We Keep Coding

Attempt to invoke virtual method (null object reference)

Currently, I'm developing a media player, and I want hide a element when audio finishes. But when it happens, the app crash with this error: Attempt to invoke virtual method 'void android.widget.LinearLayout.setVisibility(int)' on a null object reference. Check my current code:
meplayer.java
package etes.xddda.music;
import android.app.Activity;
import android.content.Context;
import android.media.MediaPlayer;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.LinearLayout;
import android.widget.Toast;
public class meplayer extends Activity {
public static MediaPlayer mediaPlayer;
public LinearLayout menu_dialog;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
menu_dialog = findViewById(R.id.menu_dialog);
}
public void initAudio(final Context context, final String url) {
if (mediaPlayer == null) {
mediaPlayer = MediaPlayer.create(context, Uri.parse(url));
}
mediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
public LinearLayout menu_dialog;
#Override
public void onCompletion(MediaPlayer mp) {
//Toast.makeText(context, "TEST", Toast.LENGTH_LONG).show();
killMediaPlayer();
menu_dialog.setVisibility(View.GONE);
}
});
mediaPlayer.start();
}
private void killMediaPlayer() {
if (mediaPlayer != null) {
try {
mediaPlayer.reset();
mediaPlayer.release();
mediaPlayer = null;
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
RecyclerViewAdapter
package etes.xddda.music;
import android.app.Dialog;
import android.content.Context;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.media.MediaPlayer;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;
import java.util.List;
public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.MyViewHolder> implements View.OnClickListener{
Context mContext;
List<mList> mData;
Dialog myDialog;
private MediaPlayer mediaPlayer;
private int playbackPosition=0;
meplayer media;
private LinearLayout menu_dialog;
public RecyclerViewAdapter(Context mContext, List<mList> mData) {
this.mContext = mContext;
this.mData = mData;
}
public void onClick(View view) {
}
#Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v;
v = LayoutInflater.from(mContext).inflate(R.layout.item_list, parent, false);
final MyViewHolder vHolder = new MyViewHolder(v);
// Dialog ini
myDialog = new Dialog(mContext);
myDialog.setContentView(R.layout.dialog);
myDialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
vHolder.item_play.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v)
{
TextView dialog_name_tv = (TextView) myDialog.findViewById(R.id.dialog_name_id);
TextView dialog_phone_tv = (TextView) myDialog.findViewById(R.id.dialog_author_id);
ImageView dialog_contact_img = (ImageView) myDialog.findViewById(R.id.dialog_img);
dialog_name_tv.setText(mData.get(vHolder.getAdapterPosition()).getName());
dialog_phone_tv.setText(mData.get(vHolder.getAdapterPosition()).getPhone());
dialog_contact_img.setImageResource(mData.get(vHolder.getAdapterPosition()).getPhoto());
//Toast.makeText(mContext, "Test click "+String.valueOf(vHolder.getAdapterPosition()), Toast.LENGTH_SHORT).show();
myDialog.show();
}
});
vHolder.menu_play.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v)
{
menu_dialog = v.getRootView().findViewById(R.id.menu_dialog);
menu_dialog.setVisibility(v.VISIBLE);
media = new meplayer();
media.initAudio(v.getContext(), mData.get(vHolder.getAdapterPosition()).getURL());
MainActivity.setMargins(v.getRootView().findViewById(R.id.viewpager_id), 0,0,0,100);
}
});
return vHolder;
}
#Override
public void onBindViewHolder(MyViewHolder holder, int position) {
holder.tv_name.setText(mData.get(position).getName());
holder.tv_author.setText(mData.get(position).getPhone());
holder.img.setImageResource(mData.get(position).getPhoto());
}
#Override
public int getItemCount() {
return mData.size();
}
public static class MyViewHolder extends RecyclerView.ViewHolder {
private ImageButton item_play;
private LinearLayout menu_play;
private TextView tv_name;
private TextView tv_author;
private TextView tv_url;
private ImageView img;
public MyViewHolder(View itemView) {
super(itemView);
item_play = itemView.findViewById(R.id.info_id);
menu_play = itemView.findViewById(R.id.list_item_id);
tv_name = (TextView) itemView.findViewById(R.id.name_list);
tv_author = (TextView) itemView.findViewById(R.id.author_list);
img = (ImageView) itemView.findViewById(R.id.img_contact);
}
}
}
fragmentList
package etes.xddda.music;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;
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.Volley;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.List;
public class fragmentList extends Fragment {
View v;
private RecyclerView myrecyclerview;
private List<mList> lstContact;
private String URL_JSON = "https://pastebin.com/raw/fG3zd40U";
private JsonArrayRequest ArrayRequest;
private RequestQueue requestQueue ;
public fragmentList() {
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
v = inflater.inflate(R.layout.list_fragment,container,false);
myrecyclerview = (RecyclerView) v.findViewById(R.id.list_recyclerview);
RecyclerViewAdapter recyclerViewAdapter = new RecyclerViewAdapter(getContext(), lstContact);
myrecyclerview.setLayoutManager(new LinearLayoutManager(getActivity()));
myrecyclerview.setAdapter(recyclerViewAdapter);
return v;
}
#Override
public void onCreate(#Nullable Bundle savedInstaceState) {
super.onCreate(savedInstaceState);
_JSONcall();
}
public void _JSONcall() {
lstContact = new ArrayList<>();
ArrayRequest = new JsonArrayRequest(URL_JSON, new Response.Listener<JSONArray>() {
#Override
public void onResponse(JSONArray response) {
JSONObject jsonObject = null;
for (int i = 0 ; i<response.length();i++) {
try {
jsonObject = response.getJSONObject(i);
lstContact.add(new mList(jsonObject.getString("name"), jsonObject.getString("description"), jsonObject.getString("link"), R.drawable.ic_play_circle_filled_black_24dp));
}
catch (JSONException e) {
e.printStackTrace();
Toast.makeText(getActivity(), "Error 1!",
Toast.LENGTH_LONG).show();
}
}
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(getActivity(), "Error 3!",
Toast.LENGTH_LONG).show();
}
});
requestQueue = Volley.newRequestQueue(getActivity().getApplicationContext());
requestQueue.add(ArrayRequest);
}
}
MainActivity
package etes.xddda.music;
import android.annotation.SuppressLint;
import android.support.design.widget.TabLayout;
import android.support.v4.view.ViewPager;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageButton;
import android.widget.LinearLayout;
public class MainActivity extends AppCompatActivity {
private DrawerLayout nDrawerLayout;
private ActionBarDrawerToggle mToggle;
private TabLayout tabLayout;
private ViewPager viewPager;
private viewPagerAdapter adapter;
public LinearLayout menu_dialog;
private String player_status = "playing";
private ImageButton player_img;
#SuppressLint("RestrictedApi")
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
nDrawerLayout = findViewById(R.id.drawer);
menu_dialog = findViewById(R.id.menu_dialog);
menu_dialog.setVisibility(View.GONE);
player_img = findViewById(R.id.playorpause);
player_img.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//setMargins(viewPager, 0,0,0,110);
if (player_status == "playing") {
player_img.setImageResource(R.drawable.ic_play_arrow_black_24dp);
meplayer.pauseAudio();
player_status = "paused";
} else {
player_img.setImageResource(R.drawable.ic_pause_black_24dp);
meplayer.startAudio();
player_status = "playing";
}
}
});
//menu_dialog.setLayoutParams(new LinearLayout.LayoutParams(0, 0));
mToggle = new ActionBarDrawerToggle(this, nDrawerLayout, R.string.open, R.string.close);
nDrawerLayout.addDrawerListener(mToggle);
getSupportActionBar().setDefaultDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
tabLayout = findViewById(R.id.tablayout_id);
viewPager = findViewById(R.id.viewpager_id);
//viewPager.setLayoutParams(new ViewPager.LayoutParams(0, 0));
//setMarginBottom(viewPager, 0);
setMargins(viewPager, 0,0,0,0);
adapter = new viewPagerAdapter(getSupportFragmentManager());
//Add fragments here
adapter.addFragment(new fragmentList(), ""); //Lista de música
adapter.addFragment(new fragmentFrequent(), ""); //Frequentes
adapter.addFragment(new fragmentPlayList(), ""); //Playlist
viewPager.setAdapter(adapter);
tabLayout.setupWithViewPager(viewPager);
tabLayout.getTabAt(0).setIcon(R.drawable.ic_music_note_black_24dp); //Lista de música
tabLayout.getTabAt(1).setIcon(R.drawable.ic_filter_list_black_24dp); // Frequentes
tabLayout.getTabAt(2).setIcon(R.drawable.ic_queue_music_black_24dp); // Playlist
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
if (mToggle.onOptionsItemSelected(item)) {
return true;
}
return super.onOptionsItemSelected(item);
}
#Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
// Sync the toggle state after onRestoreInstanceState has occurred.
mToggle.syncState();
}
public static void setMargins (View v, int l, int t, int r, int b) {
if (v.getLayoutParams() instanceof ViewGroup.MarginLayoutParams) {
ViewGroup.MarginLayoutParams p = (ViewGroup.MarginLayoutParams) v.getLayoutParams();
p.setMargins(l, t, r, b);
v.requestLayout();
}
}
}
mList
package etes.xddda.music;
public class mList {
private String Name;
private String Author;
private String URL;
private int Photo;
public mList() {
}
public mList(String name, String phone, String url, int photo) {
Name = name;
Author = phone;
URL = url;
Photo = photo;
}
//Get User
public String getName() {
return Name;
}
public String getPhone() {
return Author;
}
public String getURL() {
return URL;
}
public int getPhoto() {
return Photo;
}
//Setter
public void setName(String name) {
Name = name;
}
public void setPhone(String phone) {
Author = phone;
}
public void setURL(String url) {
URL = url;
}
public void setPhoto(int photo) {
Photo = photo;
}
}
There are no errors in this script, the app just crash when audio finishes. The problem is related to line menu_dialog.setVisibility(View.GONE); and I have already defined menu_dialog in onCreate. So, can you help me?
P.S.: menu_dialog belongs to activity_main.xml
Thank you!

