Null Pointer Exception need help figuring it out

Question

I'm attempting to create an application that keeps track of statistics throughout your golf game and generates a tip catered to your golf game if need be. I am keeping track of the holes by putting them into an array list. I found that you can pass objects between activities using googles GSON, I followed the tutorial but I feel that this passing of the array between activities is what ultimately is causing the NPE, but I am not sure.

Here is the full stack trace

11-04 11:06:02.218: E/Trace(774): error opening trace file: No such file or directory (2)
11-04 11:06:02.949: D/dalvikvm(774): GC_FOR_ALLOC freed 77K, 2% free 10958K/11143K, paused 46ms, total 48ms
11-04 11:06:03.048: D/dalvikvm(774): GC_CONCURRENT freed 168K, 3% free 11241K/11527K, paused >25ms+5ms, total 65ms
11-04 11:06:03.058: D/dalvikvm(774): WAIT_FOR_CONCURRENT_GC blocked 29ms
11-04 11:06:03.448: D/gralloc_goldfish(774): Emulator without GPU emulation detected.
11-04 11:06:06.168: D/AndroidRuntime(774): Shutting down VM
11-04 11:06:06.168: W/dalvikvm(774): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
11-04 11:06:06.208: E/AndroidRuntime(774): FATAL EXCEPTION: main
11-04 11:06:06.208: E/AndroidRuntime(774): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.testapp/com.example.testapp.StatActivity}: java.lang.NullPointerException
11-04 11:06:06.208: E/AndroidRuntime(774):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1983)
11-04 11:06:06.208: E/AndroidRuntime(774):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
11-04 11:06:06.208: E/AndroidRuntime(774):  at android.app.ActivityThread.access$600(ActivityThread.java:130)
11-04 11:06:06.208: E/AndroidRuntime(774):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
11-04 11:06:06.208: E/AndroidRuntime(774):  at android.os.Handler.dispatchMessage(Handler.java:99)
11-04 11:06:06.208: E/AndroidRuntime(774):  at android.os.Looper.loop(Looper.java:137)
11-04 11:06:06.208: E/AndroidRuntime(774):  at android.app.ActivityThread.main(ActivityThread.java:4745)
11-04 11:06:06.208: E/AndroidRuntime(774):  at java.lang.reflect.Method.invokeNative(Native Method)
11-04 11:06:06.208: E/AndroidRuntime(774):  at java.lang.reflect.Method.invoke(Method.java:511)
11-04 11:06:06.208: E/AndroidRuntime(774):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
11-04 11:06:06.208: E/AndroidRuntime(774):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-04 11:06:06.208: E/AndroidRuntime(774):  at dalvik.system.NativeStart.main(Native Method)
11-04 11:06:06.208: E/AndroidRuntime(774): Caused by: java.lang.NullPointerException
11-04 11:06:06.208: E/AndroidRuntime(774):  at android.app.Activity.findViewById(Activity.java:1825)
11-04 11:06:06.208: E/AndroidRuntime(774):  at com.example.testapp.StatActivity.<init>(StatActivity.java:38)
11-04 11:06:06.208: E/AndroidRuntime(774):  at java.lang.Class.newInstanceImpl(Native Method)
11-04 11:06:06.208: E/AndroidRuntime(774):  at java.lang.Class.newInstance(Class.java:1319)
11-04 11:06:06.208: E/AndroidRuntime(774):  at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
11-04 11:06:06.208: E/AndroidRuntime(774):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1974)
11-04 11:06:06.208: E/AndroidRuntime(774):  ... 11 more
11-04 11:06:06.388: D/dalvikvm(774): GC_CONCURRENT freed 266K, 4% free 11366K/11719K, paused >17ms+64ms, total 142ms
11-04 11:11:06.349: I/Process(774): Sending signal. PID: 774 SIG: 9

and the relevant activities

StatActivity

  package com.example.testapp;

import java.util.ArrayList;
import java.util.List;

import com.example.testapp.StatActivity;
import com.example.testapp.CustomOnItemSelectedListener;
import com.example.testapp.R;
import com.google.gson.Gson;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.Toast;

