I cannot for the life of me figure out why I'm getting a NullPointerException.

When a user clicks on a particular image, a dialog window is supposed to pop-up and display a larger version of said image:

private OnClickListener coverListener = new OnClickListener() 

{ public void onClick(View v) { showDialog(DIALOG_COVER); } };

DIALOG_COVER is set to = 0.

The associated onCreateDialog looks like this:

protected Dialog onCreateDialog(int id) {
 Dialog dialog;
 switch(id) 
 {
  case DIALOG_COVER:
   dialog = new Dialog(mContext);
   dialog.setContentView(R.layout.cover_dialog);
   dialog.setTitle(book.getTitle());
   ImageView coverLarge = (ImageView)findViewById(R.id.coverLarge);
   coverLarge.setImageBitmap(book.getCover());
      break;
  default:
      dialog = null;
 }
 return dialog;

}

For reference, this is cover_dialog.xml:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
          android:id="@+id/coverDialog"
          android:orientation="horizontal"
          android:layout_width="fill_parent"
          android:layout_height="fill_parent"
          android:padding="10dp">
<ImageView android:id="@+id/coverLarge"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:scaleType="fitStart"
           /></LinearLayout>

Now, when the image previously described is clicked, the application immediately crashes and throws the following error through LogCat:

06-08 13:29:17.727: ERROR/AndroidRuntime(2220): Uncaught handler: thread main exiting     due to uncaught exception 
06-08 13:29:17.757: ERROR/AndroidRuntime(2220): java.lang.NullPointerException
06-08 13:29:17.757: ERROR/AndroidRuntime(2220):     at org.kylehughes.android.brarian.AndroidBrarian.onCreateDialog(AndroidBrarian.java:259)

The line in question refers to this line inside of onCreateDialog:

coverLarge.setImageBitmap(book.getCover());

Basically, I don't get why coverLarge is null at that point. Any help would be much appreciated.