iOS:如何在自定义单元格上正确使用 prepareForReuse？将编辑切换到非编辑模式时，我的单元格被错误地重复使用

Question

好吧，这是我关于这个主题的最后一篇文章。我已经尽可能地缩小了它的范围，但我肯定需要帮助来解决这个问题。由于我使用的是自定义单元格和嵌入式表格 View ，因此当键盘出现并隐藏一些文本字段(每个单元格都有一个文本字段)时，我必须自己进行滚动。效果很好。但是，如果我的表格 View 向上移动了那么远，一些单元格隐藏在我的标题后面或导航 Controller 栏后面，一旦我结束编辑模式，一切都会变得一团糟。然后之前的隐藏单元格立即处于正常状态并且不会缩进。这看起来很讨厌，我不知道如何解决。如果没有细胞被隐藏，当然一切看起来都很好。

所以我查看了文档并找到了 prepareForReuse，我想这会有所帮助。知道如何解决这个问题吗？如果有人能给我必要的提示，我将非常感激......

我有一个自定义的 UITableViewCell，只有这个方法:

- (void) setEditing:(BOOL)editing animated:(BOOL)animated{
    [super setEditing:editing animated:animated];
    if (editing){
        self.title.hidden = NO;
        self.titleLabel.hidden = YES;

        self.iconButton.hidden = NO;
        self.icon.hidden = YES;
        self.costs.hidden = YES;
        self.disclosureIndicator.hidden = YES;
        self.subcategories.hidden = YES;
    }  else if (!editing){
        self.title.hidden = YES;
        self.titleLabel.text = self.title.text;
        self.titleLabel.hidden = NO;

        self.iconButton.hidden = YES;
        self.icon.hidden = NO;
        self.subcategories.hidden = NO;
        self.costs.hidden = NO;
        self.disclosureIndicator.hidden = NO;
    }
}

在这里初始化并重用:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    //Data model and cell setup
    static NSString *CellIdentifier = @"MainCategoryCell";
    MainCategoryTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
    MainCategory *mainCategory = [self.fetchedResultsController objectAtIndexPath:indexPath];

    ...

    return cell;
}

由于我使用的是嵌入式表格 View ，因此我必须自己滚动隐藏的文本字段:

- (void)registerForKeyboardNotifications
{
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWasShown:)
                                                 name:UIKeyboardDidShowNotification object:nil];

    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillBeHidden:)
                                                 name:UIKeyboardWillHideNotification object:nil];

}

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];

    //Has to be unregistered always, otherwise nav controllers down the line will call this method
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

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

- (void)keyboardWasShown:(NSNotification*)aNotification
{
    //All table views are embedded in the parent view
    //The parent view y is defined by the status and navigation bar, the height by the tab bar
    CGRect viewRect = self.view.frame;
    CGRect tableRect = self.tableView.frame;

    //The keyboard size will be adjusted that the height is really only the height overlapping the table
    NSDictionary* info = [aNotification userInfo];
    CGSize kbOriginalSize = [[info objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size;
    CGFloat effectiveKeyBoardHeight = kbOriginalSize.height - TABBARHEIGHT - (viewRect.size.height - tableRect.size.height - tableRect.origin.y); //the last origin property is important to find out if there is a header
    CGSize kbSize = CGSizeMake(kbOriginalSize.width, effectiveKeyBoardHeight);

    //Now the content insets will be adjusted for the calculated part of the keyboard overlapping the table
    UIEdgeInsets contentInsets = UIEdgeInsetsMake(0.0, 0.0, kbSize.height, 0.0);
    self.tableView.contentInset = contentInsets;
    self.tableView.scrollIndicatorInsets = contentInsets;

    // If active text field is hidden by keyboard, scroll it so it's visible
    // I've changed the apple code here! They use viewRect..in my app this doesn't make any sense, tableRect is key
    tableRect.size.height -= kbSize.height;
    if (!CGRectContainsPoint(tableRect, self.activeField.frame.origin) ) {
        [self.tableView scrollRectToVisible:self.activeField.frame animated:YES];
    }
}

- (void)keyboardWillBeHidden:(NSNotification*)aNotification
{
    UIEdgeInsets contentInsets = UIEdgeInsetsZero;
    self.tableView.contentInset = contentInsets;
    self.tableView.scrollIndicatorInsets = contentInsets;
}

Answer 1

我认为问题可能是 tableview contentInset 的设置不会调用 tableView 的 prepareForReuse 方法或任何其他方法来调用 cellForRow，这会导致隐藏的单元格出现奇怪的状态。所以在键盘隐藏方法中，配置所有可能显示单元格状态，然后重新加载数据将有助于正确显示单元格。