number_pref.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
		android:orientation='vertical' 
		android:layout_width='wrap_content'
		android:layout_height='wrap_content'
		android:padding='3dp'
		android:paddingLeft='8dp'
		android:paddingRight='8dp'>
	<!-- This layout is used by setting the 'dialogLayout' attribute in DialogPreference -->
		
		<!-- This is filled by the 'message' attribute on DialogPreference: -->
		<TextView android:id='@android:id/message'
			android:layout_width='fill_parent'
			android:layout_height='wrap_content'
			android:textAppearance='?android:attr/textAppearanceMedium' 
			android:layout_marginBottom='10dp' />
    <com.quietlycoding.android.picker.NumberPicker
      android:id="@+id/pref_num_picker"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content" />
</LinearLayout>

NumberPickerPreference.java

import android.content.Context;
import android.content.DialogInterface;
import android.content.res.TypedArray;
import android.preference.DialogPreference;
import android.util.AttributeSet;
import android.view.View;

import com.quietlycoding.android.picker.NumberPicker;

public class NumberPickerPreference extends DialogPreference {

	NumberPicker picker;
	Integer initialValue;
	
	public NumberPickerPreference(Context context, AttributeSet attrs) {
		super(context, attrs);
	}
	
	@Override
	protected void onBindDialogView(View view) {
		super.onBindDialogView(view);
		this.picker = (NumberPicker)view.findViewById(R.id.pref_num_picker);
		// TODO this should be an XML parameter:
		picker.setRange(1, 7);
		if ( this.initialValue != null ) picker.setCurrent(initialValue);
	}
	
	@Override
	public void onClick(DialogInterface dialog, int which) {
		super.onClick(dialog, which);
		if ( which == DialogInterface.BUTTON_POSITIVE ) {
			this.initialValue = picker.getCurrent();
			persistInt( initialValue );
			callChangeListener( initialValue );
		}
	}
	
	@Override
	protected void onSetInitialValue(boolean restorePersistedValue,
			Object defaultValue) {
		int def = ( defaultValue instanceof Number ) ? (Integer)defaultValue
				: ( defaultValue != null ) ? Integer.parseInt(defaultValue.toString()) : 1;
		if ( restorePersistedValue ) {
			this.initialValue = getPersistedInt(def);
		}
		else this.initialValue = (Integer)defaultValue;
	}
		
	@Override
	protected Object onGetDefaultValue(TypedArray a, int index) {
		return a.getInt(index, 1);
	}
}