Number Preferences in Preference Activity in Android
Use an EditTextPreference and set the input type to TYPE_CLASS_NUMBER. This will force the user to enter numbers and not letters.
EditTextPreference pref = (EditTextPreference)findPreference("preference_name");pref.getEditText().setInputType(InputType.TYPE_CLASS_NUMBER);
You can also enforce it with the xml attribute android:numeric. The possible relevant values for this attribute are decimal and integer.
You can also do this directly in your preferences.xml. Something like this would work:
<EditTextPreference android:defaultValue="100" android:dialogTitle="@string/pref_query_limit" android:inputType="number" android:key="pref_query_limit" android:summary="@string/pref_query_limit_summ" android:title="@string/pref_query_limit" />