Remove the local variable menu_dialog that you have defined inside the OnCompletionListener:
package etes.xddda.music;
import android.app.Activity;
import android.content.Context;
import android.media.MediaPlayer;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.LinearLayout;
import android.widget.Toast;
public class meplayer extends Activity {
public static MediaPlayer mediaPlayer;
public LinearLayout menu_dialog;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
menu_dialog = findViewById(R.id.menu_dialog);
}
public void initAudio(final Context context, final String url) {
if (mediaPlayer == null) {
mediaPlayer = MediaPlayer.create(context, Uri.parse(url));
}
mediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
//public LinearLayout menu_dialog; REMOVE THIS
#Override
public void onCompletion(MediaPlayer mp) {
//Toast.makeText(context, "TEST", Toast.LENGTH_LONG).show();
killMediaPlayer();
menu_dialog.setVisibility(View.GONE);
}
});
mediaPlayer.start();
}
private void killMediaPlayer() {
if (mediaPlayer != null) {
try {
mediaPlayer.reset();
mediaPlayer.release();
mediaPlayer = null;
} catch (Exception e) {
e.printStackTrace();
}
}
}
}

Attempt to invoke virtual method [Null object reference] [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 4 years ago.
I'm spending the last 5 days trying solve this problem. I really do not have any idea about how to solve it. I'm getting Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference. Check my code:
RecyclerView.java
package etes.xdda.music;
import android.app.Dialog;
import android.content.Context;
import android.content.Intent;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.media.MediaPlayer;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;
import java.util.List;
public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.MyViewHolder> implements View.OnClickListener{
Context mContext;
List<mList> mData;
Dialog myDialog;
private MediaPlayer mediaPlayer;
private int playbackPosition=0;
private LinearLayout menu_dialog;
public RecyclerViewAdapter(Context mContext, List<mList> mData) {
this.mContext = mContext;
this.mData = mData;
}
public void onClick(View view) {
}
#Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v;
v = LayoutInflater.from(mContext).inflate(R.layout.item_list, parent, false);
final MyViewHolder vHolder = new MyViewHolder(v);
// Dialog ini
myDialog = new Dialog(mContext);
myDialog.setContentView(R.layout.dialog);
myDialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
vHolder.item_play.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v)
{
TextView dialog_name_tv = (TextView) myDialog.findViewById(R.id.dialog_name_id);
TextView dialog_phone_tv = (TextView) myDialog.findViewById(R.id.dialog_author_id);
ImageView dialog_contact_img = (ImageView) myDialog.findViewById(R.id.dialog_img);
dialog_name_tv.setText(mData.get(vHolder.getAdapterPosition()).getName());
dialog_phone_tv.setText(mData.get(vHolder.getAdapterPosition()).getPhone());
dialog_contact_img.setImageResource(mData.get(vHolder.getAdapterPosition()).getPhoto());
//Toast.makeText(mContext, "Test click "+String.valueOf(vHolder.getAdapterPosition()), Toast.LENGTH_SHORT).show();
myDialog.show();
}
});
vHolder.menu_play.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v)
{
menu_dialog = v.getRootView().findViewById(R.id.menu_dialog);
menu_dialog.setVisibility(v.VISIBLE);
MainActivity a = new MainActivity();
a.initAudio(v.getContext(), mData.get(vHolder.getAdapterPosition()).getURL());
MainActivity.setMargins(v.getRootView().findViewById(R.id.viewpager_id), 0,0,0,100);
}
});
return vHolder;
}
#Override
public void onBindViewHolder(MyViewHolder holder, int position) {
holder.tv_name.setText(mData.get(position).getName());
holder.tv_author.setText(mData.get(position).getPhone());
holder.img.setImageResource(mData.get(position).getPhoto());
}
#Override
public int getItemCount() {
return mData.size();
}
public static class MyViewHolder extends RecyclerView.ViewHolder {
private ImageButton item_play;
private LinearLayout menu_play;
private TextView tv_name;
private TextView tv_author;
private TextView tv_url;
private ImageView img;
public MyViewHolder(View itemView) {
super(itemView);
item_play = itemView.findViewById(R.id.info_id);
menu_play = itemView.findViewById(R.id.list_item_id);
tv_name = (TextView) itemView.findViewById(R.id.name_list);
tv_author = (TextView) itemView.findViewById(R.id.author_list);
img = (ImageView) itemView.findViewById(R.id.img_contact);
}
}
}
Note that I'm invoking MainActivity.java in this part:
vHolder.menu_play.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v)
{
menu_dialog = v.getRootView().findViewById(R.id.menu_dialog);
menu_dialog.setVisibility(v.VISIBLE);
MainActivity a = new MainActivity();
a.initAudio(v.getContext(), mData.get(vHolder.getAdapterPosition()).getURL());
MainActivity.setMargins(v.getRootView().findViewById(R.id.viewpager_id), 0,0,0,100);
}
});
And here's my MainActivity.java
package etes.xdda.music;
import android.annotation.SuppressLint;
import android.content.Context;
import android.media.MediaPlayer;
import android.net.Uri;
import android.support.design.widget.TabLayout;
import android.support.v4.view.ViewPager;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageButton;
import android.widget.LinearLayout;
public class MainActivity extends AppCompatActivity {
private DrawerLayout nDrawerLayout;
private ActionBarDrawerToggle mToggle;
private TabLayout tabLayout;
