NullPointer thrown not sure why

Question

I'm not sure why i am getting this error, it was working before, any help is appreciated. Trying to spawn a new activity upon spinner selection ( I have a working version with a list view inside, I decided to branch off to try a spinner, got pretty far and then got lost trying to figure out this error). It was working perfectly too, so I know that i has to be like 1-5 lines of code or something. Again, any help is appreciated.

Logcat

02-19 23:57:15.980: E/AndroidRuntime(350): FATAL EXCEPTION: main
02-19 23:57:15.980: E/AndroidRuntime(350): java.lang.RuntimeException: Unable to instantiate activity
ComponentInfo{com.example.jordanmaxportfolio/com.example.jordanmaxportfolio.MainActivity}: java.lang.NullPointerException
02-19 23:57:15.980: E/AndroidRuntime(350):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1569)
02-19 23:57:15.980: E/AndroidRuntime(350):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
02-19 23:57:15.980: E/AndroidRuntime(350):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
02-19 23:57:15.980: E/AndroidRuntime(350):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
02-19 23:57:15.980: E/AndroidRuntime(350):  at android.os.Handler.dispatchMessage(Handler.java:99)
02-19 23:57:15.980: E/AndroidRuntime(350):  at android.os.Looper.loop(Looper.java:123)
02-19 23:57:15.980: E/AndroidRuntime(350):  at android.app.ActivityThread.main(ActivityThread.java:3683)

Main Activity

package com.example.jordanmaxportfolio;


import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Spinner;
import android.widget.TextView;

public class MainActivity extends Activity
implements AdapterView.OnItemSelectedListener {

TextView selection;
ListView list;
Spinner spin = (Spinner) findViewById(R.id.spinner2);
public final static String exID="com.example.portfolio.MainActivity";

static final String[] items = new String[] {
    "36-2510 Game Engine Scripting I",  
    "36-2551 C++ I",    
    "36-3210 Game AI Programming",
    "36-3405 Authoring Interactive Media I & II" 
     };


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    list = (ListView)findViewById(R.id.listView1);
    String[] items = getResources().getStringArray(R.array.Classes);

    list.setAdapter(new ArrayAdapter<String>(MainActivity.this,android.R.layout.simple_list_item_1,items));

    list.setOnItemClickListener(new OnItemClickListener(){
        public void onItemClick(AdapterView<?> parent, View view,
                int postion, long id){

            Intent i =new Intent(MainActivity.this,ClassPage.class);
            i.putExtra(exID, String.valueOf(id));
            startActivity(i);
        }
        });

    selection = (TextView) findViewById(R.id.textView1);

    Spinner spin = (Spinner) findViewById(R.id.spinner2);
    spin.setOnItemSelectedListener(this);

    ArrayAdapter<String> aa = new ArrayAdapter<String>(
            this,
            android.R.layout.simple_spinner_item, 
            items);

    aa.setDropDownViewResource(
       android.R.layout.simple_spinner_dropdown_item);
    spin.setAdapter(aa);
}

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

public void onItemSelected(AdapterView<?> parent, View v, int position,
        long id) {
    // TODO Auto-generated method stub
    selection.setText(items[position]);
    Intent i =new Intent(MainActivity.this,ClassPage.class);
    i.putExtra(exID, String.valueOf(position));
    startActivity(i); 

}

/*spin.setOnItemSelectedListener(new OnItemSelectedListener()
{
    @Override
    public void onItemSelected(AdapterView<?> parent, View v, int position,
            long id) {
        Intent i =new Intent(MainActivity.this,ClassPage.class);
        i.putExtra(exID, String.valueOf(id));
        startActivity(i);  

    @Override
    public void onNothingSelected(AdapterView<?> parent) {
        // TODO Auto-generated method stub
    }
    }
});*/


  /* example I saw online, however not quite right */



public void onNothingSelected(AdapterView<?> parent) {
    // TODO Auto-generated method stub
    selection.setText("");

}

}

ClassPage

package com.example.jordanmaxportfolio;


import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.support.v4.app.NavUtils;
import android.annotation.TargetApi;
import android.content.Intent;
import android.os.Build;

public class ClassPage extends Activity {


private TextView passedView = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_class);

    String passedVar = getIntent().getStringExtra(MainActivity.exID);
    passedView = (TextView)findViewById(R.id.tv1);

    //passedView.setText("You have clicked item id: "+passedVar);
    if(passedVar.equals("0"))
    {
        passedView.setText("YAYY");

