iphone - postNotification 正确触发功能，但 userinfo(NSDictionary) 什么都没有

Question

我使用下面的代码来通知菜单选择索引

    NSDictionary *userInfo=  [NSDictionary dictionaryWithObject:[NSString stringWithFormat:@"123"] 
                                              forKey:@"Index"];
   [[NSNotificationCenter defaultCenter] postNotificationName: @"notifyToMenuSelectionNotification"
                                                    object: userInfo];



-(void)menuSelectionNotification:(NSNotification *)notification
{
  NSLog(@"%@", notification.userInfo);


}

menuSelectionNotification 被正确触发，

但 NSLog 输出 notification.userInfo 仍然是 {null}

欢迎任何评论1

Answer 1

你以错误的方式传递对象。请试试这个 -

NSDictionary *userInfo=  [NSDictionary dictionaryWithObject:[NSString stringWithFormat:@"123"] 
                                              forKey:@"Index"];

[[NSNotificationCenter defaultCenter] postNotificationName:@"notifyToMenuSelectionNotification"
                                      object:nil
                                      userInfo:userInfo];

Answer 2

您必须将字典设置为 userInfo 参数，而不是对象。你可能想试试

[[NSNotificationCenter defaultCenter] postNotificationName:@"notifyToMenuSelectionNotification" object:nil userInfo:userInfo];

Answer 3

userInfo您应该在参数中发布字典，例如

[[NSNotificationCenter defaultCenter] postNotificationName:@"notifyToMenuSelectionNotification" object:nil userInfo:userInfo];

有关更多详细信息，请。请参阅NSNotificationCenter文档

Answer 4

请试试这个

[[NSNotificationCenter defaultCenter] postNotificationName:@"notifyToMenuSelectionNotification" object:userInfo userInfo:nil];

-(void)menuSelectionNotification:(NSNotification *)notification{
NSDictionary *userInfo =   (NSDictionary*)notification.object;
}