top_sheet.java

@Override
public boolean onLayoutChild(CoordinatorLayout parent, V child, int layoutDirection) {
    if (ViewCompat.getFitsSystemWindows(parent) && !ViewCompat.getFitsSystemWindows(child))
        ViewCompat.setFitsSystemWindows(child, true);

    int savedTop = child.getTop();
    
    // First let the parent lay it out
    parent.onLayoutChild(child, layoutDirection);
    
    // Offset the top sheet
    mMinOffset = Math.max(-child.getHeight(), -(child.getHeight() - mPeekHeight));
    mMaxOffset = 0;
    
    if (mState == STATE_EXPANDED)
        ViewCompat.offsetTopAndBottom(child, mMaxOffset);
    else if (mHideable && mState == STATE_HIDDEN)
        ViewCompat.offsetTopAndBottom(child, -child.getHeight());
    else if (mState == STATE_COLLAPSED)
        ViewCompat.offsetTopAndBottom(child, mMinOffset);
    else if (mState == STATE_DRAGGING || mState == STATE_SETTLING)
        ViewCompat.offsetTopAndBottom(child, savedTop - child.getTop());

    if (mViewDragHelper == null)
        mViewDragHelper = ViewDragHelper.create(parent, mDragCallback);
    
    mViewRef = new WeakReference<>(child);
    mNestedScrollingChildRef = new WeakReference<>(findScrollingChild(child));
    return true;
}