Objective c NSN通知发送一次，但收到多次

我正在两个班级之间与NSNotificationCenter进行交流。我的问题是，尽管我点击了一次按钮（该按钮只会触发一次），但我无意中从一次对NSNotificationCenter的呼叫中生成了越来越多的通知

下面是对该问题的更好解释，代码如下：

---

我的两个类是主视图类和菜单类

点击mainView类中的视图时，它将启动一个由菜单创建和管理的视图。初始化mainView时调用此代码：

menu=[[MyMenu alloc] init];
UITapGestureRecognizer * tap=[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(onTapped:)];
[tap setNumberOfTapsRequired:1];
[container addGestureRecognizer:tap];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(onChangeItem:) name:@"ItemChange" object:nil];

此手势识别器也在mainView类中触发此方法：

- (void) onTapped: (UIGestureRecognizer*) recognizer {
    NSLog(@"tap");
    [menu displayMenu];
}

- (void) displayMenu {
    [viewForMenu addSubview:menuView];
}

- (UICollectionViewCell*) collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewCell * cell=[collectionView dequeueReusableCellWithReuseIdentifier:@"cell" forIndexPath:indexPath];
    [cell setTag:indexPath.row];
    UITapGestureRecognizer * tap=[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(onButtonTapped:)];
    [tap setNumberOfTapsRequired:1];
    [cell addGestureRecognizer:tap];
    NSLog(@"button tapped : %d",indexPath.row);
    return cell;
}

- (void) onButtonTapped:(UIGestureRecognizer*) recognizer {
    NSInteger buttonTapped=[[recognizer view] tag];
    [[NSNotificationCenter defaultCenter] postNotificationName:@"ItemChange" object:nil userInfo:@{@"selected":@(buttonTapped)}];
[self clearMenu];
}

- (void) onChangeItem: (NSNotification*) notification {
    NSLog(@"change item to %d",[[[notification userInfo] objectForKey:@"clock"] intValue]);
}

以下是菜单类初始化的方式：

- (MyMenu*) init {
    self=[super init];
    UICollectionViewFlowLayout * layout=[[UICollectionViewFlowLayout alloc] init];
    menuView=[[UICollectionView alloc] initWithFrame:CGRectMake(0, 0, 200, 200) collectionViewLayout:layout];
    [menuView setDataSource:self];
    [menuView setDelegate:self];
    [menuView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"cell"];
    [menuView setAutoresizesSubviews:YES];
    [menuView setAutoresizingMask:UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth];
    [menuView setBackgroundColor:[UIColor clearColor]];
    [menuView setIndicatorStyle:UIScrollViewIndicatorStyleWhite];
    return self;
}

这是

displayMenu

类中的菜单方法：

- (void) onTapped: (UIGestureRecognizer*) recognizer {
    NSLog(@"tap");
    [menu displayMenu];
}

- (void) displayMenu {
    [viewForMenu addSubview:menuView];
}

- (UICollectionViewCell*) collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewCell * cell=[collectionView dequeueReusableCellWithReuseIdentifier:@"cell" forIndexPath:indexPath];
    [cell setTag:indexPath.row];
    UITapGestureRecognizer * tap=[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(onButtonTapped:)];
    [tap setNumberOfTapsRequired:1];
    [cell addGestureRecognizer:tap];
    NSLog(@"button tapped : %d",indexPath.row);
    return cell;
}

- (void) onButtonTapped:(UIGestureRecognizer*) recognizer {
    NSInteger buttonTapped=[[recognizer view] tag];
    [[NSNotificationCenter defaultCenter] postNotificationName:@"ItemChange" object:nil userInfo:@{@"selected":@(buttonTapped)}];
[self clearMenu];
}

- (void) onChangeItem: (NSNotification*) notification {
    NSLog(@"change item to %d",[[[notification userInfo] objectForKey:@"clock"] intValue]);
}

