private void updatePreviewBtnState(List<BaseMedia> medias) {
        if (mPreBtn == null || medias == null) {
            return;
        }
        boolean enabled = medias.size() > 0 && medias.size() <= mMaxCount;
        mPreBtn.setEnabled(enabled);
    }
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