實際上分頁器或者分頁組件在現(xiàn)實中都有廣泛著的應(yīng)用，照理來說老衛(wèi)沒有必要單獨撰文來提這茬。事實是，我近期剛好在寫一門關(guān)于Spring Data、Thymeleaf 3、Bootstrap 4 的應(yīng)用課程，所以用了Bootstrap 4的樣式，結(jié)果之前很多例如 Bootstrap 3 的表格、分頁器啊之類的插件都不能很好的兼容，百度谷歌無果，而且 Bootstrap 4 還沒有出穩(wěn)定版本，官網(wǎng)的示例也是少的可憐，最終下決心要自己寫個分頁器了，所用到的技術(shù)就是 Spring Data、Thymeleaf 3、Bootstrap 4 。
分頁器有哪些需求
中國式報表從來都是最復(fù)雜的，隨之衍生而來的分頁器要求也是錯綜復(fù)雜。本例為求把分頁器原理告訴給大家，所以，將分頁組件的抽象為以下通用的內(nèi)容：
- 顯示頁碼的列表；
- 該列表的第一項是“上一頁”，最后一項是“下一頁”；
- 當(dāng)前選中的頁碼要高亮；
- 當(dāng)當(dāng)前頁的上一頁沒有頁碼可選時，則“上一頁”置為不可點擊的狀態(tài)；
- 當(dāng)當(dāng)前頁的下一頁沒有頁碼可選時，則“下一頁”置為不可點擊的狀態(tài)；
我們很容易就能找到一個 Bootstrap 分頁器的設(shè)計原型，如下圖：
你可以參考 Bootstrap 官網(wǎng)的介紹 http://getbootstrap.com/components/#pagination，但建議你不要直接用上面的樣式，因為這個樣式是 Bootstrap 3版本的。 最后，我找到的了Bootstrap 4 里面的樣式，卻不在官網(wǎng) http://www.quackit.com/bootstrap/bootstrap_4/tutorial/bootstrap_pagination.cfm。感謝 books-collection 項目帶給程序員的開源、免費圖書集合！
Spring Data 能做什么
org.springframework.data.domain.Page 是 Spring Data 提供的一個分頁器接口，提供了常用的方法，比如：
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List getContent(); // 返回分頁后的數(shù)據(jù)的列表int getTotalPages(); // 總頁數(shù)long getTotalElements(); // 總數(shù)據(jù)量boolean isFirst(); // 是否是第一個數(shù)據(jù)；boolean isLast(); // 是否是最后一個數(shù)據(jù)；int getNumber(); // 當(dāng)前頁面索引 |
構(gòu)造一個 Page，通常需要傳入一個 org.springframework.data.domain.PageRequest.PageRequest對象，所需參數(shù)為 (int page, int size)，其中 page 就是 要請求的頁面的索引，size 是頁面的大小（一頁最多有多少個數(shù)據(jù)）。
Spring Data 可以說提供了我們前端分頁器所需要的所有元素了。
Thymeleaf 牛刀小試
Thymeleaf 作為模版引擎，其好處就是可以綁定數(shù)據(jù)源，并且根據(jù)數(shù)據(jù)源來渲染頁面。最爽的莫過于根據(jù)綁定的數(shù)據(jù)列表來遍歷生成頁面元素，比如：
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<ul class="pagination" > <!-- 上一頁 --> <li class="page-item" data-th-classappend="*{first} ? 'disabled' : ''"> <a href="javascript:void(0);" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="page-link" data-th-attr="pageIndex=${page.number} - 1" aria-label="Previous"> <span aria-hidden="true">«</span> </a> </li> <!-- 迭代生成頁碼 --> <li class="page-item" data-th-each="i : ${#numbers.sequence(1, page.totalPages)}" data-th-classappend="${(page.number + 1) eq i} ? 'active' : ''" > <a class="page-link" data-th-attr="pageIndex=${i} - 1" href="javascript:void(0);" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" > <span data-th-text="${i}"></span> </a> </li> <!-- 下一頁 --> <li class="page-item" data-th-classappend="*{last} ? 'disabled' : ''"> <a href="javascript:void(0);" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="page-link" data-th-attr="pageIndex=${page.number} + 1" aria-label="Next"> <span aria-hidden="true">»</span> </a> </li></ul> |
這個就是簡單版本的分頁器了，可以看到我們的分頁器的“上一頁”和“下一頁”是固定不變的，中間根據(jù) totalPages（總頁數(shù)）來動態(tài)生成頁面。同時，我們根據(jù)是否是當(dāng)前頁（number + 1）來設(shè)置樣式是否高亮（active）。“上一頁”和“下一頁”是需要做一下判斷的，若當(dāng)前頁是第一頁（first）則“上一頁”不能點擊（disabled）；如果當(dāng)前頁是最后一頁（last）則“下一頁”不能點擊（disabled）。
考慮的再多一點
實際上，上面版本可以應(yīng)付大多數(shù)的應(yīng)用場景了。但是，可能會有點不完美，比如，我的頁數(shù)很多怎么辦？那么我們的分頁列表可能被拉得很長了，領(lǐng)導(dǎo)們可能會不滿意的！絕對要把這種不滿意的情緒扼殺在搖籃里。
可以看到，假如要做得更加完美，則還需要考慮，當(dāng)頁數(shù)太多時，應(yīng)該將某些用省略號。這就涉及到三種情況了：
- 當(dāng)當(dāng)前頁頁碼接近首頁時，省略號在后部出現(xiàn)；
- 當(dāng)當(dāng)前頁頁碼接最后頁時，省略號在前部出現(xiàn)；
- 最煩的要屬于，當(dāng)當(dāng)前頁在中部時，前部、后部都需要省略號；
帶省略號的分頁器
聰明的工程師們應(yīng)該馬上行動起來，大致的把算法畫了個草圖：
為求簡單，我們預(yù)設(shè)頁碼的列表最多在 7 頁（你也可以根據(jù)需要來改），也就是說，當(dāng) totalPages（總頁數(shù)）超過 7時，我們才需要考慮省略號的事情。
- “上一頁”和“下一頁”的算法于我們上面的簡單版本類似，這里就不贅述了。
- 當(dāng)前頁面頁碼小于等于4時，省略號在列表后部的倒數(shù)第二個出現(xiàn)；
- 最后一頁與當(dāng)前頁面之差小于等于3時，省略號在列表前部的第二個位置出現(xiàn)；
- 其余情況，則當(dāng)前頁適中處于中間位置，省略號同時在列表第二個位置及倒數(shù)第二個位置出現(xiàn)。
實現(xiàn)方式如下：
