pageInfo类属性含义小结

pageInfo类可用于分页操作。以下为属性含义：

private static final long serialVersionUID = 1L;
    private int pageNum;      //当前页的页码
    private int pageSize;      //每页的数量
    private int size;            //当前页的数量

可以在页面中"显示startRow到endRow 共size条数据"
    private int startRow; //当前页面第一个元素在数据库中的行号
    private int endRow;//当前页面最后一个元素在数据库中的行号
    
    private long total;     //总记录数
    private int pages;       //总页数
    private List<T> list;      //结果集
    
    private int prePage;    //上一页
    private int nextPage;   //下一页
    
    private boolean isFirstPage;   //是否为第一页
    private boolean isLastPage;   //是否为最后一页
    private boolean hasPreviousPage;       //是否有前一页
    private boolean hasNextPage;          //是否有下一页
    
    private int navigatePages;          //导航页码数
    private int[] navigatepageNums;       //所有导航页号
    private int navigateFirstPage;       //导航条上的第一页
    private int navigateLastPage;     //导航条上的最后一页

           

构造函数

public PageInfo() {
        this.isFirstPage = false;
        this.isLastPage = false;
        this.hasPreviousPage = false;
        this.hasNextPage = false;
    }
 /** 
     * 包装Page对象 
     * 
     * @param list 
     */  
    public PageInfo(List<T> list) {
        this(list, 8);
    }
 /** 
     * 包装Page对象 
     * 
     * @param list          page结果 
     * @param navigatePages 页码数量 
     */  
    public PageInfo(List<T> list, int navigatePages) {
        this.isFirstPage = false;
        this.isLastPage = false;
        this.hasPreviousPage = false;
        this.hasNextPage = false;
        if (list instanceof Page) {
            Page page = (Page)list;
            this.pageNum = page.getPageNum();
            this.pageSize = page.getPageSize();
            this.pages = page.getPages();
            this.list = page;
            this.size = page.size();
            this.total = page.getTotal();
            if (this.size == 0) {
                this.startRow = 0;
                this.endRow = 0;
            } else {
            //由于结果是>startRow的，所以实际的需要+1  
                this.startRow = page.getStartRow() + 1;
                 //计算实际的endRow（最后一页的时候特殊）  
                this.endRow = this.startRow - 1 + this.size;
            }
        } else if (list instanceof Collection) {
            this.pageNum = 1;
            this.pageSize = list.size();
            this.pages = this.pageSize > 0 ? 1 : 0;
            this.list = list;
            this.size = list.size();
            this.total = (long)list.size();
            this.startRow = 0;
            this.endRow = list.size() > 0 ? list.size() - 1 : 0;
        }

        if (list instanceof Collection) {
            this.navigatePages = navigatePages;
            this.calcNavigatepageNums();       //计算导航页 
            this.calcPage();          //计算前后页，第一页，最后一页  
            this.judgePageBoudary();     //判断页面边界
        }

    }
           

计算导航页

private void calcNavigatepageNums() {
        int i;
        if (this.pages <= this.navigatePages) {
            this.navigatepageNums = new int[this.pages];

            for(i = 0; i < this.pages; ++i) {
                this.navigatepageNums[i] = i + 1;
            }
        } else {
            this.navigatepageNums = new int[this.navigatePages];
            i = this.pageNum - this.navigatePages / 2;
            int endNum = this.pageNum + this.navigatePages / 2;
            int i;
            if (i < 1) {
                i = 1;

                for(i = 0; i < this.navigatePages; ++i) {
                    this.navigatepageNums[i] = i++;
                }
            } else if (endNum > this.pages) {
                endNum = this.pages;

                for(i = this.navigatePages - 1; i >= 0; --i) {
                    this.navigatepageNums[i] = endNum--;
                }
            } else {
                for(i = 0; i < this.navigatePages; ++i) {
                    this.navigatepageNums[i] = i++;
                }
            }
        }

    }
           

计算前后页，第一页，最后一页

private void calcPage() {
        if (this.navigatepageNums != null && this.navigatepageNums.length > 0) {
            this.navigateFirstPage = this.navigatepageNums[0];
            this.navigateLastPage = this.navigatepageNums[this.navigatepageNums.length - 1];
            if (this.pageNum > 1) {
                this.prePage = this.pageNum - 1;
            }

            if (this.pageNum < this.pages) {
                this.nextPage = this.pageNum + 1;
            }
        }

    }
           

判断页面边界

private void judgePageBoudary() {
        this.isFirstPage = this.pageNum == 1;
        this.isLastPage = this.pageNum == this.pages || this.pages == 0;
        this.hasPreviousPage = this.pageNum > 1;
        this.hasNextPage = this.pageNum < this.pages;
    }
           

转载来源：https://www.e-learn.cn/content/qita/758537