Return extras onActivityResult always null

Issue

I am building my first app and I am running into an issue with passing on extras in an intent for onActivityResult. I tried looking for the answer but I cant find one that seems to fit. As far as I can tell i follow the "normal" structure of using intents to pass data making sure to use the intent passed by the setResult() and not the intent of the activity. But my knowledge is very limited so probably I am just overlooking something obvious.

The idea of the app is score tracking during a card game.

My apps consists for now out of 3 activities.

1. MainActivity is the home screen to fill in the player names.
2. StartToWiez takes those names and creates a table that will keep score.
3. From this page a new activity (StartRound) is started to calculate the score based on input of the user.
4. This score should then be passed back to the StartToWiez activity and the StartToWiez activity should populate the table with the score.

I tried passing a bundle in the extras of the intent that is passed in the setResult(). And I tried putting the score as direct extras of the intent. With both ways I get the same error. So it looks like the returned extras do not exist in the returned intent. But I do not understand why not as with the setResult() the intent has the extras.

Error:

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.wiezen, PID: 7924
java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=Intent { (has extras) }} to activity {com.example.wiezen/com.example.wiezen.StartToWiez}: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.Integer.intValue()' on a null object reference
    at android.app.ActivityThread.deliverResults(ActivityThread.java:4976)
    at android.app.ActivityThread.handleSendResult(ActivityThread.java:5017)
    at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:51)
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2123)
    at android.os.Handler.dispatchMessage(Handler.java:107)
    at android.os.Looper.loop(Looper.java:214)
    at android.app.ActivityThread.main(ActivityThread.java:7710)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:516)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.Integer.intValue()' on a null object reference
    at com.example.wiezen.StartToWiez.onActivityResult(StartToWiez.java:65)
    at android.app.Activity.dispatchActivityResult(Activity.java:8140)
    at android.app.ActivityThread.deliverResults(ActivityThread.java:4969)
    at android.app.ActivityThread.handleSendResult(ActivityThread.java:5017) 
    at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:51) 
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2123) 
    at android.os.Handler.dispatchMessage(Handler.java:107) 
    at android.os.Looper.loop(Looper.java:214) 
    at android.app.ActivityThread.main(ActivityThread.java:7710) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:516) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:950) 

Activity: MainActivity.java

package com.example.wiezen;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.view.View;
import android.widget.EditText;


public class MainActivity extends AppCompatActivity {

//create a Bundle object
Bundle extras = new Bundle();
SharedPreferences sharedpreferences;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    sharedpreferences = getSharedPreferences("Settings", Context.MODE_PRIVATE);
}
/** Called when the user taps the Send button */
public void startToWiez(View view) {
    Intent intent = new Intent(this, StartToWiez.class);
    EditText player1Name = (EditText) findViewById(R.id.Player1Name);
    String player1NameText = player1Name.getText().toString();

    EditText player2Name = (EditText) findViewById(R.id.Player2Name);
    String player2NameText = player2Name.getText().toString();

    EditText player3Name = (EditText) findViewById(R.id.Player3Name);
    String player3NameText = player3Name.getText().toString();

    EditText player4Name = (EditText) findViewById(R.id.Player4Name);
    String player4NameText = player4Name.getText().toString();

    SharedPreferences.Editor editor = sharedpreferences.edit();
    editor.putString("PLAYER1_NAME", player1NameText);
    editor.putString("PLAYER2_NAME", player2NameText);
    editor.putString("PLAYER3_NAME", player3NameText);
    editor.putString("PLAYER4_NAME", player4NameText);
    editor.apply();

    startActivity(intent);
}}

Activity StartToWiez.java

package com.example.wiezen;

import androidx.appcompat.app.AppCompatActivity;

import android.annotation.SuppressLint;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.EditText;
import android.widget.TableLayout;
import android.widget.TableRow;
import android.widget.TextView;

public class StartToWiez extends AppCompatActivity {

Bundle extras;
SharedPreferences sharedpreferences;
Integer player1Score;
Integer player2Score;
Integer player3Score;
Integer player4Score;
Integer aantalRondes = 0;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_start_to_wiez);
    // Get the Intent that started this activity and extract the string
    Intent intent = getIntent();
    sharedpreferences = getSharedPreferences("Settings", Context.MODE_PRIVATE);
    extras = intent.getExtras();
    // Capture the layout's TextView and set the string as its text
    TextView header1 = findViewById(R.id.Player1Header);
    TextView header2 = findViewById(R.id.Player2Header);
    TextView header3 = findViewById(R.id.Player3Header);
    TextView header4 = findViewById(R.id.Player4Header);
    header1.setText(sharedpreferences.getString("PLAYER1_NAME", "Player 1"));
    header2.setText(sharedpreferences.getString("PLAYER2_NAME", "Player 2"));
    header3.setText(sharedpreferences.getString("PLAYER3_NAME", "Player 3"));
    header4.setText(sharedpreferences.getString("PLAYER4_NAME", "Player 4"));
}

public void startRound(View view) {
    Intent intent = new Intent(this, StartRound.class);
    startActivityForResult(intent, 1);


}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (resultCode == RESULT_OK) {
        aantalRondes++;

        TableLayout table = (TableLayout) StartToWiez.this.findViewById(R.id.tableLayout);
        // Inflate your row "template" and fill out the fields.
        TableRow row = (TableRow) LayoutInflater.from(StartToWiez.this).inflate(R.layout.tablerow, null);

        player1Score += data.getIntExtra("Player1Score", 0);
        player2Score += data.getIntExtra("Player2Score", 0);
        player3Score += data.getIntExtra("Player3Score", 0);
        player4Score += data.getIntExtra("Player4Score", 0);

