时间格式转换
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSDate *date =[[[NSDate alloc]initWithTimeIntervalSince1970:[cobj.time doubleValue]]autorelease];
// NSLog(@"%@", date);
NSString *strDate = [dateFormatter stringFromDate:date];
[dateFormatter release];