private ViewPager viewPager;
private viewPagerAdapter adapter;
public LinearLayout menu_dialog;
private String player_status = "playing";
private ImageButton player_img;
private static MediaPlayer mediaPlayer;
#SuppressLint("RestrictedApi")
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
nDrawerLayout = findViewById(R.id.drawer);
menu_dialog = findViewById(R.id.menu_dialog);
menu_dialog.setVisibility(View.GONE);
player_img = findViewById(R.id.playorpause);
player_img.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//setMargins(viewPager, 0,0,0,110);
if (player_status == "playing") {
player_img.setImageResource(R.drawable.ic_play_arrow_black_24dp);
meplayer.pauseAudio();
player_status = "paused";
} else {
player_img.setImageResource(R.drawable.ic_pause_black_24dp);
meplayer.startAudio();
player_status = "playing";
}
}
});
//menu_dialog.setLayoutParams(new LinearLayout.LayoutParams(0, 0));
mToggle = new ActionBarDrawerToggle(this, nDrawerLayout, R.string.open, R.string.close);
nDrawerLayout.addDrawerListener(mToggle);
getSupportActionBar().setDefaultDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
tabLayout = findViewById(R.id.tablayout_id);
viewPager = findViewById(R.id.viewpager_id);
//viewPager.setLayoutParams(new ViewPager.LayoutParams(0, 0));
//setMarginBottom(viewPager, 0);
setMargins(viewPager, 0,0,0,0);
adapter = new viewPagerAdapter(getSupportFragmentManager());
//Add fragments here
adapter.addFragment(new fragmentList(), ""); //Lista de música
adapter.addFragment(new fragmentFrequent(), ""); //Frequentes
adapter.addFragment(new fragmentPlayList(), ""); //Playlist
viewPager.setAdapter(adapter);
tabLayout.setupWithViewPager(viewPager);
tabLayout.getTabAt(0).setIcon(R.drawable.ic_music_note_black_24dp); //Lista de música
tabLayout.getTabAt(1).setIcon(R.drawable.ic_filter_list_black_24dp); // Frequentes
tabLayout.getTabAt(2).setIcon(R.drawable.ic_queue_music_black_24dp); // Playlist
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
if (mToggle.onOptionsItemSelected(item)) {
return true;
}
return super.onOptionsItemSelected(item);
}
#Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
// Sync the toggle state after onRestoreInstanceState has occurred.
mToggle.syncState();
}
public static void setMargins (View v, int l, int t, int r, int b) {
if (v.getLayoutParams() instanceof ViewGroup.MarginLayoutParams) {
ViewGroup.MarginLayoutParams p = (ViewGroup.MarginLayoutParams) v.getLayoutParams();
p.setMargins(l, t, r, b);
v.requestLayout();
}
}
public void initAudio(final Context context, final String url) {
if (mediaPlayer == null) {
mediaPlayer = MediaPlayer.create(context, Uri.parse(url));
}
mediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
#Override
public void onCompletion(MediaPlayer mp) {
//Toast.makeText(context, "TEST", Toast.LENGTH_LONG).show();
killMediaPlayer();
updateLayout();
}
});
mediaPlayer.start();
}
private static void killMediaPlayer() {
if (mediaPlayer != null) {
try {
mediaPlayer.reset();
mediaPlayer.release();
mediaPlayer = null;
} catch (Exception e) {
e.printStackTrace();
}
}
}
private void updateLayout() {
try {
menu_dialog = findViewById(R.id.menu_dialog);
menu_dialog.setVisibility(View.GONE);
} catch (Exception e) {
e.printStackTrace();
}
}
And the part of code that is giving crash is this:
private void updateLayout() {
try {
menu_dialog = findViewById(R.id.menu_dialog);
menu_dialog.setVisibility(View.GONE);
} catch (Exception e) {
e.printStackTrace();
}
}
#edit: I have added this piece of code, I don't know if can help
fragmentList.java
package etes.xdda.music;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;
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.Volley;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.List;
public class fragmentList extends Fragment {
View v;
private RecyclerView myrecyclerview;
private List<mList> lstContact;
private String URL_JSON = "https://pastebin.com/raw/fG3zd40U";
private JsonArrayRequest ArrayRequest;
private RequestQueue requestQueue ;
MainActivity activity;
public fragmentList() {
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
v = inflater.inflate(R.layout.list_fragment,container,false);
myrecyclerview = (RecyclerView) v.findViewById(R.id.list_recyclerview);
RecyclerViewAdapter recyclerViewAdapter = new RecyclerViewAdapter(activity, lstContact);
myrecyclerview.setLayoutManager(new LinearLayoutManager(getActivity()));
myrecyclerview.setAdapter(recyclerViewAdapter);
return v;
}
#Override
public void onCreate(#Nullable Bundle savedInstaceState) {
super.onCreate(savedInstaceState);
_JSONcall();
}
public void _JSONcall() {
lstContact = new ArrayList<>();
ArrayRequest = new JsonArrayRequest(URL_JSON, new Response.Listener<JSONArray>() {
#Override
public void onResponse(JSONArray response) {
JSONObject jsonObject = null;
for (int i = 0 ; i<response.length();i++) {
try {
jsonObject = response.getJSONObject(i);
lstContact.add(new mList(jsonObject.getString("name"), jsonObject.getString("description"), jsonObject.getString("link"), R.drawable.ic_play_circle_filled_black_24dp));
}
catch (JSONException e) {
e.printStackTrace();
Toast.makeText(getActivity(), "Error 1!",
Toast.LENGTH_LONG).show();
}
}
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(getActivity(), "Error 3!",
Toast.LENGTH_LONG).show();
}
});
requestQueue = Volley.newRequestQueue(getActivity().getApplicationContext());
requestQueue.add(ArrayRequest);
}
}
Please, help me, I have no more ideas about what I should do. Thank you

