Activity re-creation (such as from a configuration change). This can only be used with fragments not in the back stack. If set, the fragment lifecycle will be slightly different when an activity is recreated""
Thanks