SpaceDecoration.java

package com.youth.xframe.adapter.decoration;

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

import com.youth.xframe.adapter.XRecyclerViewAdapter;

import static android.widget.LinearLayout.VERTICAL;

public class SpaceDecoration extends RecyclerView.ItemDecoration {

    private int space;
    private int headerCount = -1;
    private int footerCount = Integer.MAX_VALUE;
    private boolean mPaddingEdgeSide = true;
    private boolean mPaddingStart = true;
    private boolean mPaddingHeaderFooter = false;


    public SpaceDecoration(int space) {
        this.space = space ;
    }

    public void setPaddingEdgeSide(boolean mPaddingEdgeSide) {
        this.mPaddingEdgeSide = mPaddingEdgeSide;
    }

    public void setPaddingStart(boolean mPaddingStart) {
        this.mPaddingStart = mPaddingStart;
    }

    public void setPaddingHeaderFooter(boolean mPaddingHeaderFooter) {
        this.mPaddingHeaderFooter = mPaddingHeaderFooter;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        int position = parent.getChildAdapterPosition(view);
        int spanCount = 0;
        int orientation = 0;
        int spanIndex = 0;
        int headerCount = 0,footerCount = 0;
        if (parent.getAdapter() instanceof XRecyclerViewAdapter){
            headerCount = ((XRecyclerViewAdapter) parent.getAdapter()).getHeaderCount();
            footerCount = ((XRecyclerViewAdapter) parent.getAdapter()).getFooterCount();
        }

        RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
         if (layoutManager instanceof StaggeredGridLayoutManager){
             orientation = ((StaggeredGridLayoutManager) layoutManager).getOrientation();
             spanCount = ((StaggeredGridLayoutManager) layoutManager).getSpanCount();
             spanIndex = ((StaggeredGridLayoutManager.LayoutParams) view.getLayoutParams()).getSpanIndex();
        }else if (layoutManager instanceof GridLayoutManager){
             orientation = ((GridLayoutManager) layoutManager).getOrientation();
             spanCount = ((GridLayoutManager) layoutManager).getSpanCount();
             spanIndex = ((GridLayoutManager.LayoutParams) view.getLayoutParams()).getSpanIndex();
        }else if (layoutManager instanceof LinearLayoutManager){
             orientation = ((LinearLayoutManager) layoutManager).getOrientation();
             spanCount = 1;
             spanIndex = 0;
        }

        /**
         * 普通Item的尺寸
         */
        if ((position>=headerCount&&position<parent.getAdapter().getItemCount()-footerCount)) {

            if (orientation == VERTICAL) {
                float expectedWidth = (float) (parent.getWidth() - space * (spanCount + (mPaddingEdgeSide ? 1 : -1))) / spanCount;
                float originWidth = (float) parent.getWidth() / spanCount;
                float expectedX = (mPaddingEdgeSide ? space : 0) + (expectedWidth + space) * spanIndex;
                float originX = originWidth * spanIndex;
                outRect.left = (int) (expectedX - originX);
                outRect.right = (int) (originWidth - outRect.left - expectedWidth);
                if (position - headerCount < spanCount && mPaddingStart) {
                    outRect.top = space;
                }
                outRect.bottom = space;
                return;
            } else {
                float expectedHeight = (float) (parent.getHeight() - space * (spanCount + (mPaddingEdgeSide ? 1 : -1))) / spanCount;
                float originHeight = (float) parent.getHeight() / spanCount;
                float expectedY = (mPaddingEdgeSide ? space : 0) + (expectedHeight + space) * spanIndex;
                float originY = originHeight * spanIndex;
                outRect.bottom = (int) (expectedY - originY);
                outRect.top = (int) (originHeight - outRect.bottom - expectedHeight);
                if (position - headerCount < spanCount && mPaddingStart) {
                    outRect.left = space;
                }
                outRect.right = space;
                return;
            }
        }else if (mPaddingHeaderFooter){
            if (orientation == VERTICAL){outRect.right = outRect.left = mPaddingEdgeSide ? space : 0;
                outRect.top = mPaddingStart?space : 0;
            }else { outRect.top = outRect.bottom = mPaddingEdgeSide ? space : 0;
                outRect.left = mPaddingStart?space : 0;
            }
        }

    }

}