    }
    if(passedVar.equals("1"))
    {
        passedView.setText("Game Engine Scripting I");
        ImageView iv = (ImageView)findViewById(R.id.imageView1);
        iv.setImageResource(R.drawable.asteroids);
        TextView tv2 = (TextView)findViewById(R.id.tv2);
        tv2.setText("Using C# and Unity, I created a remake of the classic 'Asteroids!'. Dynamic difficulty level is the next addition.");
    }
    else if(passedVar.equals("2"))
    {
        passedView.setText("C++ I");
        ImageView iv = (ImageView)findViewById(R.id.imageView1);
        iv.setImageResource(R.drawable.poker);
        TextView tv2 = (TextView)findViewById(R.id.tv2);
        tv2.setText("Console GUI C++ Texas Hole 'Em Poker created by Neil Inglese and Jordan Max. Basic concept of game was to eliminate cursors. The game was completed, however we are re-doing it for our C++ II class to make it into the Xbox Live and Windows Store.");
    }
    else if(passedVar.equals("3"))
    {
        passedView.setText("Game AI Programming");
        ImageView iv = (ImageView)findViewById(R.id.imageView1);
        iv.setImageResource(R.drawable.game);
        TextView tv2 = (TextView)findViewById(R.id.tv2);
        tv2.setText("Currently enrolled in this class, we are learning about FSM's and C++ data structures such as stacks, vectors and queues. ");
    }
    else
    {
        passedView.setText("Authoring Interactive Media I & II");
        ImageView iv = (ImageView)findViewById(R.id.imageView1);
        iv.setImageResource(R.drawable.p);
        TextView tv2 = (TextView)findViewById(R.id.tv2);
        tv2.setText("Learned basic skills for HTML and CSS. Also divulged into HTML5, PHP, jQuery, and Javascript for web programming. Created my portfolio website based off knowledge learned.");
    }

    Button btn1 = (Button)findViewById(R.id.button1);

    // Show the Up button in the action bar.
    setupActionBar();
}
public void btnClicked(View view){
    Intent i = new Intent(this,MainActivity.class);
    startActivity(i);


}

/**
 * Set up the {@link android.app.ActionBar}, if the API is available.
 */
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
private void setupActionBar() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
        getActionBar().setDisplayHomeAsUpEnabled(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.class_page, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    case android.R.id.home:
        // This ID represents the Home or Up button. In the case of this
        // activity, the Up button is shown. Use NavUtils to allow users
        // to navigate up one level in the application structure. For
        // more details, see the Navigation pattern on Android Design:
        //
        // http://developer.android.com/design/patterns/navigation.html#up-vs-back
        //
        NavUtils.navigateUpFromSameTask(this);
        return true;
    }
    return super.onOptionsItemSelected(item);
}

}

acitvity_class.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: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=".ClassPage" >

<TextView
    android:id="@+id/tv1"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentRight="true"
    android:text="@string/hello_world" />

<ImageView
    android:id="@+id/imageView1"
    android:layout_width="wrap_content"
    android:layout_height="200dp"
    android:layout_alignLeft="@+id/tv1"
    android:layout_alignRight="@+id/tv1"
    android:layout_below="@+id/tv1"
    android:layout_marginTop="46dp"
    android:maxHeight="500dp"
    android:src="@drawable/ic_launcher" />

<TextView
    android:id="@+id/tv2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/imageView1"
    android:layout_alignParentRight="true"
    android:layout_below="@+id/imageView1"
    android:layout_marginLeft="21dp"
    android:layout_marginTop="60dp"
    android:text="TextView" />

<Button
    android:id="@+id/button1"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_alignRight="@+id/tv2"
    android:layout_below="@+id/tv2"
    android:layout_marginTop="20dp"
    android:onClick="btnClicked"
    android:text="Go Back" />

</RelativeLayout>

activity_main.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: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=".MainActivity" >

<TextView
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/hello_world" />

<ListView
    android:id="@+id/listView1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_below="@+id/spinner1" >
</ListView>

<Spinner
    android:id="@+id/spinner1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/textView1"
    android:layout_marginTop="67dp"
    android:layout_toLeftOf="@+id/listView1" />

<TextView
    android:id="@+id/textView2"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/textView1"
    android:layout_below="@+id/textView1"
    android:text="@string/hello" />

<Spinner
    android:id="@+id/spinner2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/textView2"
    android:layout_below="@+id/textView2"
    android:layout_marginLeft="57dp" />

</RelativeLayout>

Answer 1

You are attempting to initialize the class member spin with a call to findViewById(). However, at the time your Activity class is constructed, the layout will not yet be inflated. This means you must wait until onCreate() to do this initialization. As other's have answered, you need to put spin = (Spinnder) findViewById(R.id.spinner2) in the onCreate() method after the call to setContentView().

To understand this in more detail, I strongly suggest that you read about the Activity life-cycle.

Answer 2

add this

Spinner spin=(Spinner)findViewById(R.id.spinner2);

in your mainactivity.

Answer 3

Put this

Spinner spin = (Spinner) findViewById(R.id.spinner2);

Inside your onCreate() after setContentView(R.layout.activity_main);

Answer 4

Try this..

Do this inside OnCreate after setContentView(R.layout.activity_main); in MainActivity

Spinner spin = (Spinner) findViewById(R.id.spinner2);

OR

Remove Spinner spin = (Spinner) findViewById(R.id.spinner2); from Global variable