public BadgeItem setGravity(int gravity) {
        this.mGravity = gravity;
        if (isWeakReferenceValid()) {
            TextView textView = mTextViewRef.get();
            FrameLayout.LayoutParams layoutParams = (FrameLayout.LayoutParams) textView.getLayoutParams();
            layoutParams.gravity = gravity;
            textView.setLayoutParams(layoutParams);
        }
        return this;
    }
@param gravity gravity of badge (TOP|LEFT ..etc)
@return this, to allow builder pattern
common/src/main/java/com/sxjs/common/widget/bottomnavigation/BadgeItem.java