public final void setPeekHeight(int peekHeight) {
        boolean layout = false;
        if (peekHeight == PEEK_HEIGHT_AUTO) {
            if (!mPeekHeightAuto) {
                mPeekHeightAuto = true;
                layout = true;
            }
        } else if (mPeekHeightAuto || mPeekHeight != peekHeight) {
            mPeekHeightAuto = false;
            mPeekHeight = Math.max(0, peekHeight);
            mMaxOffset = mParentHeight - peekHeight;
            layout = true;
        }
        if (layout && mState == STATE_COLLAPSED && mViewRef != null) {
            V view = mViewRef.get();
            if (view != null) {
                view.requestLayout();
            }
        }
    }
Sets the height of the bottom sheet when it is collapsed.

@param peekHeight The height of the collapsed bottom sheet in pixels, or
                  {@link #PEEK_HEIGHT_AUTO} to configure the sheet to peek automatically
                  at 16:9 ratio keyline.
@attr ref android.support.design.R.styleable#BottomSheetBehavior_Layout_behavior_peekHeight
vpbs/src/main/java/biz/laenger/android/vpbs/ViewPagerBottomSheetBehavior.java