Android - horizontal flow layout

If you use a LinearLayout which has horizontal orientation and limited width, you'll notice that the child views you add to this LinearLayout are placed one after another left-to-right up to and beyond the width of the LinearLayout. The child views will not wrap to a new line and there is no native layout to do this. So! I've wrote one, as below. It's an adaptation of a view I found on Nishant Nair's Blog here:
https://nishantvnair.wordpress.com/2010/09/28/flowlayout-in-android

UPDATE: For the latest version of the HorizontalFlowLayout class, see this repository:
https://bitbucket.org/adilson05uk/android-utils

 
 
/**
 * Custom view which extends {@link RelativeLayout}
 * and which places its children horizontally,
 * flowing over to a new line whenever it runs out of width.
 */
public class HorizontalFlowLayout extends RelativeLayout {

  /**
   * Constructor to use when creating View from code.
   */
  public HorizontalFlowLayout(Context context) {
    super(context);
  }

  /**
   * Constructor that is called when inflating View from XML.
   */
  public HorizontalFlowLayout(Context context, AttributeSet attrs) {
    super(context, attrs);
  }

  /**
   * Perform inflation from XML and apply a class-specific base style.
   */
  public HorizontalFlowLayout(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
  }

  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    // need to call super.onMeasure(...) otherwise get some funny behaviour
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);

    final int width = MeasureSpec.getSize(widthMeasureSpec);
    int height = MeasureSpec.getSize(heightMeasureSpec);

    // increment the x position as we progress through a line
    int xpos = getPaddingLeft();
    // increment the y position as we progress through the lines
    int ypos = getPaddingTop();
    // the height of the current line
    int line_height = 0;

    // go through children
    // to work out the height required for this view

    // call to measure size of children not needed I think?!
    // getting child's measured height/width seems to work okay without it
    //measureChildren(widthMeasureSpec, heightMeasureSpec);

    View child;
    MarginLayoutParams childMarginLayoutParams;
    int childWidth, childHeight, childMarginLeft, childMarginRight, childMarginTop, childMarginBottom;

    for (int i = 0; i < getChildCount(); i++) {
      child = getChildAt(i);

      if (child.getVisibility() != GONE) {
        childWidth = child.getMeasuredWidth();
        childHeight = child.getMeasuredHeight();

        if (child.getLayoutParams() != null
            && child.getLayoutParams() instanceof MarginLayoutParams) {
          childMarginLayoutParams = (MarginLayoutParams)child.getLayoutParams();

          childMarginLeft = childMarginLayoutParams.leftMargin;
          childMarginRight = childMarginLayoutParams.rightMargin;
          childMarginTop = childMarginLayoutParams.topMargin;
          childMarginBottom = childMarginLayoutParams.bottomMargin;
        }
        else {
          childMarginLeft = 0;
          childMarginRight = 0;
          childMarginTop = 0;
          childMarginBottom = 0;
        }

        if (xpos + childMarginLeft + childWidth + childMarginRight + getPaddingRight() > width) {
          // this child will need to go on a new line

          xpos = getPaddingLeft();
          ypos += line_height;

          line_height = childMarginTop + childHeight + childMarginBottom;
        }
        else {
          // enough space for this child on the current line
          line_height = Math.max(
              line_height,
              childMarginTop + childHeight + childMarginBottom);
        }

        xpos += childMarginLeft + childWidth + childMarginRight;
      }
    }

    ypos += line_height + getPaddingBottom();

    if (MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.UNSPECIFIED) {
      // set height as measured since there's no height restrictions
      height = ypos;
    }
    else if (MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.AT_MOST
        && ypos < height) {
      // set height as measured since it's less than the maximum allowed
      height = ypos;
    }

    setMeasuredDimension(width, height);
  }

  @Override
  protected void onLayout(boolean changed, int l, int t, int r, int b) {
    // increment the x position as we progress through a line
    int xpos = getPaddingLeft();
    // increment the y position as we progress through the lines
    int ypos = getPaddingTop();
    // the height of the current line
    int line_height = 0;

    View child;
    MarginLayoutParams childMarginLayoutParams;
    int childWidth, childHeight, childMarginLeft, childMarginRight, childMarginTop, childMarginBottom;

    for (int i = 0; i < getChildCount(); i++) {
      child = getChildAt(i);

      if (child.getVisibility() != GONE) {
        childWidth = child.getMeasuredWidth();
        childHeight = child.getMeasuredHeight();

        if (child.getLayoutParams() != null
            && child.getLayoutParams() instanceof MarginLayoutParams) {
          childMarginLayoutParams = (MarginLayoutParams)child.getLayoutParams();

          childMarginLeft = childMarginLayoutParams.leftMargin;
          childMarginRight = childMarginLayoutParams.rightMargin;
          childMarginTop = childMarginLayoutParams.topMargin;
          childMarginBottom = childMarginLayoutParams.bottomMargin;
        }
        else {
          childMarginLeft = 0;
          childMarginRight = 0;
          childMarginTop = 0;
          childMarginBottom = 0;
        }

        if (xpos + childMarginLeft + childWidth + childMarginRight + getPaddingRight() > r - l) {
          // this child will need to go on a new line

          xpos = getPaddingLeft();
          ypos += line_height;

          line_height = childHeight + childMarginTop + childMarginBottom;
        }
        else {
          // enough space for this child on the current line
          line_height = Math.max(
              line_height,
              childMarginTop + childHeight + childMarginBottom);
        }

        child.layout(
            xpos + childMarginLeft,
            ypos + childMarginTop,
            xpos + childMarginLeft + childWidth,
            ypos + childMarginTop + childHeight);

        xpos += childMarginLeft + childWidth + childMarginRight;
      }
    }
  }
}