Decorator

In Android, when you work with RecyclerViews, the standard way of working with paddings and margins is to work with fixed dimensions inside of the layout files.

While this works for many applications, sometimes the margins inside the layout files shouldn't be applied in every screen.

Decorator is a library that helps creating composable margins and dividers in RecyclerViews.

Install

implementation 'io.cabriole:decorator:1.1.0'

Replace x.x.x with the latest version available

How to use

Just create one of the decorations provided in the next examples and add them to the RecyclerView using:

recyclerView.addItemDecoration(decoration)

Margin decorations

These decorations draw a margin between the items.

LinearMarginDecoration

recyclerView.addItemDecoration(LinearMarginDecoration(
    leftMargin = resources.dpToPx(16),
    topMargin = resources.dpToPx(16),
    rightMargin = resources.dpToPx(16),
    bottomMargin = resources.dpToPx(16),
    orientation = RecyclerView.VERTICAL
))

GridMarginDecoration

recyclerView.addItemDecoration(GridMarginDecoration(
    margin = resources.dpToPx(16),
    columnProvider = object : ColumnProvider {
        override fun getNumberOfColumns(): Int = 3
    },
    orientation = RecyclerView.VERTICAL
))

GridSpanDecoration

recyclerView.addItemDecoration(GridSpanMarginDecoration(
    margin = resources.dpToPx(8),
    gridLayoutManager = gridLayoutManager,
    orientation = RecyclerView.VERTICAL
))

Divider decorations

These decorations draw a divider between the items

LinearDividerDecoration

recyclerView.addItemDecoration(LinearDividerDecoration.create(
    color = ContextCompat.getColor(context, R.color.colorDivider),
    size = resources.dpToPx(4),
    leftMargin = resources.dpToPx(64),
    topMargin = resources.dpToPx(16),
    rightMargin = resources.dpToPx(64),
    bottomMargin = resources.dpToPx(16),
    orientation = RecyclerView.VERTICAL
))

GridDividerDecoration

recyclerView.addItemDecoration(GridDividerDecoration.create(
    color = ContextCompat.getColor(context, R.color.colorDivider),
    size = resources.dpToPx(2),
    columnProvider = object : ColumnProvider {
        override fun getNumberOfColumns(): Int = 3
    },
    widthMargin = resources.dpToPx(16),
    heightMargin = resources.dpToPx(16),
    orientation = RecyclerView.VERTICAL
))

Bounds margin decorations

These decorations are similar to the margin decorations,
but they only draw a margin in the bounds of the list.

LinearBoundsMarginDecoration

recyclerView.addItemDecoration(LinearBoundsMarginDecoration.create(
    margin = resources.dpToPx(8),
    orientation = RecyclerView.VERTICAL
))

GridBoundsMarginDecoration

recyclerView.addItemDecoration(GridBoundsMarginDecoration.create(
    margin = resources.dpToPx(16),
    columnProvider = object : ColumnProvider {
        override fun getNumberOfColumns(): Int = 3
    }
))

Composing decorations

If you want to apply multiple decorations, you just need to add the decorations in the correct order.

Example for a vertical RecyclerView:

// Add a vertical margin to the first and last items. 
// The first item will have a top margin and the last item a bottom margin
recyclerView.addItemDecoration(
    LinearBoundsMarginDecoration(
        leftMargin = 0,
        rightMargin = 0,
        topMargin = edgeDecorationSize,
        bottomMargin = edgeDecorationSize
    )
)

// Add a margin between all items
recyclerView.addItemDecoration(
    LinearMarginDecoration(
        leftMargin = 0,
        rightMargin = 0,
        topMargin = marginDecorationSize,
        bottomMargin = marginDecorationSize
    )
)

// Finally, add a divider between the items while respecting the previous margins:
recyclerView.addItemDecoration(LinearDividerDecoration.create(
    color = ContextCompat.getColor(context, R.color.colorDivider),
    size = fragment.dpToPx(2)
))

You can also decide if an item at a given position should have a decoration applied:

decoration.setDecorationLookup(object : DecorationLookup {

    // Don't apply the decoration on position 4
    override fun shouldApplyDecoration(position: Int, itemCount: Int): Boolean {
        return position != 4
    }
    
})

GitHub