01_before.java

@PreferenceWrapper(BuildConfig.APPLICATION_ID)
public abstract class Settings {
  @Preference(key="pref_theme_id") String themeId;
  @Preference boolean fullHostmask;
  int textSize;
}

02_after.java

public final class WrappedSettings {
  public final BooleanPreference fullHostmask;

  public final IntPreference textSize;

  public final StringPreference themeId;

  public WrappedSettings(SharedPreferences pref) {
    this.fullHostmask = new BooleanPreference(pref, "pref_full_hostmask", null);
    this.textSize = new IntPreference(pref, "pref_text_size", null);
    this.themeId = new StringPreference(pref, "pref_theme_id", null);
    pref.registerOnSharedPreferenceChangeListener(new SharedPreferences.OnSharedPreferenceChangeListener() {
      @Override
      public void onSharedPreferenceChanged(SharedPreferences preferences, String key) {
        if (key == "pref_full_hostmask") fullHostmask.change();
        if (key == "pref_text_size") textSize.change();
        if (key == "pref_theme_id") themeId.change();
      }
    });
  }

  public WrappedSettings(Context ctx) {
    this(ctx.getSharedPreferences("de.kuschku.testapp", 0));
  }
}

03_types.java

public class StringPreference extends AbstractPreferenceElement<String> {
    public StringPreference(SharedPreferences pref, String key, String init) {
        super(pref, key, init);
    }

    @Override
    protected void put(String value) {
        edit.putString(key, value);
    }

    @Override
    public String get() {
        return pref.getString(key, defValue);
    }
}

public abstract class AbstractPreferenceElement<T> implements PreferenceElement<T>, OnChangeListener<T> {
    private final Set<OnChangeListener<T>> listeners = new HashSet<>();
    protected SharedPreferences pref;
    protected SharedPreferences.Editor edit;
    protected String key;
    protected T defValue;

    public AbstractPreferenceElement(SharedPreferences pref, String key, T defValue) {
        this.pref = pref;
        this.key = key;
        this.defValue = defValue;
    }

    public void change() {
        change(get());
    }

    public void change(T value) {
        for (OnChangeListener<T> listener : listeners)
            listener.change(value);
    }

    public void addChangeListener(OnChangeListener<T> listener) {
        listeners.add(listener);
    }
    public void removeChangeListener(OnChangeListener<T> listener) {
        listeners.remove(listener);
    }

    protected abstract void put(T value);

    public void batch(SharedPreferences.Editor edit) {
        if (this.edit != null) this.edit.commit();
        this.edit = edit;
    }

    public void set(T value) {
        edit = pref.edit();
        put(value);
        edit.commit();
    }
}

public interface PreferenceElement<T> {
    void addChangeListener(OnChangeListener<T> listener);
    void removeChangeListener(OnChangeListener<T> listener);

    T get();
    void set(T value);
}