本文深入解析 dropload.js 在复杂业务场景下的应用,重点解决服务端分页、多条件筛选及排序导致的上拉加载失效问题。通过详解 setHasData、resetload、lock 与 unlock 接口的配合使用,确保在数据量变化或筛选条件切换时,滚动计算与加载状态正确同步,避免“拉不动”等常见 Bug。
dropload.js 基础与复杂场景挑战
dropload.js 提供了基础的上下拉刷新与翻页功能,适用于服务端一次性返回所有数据的场景。然而,实际业务中常需支持服务端分页、搜索、排序及多条件筛选(类似美团美食列表),这对插件的默认行为提出了更高要求。
一、解决方案
分页与筛选状态同步解决方案
改进1:针对分页、搜索、排序及多条件筛选场景,页面可能无需上拉操作,甚至初始加载无数据(如搜索不存在的名称)。为此,需引入 setHasData 接口进行状态控制。
MyDropLoad.prototype.setHasData = function(ishasData) {
var me = this;
if (ishasData) {
me.isData = true;
me.$domDown.html(me.opts.domDown.domRefresh);
fnRecoverContentHeight(me);
} else {
me.isData = false;
me.$domDown.html(me.opts.domDown.domNoData);
fnRecoverContentHeight(me);
}
};
改进2:上述需求引发的 Bug 在于,切换筛选条件后上拉加载更多无反应。原因复杂,例如不同筛选条件数据量不同,若不执行 resetload,上拉距离计算将出错。解决方案:1. 无论 API 请求成功或失败,必须执行 resetload;成功时需在新数据加载完毕后调用。2. 修改 resetload 逻辑,增加屏幕尺寸计算方法。
MyDropLoad.prototype.resetload = function() {
var me = this;
if (me.direction == 'down' && me.upInsertDOM) {
me.$domUp.css({ 'height': '0' }).on('webkitTransitionEnd mozTransitionEnd transitionend', function() {
me.loading = false;
me.upInsertDOM = false;
$(this).remove();
fnRecoverContentHeight(me);
});
} else if (me.direction == 'up') {
me.loading = false;
if (me.isData) {
me.$domDown.html(me.opts.domDown.domRefresh);
fnRecoverContentHeight(me);
} else {
me.$domDown.html(me.opts.domDown.domNoData);
}
}
}
3. 解决上述问题可覆盖 90% 场景,剩余难点在于 setHasData(false) 后的处理(假设每页 count 为 20)。Bug 现象:筛选条件1返回 20 条,上拉加载返回 10 条后设置 setHasData(false);切换至筛选条件2返回 20 条,上拉时无法加载。原因:setHasData(false) 后状态锁定为“无更多数据”,切换条件未解除锁定。解决方法:每次更改搜索、筛选或排序条件时,必须调用 setHasData(true)。
核心接口调用与状态管理详解
二、调用方法 整体页面逻辑较复杂。这里在整体解释一遍。 1. 选择要上拉加载的DIV,添加调用方法。 注意事项: (1)记得保存返回对象。 (2)LoadDownFn时上拉加载后的回调,这里自己要处理的逻辑。我这里时翻页发API,API参数中offset加20,然后发API。 (3)无论API返回失败成功,都必须resetload。 这里强调: fetchData函数调用发API,失败或者成功都必须self.moreFund.resetload()。 并且失败时直接调用self.moreFund.resetload()即可。成功时要在新的数据返回后,要先用JS动态加载HTML,加载完成后在执行self.moreFund.resetload()。
self.moreFund = $('#table-fundlist').dropload({
scrollArea: window,
domDown: {
domClass: 'dropload-down',
domRefresh: '<div class="dropload-refresh"><img class="drop-up-icon" src="images/dropload_up.png"><span>上拉加载更多</span></div>',
domLoad: '<div class="dropload-load"><img class="loading-icon" src="images/droploading.gif"></div>',
domNoData: ''
},
loadDownFn: function() {
self.apiParams.offset += 20;
self.fetchData(true);
}
});
2. setHasData详解 (1)什么时候需要设置true。 当非翻页API触发之前。即选择新的筛选条件,选择新的搜索字段,选择新的排序字段。这个时候必须setHasData(true)。 this.moreFund.setHasData(true); (2)什么时候设置false。 服务端返回数据后,比较服务端返回的条目数与API发送的条目数是否一致,不一致设置setHasData(false)。
if (data.length < this.apiParams.count){
this.moreFund.setHasData(false);
this.moreFund.lock();
}
3. lock与unlock详解 (1)什么时候设置lock。 服务端返回数据后,比较服务端返回的条目数与API发送的条目数是否一致,不一致设置lock()。 当前页面状态不需要上拉加载时需要设置lock()。例如:在搜索框输入的状态。 (2)什么时候设置unlock。 只有一个地方需要调用。发送API之前设置unlock。
if (self.moreFund) {
self.moreFund.unlock();
}
JS与CSS源代码实现
三、JS和CSS源代码
js:
(function($) {
'use strict';
var win = window;
var doc = document;
var $win = $(win);
var $doc = $(doc);
$.fn.dropload = function(options) {
return new MyDropLoad(this, options);
};
var MyDropLoad = function(element, options) {
var me = this;
me.$element = $(element);
me.upInsertDOM = false;
me.loading = false;
me.isLockUp = false;
me.isLockDown = false;
me.isData = true;
me._scrollTop = 0;
me.init(options);
};
MyDropLoad.prototype.init = function(options) {
var me = this;
me.opts = $.extend({}, {
scrollArea: me.$element,
domUp: {
