大家好，我初学Extjs4,有很多问题不懂，希望大家帮我看看如何实现这样的要求：要在左边添加多选框，把查询那个地方变成一个下拉列表如图：

如下是我的代码和效果图：（但是我不知道在哪里添加什么代码，希望大神帮我添加）

initComponent : function(){
    	
       this.store=new Ext.data.JsonStore({
		id:"id",
       	url: this.formatUrl('list'),
       	root:"result",
  		totalProperty:"rowCount",
  		remoteSort:true,  		
  		fields:this.storeMapping});
  		this.store.baseParams=Ext.apply({},{limit:this.pageSize||""},{});
        if(this.baseQueryParameter){
            this.store.on('beforeload',function(store,options){
                Ext.apply(store.baseParams,this.baseQueryParameter);
            },this);
        }
      	this.store.paramNames.sort="orderBy";
	 	this.store.paramNames.dir="orderType";	  
      	this.cm.defaultSortable=true;
      	
        EasyJF.Ext.CrudPanel.superclass.initComponent.call(this);
        var viewConfig=Ext.apply({forceFit:true},this.gridViewConfig);  
        this.searchField=new EasyJF.Ext.CrudSearchField({hidden:!this.showSearchField,width:this.searchFieldWidth||100,store:this.store});
        var tbar=[
             {    
                text: '添加',  
                handler: this.create,
                cls : "x-btn-text-icon",
                icon : "images/icons/add.png",
                scope:this
            },
            {    
                text: '修改', 
                handler: this.edit,
                cls : "x-btn-text-icon",
                icon : "images/icons/edit.png",
                scope:this
            },
            {    
                text: '删除', 
                handler: this.removeData,
                cls : "x-btn-text-icon",
                icon : "images/icons/delete.png",
                scope:this
            },
             {    
                text: '刷新',  
                handler: this.refresh,
                cls : "x-btn-text-icon",
                icon : "images/icons/f5.png",
                scope:this
            },
            {    
                text: '导出',  
                handler: this.exportDatas,
                cls : "x-btn-text-icon",
                icon : "images/icons/excel.png",
               // hidden:!this.showExportData,
                scope:this
            },
            {    
                text: '导入',  
                handler: this.importDatas,
                cls : "x-btn-text-icon",
                icon : "images/icons/import.png",
               // hidden:!this.showImportData,
                scope:this
            }];
            
        if(this.gridButtons)tbar=tbar.concat(this.gridButtons);
        
        tbar=tbar.concat(["->",'查询: ',this.searchField]);
        this.grid=new Ext.grid.GridPanel({
        store: this.store,
        cm: this.cm,     
        trackMouseOver:false,
        loadMask: true,
        region:"center",
        viewConfig:viewConfig,
        tbar:tbar,
        bbar: new Ext.PagingToolbar({
        	
            pageSize: this.pageSize,
            store: this.store,
            displayInfo: true,
            displayMsg: '记录 {0} - {1} of {2}',
            emptyMsg: "没有数据记录"
        })
   		});   		   		
   		this.grid.on("celldblclick",this.edit,this);       
   		this.add(this.grid);
   		this.store.load();
   		
        }
});