import android.graphics.Rect;
import android.view.View;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

public class MarginItemDecoration extends RecyclerView.ItemDecoration {

    private final int columnCount;
    private final int margin;

    public MarginItemDecoration(int margin, int columnCount) {
        this.columnCount = columnCount;
        this.margin = margin;
    }

    @Override
    public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);

        int position = parent.getChildAdapterPosition(view);

        boolean firstInRow = position % columnCount == 0;
        boolean lastInRow = position % columnCount == columnCount - 1;
        boolean isInLastRow = position > state.getItemCount() - columnCount - 1;

        //top
        outRect.top = margin;

        //left
        if (firstInRow) outRect.left = margin;
        else outRect.left = margin / 2;

        //right
        if (lastInRow) outRect.right = margin;
        else outRect.right = margin / 2;

        //bottom
        if (isInLastRow) outRect.bottom = margin;
    }
}