private void updateOkBtnState(List<BaseMedia> medias) {
        if (mOkBtn == null || medias == null) {
            return;
        }
        boolean enabled = medias.size() > 0 && medias.size() <= mMaxCount;
        mOkBtn.setEnabled(enabled);
        mOkBtn.setText(enabled ? getString(R.string.boxing_image_select_ok_fmt, String.valueOf(medias.size())
                , String.valueOf(mMaxCount)) : getString(R.string.boxing_ok));
    }
A full implement for {@link com.bilibili.boxing.presenter.PickerContract.View} supporting all the mode
in {@link BoxingConfig.Mode}.
use this to pick the picture.

@author ChenSL
boxing-impl/src/main/java/com/bilibili/boxing_impl/ui/BoxingViewFragment.java