Just taking a look at your code, it looks like you are doing many things wrong. Such as this line
MainActivity a = new MainActivity();
You can't instantiate lifecycle components like Services, Activities, Fragments etc this way. Android provides you these components when you call start methods etc. The activity that is created as a result of the above line doesn't go through the lifecycle calls that an activity that is started via using startActivity. As a result, the setContentView of the activity is never called and you get this error. You have to remove this line and implement this properly and the error will go away.
Also just to add, you are actually creating a new instance of the activity when one is already running when you need to call the methods on the old instance that was started.
Edit: Try like this.
MainActivity activity;
List<mList> mData;
Dialog myDialog;
private MediaPlayer mediaPlayer;
private int playbackPosition=0;
private LinearLayout menu_dialog;
public RecyclerViewAdapter(MainActivity activity, List<mList> mData) {
this.activity = activity;
this.mData = mData;
}
And then
vHolder.menu_play.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v)
{
menu_dialog = v.getRootView().findViewById(R.id.menu_dialog);
menu_dialog.setVisibility(v.VISIBLE);
activity.initAudio(v.getContext(), mData.get(vHolder.getAdapterPosition()).getURL());
activity.setMargins(v.getRootView().findViewById(R.id.viewpager_id), 0,0,0,100);
}
});
Also remove static from the main activity functions

findfragmentbyid returns null in mainActivity hosting 3 fragments under a viewpager

I am trying to write different functionalities for my FloatingActionButton depending on the fragment that the mainActivity is currently hosting. Yet for for reason in my onClick() method, getSupportFragmentManager().findFragmentById() returns null.
I haven't seen any examples of this question implemented with a viewpager and I am curious if there is a different approach I have to take.
MainActivity
import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.View;
public class MainActivity extends FragmentActivity {
private Adapter mAdapter;
private ViewPager mViewPager;
private static FloatingActionButton bButton;
private static String UID;
private Intent intent;
public static String getUID(){
return UID;
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mAdapter = new Adapter(getSupportFragmentManager());
mViewPager = (ViewPager)findViewById(R.id.vPager);
mViewPager.setAdapter(mAdapter);
intent = getIntent();
UID = intent.getStringExtra("uid");
bButton = (FloatingActionButton)findViewById(R.id.bButton);
bButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.fragContainer);
if(fragment == null){
Log.e("TAG","FRAGMENT IS NULL!!");
}
else{
Log.e("TAG","FRAGMENT IS NOT NULL!!");
}
}
});
}
}
NewsFeedFragment
import android.os.Bundle;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.ListFragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import com.firebase.client.Firebase;
import com.firebase.client.FirebaseError;
import com.mycompany.neighbors.R;
import com.mycompany.neighbors.SinglePost;
import java.util.ArrayList;
/**
* Created by joshua on 5/25/2016.
*/
public class NewsFeedFragment extends ListFragment implements AdapterView.OnItemClickListener{
private ListView lv;
private TextView tvUserName;
private TextView tvStatus;
private ArrayList<SinglePost> posts = new ArrayList<>();
private static final String POSTS_PATH = "MY_PATH";
private Firebase postsRef;
// private static final String FRAGMENT_POST = "post";
public void postFragment(){
Log.d("TAG", "Doing something else");
PostFragment postFragment = new PostFragment();
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.fragContainer,postFragment)
.addToBackStack(null)
.commit();
}
#Override
public void onViewCreated(View v, Bundle s){
lv = getListView();
lv.setOnItemClickListener(this);
}
#Override
public void onCreate(Bundle savedInstance){
super.onCreate(savedInstance);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState){
View v = inflater.inflate(R.layout.fragment_post_feed_item,parent,false);//changed
tvUserName = (TextView)v.findViewById(R.id.tvUN);
tvStatus = (TextView)v.findViewById(R.id.tvStatus);
postsRef = new Firebase(POSTS_PATH);
postsRef.addChildEventListener(new com.firebase.client.ChildEventListener() {
#Override
public void onChildAdded(com.firebase.client.DataSnapshot dataSnapshot, String s) {
SinglePost post = dataSnapshot.getValue(SinglePost.class);
post.setKey(dataSnapshot.getKey());
posts.add(0, post);
if(posts.size() > 0) {
PostAdapter adapter = new PostAdapter(posts);
setListAdapter(adapter);
}else{
Toast toast = Toast.makeText(getActivity(),"No data", Toast.LENGTH_SHORT);
toast.show();
}
}
#Override
public void onChildChanged(com.firebase.client.DataSnapshot dataSnapshot, String s) {
}
#Override
public void onChildRemoved(com.firebase.client.DataSnapshot dataSnapshot) {
}
#Override
public void onChildMoved(com.firebase.client.DataSnapshot dataSnapshot, String s) {
}
#Override
public void onCancelled(FirebaseError firebaseError) {
}
});
return v;
}
#Override
public void onListItemClick(ListView l, View v, int position, long id){
SinglePost p = ((PostAdapter) getListAdapter()).getItem(position);
}
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
}
private class PostAdapter extends ArrayAdapter<SinglePost>{
public PostAdapter(ArrayList<SinglePost> singlePost){
super(getActivity(),android.R.layout.simple_list_item_1,singlePost);
}
#Override
public View getView(int position, View convertView, ViewGroup parent){
if(convertView == null){
convertView = getActivity().getLayoutInflater().inflate(R.layout.fragment_post_feed_item,null);
}
SinglePost p = getItem(position);
TextView tvUserName = (TextView)convertView.findViewById(R.id.tvUN);
tvUserName.setText(p.getUserName());
TextView tvStatus = (TextView)convertView.findViewById(R.id.tvStatus);
tvStatus.setText(p.getStatus());
return convertView;
}
}
}
I have 2 other fragments but i'll post one as an example. Here is my adapter for the viewpager.
Adapter
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import com.mycompany.neighbors.Fragments.MapFragment;
import com.mycompany.neighbors.Fragments.NewsFeedFragment;
import com.mycompany.neighbors.Fragments.ProfileFragment;
/**
* Created by joshua on 5/25/2016.
*/
public class Adapter extends FragmentPagerAdapter {
private String Fragment[] = {"Posts" , "Map" , "Profile"};
public Adapter(FragmentManager fm){
super (fm);
}
#Override
public Fragment getItem(int position) {
switch(position){
case 0:
return new NewsFeedFragment();
case 1:
return new MapFragment();
case 2:
return new ProfileFragment();
default:
return null;
}
}
#Override
public int getCount(){return Fragment.length;}
#Override
public CharSequence getPageTitle(int position) {
return Fragment[position];
}
}

