getResponsiveGridListItems method

List<Widget> getResponsiveGridListItems(double maxWidth)

Method to generate a list of ResponsiveGridRow's with spacing in between them.

maxWidth is the maximum width of the current layout.

Implementation

List<Widget> getResponsiveGridListItems(double maxWidth) {
  // Start with the minimum allowed number of items per row.
  var itemsPerRow = minItemsPerRow;

  // Calculate the current width according to the items per row
  var currentWidth =
      itemsPerRow * minItemWidth + (itemsPerRow - 1) * horizontalGridSpacing;

  // Add outer margin (vertical) if set
  if (horizontalGridMargin != null) {
    currentWidth += 2 * horizontalGridMargin!;
  }

  // While another pair of spacing + minItemWidth fits the row, add it to
  // the variables. Only add items while maxItemsPerRow is not reached.
  while (currentWidth < maxWidth &&
      (maxItemsPerRow == null || itemsPerRow < maxItemsPerRow!)) {
    if (currentWidth + (minItemWidth + horizontalGridSpacing) <= maxWidth) {
      // If another spacing + item fits in the row, add one item to the row
      // and update the currentWidth
      currentWidth += minItemWidth + horizontalGridSpacing;
      itemsPerRow++;
    } else {
      // If no other item + spacer fits into the row, break
      break;
    }
  }

  // Calculate the spacers per row (they are only in between the items, not
  // at the edges)
  final spacePerRow = itemsPerRow - 1;

  // Calculate the itemWidth that results from the maxWidth and number of
  // spacers and outer margin (horizontal)
  final itemWidth = (maxWidth -
          (spacePerRow * horizontalGridSpacing) -
          (2 * (horizontalGridMargin ?? 0))) /
      itemsPerRow;

  // Partition the items into groups of itemsPerRow length and map them
  // to ResponsiveGridRow's
  final items = partition(children, itemsPerRow)
      .map<Widget>(
        (e) => ResponsiveGridRow(
          rowItems: e,
          spacing: horizontalGridSpacing,
          horizontalGridMargin: horizontalGridMargin,
          itemWidth: itemWidth,
        ),
      )
      .toList();

  // Join the rows width spacing in between them (vertical)
  final responsiveGridListItems =
      items.genericJoin(SizedBox(height: verticalGridSpacing));

  // Add outer margin (vertical) if set
  if (verticalGridMargin != null) {
    return [
      SizedBox(height: verticalGridMargin),
      ...responsiveGridListItems,
      SizedBox(height: verticalGridMargin),
    ];
  }

  return responsiveGridListItems;
}