Question

我正在使用UITextView的text属性获得关键值观察的最糟糕时间。我可以成功添加观察者，我甚至可以删除同一个观察者。我有一个包含几个单元格的tableview - 一些有UITextFields，一些有UISegmentSelectors，另一个有UITextView。对于UITextView，我的核心数据对象（NSMangedObject的子类）EXCEPT成功观察到所有其余字段。如果需要，我可以发布代码。

发布代码：

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *UserProfileCellIdentifier = @"UserProfileCellIdentifier";

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:
                         UserProfileCellIdentifier];
if (cell == nil) 
{
    [_tableCellsNib instantiateWithOwner:self options:nil];

    switch (indexPath.row)
    {
            // UserName Row
        case UserNameRowIndex:
            _textFieldCell.cellLabel.text = NSLocalizedString(@"UserNameLabel", @"User Profile TableView");
            _textFieldCell.cellType = CellTypeNormal;
            _textFieldCell.boundProperty = @"UserName";
            _textFieldCell.tag = indexPath.row;
            _textFieldCell.errorHandler = self;
            _textFieldCell.boundControl = _textFieldCell.cellTextField;

            [_textFieldCell addObserver:[MBUtilities getAppDelegate].userProfile forKeyPath:@"cellTextField.text" options:NSKeyValueObservingOptionNew context:NULL];

            cell = _textFieldCell;

            self.textFieldCell = nil;
            break;
        case PasswordRowIndex:
            _textFieldCell.cellLabel.text = NSLocalizedString(@"PasswordLabel", @"User Profile TableView");
            _textFieldCell.cellType = CellTypeNormal;
            _textFieldCell.cellTextField.secureTextEntry = YES;
            _textFieldCell.boundProperty = @"Password";
            _textFieldCell.tag = indexPath.row;
            _textFieldCell.errorHandler = self;
            _textFieldCell.boundControl = _textFieldCell.cellTextField;

            [_textFieldCell addObserver:[MBUtilities getAppDelegate].userProfile forKeyPath:@"cellTextField.text" options:NSKeyValueObservingOptionNew context:NULL];

            cell = _textFieldCell;

            self.textFieldCell = nil;
            break;
        case PasswordConfirmRowIndex:
            _textFieldCell.cellLabel.text = NSLocalizedString(@"PasswordConfirmLabel", @"User Profile TableView");
            _textFieldCell.cellType = CellTypeNormal;
            _textFieldCell.cellTextField.secureTextEntry = YES;
            _textFieldCell.tag = indexPath.row;

            cell = _textFieldCell;

            self.textFieldCell = nil;
            break;
        case FirstNameRowIndex:
            _textFieldCell.cellLabel.text = NSLocalizedString(@"FirstNameLabel", @"User Profile TableView");
            _textFieldCell.cellType = CellTypeNormal;
            _textFieldCell.boundProperty = @"FirstName";
            _textFieldCell.tag = indexPath.row;
            _textFieldCell.errorHandler = self;
            _textFieldCell.boundControl = _textFieldCell.cellTextField;

            [_textFieldCell addObserver:[MBUtilities getAppDelegate].userProfile forKeyPath:@"cellTextField.text" options:NSKeyValueObservingOptionNew context:NULL];
            cell = _textFieldCell;

            self.textFieldCell = nil;
            break;
        case LastNameRowIndex:
            _textFieldCell.cellLabel.text = NSLocalizedString(@"LastNameLabel", @"User Profile TableView");
            _textFieldCell.cellType = CellTypeNormal;
            _textFieldCell.boundProperty = @"LastName";
            _textFieldCell.tag = indexPath.row;
            _textFieldCell.errorHandler = self;
            _textFieldCell.boundControl = _textFieldCell.cellTextField;

            [_textFieldCell addObserver:[MBUtilities getAppDelegate].userProfile forKeyPath:@"cellTextField.text" options:NSKeyValueObservingOptionNew context:NULL];
            cell = _textFieldCell;

            self.textFieldCell = nil;
            break;
        case DateOfBirthRowIndex:
            _textFieldCell.cellLabel.text = NSLocalizedString(@"BirthDateLabel", @"User Profile TableView");
            _textFieldCell.cellType = CellTypeDatePicker;
            _textFieldCell.boundProperty = @"DateOfBirth";
            _textFieldCell.tag = indexPath.row;
            _textFieldCell.errorHandler = self;
            _textFieldCell.boundControl = _textFieldCell.cellTextField;