Please check below link, It has very good explanation for your problem:
http://tamsler.blogspot.in/2011/11/android-viewpager-and-fragments-part-ii.html
Or you can try below code snippet:
1.Where you add fragment in view pager or view pager adapter:
MyFragment myFragment = MyFragment.newInstance();
mPageReferenceMap.put(index, "Some Tag");
getSupportFragmentManager().beginTransaction().add(myFragment,"Some Tag").commit();
2.To get the tag for the currently visible page, you then call:
int index = mViewPager.getCurrentItem();
String tag = mPageReferenceMap.get(index);
3.and then get the fragment page:
Fragment myFragment = getSupportFragmentManager().findFragmentByTag(tag);

NullPointerException in runOnUIThread() [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 6 years ago.
I have created a movie application that queries a REST API at themoviedb.org. On selecting a movie from a grid the user is brought to a details screen where further details about the movie are shown details being a list of trailers and a list of reviews. The problem is that SOMETIMES my code for populating the list of reviews and trailers hits a NullPointerException. It doesn't happen alway and it's not specific to a particular movie entry, it's totally random.
To be precise, I randomly get NullPointerExceptions when I am refreshing my RecyclerView Adapter with data inside the runOnUIThread() after a succesful network response.
Here's the GitHub repo link-https://github.com/Hackertronix/Project-Motion/tree/Stage_2
Following is my code along with the stack trace
I have added comments to show the line numbers
DetailsFragment.java
package com.execube.genesis.views.fragments;
import android.annotation.TargetApi;
import android.content.Intent;
import android.graphics.Color;
import android.graphics.Typeface;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.design.widget.CoordinatorLayout;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.app.Fragment;
import android.support.v4.content.ContextCompat;
import android.support.v7.widget.CardView;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.RatingBar;
import android.widget.TextView;
import android.widget.Toast;
import com.execube.genesis.R;
import com.execube.genesis.model.Event;
import com.execube.genesis.model.Movie;
import com.execube.genesis.model.Review;
import com.execube.genesis.model.Trailer;
import com.execube.genesis.utils.API;
import com.execube.genesis.utils.EventBus;
import com.execube.genesis.utils.JSONParser;
import com.execube.genesis.utils.OkHttpHandler;
import com.orm.SugarRecord;
import com.squareup.picasso.Picasso;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import okhttp3.Call;
import okhttp3.Response;
import static com.execube.genesis.R.drawable.ic_favorite_black_24dp;
/**
* Created by Prateek Phoenix on 4/30/2016.
*/
public class DetailsFragment extends Fragment {
private static final String TAG = "DETAILS";
private static final int DEFAULT_NUM_COLORS = 5;
private Movie mMovie;
private Movie entry,tempMovie;
private List<Movie> movie;
public Intent intent;
private TextView mDetailTitle;
private TextView mReleaseDate;
private TextView mOverview;
private TextView mOverviewHeader;
private TextView mReviesHeader;
private TextView mTrailersHeader;
private ImageView mBackdrop;
private Toolbar mToolbar;
private RatingBar mRatingBar;
private ArrayList<Review> mReviews=new ArrayList<>();
private ArrayList<Trailer> mTrailers=new ArrayList<>();
private List<Movie> updatedFavsList= new ArrayList<>();
public static final String MOVIE_REVIEWS_ARRAY ="movie_details";
private static final String MOVIE_TRAILERS_ARRAY = "movie_reviews";
private Typeface fontBold;
private Typeface fontMediumLight;
private Typeface fontMedium;
private RecyclerView mReviewRecyclerView;
private RecyclerView mTrailerRecyclerView;
private ProgressBar mReviewsProgressbar;
private ProgressBar mTrailersProgressbar;
private CoordinatorLayout mCoordinatorLayout;
private CardView mReviewsCardView;
private FloatingActionButton mFloatingActionButton;
private ReviewsAdapter mReviewAdapter;
private int NumOfReviews;
private TrailersAdapter mTrailerAdapter;
private String id;
private boolean isFav;
public DetailsFragment() {
}
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public void onSaveInstanceState(Bundle outState) {
Log.v(TAG,"Saving state in onSaveInstanceState");
outState.putParcelableArrayList(MOVIE_REVIEWS_ARRAY,mReviews);
outState.putParcelableArrayList(MOVIE_TRAILERS_ARRAY,mTrailers);
super.onSaveInstanceState(outState);
}
#TargetApi(Build.VERSION_CODES.LOLLIPOP)
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_detail, container, false);
mBackdrop = (ImageView) view.findViewById(R.id.details_poster);
mDetailTitle = (TextView) view.findViewById(R.id.detail_title_text);
mReleaseDate = (TextView) view.findViewById(R.id.release_date);
mOverview = (TextView) view.findViewById(R.id.overview);
mOverviewHeader = (TextView) view.findViewById(R.id.overview_header);
mReviesHeader=(TextView)view.findViewById(R.id.review_header);
mTrailersHeader=(TextView)view.findViewById(R.id.trailer_header);
mRatingBar = (RatingBar) view.findViewById(R.id.movie_rating);
mCoordinatorLayout=(CoordinatorLayout)view.findViewById(R.id.coordinator_layout);
mReviewRecyclerView= (RecyclerView)view.findViewById(R.id.review_recycler_view);
mTrailerRecyclerView=(RecyclerView)view.findViewById(R.id.trailer_recycler_view);
mReviewsProgressbar=(ProgressBar)view.findViewById(R.id.reviews_progressbar);
mTrailersProgressbar=(ProgressBar)view.findViewById(R.id.trailers_progressbar);
mFloatingActionButton=(FloatingActionButton)view.findViewById(R.id.fab);
mReviewsCardView= (CardView) view.findViewById(R.id.reviews_card);
intent = getActivity().getIntent();
Bundle bundle=getArguments();
mMovie=bundle.getParcelable("PARCEL");
tempMovie=mMovie;
id = String.valueOf(mMovie.getMovieId());
checkFav();
mFloatingActionButton.show();
assert mMovie != null;
//PREPPING THE URL FOR QUERY
String reviewQueryUrl = API.MOVIES_BASE_URL + id + "/reviews" + API.API_KEY;
String trailerQueryUrl = API.MOVIES_BASE_URL + id + "/videos" + API.API_KEY;
mDetailTitle.setText(mMovie.getTitle());
mReleaseDate.setText(mMovie.getReleaseDate());
mRatingBar.setProgress((int) mMovie.getVoteAverage());
mOverview.setText(mMovie.getOverview());
if (Build.VERSION.SDK_INT != 21) {
fontBold = Typeface.createFromAsset(getActivity().getAssets(), "fonts/Gotham-Rounded-Bold.ttf");
fontMedium = Typeface.createFromAsset(getActivity().getAssets(), "fonts/Gotham-Rounded-Medium.ttf");
fontMediumLight = Typeface.createFromAsset(getActivity().getAssets(), "fonts/Gotham-Rounded-Book_.ttf");
mDetailTitle.setTypeface(fontBold);
mReleaseDate.setTypeface(fontMedium);
mOverview.setTypeface(fontMediumLight);
mOverviewHeader.setTypeface(fontBold);
mReviesHeader.setTypeface(fontBold);
mTrailersHeader.setTypeface(fontBold);
}
//FETCHING JSON HERE
if(savedInstanceState!=null&&savedInstanceState.containsKey(MOVIE_REVIEWS_ARRAY))
{
Log.v(TAG,"Restoring from bundle");
mReviews=savedInstanceState.getParcelableArrayList(MOVIE_REVIEWS_ARRAY);
mTrailers=savedInstanceState.getParcelableArrayList(MOVIE_TRAILERS_ARRAY);
mReviewsProgressbar.setVisibility(View.GONE);
mTrailersProgressbar.setVisibility(View.GONE);
}
else {
OkHttpHandler reviewsHandler = new OkHttpHandler(reviewQueryUrl, reviewsCallback);
