我的后端是 Parse 的 BAAS。为了首先获取最新记录并通过以前的记录进行分页，我需要按创建的时间戳降序排列，并使用“跳过”一定数量的记录以及每次提取的“限制”记录数。skip 和 limit 都是 +ve 数字。
我在 ST 中有一个列表，需要在底部有最新记录。当用户输入一条记录时，该记录需要追加到底部。当用户滚动到顶部时，列表需要使用分页获取以前的记录。
第一个问题：为了在底部显示最新消息，我在 ST 上按创建时间戳的升序对列表进行排序——有没有办法在没有排序的情况下实现这一点？
第二个问题：我有一个自定义插件（列表分页插件的一个小变种），它在滚动到顶部时获取以前的记录，但即使我动态地将 scrollToTop 设置为 false，一旦商店加载，列表会继续滚动到顶部（不带动画）。我怎样才能避免这种情况？
任何帮助深表感谢！谢谢！
这是我的插件代码：
/**
* Adds a Load More button at the bottom of the list. When the user presses this button,
* the next page of data will be loaded into the store and appended to the List.
*
* By specifying `{@link #autoPaging}: true`, an 'infinite scroll' effect can be achieved,
* i.e., the next page of content will load automatically when the user scrolls to the
* bottom of the list.
*
* ## Example
*
* Ext.create('Ext.dataview.List', {
*
* store: Ext.create('TweetStore'),
*
* plugins: [
* {
* xclass: 'Ext.plugin.ListPaging',
* autoPaging: true
* }
* ],
*
* itemTpl: [
* '<img src="{profile_image_url}" />',
* '<div class="tweet">{text}</div>'
* ]
* });
*/
Ext.define('MyApp.ux.plugin.ListReversePaging', {
extend: 'Ext.Component',
alias: 'plugin.listreversepaging',
config: {
/**
* @cfg {Boolean} autoPaging
* True to automatically load the next page when you scroll to the bottom of the list.
*/
autoPaging: false,
/**
* @cfg {String} loadMoreText The text used as the label of the Load More button.
*/
loadMoreText: '',
/**
* @cfg {String} noMoreRecordsText The text used as the label of the Load More button when the Store's
* {@link Ext.data.Store#totalCount totalCount} indicates that all of the records available on the server are
* already loaded
*/
noMoreRecordsText: '',
/**
* @private
* @cfg {String} loadTpl The template used to render the load more text
*/
loadTpl: [
'<div class="{cssPrefix}loading-spinner" style="font-size: 180%; margin: 10px auto;">',
'<span class="{cssPrefix}loading-top"></span>',
'<span class="{cssPrefix}loading-right"></span>',
'<span class="{cssPrefix}loading-bottom"></span>',
'<span class="{cssPrefix}loading-left"></span>',
'</div>',
'<div class="{cssPrefix}list-paging-msg">{message}</div>'
].join(''),
/**
* @cfg {Object} loadMoreCmp
* @private
*/
loadMoreCmp: {
xtype: 'component',
baseCls: Ext.baseCSSPrefix + 'list-paging',
scrollDock: 'top',
hidden: true
},
/**
* @private
* @cfg {Boolean} loadMoreCmpAdded Indicates whether or not the load more component has been added to the List
* yet.
*/
loadMoreCmpAdded: false,
/**
* @private
* @cfg {String} loadingCls The CSS class that is added to the {@link #loadMoreCmp} while the Store is loading
*/
loadingCls: Ext.baseCSSPrefix + 'loading',
/**
* @private
* @cfg {Ext.List} list Local reference to the List this plugin is bound to
*/
list: null,
/**
* @private
* @cfg {Ext.scroll.Scroller} scroller Local reference to the List's Scroller
*/
scroller: null,
/**
* @private
* @cfg {Boolean} loading True if the plugin has initiated a Store load that has not yet completed
*/
loading: false
},
/**
* @private
* Sets up all of the references the plugin needs
*/
init: function(list) {
var scroller = list.getScrollable().
getScroller(),
store = list.getStore();
this.setList(list);
this.setScroller(scroller);
this.bindStore(list.getStore());
this.addLoadMoreCmp();
// The List's Store could change at any time so make sure we are informed when that happens
list.updateStore = Ext.Function.createInterceptor(list.updateStore, this.bindStore, this);
if (this.getAutoPaging()) {
scroller.on({
scrollend: this.onScrollEnd,
scope: this
});
}
},
/**
* @private
*/
bindStore: function(newStore, oldStore) {
if (oldStore) {
oldStore.un({
beforeload: this.onStoreBeforeLoad,
load: this.onStoreLoad,
filter: this.onFilter,
scope: this
});
}
if (newStore) {
newStore.on({
beforeload: this.onStoreBeforeLoad,
load: this.onStoreLoad,
filter: this.onFilter,
scope: this
});
}
},
/**
* @private
* Removes the List/DataView's loading mask because we show our own in the plugin. The logic here disables the
* loading mask immediately if the store is autoloading. If it's not autoloading, allow the mask to show the first
* time the Store loads, then disable it and use the plugin's loading spinner.
