为甚麽extjs 的PagingToolbar 显示的总页数 一直是1

[funnyone]

我返回的结果 totalPage":"4" store.getTotalCount()也是4

 var store = new Ext.data.Store({
			url: '/extjs/movie.do',
			reader: new Ext.data.JsonReader({
				root:'rows',
				totalProperty:'totalPage',
				id:'id'
			}, [
				'id',
				'coverthumb',
				'title',
				'director',
				{name: 'released', type: 'date', dateFormat: 'Y-m-d'},
				'genre',
				'tagline',
				{name: 'price', type: 'float'},
				{name: 'available', type: 'bool'}
			])
	    });
	
		store.load();
	
		var grid = new Ext.grid.GridPanel({
			renderTo: document.body,
			frame:true,
			title: 'Movie Database',
			height:300,
			width:520,
			store: store,
			autoExpandColumn: 'title',
			columns: [
		      {header: "Title", dataIndex: 'title', renderer: title_img, id: 'title', sortable: true},
		      {header: "Director", dataIndex: 'director', hidden: true},
		      {header: "Released", dataIndex: 'released', sortable: true,  
					renderer: Ext.util.Format.dateRenderer('m/d/Y')},
		      {header: "Genre", dataIndex: 'genre', sortable: true},
		      {header: "Tagline", dataIndex: 'tagline', hidden: true},
			  {header: "Price", dataIndex: 'price', renderer: 'usMoney', sortable: true}
		    ],
			sm: new Ext.grid.RowSelectionModel({
				singleSelect: true,
				listeners: {
					rowselect: {
						fn: function(sm,index,record) { Ext.Msg.alert('getTotalCount',store.getTotalCount()); }
					}
				}
			}),
			bbar: new Ext.PagingToolbar({
				pageSize: 5,
				store: store,
				 displayInfo: true,
		         displayMsg: '当前显示记录: {0} - {1} 共计: {2}',
		         emptyMsg: "没有记录可以显示"
			})
		 });
		
	});