reviewsHandler.fetchData();
OkHttpHandler trailersHandler= new OkHttpHandler(trailerQueryUrl, trailersCallback);
trailersHandler.fetchData();
}
Picasso.with(getActivity()).load(API.IMAGE_URL + API.IMAGE_SIZE_500 + mMovie.getPosterPath())
.placeholder(R.drawable.placeholder)
.error(R.drawable.error)
.into(mBackdrop);
getActivity().startPostponedEnterTransition();
mReviewRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
mReviewAdapter= new ReviewsAdapter();
mReviewRecyclerView.setAdapter(mReviewAdapter);
LinearLayoutManager layoutmanager= new LinearLayoutManager(getActivity(),LinearLayoutManager.HORIZONTAL,false);
mTrailerRecyclerView.setLayoutManager(layoutmanager);
mTrailerAdapter= new TrailersAdapter();
mTrailerRecyclerView.setAdapter(mTrailerAdapter);
return view;
}
private void checkFav() {
movie=new ArrayList<>();
movie=SugarRecord.find(Movie.class,"m_id=?",id);
if(movie.size()==0)
{
Log.v(TAG,"Null");
mFloatingActionButton.setImageResource(R.drawable.ic_favorite_border_black_24dp);
}
else {
Log.v(TAG,"NOT Null");
mFloatingActionButton.setImageResource(R.drawable.ic_favorite_black_24dp);
}
mFloatingActionButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
movie=SugarRecord.find(Movie.class,"m_id=?",id);
if(movie.size()>0)
{
entry = movie.get(0);
entry.delete();
Event event = new Event("Database has been modified!!");
EventBus.getBus().post(event);
mFloatingActionButton.setImageResource(R.drawable.ic_favorite_border_black_24dp);
Snackbar snackbar = Snackbar.make(mCoordinatorLayout,"Movie removed from Favourites!!",Snackbar.LENGTH_SHORT);
View view= snackbar.getView();
TextView textView = (TextView)view.findViewById(android.support.design.R.id.snackbar_text);
textView.setTextColor(Color.YELLOW);
snackbar.show();
}
else
{
entry = tempMovie;
entry.save();
Event event = new Event("Database has been modified!!");
EventBus.getBus().post(event);
mFloatingActionButton.setImageResource(R.drawable.ic_favorite_black_24dp);
Snackbar snackbar = Snackbar.make(mCoordinatorLayout,"Movie added to Favourites!!",Snackbar.LENGTH_SHORT);
View view= snackbar.getView();
TextView textView = (TextView)view.findViewById(android.support.design.R.id.snackbar_text);
textView.setTextColor(Color.YELLOW);
snackbar.show();
}
}
});
}
//OKHTTP CALLBACK FOR NETWORK CALL
private okhttp3.Callback reviewsCallback = new okhttp3.Callback() {
#Override
public void onFailure(Call call, IOException e) {
//TODO handle failure on UI thread
}
#Override
public void onResponse(Call call, Response response) throws IOException {
try {
String JSONData= response.body().string();
JSONObject jsonObject = new JSONObject(JSONData);
NumOfReviews = jsonObject.getInt("total_results");
JSONParser parser = new JSONParser();
mReviews=parser.parseReviews(JSONData);
} catch (JSONException e) {}
getActivity().runOnUiThread(new Runnable() {
#Override //THIS IS THE FIRST LINE WHERE I GET A NULL POINTER EXCEPTION
public void run() {
if(mReviewAdapter!=null)
{
mReviewsProgressbar.setVisibility(View.GONE);
mReviewAdapter.notifyDataSetChanged();
}
}
});
getActivity().runOnUiThread(new Runnable() {
#Override
public void run() {
if (NumOfReviews==0)
{
mReviewsCardView.setVisibility(View.INVISIBLE);
}
}
});
}
};
private okhttp3.Callback trailersCallback = new okhttp3.Callback() {
#Override
public void onFailure(Call call, IOException e) {
//TODO handle failure on UI thread
}
#Override
public void onResponse(Call call, Response response) throws IOException {
try {
String json1= response.body().string();
JSONParser parser= new JSONParser();
mTrailers = parser.parseTrailers(json1);
} catch (JSONException e) {}
getActivity().runOnUiThread(new Runnable() {
#Override
public void run() { //THIS IS THE 2nd LINE WHERE I GET A NULL POINTER EXCEPTION
if(mTrailerAdapter!=null)
{
mTrailersProgressbar.setVisibility(View.GONE);
mTrailerAdapter.notifyDataSetChanged();
}
}
});
}
};
private class ReviewViewHolder extends RecyclerView.ViewHolder{
private TextView mAuthorText;
private TextView mReviewText;
private Review mReview;
public ReviewViewHolder(View itemView) {
super(itemView);
mAuthorText= (TextView) itemView.findViewById(R.id.author_textview);
mReviewText= (TextView) itemView.findViewById(R.id.review_textview);
}
public void bind(Review review)
{
mReview= review;
mAuthorText.setText(mReview.getAuthor());
mReviewText.setText(mReview.getContent());
if(Build.VERSION.SDK_INT>=Build.VERSION_CODES.LOLLIPOP)
{
mAuthorText.setTypeface(fontBold);
mReviewText.setTypeface(fontMediumLight);
}
}
}
private class ReviewsAdapter extends RecyclerView.Adapter<ReviewViewHolder>{
#Override
public ReviewViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view= LayoutInflater.from(getActivity()).inflate(R.layout.review_item,parent,false);
return new ReviewViewHolder(view);
}
#Override
public void onBindViewHolder(ReviewViewHolder holder, int position) {
Review review= mReviews.get(position);
holder.bind(review);
}
#Override
public int getItemCount() {
if(mReviews==null)
{ return 0;}
else
{return mReviews.size();}
}
}
private class TrailerViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
private ImageView mTrailerThumbnail;
private Trailer mTrailer;
public TrailerViewHolder(View itemView) {
super(itemView);
mTrailerThumbnail=(ImageView)itemView.findViewById(R.id.trailer_thumbnail);
itemView.setOnClickListener(this);
}
public void bind(Trailer trailer)
{
mTrailer=trailer;
Picasso picasso =Picasso.with(getActivity());
picasso.setIndicatorsEnabled(true);
picasso.load(API.YOUTUBE_THUMBNAIL_URL+mTrailer.getKey()+API.THUMBNAIL_QUALITY)
.into(mTrailerThumbnail);
}
#Override
public void onClick(View v) {
Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(API.YOUTUBE_TRAILER_URL+mTrailer.getKey()));
startActivity(intent);
}
}
private class TrailersAdapter extends RecyclerView.Adapter<TrailerViewHolder>
{
#Override
public TrailerViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view= LayoutInflater.from(getActivity()).inflate(R.layout.trailer_item,parent,false);
return new TrailerViewHolder(view);
}
#Override
public void onBindViewHolder(TrailerViewHolder holder, int position) {
Trailer trailer= mTrailers.get(position);
holder.bind(trailer);
}
#Override
public int getItemCount() {
return mTrailers.size();
}
}
}
Stack Trace
06-10 02:02:30.548 25094-27219/? E/AndroidRuntime: FATAL EXCEPTION: OkHttp Dispatcher
Process: com.execube.genesis, PID: 25094
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.app.FragmentActivity.runOnUiThread(java.lang.Runnable)' on a null object reference
at com.execube.genesis.views.fragments.DetailsFragment$3.onResponse(DetailsFragment.java:349)
at okhttp3.RealCall$AsyncCall.execute(RealCall.java:133)
at okhttp3.internal.NamedRunnable.run(NamedRunnable.java:32)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:818)
06-10 02:02:30.548 25094-27218/? E/AndroidRuntime: FATAL EXCEPTION: OkHttp Dispatcher
Process: com.execube.genesis, PID: 25094
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.app.FragmentActivity.runOnUiThread(java.lang.Runnable)' on a null object reference
at com.execube.genesis.views.fragments.DetailsFragment$2.onResponse(DetailsFragment.java:308)
at okhttp3.RealCall$AsyncCall.execute(RealCall.java:133)
at okhttp3.internal.NamedRunnable.run(NamedRunnable.java:32)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:818)

