GridSpacingItemDecoration

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

import androidx.recyclerview.widget.RecyclerView;

public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {

    private int spanCount;
    private int spacing;
    private boolean includeEdge;

    public GridSpacingItemDecoration(int spanCount, int spacing, boolean includeEdge) {
        this.spanCount = spanCount;
        this.spacing = spacing;
        this.includeEdge = includeEdge;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        int position = parent.getChildAdapterPosition(view); // item position
        int column = position % spanCount; // item column

        if (includeEdge) {
            outRect.left = spacing - column * spacing / spanCount; // spacing - column * ((1f / spanCount) * spacing)
            outRect.right = (column + 1) * spacing / spanCount; // (column + 1) * ((1f / spanCount) * spacing)

            if (position < spanCount) { // top edge
                outRect.top = spacing;
            }
            outRect.bottom = spacing; // item bottom
        } else {
            outRect.left = column * spacing / spanCount; // column * ((1f / spanCount) * spacing)
            outRect.right = spacing - (column + 1) * spacing / spanCount; // spacing - (column + 1) * ((1f /    spanCount) * spacing)
            if (position >= spanCount) {
                outRect.top = spacing; // item top
            }
        }
    }
}

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Usage 

rvFeatured.addItemDecoration(new GridSpacingItemDecoration(3, (int) convertDpToPx(10) , false));




Can use as per your need





public static float convertPixelsToDp(float px){
 DisplayMetrics metrics = Resources.getSystem().getDisplayMetrics();
 float dp = px / (metrics.densityDpi / 160f);
 return Math.round(dp);
}
 
public static float convertDpToPixel(float dp){
 DisplayMetrics metrics = Resources.getSystem().getDisplayMetrics();
 float px = dp * (metrics.densityDpi / 160f);
 return Math.round(px);
}


private int convertDpToPx(int dp){
    return Math.round(dp*(getResources().getDisplayMetrics().xdpi/DisplayMetrics.DENSITY_DEFAULT));
  
}
 
private int convertPxToDp(int px){
    return Math.round(px/(Resources.getSystem().getDisplayMetrics().xdpi/DisplayMetrics.DENSITY_DEFAULT));
}


private float dpFromPx(float px)
{
    return px / this.getContext().getResources().getDisplayMetrics().density;
}


private float pxFromDp(float dp)
{
    return dp * this.getContext().getResources().getDisplayMetrics().density;
}