获取对象的全部字段，判断其是否自定义字段

Map<String, Schema.SObjectType> schemaMap = Schema.getGlobalDescribe();
Schema.SObjectType leadSchema = schemaMap.get('Opportunity');
Map<String, Schema.SObjectField> fieldMap = leadSchema.getDescribe().fields.getMap();
for(string fieldName :fieldMap.keySet())
{  

   //fieldName 为字段api    

     System.debug(fieldName+'--------fieldName------');
    Schema.DescribeFieldResult DescField =fieldMap.get(fieldName).getDescribe();
    System.debug(DescField.isCustom()+':自定义字段返回True,标准字段返回false');

}