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<!-- 處理頁數(shù)大于7 的情況 --><ul class="pagination" data-th-if="${page.totalPages gt 7}" > <!-- 上一頁 --> <li class="page-item" data-th-classappend="*{first} ? 'disabled' : ''"> <a href="javascript:void(0);" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="page-link" data-th-attr="pageIndex=${page.number} - 1" aria-label="Previous"> <span aria-hidden="true">«</span> </a> </li> <!-- 首頁 --> <li class="page-item" data-th-classappend="${(page.number + 1) eq 1} ? 'active' : ''" > <a href="javascript:void(0);" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="page-link" data-th-attr="pageIndex=0">1</a> </li> <!-- 當(dāng)前頁面小于等于4 --> <li class="page-item" data-th-if="${(page.number + 1) le 4}" data-th-each="i : ${#numbers.sequence(2,5)}" data-th-classappend="${(page.number + 1) eq i} ? 'active' : ''" > <a class="page-link" href="javascript:void(0);" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" data-th-attr="pageIndex=${i} - 1"> <span data-th-text="${i}"></span> </a> </li> <li class="page-item disabled" data-th-if="${(page.number + 1) le 4}"> <a href="javascript:void(0);" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="page-link"> <span aria-hidden="true">...</span> </a> </li> <!-- 最后一頁與當(dāng)前頁面之差，小于等于3 --> <li class="page-item disabled" data-th-if="${(page.totalPages-(page.number + 1)) le 3}"> <a href="javascript:void(0);" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="page-link"> <span aria-hidden="true">...</span> </a> </li> <li class="page-item" data-th-if="${(page.totalPages-(page.number + 1)) le 3}" data-th-each="i : ${#numbers.sequence(page.totalPages-4, page.totalPages-1)}" data-th-classappend="${(page.number + 1) eq i} ? 'active' : ''" > <a class="page-link" href="javascript:void(0);" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" data-th-attr="pageIndex=${i} - 1"> <span data-th-text="${i}"></span> </a> </li> <!-- 最后一頁與當(dāng)前頁面之差大于3，且 當(dāng)前頁面大于4--> <li class="page-item disabled" data-th-if="${((page.number + 1) gt 4) && ((page.totalPages-(page.number + 1)) gt 3 )}"> <a href="javascript:void(0);" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="page-link"> <span aria-hidden="true">...</span> </a> </li> <li class="page-item" data-th-if="${((page.number + 1) gt 4) && ((page.totalPages-(page.number + 1)) gt 3 )}" > <a href="javascript:void(0);" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="page-link" data-th-attr="pageIndex=${page.number}">[[${page.number}]]</a> </li> <li class="page-item active" data-th-if="${((page.number + 1) gt 4) && ((page.totalPages-(page.number + 1)) gt 3 )}"> <a href="javascript:void(0);" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="page-link" data-th-attr="pageIndex=${page.number} + 1">[[${page.number + 1}]]</a> </li> <li class="page-item" data-th-if="${((page.number + 1) gt 4) && ((page.totalPages-(page.number + 1)) gt 3 )}"> <a href="javascript:void(0);" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="page-link" data-th-attr="pageIndex=${page.number} + 2">[[${page.number + 2}]]</a> </li> <li class="page-item disabled" data-th-if="${((page.number + 1) gt 4) && ((page.totalPages-(page.number + 1)) gt 3 )}"> <a href="javascript:void(0);" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="page-link"> <span aria-hidden="true">...</span> </a> </li> <!-- 最后一頁 --> <li class="page-item" data-th-classappend="${(page.number + 1) eq page.totalPages} ? 'active' : ''" > <a href="javascript:void(0);" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="page-link" data-th-attr="pageIndex=${page.totalPages} - 1">[[${page.totalPages}]]</a> </li> <!-- 下一頁 --> <li class="page-item" data-th-classappend="*{last} ? 'disabled' : ''"> <a href="javascript:void(0);" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="page-link" data-th-attr="pageIndex=${page.number} + 1" aria-label="Next"> <span aria-hidden="true">»</span> </a> </li></ul> |
還要再考慮的多一點？
當(dāng)然，正如我們開篇所講，中國式報表的需求千奇百怪，本文也只是從大部分通用需求出發(fā)，給個思路， 不一定能滿足所有人的需求。如果可能的話，再考慮多一點，比如：
- 是否可以選擇頁面的最大頁？
- 是否可以選擇任意頁面的索引？
等等，尼瑪看來下表快凌晨1點了。頂不順了，要睡了。各位讀者朋友可以繼續(xù)完善~
最終效果
以上就是本文的全部內(nèi)容，希望對大家的學(xué)習(xí)有所幫助，也希望大家多多支持服務(wù)器之家。
原文鏈接：http://www.importnew.com/24722.html?utm_source=tuicool&utm_medium=referral