            [_textFieldCell addObserver:[MBUtilities getAppDelegate].userProfile forKeyPath:@"cellTextField.text" options:NSKeyValueObservingOptionNew context:NULL];
            cell = _textFieldCell;

            self.textFieldCell = nil;
            break;
        case GenderSelfRowIndex:
            _genderSelectCell.cellLabel.text = NSLocalizedString(@"UserSexLabel", @"User Profile TableView");
            _genderSelectCell.boundProperty = @"GenderSelf";
            _genderSelectCell.errorHandler = self;
            _genderSelectCell.boundControl = _genderSelectCell.cellGenderSegment;
            _genderSelectCell.tag = indexPath.row;

            [_genderSelectCell addObserver:[MBUtilities getAppDelegate].userProfile forKeyPath:@"cellGenderSegment.selectedSegmentIndex" options:NSKeyValueObservingOptionNew context:NULL];
            cell = _genderSelectCell;

            self.genderSelectCell = nil;
            break;
        case GenderInterestedInRowIndex:
            _genderSelectCell.cellLabel.text = NSLocalizedString(@"UserInterestedInLabel", @"User Profile TableView");
            _genderSelectCell.boundProperty = @"GenderInterestedIn";
            _genderSelectCell.errorHandler = self;
            _genderSelectCell.boundControl = _genderSelectCell.cellGenderSegment;
            _genderSelectCell.tag = indexPath.row;

            [_genderSelectCell addObserver:[MBUtilities getAppDelegate].userProfile forKeyPath:@"cellGenderSegment.selectedSegmentIndex" options:NSKeyValueObservingOptionNew context:NULL];
            cell = _genderSelectCell;

            self.genderSelectCell = nil;
            break;
        case IntroductionRowIndex:
            _textViewCell.cellLabel.text = NSLocalizedString(@"IntroductionLabel", @"User Profile TableView");
            _textViewCell.boundControl = _textViewCell.cellTextView;
            _textViewCell.errorHandler = self;
            _textViewCell.boundProperty = @"Introduction";
            _textViewCell.tag = indexPath.row;

            [_textViewCell addObserver:[MBUtilities getAppDelegate].userProfile forKeyPath:@"cellTextView.text" options:NSKeyValueObservingOptionNew context:NULL];
            cell = _textViewCell;

            self.textViewCell = nil;
            break;
    };
}

return cell;
}

讨论：每个单元格都从外部NIB文件加载，然后使用不同的属性进行初始化。所有单元格都使用键值观察，除了最后一个使用UITextView。如果需要任何其他信息，请与我们联系。

Answer 1

UIKit不保证是KVO compliant：

注意：虽然UIKit框架的类通常不支持KVO，但您仍然可以在应用程序的自定义对象中实现它，包括自定义视图。

它可能适用于某些类+键但这不可靠，并且可能会在不同的iOS版本中发生变化。见Dave’s answer to this question;戴夫在UIKit工作。

Answer 2

使用UITextViewTextDidChangeNotification更好。

我做了以下事情：

首先注册NSNotificationCenter：

- (id)init
{
    [super init];
    if (self)
    {
        NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
        [nc addObserver:self 
               selector:@selector(textDidChange:) 
                   name:UITextViewTextDidChangeNotification
                 object:nil];
    }
    return self;
}

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

然后定义通知处理程序：

- (void)textDidChange:(NSNotification *)note
{
    NSLog(@"Observation...");
}

现在，只要UITextView对象中的文本发生更改，就会调用textDidChange:方法。

Answer 3

好的，所以我没有运气找到这种行为的任何解释，除非有人能告诉我，否则我认为这是IOS中的一个错误。

我能够让它与这个黑客一起工作：

- (void)textViewDidEndEditing:(UITextView *)textView
{
    NSLog(@"Editing Ended");
    textView.text = textView.text;
}

一旦添加了代码，瞧，observeValueForKeyPath就会触发！

Answer 4

您是否尝试过实现UITextViewDelegate并将thisIsYourTextView.delegate分配给它？

好吧，我发现了这个tutorial，也许会让事情变得更加清晰。

密钥值观察是否适用于UITextView的文本属性？

4 个答案: