Question

我认为这可能是一个简单的解决方案，但我很难找到合适的解决方案我有以下内容：

ContactList - 使用UICollectionView方法加载内容的viewDidAppear:。当在集合视图中选择一个项目时，我激发了这个方法：

[self performSegueWithIdentifier:@"pushContactDetail" sender:self];

到目前为止一切顺利。一切都很好。但是，当我使用导航控制器按钮从ContactDetail页面导航回来时，我的ContactList会复制内容。

我是否应该采取措施阻止viewDidAppear:再次投放？

当我推送ContactDetail页面时，我认为我不想将集合设置为nil，因为这会导致每次重新加载内容...

以下是代码：

-(void) viewDidAppear
{
    [super viewDidAppear];
    [self.view setBackgroundColor:myColorLightGrey];
    _contactList = [[NSMutableArray alloc] init];
    [self displayLoadingAndDisableTableViewInteractions];
    [self queryData];
}


- (void) queryData
{    
    //Find the Data
     PFQuery *query = [PFUser query];
     PFUser *consumer = [PFUser currentUser];
    [query includeKey:User_followers];
    [query whereKey:@"email" equalTo:consumer.email];
    query.maxCacheAge = 60 * 60 * 24;  // One day, in seconds
    [query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error)
    {
         for (PFUser *tmpConsumer in objects)
         {
             for (PFUser *publisher in [tmpConsumer objectForKey:User_followers])
             {
                 [_contactList addObject:publisher];
             }
         }
         [_collectionView reloadData];
         [self hideLoadingAndEnableTableViewInteractions];
    }];
}

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"contactCell";
    ContactCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath];
    //SNIPPED REMAINDER OF CODE
    ...
}

Answer 1

在queryData方法中，首先清除数组

_contactList = nil;
_contactList = [NSMutableArray array]; // or [[NSMutableArray alloc] init];

像这样移动_contactList的alloc / init方法：

- (void) queryData
{    
    _contactList = nil;
    _contactList = [[NSMutablArray alloc] init];

    //Find the Data
     PFQuery *query = [PFUser query];
     PFUser *consumer = [PFUser currentUser];
    [query includeKey:User_followers];
    [query whereKey:@"email" equalTo:consumer.email];
    query.maxCacheAge = 60 * 60 * 24;  // One day, in seconds
    [query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error)
    {
         for (PFUser *tmpConsumer in objects)
         {
             for (PFUser *publisher in [tmpConsumer objectForKey:User_followers])
             {
                 [_contactList addObject:publisher];
             }
         }
         [_collectionView reloadData];
         [self hideLoadingAndEnableTableViewInteractions];
    }];
}

Answer 2

使用Animation true导航回来。它会解决你的问题。

返回导航控制器导致集合视图项目重复

2 个答案: