无法在ListPreference摘要

Question

我正在尝试更改Preference Activity中的字体，它工作得很好，所有标题和摘要字体都已更改，但ListPreference的摘要显示为默认字体

private void convertPreferenceToUseCustomFont(Preference somePreference) {

    Typeface font = Typeface.createFromAsset(getActivity().getAssets(), "font.ttf");

    Spannable ss;
                if (somePreference.getTitle() != null) {
                    ss = new SpannableStringBuilder(somePreference.getTitle().toString());
                    ss.setSpan(new CustomTypefaceSpan("" , font), 0 , ss.length(),  Spannable.SPAN_INCLUSIVE_INCLUSIVE);
                    somePreference.setTitle(ss);
                }

                if (somePreference.getSummary() != null) {
                    ss = new SpannableStringBuilder(somePreference.getSummary().toString());
                    ss.setSpan(new CustomTypefaceSpan("" , font), 0 , ss.length(),  Spannable.SPAN_INCLUSIVE_INCLUSIVE);
                    somePreference.setSummary(ss);
                }
}

这是customtypefacespan类

public class CustomTypefaceSpan extends TypefaceSpan {

    private final Typeface newType;

    public CustomTypefaceSpan(String family, Typeface type) {
        super(family);
        newType = type;
    }

    @Override
    public void updateDrawState(TextPaint ds) {
        applyCustomTypeFace(ds, newType);
    }

    @Override
    public void updateMeasureState(TextPaint paint) {
        applyCustomTypeFace(paint, newType);
    }

    private static void applyCustomTypeFace(Paint paint, Typeface tf) {
        int oldStyle;
        Typeface old = paint.getTypeface();
        if (old == null) {
            oldStyle = 0;
        } else {
            oldStyle = old.getStyle();
        }

        int fake = oldStyle & ~tf.getStyle();
        if ((fake & Typeface.BOLD) != 0) {
            paint.setFakeBoldText(true);
        }

        if ((fake & Typeface.ITALIC) != 0) {
            paint.setTextSkewX(-0.25f);
        }

        paint.setTypeface(tf);
    }
}

我正在使用这种方式

ListPreference language = (ListPreference) findPreference("language");
convertPreferenceToUseCustomFont(language);

所有复选框和preferncescreen工作字体但ListPreference的摘要没有变化