public class StatActivity extends Activity implements OnClickListener {
    private Spinner driving_spinner;
    private Spinner approach_spinner;
    private Spinner chipping_spinner;
    private Spinner sandshot_spinner;
    private Spinner putting_spinner;
    private int hole = 1;
    private boolean driving_spinner_selected = false;
    private boolean approach_spinner_selected = false;
    private boolean chipping_spinner_selected = false;
    private boolean sandshot_spinner_selected = false;
    private boolean putting_spinner_selected = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_stat);
        Button homeButton = (Button) findViewById(R.id.homeButton);
        Button helpButton = (Button) findViewById(R.id.helpButton);
        Button nextHoleButton = (Button) findViewById(R.id.nextHoleButton);
        driving_spinner = (Spinner) findViewById(R.id.drivingSpinner);
        approach_spinner = (Spinner) findViewById(R.id.approachSpinner);
        chipping_spinner = (Spinner) findViewById(R.id.chippingSpinner);
        sandshot_spinner = (Spinner) findViewById(R.id.sandShotSpinner);
        putting_spinner = (Spinner) findViewById(R.id.puttingSpinner);
        nextHoleButton.setOnClickListener(this);
        helpButton.setOnClickListener(this);
        homeButton.setOnClickListener(this);
        addItemsToDrivingSpinner();
        addItemsToChippingSpinner();
        addItemsToPuttingSpinner();
        addItemsToApproachSpinner();
        addItemsToSandShotSpinner();
        addListenerOnDrivingSpinnerItemSelection();
        addListenerOnChippingSpinnerItemSelection();
        addListenerOnPuttingSpinnerItemSelection();
        addListenerOnApproachSpinnerItemSelection();
        addListenerOnSandShotSpinnerItemSelection();

    }


    Gson gS = new Gson();
   String src = getIntent().getStringExtra("round");
   Round round = gS.fromJson(src, Round.class);

    // add items into spinner dynamically
      public void addItemsToDrivingSpinner() {

        List<String> list = new ArrayList<String>();
            list.add("Left");
            list.add("Right");
            list.add("Fairway Hit");
            list.add("Par Three");
        ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
            android.R.layout.simple_spinner_item, list);
        dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        driving_spinner.setAdapter(dataAdapter);
      }

      public void addItemsToApproachSpinner() {

          List<String> list = new ArrayList<String>();
            list.add("Left");
            list.add("Right");
            list.add("Short");
            list.add("Long");
            list.add("Green Hit");
            list.add("No Oppurtunity");
            ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
                android.R.layout.simple_spinner_item, list);
            dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            approach_spinner.setAdapter(dataAdapter);
          }

      public void addItemsToChippingSpinner() {

          List<String> list = new ArrayList<String>();
            list.add("Yes Up and Down");
            list.add("No Up and Down");
            list.add("No Oppurtunity");
            ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
                android.R.layout.simple_spinner_item, list);
            dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            chipping_spinner.setAdapter(dataAdapter);
          }

      public void addItemsToSandShotSpinner() {

          List<String> list = new ArrayList<String>();
            list.add("Yes Sand Save");
            list.add("No Sand Save");
            list.add("No Oppurtunity");
            ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
                android.R.layout.simple_spinner_item, list);
            dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            sandshot_spinner.setAdapter(dataAdapter);
          }

      public void addItemsToPuttingSpinner() {

          List<String> list = new ArrayList<String>();
            list.add("0");
            list.add("1");
            list.add("2");
            list.add("3");
            list.add("4");
            list.add("5+");
            ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
                android.R.layout.simple_spinner_item, list);
            dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
            putting_spinner.setAdapter(dataAdapter);
          }

      public void addListenerOnDrivingSpinnerItemSelection() {
            driving_spinner.setOnItemSelectedListener(new CustomOnItemSelectedListener());
            driving_spinner_selected = true;
      }
      public void addListenerOnApproachSpinnerItemSelection() {
            approach_spinner.setOnItemSelectedListener(new CustomOnItemSelectedListener());
            approach_spinner_selected = true;
      }
      public void addListenerOnChippingSpinnerItemSelection() {
            chipping_spinner.setOnItemSelectedListener(new CustomOnItemSelectedListener());
            chipping_spinner_selected = true;
      }
      public void addListenerOnPuttingSpinnerItemSelection() {
            putting_spinner.setOnItemSelectedListener(new CustomOnItemSelectedListener());
            putting_spinner_selected = true;
      }
      public void addListenerOnSandShotSpinnerItemSelection() {
            sandshot_spinner.setOnItemSelectedListener(new CustomOnItemSelectedListener());
            sandshot_spinner_selected = true;
          }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.stat, 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();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onClick(View v) {
        if(v.getId() == R.id.homeButton){
            Intent intent = new Intent(getApplicationContext(), HomeActivity.class);
            startActivity(intent);  

        }else if(v.getId() == R.id.helpButton){
            Intent intent = new Intent(getApplicationContext(), InstructionsActivity.class);
                startActivity(intent); 

