常用 RecyclerView LayoutManager ItemDecoration

LinearLayoutManager

https://github.com/yqritc/RecyclerView-FlexibleDivider

GridLayoutManager

https://gist.github.com/liangzhitao/e57df3c3232ee446d464

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

/**
 * Created by Android Studio
 * User: Ailurus([email protected])
 * Date: 2015-10-28
 * Time: 15:20
 */
public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {

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

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

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

        if (position >= 0) {
            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
                }
            }
        } else {
            outRect.left = 0;
            outRect.right = 0;
            outRect.top = 0;
            outRect.bottom = 0;
        }
    }
}

StaggeredGridLayoutManager

摘自 drknotter/episodilyzer

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

public class StaggeredGridItemDecoration extends RecyclerView.ItemDecoration {
    private int margin = 0;
    private boolean lastIsTop;
    private boolean lastIsLeft;
    private boolean lastIsRight;

    public StaggeredGridItemDecoration(int margin) {
        this.margin = margin;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        boolean isLeft;
        boolean isTop;
        boolean isRight;

        int position = parent.getChildAdapterPosition(view);
        if (position != RecyclerView.NO_POSITION) {
            StaggeredGridLayoutManager.LayoutParams params = (StaggeredGridLayoutManager.LayoutParams) view.getLayoutParams();
            int spanCount = ((StaggeredGridLayoutManager) parent.getLayoutManager()).getSpanCount();
            isTop = position < spanCount;
            isLeft = params.getSpanIndex() == 0;
            isRight = params.getSpanIndex() == spanCount - 1;
        } else {
            isTop = lastIsTop;
            isLeft = lastIsLeft;
            isRight = lastIsRight;
        }

        lastIsTop = isTop;
        lastIsLeft = isLeft;
        lastIsRight = isRight;
        outRect.set(isLeft ? margin : margin / 2, isTop ? margin : 0, isRight ? margin : margin / 2, margin);
    }

}