菜单类还有一个

clearMenu

方法：

- (void) clearMenu {
    [menuView removeFromSuperview];
}

这是UICollectionView中每个单元格的代码，包含在我的菜单类中：

- (void) onTapped: (UIGestureRecognizer*) recognizer {
    NSLog(@"tap");
    [menu displayMenu];
}

- (void) displayMenu {
    [viewForMenu addSubview:menuView];
}

- (UICollectionViewCell*) collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewCell * cell=[collectionView dequeueReusableCellWithReuseIdentifier:@"cell" forIndexPath:indexPath];
    [cell setTag:indexPath.row];
    UITapGestureRecognizer * tap=[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(onButtonTapped:)];
    [tap setNumberOfTapsRequired:1];
    [cell addGestureRecognizer:tap];
    NSLog(@"button tapped : %d",indexPath.row);
    return cell;
}

- (void) onButtonTapped:(UIGestureRecognizer*) recognizer {
    NSInteger buttonTapped=[[recognizer view] tag];
    [[NSNotificationCenter defaultCenter] postNotificationName:@"ItemChange" object:nil userInfo:@{@"selected":@(buttonTapped)}];
[self clearMenu];
}

- (void) onChangeItem: (NSNotification*) notification {
    NSLog(@"change item to %d",[[[notification userInfo] objectForKey:@"clock"] intValue]);
}

这将调用

onButtonTapped:

方法，也在我的菜单中类中：

- (void) onTapped: (UIGestureRecognizer*) recognizer {
    NSLog(@"tap");
    [menu displayMenu];
}

- (void) displayMenu {
    [viewForMenu addSubview:menuView];
}

- (UICollectionViewCell*) collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewCell * cell=[collectionView dequeueReusableCellWithReuseIdentifier:@"cell" forIndexPath:indexPath];
    [cell setTag:indexPath.row];
    UITapGestureRecognizer * tap=[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(onButtonTapped:)];
    [tap setNumberOfTapsRequired:1];
    [cell addGestureRecognizer:tap];
    NSLog(@"button tapped : %d",indexPath.row);
    return cell;
}

- (void) onButtonTapped:(UIGestureRecognizer*) recognizer {
    NSInteger buttonTapped=[[recognizer view] tag];
    [[NSNotificationCenter defaultCenter] postNotificationName:@"ItemChange" object:nil userInfo:@{@"selected":@(buttonTapped)}];
[self clearMenu];
}

- (void) onChangeItem: (NSNotification*) notification {
    NSLog(@"change item to %d",[[[notification userInfo] objectForKey:@"clock"] intValue]);
}

此通知由mymainView类使用以下代码拾取：

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(onChangeItem:) name:@"ItemChange" object:nil];

这将调用mymainView类中的

onChangeItem:

方法：

- (void) onTapped: (UIGestureRecognizer*) recognizer {
    NSLog(@"tap");
    [menu displayMenu];
}

- (void) displayMenu {
    [viewForMenu addSubview:menuView];
}

- (UICollectionViewCell*) collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    UICollectionViewCell * cell=[collectionView dequeueReusableCellWithReuseIdentifier:@"cell" forIndexPath:indexPath];
    [cell setTag:indexPath.row];
    UITapGestureRecognizer * tap=[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(onButtonTapped:)];
    [tap setNumberOfTapsRequired:1];
    [cell addGestureRecognizer:tap];
    NSLog(@"button tapped : %d",indexPath.row);
    return cell;
}

- (void) onButtonTapped:(UIGestureRecognizer*) recognizer {
    NSInteger buttonTapped=[[recognizer view] tag];
    [[NSNotificationCenter defaultCenter] postNotificationName:@"ItemChange" object:nil userInfo:@{@"selected":@(buttonTapped)}];
[self clearMenu];
}

- (void) onChangeItem: (NSNotification*) notification {
    NSLog(@"change item to %d",[[[notification userInfo] objectForKey:@"clock"] intValue]);
}

