Ext 动态添加grid 列数

在做报表的时候，需要将grid的列数做成活的，列数有数据库里的字段确定，这据需要将grid的列数做成动态的，经过多次实验已成，如下：

后台返回的json:

                {'action':true,'message':'error!','data':[
                {'number':'1','text1': '3','info1': '4','special1': '5'}
                ],'columModle':[
                {'header': '序号','dataIndex': 'number','width':40},
                {'header': '编码','dataIndex': 'text1'},
                {'header': '名称','dataIndex': 'info1'},
                {'header': '金额','dataIndex': 'special1'}
                ],'fieldsNames':[{name: 'number'},
                {name: 'text1'}, {name: 'info1'},
                {name: 'special1'}]}

            var cm = new Ext.grid.ColumnModel(json.columModle);
            var ds = new Ext.data.JsonStore({
            data:json.data,
            fields:json.fieldsNames
            });
                                      
            var grid = new Ext.grid.GridPanel({
            region: 'center',
            split: true,
            border:false,
            cm:cm,
            ds:ds
            });
            grid.render(document.body);
          
            new Ext.Viewport({
              layout: 'border',
              split: true,
              items: [grid]
            });


对于Ext动态grid这个问题，好多人都问过我，还有就是如何做多行表头，就是表头有两行以上，其中一列跨下边几列，对于多行表头的问题在这一会半会会说不清楚，只能告诉大家需要自己写插件。咱们还是说说动态表头的问题。
简单的说就是：从后台拼出json字符串--->前台取得字符串，并转化为json----->根据json创建grid
1.从后台拼出json字符串
               “{'action':true,'message':'error!','data':[
                {'number':'1','text1': '3','info1': '4','special1': '5'}
                ],'columModle':[
                {'header': '序号','dataIndex': 'number','width':40},
                {'header': '编码','dataIndex': 'text1'},
                {'header': '名称','dataIndex': 'info1'},
                {'header': '金额','dataIndex': 'special1'}
                ],'fieldsNames':[{name: 'number'},
                {name: 'text1'}, {name: 'info1'},
                {name: 'special1'}]}”
2.前台取得字符串，并转化为json
                               Ext.Ajax.request({
                                url: '自己的url',
                                params: 'method=自己的方法',
                                method: 'POST',
                                success: function(rs,request){
                                    var result = rs.responseText;//拿到结果集，此时为字符串
                                    var json = Ext.util.JSON.decode(result);//将字符串转换为json类型
                                },
                                failure: function(rs,request){
                                }
                            });
3.根据json创建grid
                               Ext.Ajax.request({
                                url: '自己的url',
                                params: 'method=自己的方法',
                                method: 'POST',
                                success: function(rs,request){
                                    var result = rs.responseText;//拿到结果集，此时为字符串
                                    var json = Ext.util.JSON.decode(result);//将字符串转换为json类型
                                    var cm = new Ext.grid.ColumnModel(json.columModle);
                                    var ds = new Ext.data.JsonStore({
                                          data:json.data,
                                          fields:json.fieldsNames
                                        });
                                     
                                    var grid = new Ext.grid.GridPanel({
                                            region: 'center',
                                            split: true,
                                            border:false,
                                            cm:cm,
                                            ds:ds
                                            });
                                   // grid.render(document.body);
         
                                  new Ext.Viewport({
                                          layout: 'border',
                                          split: true,
                                          items: [grid]
                                    });
                                },
                                failure: function(rs,request){
                                }
                            });

注意的地方：首先grid必须在sucsess方法里实例，否则会报错，json数据也只在sucess方法里起作用。Ext的灵魂就是json很多控件都可以用以上方法实现。