domClass: 'dropload-up',
domRefresh: '<div class="dropload-refresh"><img class="drop-down-icon" src="../images/dropload_down.png"><span>下拉刷新</span></div>',
domUpdate: '<div class="dropload-update"><img class="drop-up-icon" src="../images/dropload_up.png"><span>释放更新</span></div>',
domLoad: '<div class="dropload-load"><img class="loading-icon" src="../images/droploading.gif"></div>'
},
domDown: {
domClass: 'dropload-down',
domRefresh: '<div class="dropload-refresh"><img class="drop-up-icon" src="../images/dropload_up.png"><span>上拉加载更多</span></div>',
domLoad: '<div class="dropload-load"><img class="loading-icon" src="../images/droploading.gif"></div>',
domNoData: ''
//domNoData : '<div class="dropload-noData"><span>暂无数据</span></div>'
},
distance: 50, // 拉动距离
threshold: '', // 提前加载距离
loadUpFn: '', // 上方function
loadDownFn: '' // 下方function
}, options);
if (me.opts.loadDownFn != '') {
me.$element.append('<div class="' + me.opts.domDown.domClass + '">' + me.opts.domDown.domRefresh + '</div>');
me.$domDown = $('.' + me.opts.domDown.domClass);
}
if (me.opts.scrollArea == win) {
me.$scrollArea = $win;
me._scrollContentHeight = $doc.height();
me._scrollWindowHeight = doc.documentElement.clientHeight;
} else {
me.$scrollArea = me.opts.scrollArea;
me._scrollContentHeight = me.$element[0].scrollHeight;
me._scrollWindowHeight = me.$element.height();
}
$win.on('resize', function() {
if (me.opts.scrollArea == win) {
me._scrollWindowHeight = win.innerHeight;
} else {
me._scrollWindowHeight = me.$element.height();
}
});
me.$element.on('touchstart', function(e) {
if (!me.loading) {
fnTouches(e);
fnTouchstart(e, me);
}
});
me.$element.on('touchmove', function(e) {
if (!me.loading) {
fnTouches(e, me);
fnTouchmove(e, me);
}
});
me.$element.on('touchend', function() {
if (!me.loading) {
fnTouchend(me);
}
});
me.$scrollArea.on('scroll', function() {
me._scrollTop = me.$scrollArea.scrollTop();
fnRecoverContentHeight(me)
if (me.opts.threshold === '') {
me._threshold = Math.floor(me.$domDown.height() * 1 / 3);
} else {
me._threshold = me.opts.threshold;
}
if (me.opts.loadDownFn != '' && !me.loading && !me.isLockDown && me._threshold != 0 && (me._scrollContentHeight - me._threshold) <= (me._scrollWindowHeight + me._scrollTop)) {
fnLoadDown();
}
});
function fnLoadDown() {
me.direction = 'up';
me.$domDown.html(me.opts.domDown.domLoad);
me.loading = true;
me.opts.loadDownFn(me);
}
};
function fnTouches(e) {
if (!e.touches) {
e.touches = e.originalEvent.touches;
}
}
function fnTouchstart(e, me) {
me._startY = e.touches[0].pageY;
me.touchScrollTop = me.$scrollArea.scrollTop();
}
function fnTouchmove(e, me) {
me._curY = e.touches[0].pageY;
me._moveY = me._curY - me._startY;
if (me._moveY > 0) {
me.direction = 'down';
} else if (me._moveY < 0) {
me.direction = 'up';
}
var _absMoveY = Math.abs(me._moveY);
if (me.opts.loadUpFn != '' && me.touchScrollTop <= 0 && me.direction == 'down' && !me.isLockUp) {
e.preventDefault();
me.$domUp = $('.' + me.opts.domUp.domClass);
if (!me.upInsertDOM) {
me.$element.prepend('<div class="' + me.opts.domUp.domClass + '"></div>');
me.upInsertDOM = true;
}
fnTransition(me.$domUp, 0);
if (_absMoveY <= me.opts.distance) {
me._offsetY = _absMoveY;
me.$domUp.html(me.opts.domUp.domRefresh);
} else if (_absMoveY > me.opts.distance && _absMoveY <= me.opts.distance * 2) {
me._offsetY = me.opts.distance + (_absMoveY - me.opts.distance) * 0.5;
me.$domUp.html(me.opts.domUp.domUpdate);