When you're calling getActivity, it might return null when the fragment is not attached to any activity. In order to avoid a NullPointerException, be sure to first check if it's not null and then proceed with your logic.
if(getActivity!=null){
//do stuff
}

Parcelable implementation not working. App still makes network calls on device rotation

I have a fragment where I am making network calls to an API. My model implements Parcelable in order to save the state on device rotation. I have implemented the method but when the device is rotated, it still makes a network request. Somehow the Parcelable implementation isn't working.
Here's my code
Movie.java (MODEL)
package com.execube.genesis.model;
import android.content.Context;
import android.os.Parcel;
import android.os.Parcelable;
/**
* Created by Prateek Phoenix on 4/24/2016.
*/
public class Movie implements Parcelable {
private int mId;
private String mOriginalTitle;
private String mTitle;
private String mPosterPath;
private String mOverview;
private float mVoteAverage;
private Movie(Parcel source) {
mId=source.readInt();
mOriginalTitle=source.readString();
mTitle=source.readString();
mPosterPath=source.readString();
mOverview=source.readString();
mVoteAverage=source.readFloat();
}
public Movie() {
}
public int getId() {
return mId;
}
public void setId(int id) {
mId = id;
}
public String getOriginalTitle() {
return mOriginalTitle;
}
public void setOriginalTitle(String originalTitle) {
mOriginalTitle = originalTitle;
}
public String getTitle() {
return mTitle;
}
public void setTitle(String title) {
mTitle = title;
}
public String getPosterPath() {
return mPosterPath;
}
public void setPosterPath(String posterPath) {
mPosterPath = posterPath;
}
public String getOverview() {
return mOverview;
}
public void setOverview(String overview) {
mOverview = overview;
}
public float getVoteAverage() {
return mVoteAverage;
}
public void setVoteAverage(float voteAverage) {
mVoteAverage = voteAverage;
}
#Override
public int describeContents() {
return 0;
}
#Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeInt(mId);
dest.writeString(mOriginalTitle);
dest.writeString(mTitle);
dest.writeString(mPosterPath);
dest.writeString(mOverview);
dest.writeFloat(mVoteAverage);
}
public static final Parcelable.Creator<Movie> CREATOR= new Parcelable.Creator<Movie>(){
#Override
public Movie createFromParcel(Parcel source) {
return new Movie(source);
}
#Override
public Movie[] newArray(int size) {
return new Movie[0];
}
};
}
PopularMoviesFragment.java
package com.execube.genesis.views;
import android.content.res.Configuration;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.widget.GridLayoutManager;
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.ImageView;
import com.execube.genesis.R;
import com.execube.genesis.model.Movie;
import com.execube.genesis.utils.API;
import com.execube.genesis.utils.OkHttpHandler;
import com.squareup.picasso.Picasso;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.IOException;
import java.util.ArrayList;
import okhttp3.Call;
import okhttp3.Callback;
import okhttp3.Response;
/**
* Created by Prateek Phoenix on 4/24/2016.
*/
public class PopularMoviesFragment extends Fragment {
private static final String TAG = "HELLO WORLD";
private static final String POPULAR_MOVIES_ARRAY ="popular_movies" ;
private ArrayList<Movie> mMovies;
private RecyclerView popularMoviesList = null;
private View progressBarPopular = null;
public PopularMoviesFragment() {
//empty constructor required
}
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if(savedInstanceState!=null)
{
mMovies=savedInstanceState.getParcelableArrayList(POPULAR_MOVIES_ARRAY);
}
else {
String url = API.BASE_URL+API.API_KEY+API.SORT_POPULARITY;
OkHttpHandler handler= new OkHttpHandler(url, apiCallback);
handler.fetchData();
}
}
#Override
public void onSaveInstanceState(Bundle outState) {
outState.putParcelableArrayList(POPULAR_MOVIES_ARRAY,mMovies);//Saving state of the ArrayList to avoid the network calls.
super.onSaveInstanceState(outState);
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View content = inflater.inflate(R.layout.fragment_popular_movies,container,false);
popularMoviesList = (RecyclerView) content.findViewById(R.id.popular_recyclerView);
progressBarPopular = content.findViewById(R.id.progressBar_popular);
if(getActivity().getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT){
popularMoviesList.setLayoutManager(new GridLayoutManager(getActivity(), 2));
}
else{
popularMoviesList.setLayoutManager(new GridLayoutManager(getActivity(), 3));
}
PopularMoviesAdapter mAdapter = new PopularMoviesAdapter();
popularMoviesList.setAdapter(mAdapter);
return content;
}
private Callback apiCallback = new Callback() {
#Override
public void onFailure(Call call, IOException e) {
//TODO show error message from here but in UI thread
}
#Override
public void onResponse(Call call, Response response) throws IOException {
try {
mMovies= parseItems(response.body().string());
} catch (Exception e) {
Log.v(TAG,"Exception caught: ",e);
}
getActivity().runOnUiThread(new Runnable() {
#Override
public void run() {
progressBarPopular.setVisibility(View.GONE);
popularMoviesList.setVisibility(View.VISIBLE);
//TODO add adapter
}
});
}
};
private class PopularMoviesViewHolder extends RecyclerView.ViewHolder{
private ImageView mPosterImage;
public PopularMoviesViewHolder(View itemView) {
super(itemView);
mPosterImage= (ImageView)itemView.findViewById(R.id.poster);
}
}
private class PopularMoviesAdapter extends RecyclerView.Adapter<PopularMoviesViewHolder>
{
#Override
public PopularMoviesViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view= LayoutInflater.from(getActivity()).inflate(R.layout.movie_item,parent,false);
return new PopularMoviesViewHolder(view);
}
#Override
public void onBindViewHolder(PopularMoviesViewHolder holder, int position) {
final Movie movie=mMovies.get(position);
Picasso.with(getActivity()).load(API.IMAGE_URL+API.IMAGE_SIZE_185+movie.getPosterPath())
