It happens when using android.support.v14.preference.PreferenceFragment or android.support.v7.preference.PreferenceFragmentCompat even after choosing android:inputType="numberDecimal"
. This issue could be overcome by using android.preference.PreferenceFragment. Unfortunately, it's deprecated in API level 28.
Even refactoring to AndroidX, using androidx.preference.PreferenceFragment or androidx.preference.PreferenceFragmentCompat didn't fix the issue.