} else {
me._offsetY = me.opts.distance + me.opts.distance * 0.5 + (_absMoveY - me.opts.distance * 2) * 0.2;
}
me.$domUp.css({ 'height': me._offsetY });
}
}
// touchend
function fnTouchend(me) {
var _absMoveY = Math.abs(me._moveY);
if (me.opts.loadUpFn != '' && me.touchScrollTop <= 0 && me.direction == 'down' && !me.isLockUp) {
fnTransition(me.$domUp, 300);
if (_absMoveY > me.opts.distance) {
me.$domUp.css({ 'height': me.$domUp.children().height() });
me.$domUp.html(me.opts.domUp.domLoad);
me.loading = true;
me.opts.loadUpFn(me);
} else {
me.$domUp.css({ 'height': '0' }).on('webkitTransitionEnd transitionend', function() {
me.upInsertDOM = false;
$(this).remove();
});
}
me._moveY = 0;
}
}
// 重新获取文档高度
function fnRecoverContentHeight(me) {
if (me.opts.scrollArea == win) {
me._scrollContentHeight = $doc.height();
} else {
me._scrollContentHeight = me.$element[0].scrollHeight;
}
}
MyDropLoad.prototype.lock = function(direction) {
var me = this;
if (direction === undefined) {
if (me.direction == 'up') {
me.isLockDown = true;
} else if (me.direction == 'down') {
me.isLockUp = true;
} else {
me.isLockUp = true;
me.isLockDown = true;
}
} else if (direction == 'up') {
me.isLockUp = true;
} else if (direction == 'down') {
me.isLockDown = true;
}
};
MyDropLoad.prototype.unlock = function() {
var me = this;
me.isLockUp = false;
me.isLockDown = false;
};
MyDropLoad.prototype.setHasData = function(ishasData) {
var me = this;
if (ishasData) {
me.isData = true;
me.$domDown.html(me.opts.domDown.domRefresh);
fnRecoverContentHeight(me);
} else {
me.isData = false;
me.$domDown.html(me.opts.domDown.domNoData);
fnRecoverContentHeight(me);
}
};
MyDropLoad.prototype.resetload = function() {
var me = this;
if (me.direction == 'down' && me.upInsertDOM) {
me.$domUp.css({ 'height': '0' }).on('webkitTransitionEnd mozTransitionEnd transitionend', function() {
me.loading = false;
me.upInsertDOM = false;
$(this).remove();
fnRecoverContentHeight(me);
});
} else if (me.direction == 'up') {
me.loading = false;
if (me.isData) {
me.$domDown.html(me.opts.domDown.domRefresh);
fnRecoverContentHeight(me);
} else {
me.$domDown.html(me.opts.domDown.domNoData);
}
}
};
function fnTransition(dom, num) {
dom.css({
'-webkit-transition': 'all ' + num + 'ms',
'transition': 'all ' + num + 'ms'
});
}
})(window.Zepto || window.jQuery);
CSS:
.dropload-up,
.dropload-down {
background-color: #F0EFF5;
position: relative;
height: 0;
overflow: hidden;
}
.dropload-down {
height: 50px;
border-top: 1px solid #e5e5e5;
}
.dropload-refresh .drop-up-icon,
.dropload-refresh .drop-down-icon,
.dropload-update .drop-up-icon,
.dropload-update .drop-down-icon {
vertical-align: text-bottom;
margin-right: 3px;
height: 16px;
width: 12px;
}
.dropload-load .loading-icon {
vertical-align: middle;
height: 20px;
width: 20px;
}
.dropload-refresh span,
.dropload-update span {
vertical-align: middle;
line-height: 18px;
font-size: 16px;
color: #585858;
}
.dropload-noData {
border-bottom: 1px solid #e5e5e5;
background-color: #FFFFFF;
}
.dropload-noData span {
line-height: 18px;
font-size: 14px;
color: #999999;
}
.dropload-refresh,
.dropload-update,
.dropload-load,
.dropload-noData {
position: absolute;
width: 100%;
height: 50px;
bottom: 0;
line-height: 50px;
text-align: center;
}
.dropload-down .dropload-refresh,
.dropload-down .dropload-update,
.dropload-down .dropload-load {
top: 0;
bottom: auto;
}
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