Ext Grid 平添 tip 提示信息

Ext Grid 添加 tip 提示信息
1.
{header:"姓名",dataIndex:"actor",sortable:true,width:80,renderer:showTip},
2.
function showTip(data, metadata, record, rowIndex, columnIndex, store){
//moviesColumn 如果为null，可以通过record获取title值
var title=moviesColumn.getColumnHeader(columnIndex);
metadata.attr = 'ext:qtitle="'+title+'" ext:qtip="' + data + '"';  
//metadata.attr = 'ext:qtip="' + data + '"';
//return "<div ext:qtip='<img src=""+value+"" width=100 hight=100/>'>"+value+"</div>";   
return data;
}