Add equal spacing to RecyclerView items automatically. Can handle horizontal, vertical, and grid display modes

EqualSpacingItemDecoration.java

import android.graphics.Rect;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;

public class EqualSpacingItemDecoration extends RecyclerView.ItemDecoration {
  private final int spacing;
  private int displayMode;

  public static final int HORIZONTAL = 0;
  public static final int VERTICAL = 1;
  public static final int GRID = 2;

  public EqualSpacingItemDecoration(int spacing) {
    this(spacing, -1);
  }

  public EqualSpacingItemDecoration(int spacing, int displayMode) {
    this.spacing = spacing;
    this.displayMode = displayMode;
  }

  @Override
  public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
    int position = parent.getChildViewHolder(view).getAdapterPosition();
    int itemCount = state.getItemCount();
    RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
    setSpacingForDirection(outRect, layoutManager, position, itemCount);
  }

  private void setSpacingForDirection(Rect outRect,
                                      RecyclerView.LayoutManager layoutManager,
                                      int position,
                                      int itemCount) {
    
    // Resolve display mode automatically
    if (displayMode == -1) {
      displayMode = resolveDisplayMode(layoutManager);
    }

    switch (displayMode) {
      case HORIZONTAL:
        outRect.left = spacing;
        outRect.right = position == itemCount - 1 ? spacing : 0;
        outRect.top = spacing;
        outRect.bottom = spacing;
        break;
      case VERTICAL:
        outRect.left = spacing;
        outRect.right = spacing;
        outRect.top = spacing;
        outRect.bottom = position == itemCount - 1 ? spacing : 0;
        break;
      case GRID:
        if (layoutManager instanceof GridLayoutManager) {
          GridLayoutManager gridLayoutManager = (GridLayoutManager) layoutManager;
          int cols = gridLayoutManager.getSpanCount();
          int rows = itemCount / cols;

          outRect.left = spacing;
          outRect.right = position % cols == cols - 1 ? spacing : 0;
          outRect.top = spacing;
          outRect.bottom = position / cols == rows - 1 ? spacing : 0;
        }
        break;
    }
  }

  private int resolveDisplayMode(RecyclerView.LayoutManager layoutManager) {
    if (layoutManager instanceof GridLayoutManager) return GRID;
    if (layoutManager.canScrollHorizontally()) return HORIZONTAL;
    return VERTICAL;
  }
}

example.java

// Automatically infer display orientation of items
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
recyclerView.addItemDecoration(new EqualSpacingItemDecoration(16)); // 16px. In practice, you'll want to use getDimensionPixelSize

// Explicitly specify display orientation of items.
// Available display modes:
//   - HORIZONTAL
//   - VERTICAL
//   - GRID
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
recyclerView.addItemDecoration(new EqualSpacingItemDecoration(16, EqualSpacingItemDecoration.HORIZONTAL)); // 16px. In practice, you'll want to use getDimensionPixelSize

results.md

BEFORE

AFTER

Note that the third column in the "AFTER" graphic is narrower than the first two columns. It's not that noticeable in the graphic, but in my case all my items are constrained to be square and it is very obvious.

In the end, the solution for me was:

1. Set layout_margin of the item view to half the desired spacing between items
2. Set padding of RecyclerView, also to half the desired spacing between items
3. Set clipToPadding to false on the RecyclerView - this is very important, otherwise the padding in the previous step cuts off the edges of the scroll view.

Tada! All items are uniformly spaced and sized.

Yes. My exact case and your solution worked like a charm. 👍

• 1

@alexfu,

@Morphin3 is right, the change suggested by him does solve the issue when you have an odd number of items.