        ((TextView) row.findViewById(R.id.player1Score)).setText(String.valueOf(player1Score));
        ((TextView) row.findViewById(R.id.player2Score)).setText(String.valueOf(player2Score));
        ((TextView) row.findViewById(R.id.player3Score)).setText(String.valueOf(player3Score));
        ((TextView) row.findViewById(R.id.player4Score)).setText(String.valueOf(player4Score));
        table.addView(row);

        if(aantalRondes == 4){
            TableRow row2 = (TableRow) LayoutInflater.from(StartToWiez.this).inflate(R.layout.line_after_4_rounds, null);
            table.addView(row2);
            aantalRondes = 0;
        }
    }
}

}

Activity: StartRound.java

package com.example.wiezen;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.CheckedTextView;
import android.widget.Spinner;
import android.widget.TextView;

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;

public class StartRound extends AppCompatActivity {


SharedPreferences sharedpreferences;
Spinner gameType;
Spinner troef;
Spinner aantalSlagen;
ArrayAdapter<String> adapter;
ArrayAdapter<String> adapterTroef;
ArrayAdapter<String> adapterAantalSlagen;
CheckBox player1;
CheckBox player2;
CheckBox player3;
CheckBox player4;
CheckBox player1Win;
CheckBox player2Win;
CheckBox player3Win;
CheckBox player4Win;
Boolean[] winners = new Boolean[4];


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_start_round);
    // Get the Intent that started this activity and extract the string
    Intent intent = getIntent();

    //get the shared prefs that store player names
    sharedpreferences = getSharedPreferences("Settings", Context.MODE_PRIVATE);

    //set player names for the checkboxes
    player1 = findViewById(R.id.player1Checkbox);
    player2 = findViewById(R.id.player2Checkbox);
    player3 = findViewById(R.id.player3Checkbox);
    player4 = findViewById(R.id.player4Checkbox);
    player1.setText(sharedpreferences.getString("PLAYER1_NAME", "defaultValue"));
    player2.setText(sharedpreferences.getString("PLAYER2_NAME", "defaultValue"));
    player3.setText(sharedpreferences.getString("PLAYER3_NAME", "defaultValue"));
    player4.setText(sharedpreferences.getString("PLAYER4_NAME", "defaultValue"));

    player1Win = findViewById(R.id.player1Win);
    player2Win = findViewById(R.id.player2Win);
    player3Win = findViewById(R.id.player3Win);
    player4Win = findViewById(R.id.player4Win);

    //set the game type dropdown values for the spinner
    gameType = (Spinner) findViewById(R.id.gameType);
    adapter = new ArrayAdapter<String>(StartRound.this,android.R.layout.simple_list_item_1, getResources().getStringArray(R.array.typeSpel));
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    gameType.setAdapter(adapter);

    //set the game type dropdown values for the spinner
    troef = (Spinner) findViewById(R.id.troef);
    adapterTroef = new ArrayAdapter<String>(StartRound.this,android.R.layout.simple_list_item_1, getResources().getStringArray(R.array.troef));
    adapterTroef.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    troef.setAdapter(adapterTroef);

    //set the game type dropdown values for the spinner
    aantalSlagen = (Spinner) findViewById(R.id.aantalSlagen);
    adapterAantalSlagen = new ArrayAdapter<String>(StartRound.this,android.R.layout.simple_list_item_1, getResources().getStringArray(R.array.aantalSlagen));
    adapterAantalSlagen.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    aantalSlagen.setAdapter(adapterAantalSlagen);

    //on change of game type spinner do something
    gameType.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parentView, View selectedItemView, int position, long id) {

        }


        @Override
        public void onNothingSelected(AdapterView<?> parentView) {
            // your code here
        }

    });

    // using finsih()
    Button closeButton = (Button) findViewById(R.id.calculateScore);
    closeButton.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            winners[0] = player1Win.isChecked();
            winners[1] = player2Win.isChecked();
            winners[2] = player3Win.isChecked();
            winners[3] = player4Win.isChecked();
            Boolean[] players = new Boolean[4];
            players[0] = player1.isChecked();
            players[1] = player2.isChecked();
            players[2] = player3.isChecked();
            players[3] = player4.isChecked();
            int[] score = new int[4];

            Integer behaaldAantalSlagen = (Integer) Integer.parseInt(aantalSlagen.getSelectedItem().toString());
            String gametypetest = gameType.getSelectedItem().toString();

            switch(gametypetest) {
                //algorithm to define the score based on the gametype. score is added to the array score
            }
            Intent returnIntent = getIntent();
            returnIntent.putExtra("Player1Score", score[0]);
            returnIntent.putExtra("Player2Score", score[1]);
            returnIntent.putExtra("Player3Score", score[2]);
            returnIntent.putExtra("Player4Score", score[3]);
            setResult(RESULT_OK, returnIntent);
            StartRound.this.finish();
        }
    });

}

}

Solution

I think I have figured this out now. I am trying to use =+ on an unitialized integer. So on top when I define my integer it is not set to 0. Which is the starting point of the game. All players should have score 0.

So when using += on the integer it is complaining not about the intent or data, but about the fact that you cannot add to a null value integer.

Answered By - Kristijn