.into(holder.mPosterImage);
}
#Override
public int getItemCount() {
return mMovies.size();
}
}
private ArrayList<Movie> parseItems( String jsonResponse) throws JSONException{
JSONObject jsonData= new JSONObject(jsonResponse);
JSONArray moviesJSONArray= jsonData.getJSONArray("results");
ArrayList<Movie> Movies= new ArrayList<>();
for (int i = 0; i <moviesJSONArray.length() ; i++) {
Movie movie= new Movie();
JSONObject movieJson= moviesJSONArray.getJSONObject(i);
movie.setId(movieJson.getInt("id"));
movie.setOriginalTitle(movieJson.getString("original_title"));
movie.setTitle(movieJson.getString("title"));
movie.setPosterPath(movieJson.getString("poster_path"));
movie.setOverview(movieJson.getString("overview"));
movie.setVoteAverage((float) movieJson.getDouble("vote_average"));
Movies.add(movie);
}
return Movies;
}
}
OkhttpHandler.java (networking code)
package com.execube.genesis.utils;
import okhttp3.Cache;
import okhttp3.Call;
import okhttp3.Callback;
import okhttp3.OkHttpClient;
import okhttp3.Request;
/**
* Created by Prateek Phoenix on 4/24/2016.
*/
public class OkHttpHandler {
private String queryUrl;
private static final String TAG = "CustomTAG1";
private String mResponse;
private Callback mCallback;
public OkHttpHandler(String Url, Callback callback) {
this.mCallback = callback;
this.queryUrl = Url;
}
public void fetchData() {
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.url(queryUrl)
.build();
Call call = client.newCall(request);
call.enqueue(mCallback);
}
}
ViewPagerFragment.java
package com.execube.genesis.views;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.execube.genesis.R;
/**
* Created by Prateek Phoenix on 4/24/2016.
*/
public class ViewPagerFragment extends Fragment {
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view= inflater.inflate(R.layout.fragment_viewpager,container,false);
ViewPager viewPager= (ViewPager)view.findViewById(R.id.viewPager);
TabLayout tabLayout=(TabLayout)view.findViewById(R.id.tabLayout);
final PopularMoviesFragment fragment1= new PopularMoviesFragment();
final TopRatedMoviesFragment fragment2= new TopRatedMoviesFragment();
viewPager.setAdapter(new FragmentPagerAdapter(getChildFragmentManager()) {
#Override
public Fragment getItem(int position) {
return position==0?fragment1:fragment2;
}
#Override
public int getCount() {
return 2;
}
#Override
public CharSequence getPageTitle(int position) {
return position==0?"POPULAR":"TOP RATED";
}
});
tabLayout.setupWithViewPager(viewPager);
return view;
}
}
MoviesActivity.java
package com.execube.genesis.views;
import android.graphics.Color;
import android.os.Build;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import com.execube.genesis.R;
public class MoviesActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_movies);
View view= findViewById(R.id.viewpager_container);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
view.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR);
getWindow().setStatusBarColor(Color.TRANSPARENT);
}
FragmentManager fragmentManager= getSupportFragmentManager();
Fragment fragment= fragmentManager.findFragmentById(R.id.viewpager_container);
if(fragment==null)
{
fragment= new ViewPagerFragment();
fragmentManager.beginTransaction()
.add(R.id.viewpager_container,fragment)
.commit();
}
}
}

I think you maybe made an error in your Activity like add or replace your fragment when re-creating your activity (when your device is rotated, your activity is recreated too).
About handling orientation changed, you can setRetainInstance() for your Fragment. Handling Runtime Changes:
If restarting your activity requires that you recover large sets of data, re-establish a network connection, or perform other intensive operations, then a full restart due to a configuration change might be a slow user experience. Also, it might not be possible for you to completely restore your activity state
When the Android system shuts down your activity due to a configuration
change, the fragments of your activity that you have marked to retain are not destroyed. You can add such fragments to your activity to preserve stateful objects.
// this method is only called once for this fragment
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// retain this fragment
setRetainInstance(true);
}
// find the retained fragment on activity restarts
FragmentManager fm = getFragmentManager();
dataFragment = (DataFragment) fm.findFragmentByTag(“data”);
// create the fragment and data the first time
if (dataFragment == null) {
// add the fragment
dataFragment = new DataFragment();
fm.beginTransaction().add(dataFragment, “data”).commit();
// load the data from the web
dataFragment.setData(loadMyData());
}
Caution: While you can store any object, you should never pass an object that is tied to the Activity, such as a Drawable, an Adapter, a View or any other object that's associated with a Context. If you do, it will leak all the views and resources of the original activity instance. (Leaking resources means that your application maintains a hold on them and they cannot be garbage-collected, so lots of memory can be lost.)
Update
I'm not sure, but in your case, you should setRetainInstance() for you ViewPagerFragment and:
// make those fragments global variable.
PopularMoviesFragment fragment1= new PopularMoviesFragment();
TopRatedMoviesFragment fragment2= new TopRatedMoviesFragment();

Inside your activity, replace the following code:
FragmentManager fragmentManager= getSupportFragmentManager();
Fragment fragment= fragmentManager.findFragmentById(R.id.viewpager_container);
if(fragment==null)
{
fragment= new ViewPagerFragment();
fragmentManager.beginTransaction()
.add(R.id.viewpager_container,fragment)
.commit();
}
with the following instead:
if(savedInstanceState == null) {
fragment= new ViewPagerFragment();
fragmentManager.beginTransaction()
.add(R.id.viewpager_container,fragment)
.commit();
}

Try calling onSaveInstanceState in your main Activity with super.onSaveInstanceState(outState).