这就是代码

---

好的，问题是：当菜单第一次显示时，我在我的日志中看到：

...[43023:11f03] tap
...[43023:11f03] button tapped : 1
...[43023:11f03] change item to 1

这很好，这就是我所期望的。然而，第二次我发现：

...[43023:11f03] tap
...[43023:11f03] button tapped : 1
...[43023:11f03] change item to 1
...[43023:11f03] change item to 1

...[43023:11f03] tap
...[43023:11f03] button tapped : 1
...[43023:11f03] change item to 1
...[43023:11f03] change item to 1
...[43023:11f03] change item to 1
...[43023:11f03] change item to 1

我第三次听到这个：

...[43023:11f03] tap
...[43023:11f03] button tapped : 1
...[43023:11f03] change item to 1
...[43023:11f03] change item to 1

...[43023:11f03] tap
...[43023:11f03] button tapped : 1
...[43023:11f03] change item to 1
...[43023:11f03] change item to 1
...[43023:11f03] change item to 1
...[43023:11f03] change item to 1

等等。每次连续点击菜单项都会使通知呼叫量翻倍

---

首先，我认为我添加了多个视图，从而导致多个按钮点击，以及多个通知调用

但是，正如您从我的日志中看到的，情况并非如此按钮仅接收1次点击事件-这仅触发1次通知-但接收类收到多个通知。

谁能给我解释一下吗

---

抱歉发了这么长的帖子

好吧，我假设

[[NSNotificationCenter defaultCenter]addObserver:self-selector:@selector（onchangeem:）name:@“ItemChange”object:nil]被多次添加

我喜欢在添加观察者之前删除任何潜在的观察者，如下所示：

[[NSNotificationCenter defaultCenter] removeObserver:self name:@"ItemChange" object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(onChangeItem:) name:@"ItemChange" object:nil];

这样一来，将只有一个观察者回叫。
问题：我遇到了同样的问题，观察者回叫了两次，有时是三次

场景

用户点击注销按钮
HomeViewController
被取消，出现了
LoginViewController
屏幕
当用户第二次再次登录时
观察员被叫来两次（有时三次）
问题是
[[NSNotificationCenter defaultCenter]removeObserver:self]HomeViewController
的
dealloc
方法中的code>根本没有被调用，这实际上会从通知中心一起删除一个对象

ℹ️ <代码>解除锁定

是由 当对象不再为其所有时，对象的Objective-C运行时 应用程序的任何部分

解决方案：创建自己的方法

dispose

，并在用户点击

注销时调用该方法

- (void)dealloc { 
    [[NSNotificationCenter defaultCenter] removeObserver:self];
    // ....
}

- (void)dispose { 
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

- (void)logoutTapped { 
    [self dispose];
    // ....
}

其中，在您调用的代码中，
[[NSNotificationCenter defaultCenter]addObserver:自选择器：@selector（onChangeItem:）name:@“ItemChange”对象：nil]并删除它？在您的
onChangeItem:
方法中，打印正在观察通知
NSLog（@“%p”，self）的
self
的内存地址并显示您在控制台中看到的内容。这在初始化mainView时调用。所以它只被调用一次。您可以添加
NSLog（@“%p”，self）
在您的
onChangeItem:
方法中，并向我们展示您在控制台中看到的内容每次重复使用单元格时，您都会向单元格添加一个新的点击手势识别器。在添加一个之前，您应该先检查单元格中是否存在一个。@rdelmar如何检查是否存在一个？@Jimmery如果您对“addObserver”进行全局搜索，每个单元格上方是否有一个“removeObserver:”？哦。好啊我是个白痴，我把你的代码放错地方了。现在，它在正确的地方，它修复了我的错误！非常感谢：）我希望我能提供给你的不仅仅是虚假的互联网积分！我也有同样的问题，但我确信我只调用了addObserver一次，但我得到了两次回调，4年后使用了完全相同的通知对象（通知具有相同的内存地址和内容），并且你得到了更多的假互联网点！这帮我摆脱了困境！