list实现PageInfo方式手动分页

项目中有时候遇到list多种来源，不能使用PageInfo在查询数据库时分页，需要查询全部之后，手动分页。

//list自定义排序

ComparatorUser comparator=new ComparatorUser();
Collections.sort(list, comparator);

//list分页开始

int fromIndex = 0;
int toIndex = 0;
int total = list.size();  //取出总记录数
if(total/pageSize == 0 && total%pageSize > 0){
	fromIndex = 0;
	toIndex = total;
}else{
	if(total/pageSize >= 1 && total % pageSize >= 0){
	   fromIndex = pageSize * (pageIndex-1);
	   if(pageSize * pageIndex >= total){
		toIndex = total;
	   }else{
			toIndex = pageSize * pageIndex;
	   }
	}
}
list = list.subList(fromIndex, toIndex);
PageInfo<User> pageinfo = new PageInfo<User>(list);
pageinfo = PageHelperTool.initPageInfoObj(pageIndex,total,pageSize,pageinfo);

import java.util.Comparator;
/**
 * @author yang
 * @Title: ComparatorUser .java
 * @Package 
 * @Description: 自定义排序
 * @date 2019年07月09日 10:01
 */
public class ComparatorUser implements Comparator {

    public int compare(Object arg0, Object arg1) {
        User user1=(User)arg0;
        User user2=(User)arg1;

        //首先比较年龄，如果年龄相同，则比较名字

        int flag=user1.getAge().compareTo(user2.getAge());

        if(flag==0){
            return user1.getName().compareTo(user2.getName());
        }else{
            return flag;
        }
    }
}

//分页工具类

import com.github.pagehelper.PageInfo;

/**
 * @author yang
 * @Title: PageHelperTool.java
 * @Package 
 * @Description: 分页工具类
 * @date 2019年07月09日 10:01
 */
public class PageHelperTool {
    /**
     * PageHelper中，如果当前页是最后一页，则返回的nextPage是0，即首页，而有时我们需要最后一页的nextPage是lastPage，因此写此方法
     * @param currentPage
     * @param pageObj
     * @return
     */
    public static <T> PageInfo<T> lastPageSetNextPage(int currentPage, PageInfo<T> pageObj) {
        if (currentPage == pageObj.getPages()) {
            pageObj.setNextPage(pageObj.getPages());
        }
        return pageObj;
    }

    public static <T> PageInfo<T> initPageInfoObj(int currentPage, int total, int pageSize, PageInfo<T> pageInfo) {
        pageInfo.setNextPage(currentPage < ((total + pageSize - 1) / pageSize) ? currentPage + 1 : currentPage);
        pageInfo.setTotal(total);
        pageInfo.setPageNum(currentPage);
        pageInfo.setPages((total + pageSize - 1) / pageSize);
        pageInfo.setLastPage((total + pageSize - 1) / pageSize);
        pageInfo.setPrePage(currentPage > 1 ? currentPage - 1 : currentPage);
        pageInfo.setIsFirstPage(currentPage == 1 ? true : false);
        pageInfo.setIsLastPage(currentPage == (total + pageSize - 1) / pageSize ? true : false);
        pageInfo.setHasPreviousPage(currentPage == 1 ? false : true);
        pageInfo.setHasNextPage(currentPage == (total + pageSize - 1) / pageSize ? false : true);
        return calcNavigatepageNums(pageInfo);
    }

    private static <T> PageInfo<T> calcNavigatepageNums(PageInfo<T> pageInfo) {
        //当总页数小于或等于导航页码数时
        if (pageInfo.getPages() <= pageInfo.getNavigatePages()) {
            pageInfo.setNavigatepageNums(new int[pageInfo.getPages()]);
            for (int i = 0; i < pageInfo.getPages(); i++) {
                pageInfo.getNavigatepageNums()[i] = i + 1;
            }
        } else { //当总页数大于导航页码数时
            pageInfo.setNavigatepageNums(new int[pageInfo.getNavigatePages()]);
            int startNum = pageInfo.getPageNum() - pageInfo.getNavigatePages() / 2;
            int endNum = pageInfo.getPageNum() + pageInfo.getNavigatePages() / 2;

            if (startNum < 1) {
                startNum = 1;
                //(最前navigatePages页
                for (int i = 0; i < pageInfo.getNavigatePages(); i++) {
                    pageInfo.getNavigatepageNums()[i] = startNum++;
                }
            } else if (endNum > pageInfo.getPages()) {
                endNum = pageInfo.getPages();
                //最后navigatePages页
                for (int i = pageInfo.getNavigatePages() - 1; i >= 0; i--) {
                    pageInfo.getNavigatepageNums()[i] = endNum--;
                }
            } else {
                //所有中间页
                for (int i = 0; i < pageInfo.getNavigatePages(); i++) {
                    pageInfo.getNavigatepageNums()[i] = startNum++;
                }
            }
        }
        return pageInfo;
    }
}