* @param {Ext.data.Store} store The store that is bound to the DataView
*/
disableDataViewMask: function() {
var list = this.getList();
this._listMask = list.getLoadingText();
list.setLoadingText(null);
},
enableDataViewMask: function() {
if (this._listMask) {
var list = this.getList();
list.setLoadingText(this._listMask);
delete this._listMask;
}
},
/**
* @private
*/
applyLoadTpl: function(config) {
return (Ext.isObject(config) && config.isTemplate) ? config : new Ext.XTemplate(config);
},
/**
* @private
*/
applyLoadMoreCmp: function(config) {
config = Ext.merge(config, {
html: this.getLoadTpl().
apply({
cssPrefix: Ext.baseCSSPrefix,
message: this.getLoadMoreText()
}),
scrollDock: 'bottom',
listeners: {
tap: {
fn: this.loadNextPage,
scope: this,
element: 'element'
}
}
});
return Ext.factory(config, Ext.Component, this.getLoadMoreCmp());
},
/**
* @private
* If we're using autoPaging and detect that the user has scrolled to the bottom, kick off loading of the next page
*/
onScrollEnd: function(scroller, x, y) {
var list = this.getList();
if (!this.getLoading() && y <= 50) {
this.currentScrollToTopOnRefresh = list.getScrollToTopOnRefresh();
list.setScrollToTopOnRefresh(false);
this.loadNextPage();
}
},
/**
* @private
* Makes sure we add/remove the loading CSS class while the Store is loading
*/
updateLoading: function(isLoading) {
var loadMoreCmp = this.getLoadMoreCmp(),
loadMoreCls = this.getLoadingCls();
if (isLoading) {
loadMoreCmp.addCls(loadMoreCls);
} else {
loadMoreCmp.removeCls(loadMoreCls);
}
},
/**
* @private
* If the Store is just about to load but it's currently empty, we hide the load more button because this is
* usually an outcome of setting a new Store on the List so we don't want the load more button to flash while
* the new Store loads
*/
onStoreBeforeLoad: function(store) {
if (store.getCount() === 0) {
this.getLoadMoreCmp().
hide();
}
},
/**
* @private
*/
onStoreLoad: function(store) {
var loadCmp = this.getLoadMoreCmp(),
template = this.getLoadTpl(),
message = this.storeFullyLoaded() ? this.getNoMoreRecordsText() : this.getLoadMoreText();
if (store.getCount()) {
loadCmp.show();
}
this.setLoading(false);
//if we've reached the end of the data set, switch to the noMoreRecordsText
loadCmp.setHtml(template.apply({
cssPrefix: Ext.baseCSSPrefix,
message: message
}));
if (this.currentScrollToTopOnRefresh !== undefined) {
this.getList().
setScrollToTopOnRefresh(false);
delete this.currentScrollToTopOnRefresh;
}
this.enableDataViewMask();
},
onFilter: function(store) {
if (store.getCount() === 0) {
this.getLoadMoreCmp().
hide();
} else {
this.getLoadMoreCmp().
show();
}
},
/**
* @private
* Because the attached List's inner list element is rendered after our init function is called,
* we need to dynamically add the loadMoreCmp later. This does this once and caches the result.
*/
addLoadMoreCmp: function() {
var list = this.getList(),
cmp = this.getLoadMoreCmp();
if (!this.getLoadMoreCmpAdded()) {
list.add(cmp);
/**
* @event loadmorecmpadded Fired when the Load More component is added to the list. Fires on the List.
* @param {Ext.plugin.ListPaging} this The list paging plugin
* @param {Ext.List} list The list
*/
list.fireEvent('loadmorecmpadded', this, list);
this.setLoadMoreCmpAdded(true);
}
return cmp;
},
/**
* @private
* Returns true if the Store is detected as being fully loaded, or the server did not return a total count, which
* means we're in 'infinite' mode
* @return {Boolean}
*/
storeFullyLoaded: function() {
var store = this.getList().
getStore(),
total = store.getTotalCount();
return total !== null ? store.getTotalCount() <= (store.currentPage * store.getPageSize()) : false;
},
/**
* @private
*/
loadNextPage: function() {
var me = this;
if (!me.storeFullyLoaded()) {
me.disableDataViewMask();
me.setLoading(true);
me.getList().
getStore().
nextPage({addRecords: true});
}
}
});