        }else if(v.getId() == R.id.nextHoleButton){
            boolean filledIn = false;
            if(driving_spinner_selected && chipping_spinner_selected && putting_spinner_selected && sandshot_spinner_selected && approach_spinner_selected)
                filledIn = true;
            if(filledIn) {
            hole++;
            round.setStats(String.valueOf(driving_spinner.getSelectedItem()),String.valueOf(putting_spinner.getSelectedItem()),String.valueOf(sandshot_spinner.getSelectedItem()),String.valueOf(chipping_spinner.getSelectedItem()),String.valueOf(approach_spinner.getSelectedItem()),hole);
             Intent intent = new Intent(getApplicationContext(), StatActivity.class);
                String target = gS.toJson(round);
                intent.putExtra("round", target);
            if(round.needTip()) {

                String tip  = round.generateTip();
                Toast.makeText(StatActivity.this,
                    tip,
                Toast.LENGTH_LONG).show();
            }
            startActivity(intent);
            }
            else {
                Toast.makeText(StatActivity.this,
                        "Please fill in all statistics before continuing.",
                    Toast.LENGTH_SHORT).show();
            }
          }
        }
    }

HomeActivity

package com.example.testapp;

import com.google.gson.Gson;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;


public class HomeActivity extends Activity implements OnClickListener{



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);
        Button startRoundButton = (Button) findViewById(R.id.startRoundButton);
        Button homeHelpButton = (Button) findViewById(R.id.homeHelpButton);
        homeHelpButton.setOnClickListener(this);
        startRoundButton.setOnClickListener(this);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.home, menu);
        return true;
    }

    public void onClick(View v)
    {
        if(v.getId() == R.id.startRoundButton){
            Round round = new Round();
            Intent i = new Intent(getApplicationContext(),StatActivity.class);
            Gson gS = new Gson();
            String target = gS.toJson(round);
            i.putExtra("round", target);
            startActivity(i);



        }else if(v.getId() == R.id.homeHelpButton){
            Intent intent = new Intent(getApplicationContext(), InstructionsActivity.class);
                startActivity(intent);  
        }
    }

    @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();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.testapp"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="14"
        android:targetSdkVersion="19" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".HomeActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".StatActivity"
            android:label="@string/title_activity_stat" >
        </activity>
        <activity
            android:name=".InstructionsActivity"
            android:label="@string/title_activity_instructions" >
        </activity>
    </application>

</manifest>

Activity_Stat.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/here_link"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.testapp.StatActivity" >

    <Spinner
        android:id="@+id/puttingSpinner"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/approachSpinner"
        android:layout_alignLeft="@+id/approachSpinner"
        android:entries="@array/puttArr"
        android:prompt="@string/putting" />

    <Button
        android:id="@+id/nextHoleButton"
        android:layout_width="150dp"
        android:layout_height="100dp"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:background="@drawable/next_button_background" />

    <Spinner
        android:id="@+id/approachSpinner"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/sandShotSpinner"
        android:layout_alignLeft="@+id/sandShotSpinner"
        android:entries="@array/approachArr"
        android:prompt="@string/aproach" />

    <Spinner
        android:id="@+id/sandShotSpinner"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/nextHoleButton"
        android:layout_alignLeft="@+id/drivingSpinner"
        android:layout_marginBottom="19dp"
        android:entries="@array/sandShotArr"
        android:prompt="@string/sand_shot" />

    <Spinner
        android:id="@+id/drivingSpinner"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/puttingSpinner"
        android:layout_centerHorizontal="true"
        android:entries="@array/drivingArr"
        android:prompt="@string/driving" />

    <Button
        android:id="@+id/helpButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@+id/sandShotSpinner"
        android:layout_alignTop="@+id/homeButton"
        android:text="@string/help" />

    <Button
        android:id="@+id/homeButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/nextHoleButton"
        android:layout_alignParentLeft="true"
        android:text="@string/home" />

    <Spinner
        android:id="@+id/chippingSpinner"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_alignRight="@+id/drivingSpinner"
        android:entries="@array/chippingArr"
        android:prompt="@array/chippingArr" />

</RelativeLayout>

the Home activity is launched upon opening the app (which works) then the stat activity is started when Start round button is clicked and this is when the app stops. any thoughts or ideas will be helpful. Thank you!

Answer 1

This line

String src = getIntent().getStringExtra("round");

is your problem. When it's invoked, there's no intent to get.

All setup that needs the intent needs to be done inside onCreate(), by which time the intent is available. Your code is being run at construction time, which is too early.

You haven't really provided enough info to determine whether this is what's generating the NPE that you're hitting, but it's certainly going to need fixing even if there's something else wrong too.