I've been researching this and attempting for hours. I've taken after this post for an example of how to pass arguments to a fragment: Send data from activity to fragment in android
I'm trying to pass a custom object from an activity, to a fragment. I chose to implement serializable and pass the object using:
bundle.putSerializable("key", Serializable).
I'm getting the error
java.lang.NullPointerException:Attempt to invoke virtual methodjava.io.Serializable android.os.Bundle.getSerializable(java.lang.String)on a null object reference
when I'm trying to set my object equal to the arguments passed in from the activity.
here is my object
public class Player implements Serializable {
   int attack;
   private int tempAttack;
   int defense;
   private int tempDefense;
   int pop;
   int level;
   String t1Evo;
   String t2Evo;
   String t3Evo;
   public Player() {
      attack = 0;
      tempAttack = 0;
      defense = 0;
      tempDefense = 0;
      pop = 20;
      level = 1;
      t1Evo = null;
      t2Evo = null;
      t3Evo = null;
   }
}
Then here is my activity from which I am passing, I eventually want to pass all four of my objects, but I right now I'm trying to get at least one to successfully pass.
public class GameScreen extends FragmentActivity {
// Anytime you need to grab data from the players,
// this screen will hold them.
   private Player player1;
   private Player player2;
   private Player player3;
   private Player player4;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       requestWindowFeature(Window.FEATURE_NO_TITLE);
       setContentView(R.layout.activity_game_screen);
       // Instantiate the player objects
       player1 = new Player();
       player2 = new Player();
       player3 = new Player();
       player4 = new Player();
       // put the objects to send to our fragment in a bundle
       PlayerInformation newFragment = new PlayerInformation();
       Bundle args = new Bundle();
       args.putSerializable("Player1", player1);
       newFragment.setArguments(args);
       // start transaction
       FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
       // Replace whatever is in the fragment_player_information view with this fragment,
       transaction.add(R.id.playerInformation, newFragment);
       transaction.commit();
   }
}
And then the fragment which throws the Null Pointer Exception, I've indicated the line with "-->" package com.cs246.spencer.naturalselection;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import java.io.Serializable;
/**
 * Fragment that displays the Player information on GameScreen
 */
public class PlayerInformation extends Fragment {
   Context context;
   Player player1;
   Player player2;
   Player player3;
   Player player4;
   public PlayerInformation(){
       this.context=context;
   }
   @Override
   public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
       // grab the objects passed from GameScreen
       Bundle args = getArguments();
   --> player1 = (Player) args.getSerializable("Player1");
       player1 = (Player) getArguments().getSerializable("Player1");
       // Inflate the layout for this fragment
       return inflater.inflate(R.layout.fragment_player_information, container, false);
   }
   public void Update() {
       TextView player1Pop = (TextView) ((Activity)context).findViewById(R.id.player1Pop);
       player1Pop.setText(player1.pop);
   }
}
 
     
    