用pageInfo對List手工分頁

因業務須要，需對List，進行分頁。

List來源，多種多樣，有時不能用數據庫發送sql來進行limit的分頁

思路：

1.對List數組來源，進行subList的截取，相似於數據庫發送limit。

2.構建一個pageinfo的工具類。

List<Description> descriptionByCategoryList = descriptionService.getDescriptionByCategoryList(20); int fromIndex = 0; int toIndex = 0; int pageSize = 20; int pageIndex = pn; int total = descriptionByCategoryList.size(); // 取出總記錄數
        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; } } }

　　//作pn越界處理

    try {
          descriptionByCategoryList =descriptionByCategoryList.subList(fromIndex, toIndex);
     } catch (IndexOutOfBoundsException e) {
        fromIndex = 0;
        toIndex= pageSize;
        descriptionByCategoryList =descriptionByCategoryList.subList(fromIndex, toIndex);
      }catch(IllegalArgumentException e) {
         fromIndex = total-pageSize;
         toIndex =total;
      descriptionByCategoryList =descriptionByCategoryList.subList(fromIndex, toIndex);
     }

 descriptionByCategoryList = descriptionByCategoryList.subList(fromIndex, toIndex); //進行分頁 PageInfo<Description> page = new PageInfo<Description>(descriptionByCategoryList, 7); page = PageHelperTool.initPageInfoObj(pageIndex, total, pageSize, page); //調用分頁工具 mv.addObject("pageinfo", page);

 

分頁工具類

package cn.taotao.utils; import com.github.pagehelper.PageInfo; /** * @Title: PageHelperTool.java * @Package * @Description: 分頁工具類 */
public class PageHelperTool { /** * PageHelper中，若是當前頁是最後一頁，則返回的nextPage是0，即首頁，而有時咱們須要最後一頁的nextPage是lastPage，所以寫此方法 * * @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) { // 當總頁數小於或等於導航頁碼數時
        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 { // 當總頁數大於導航頁碼數時
            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頁
                for (int i = 0; i < pageInfo.getNavigatePages(); i++) { pageInfo.getNavigatepageNums()[i] = startNum++; } } else if (endNum > pageInfo.getPages()) { endNum = pageInfo.getPages(); // 最後navigatePages頁
                for (int i = pageInfo.getNavigatePages() - 1; i >= 0; i--) { pageInfo.getNavigatepageNums()[i] = endNum--; } } else { // 全部中間頁
                for (int i = 0; i < pageInfo.getNavigatePages(); i++) { pageInfo.getNavigatepageNums()[i] = startNum++; } } } return pageInfo; } }

 

題外另外，須要在排序的類，重寫自定義compare的規則。就是說，讓他知道如何排序