Question

I have a line of code that when I am debugging a nullpointerexception I can see that it is the cause of my app crashing.

The line of code that is causing the nullpointer is this:

ListView storeList = (ListView) findViewById(R.id.storeList);

and then in debug mode it crash when it tries to assign this:

storeList.setAdapter(arrayAdapter2);

I do not know why the object is not initializing. The ArrayAdapter below it initializes fine. If you

Below is the actual java activity file:

public class StoreListView extends Activity {
UserFunctions userFunctions  = new UserFunctions();
ArrayAdapter<String> arrayAdapter2;
ArrayList<String> spinnerArray;



protected void onCreate(Bundle savedInstanceState) {
    ListView storeList = (ListView) findViewById(R.id.storeList);
    super.onCreate(savedInstanceState);
    setContentView(R.layout.storelistviewpage);
    arrayAdapter2 = new ArrayAdapter<String>(StoreListView.this,android.R.layout.simple_list_item_1);
    spinnerArray = getIntent().getStringArrayListExtra("cusName");
    arrayAdapter2.addAll(spinnerArray);
    storeList.setAdapter(arrayAdapter2);
}


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

}

And below here is the xml file:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<ListView
    android:id="@+id/storeList"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_gravity="center_horizontal|center_vertical" >

</ListView>

Edit:
In case some are wondering I added the activity to the android mainfest

Answer 1

Move

ListView storeList = (ListView) findViewById(R.id.storeList);

after the setContentView() call.

Since your current code assigns the result of findViewById() before setContentView() is called, you will always get storeList being null, and so, you’ll get an NPE.