xcode iOS 8 scrollview布局调整无效

Question

我想动态地将标签添加到滚动视图，并根据发件人和收件人聊天文本对齐（右或左）标签。 （比如whatsapp）当键盘出现并返回时，我很难调整滚动视图的布局。我只是想创建一个像whatsapp的聊天窗口。

我一直试图从昨天开始解决这个问题。今天我试图重新使用下面显示的堆栈溢出代码（显然适用于某些人），但它没有帮助。文字字段仍然隐藏在键盘后面！

#define kOFFSET_FOR_KEYBOARD 80.0
static const CGFloat KEYBOARD_ANIMATION_DURATION = 0.3;
static const CGFloat MINIMUM_SCROLL_FRACTION = 0.2;
static const CGFloat MAXIMUM_SCROLL_FRACTION = 0.8;
static const CGFloat PORTRAIT_KEYBOARD_HEIGHT = 216;
static const CGFloat LANDSCAPE_KEYBOARD_HEIGHT = 162;
-(void)setViewMovedUp:(BOOL)movedUp
{
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:0.3]; 

    CGRect rect = self.view.frame;
    if (movedUp)
    {
        // 1. move the view's origin up so that the text field that will be hidden come above the keyboard
        // 2. increase the size of the view so that the area behind the keyboard is covered up.
        rect.origin.y -= kOFFSET_FOR_KEYBOARD;
        rect.size.height += kOFFSET_FOR_KEYBOARD;
    }
    else
    {
        // revert back to the normal state.
        rect.origin.y += kOFFSET_FOR_KEYBOARD;
        rect.size.height -= kOFFSET_FOR_KEYBOARD;
    }
    self.view.frame = rect;

    [UIView commitAnimations];
}


- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    // register for keyboard notifications
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillShow)
                                                 name:UIKeyboardWillShowNotification
                                               object:nil];

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

-(void) textFieldDidBeginEditing:(UITextField *)textField
{
    if(UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone)
    {
        CGRect textFieldRect = [self.view.window convertRect:textField.bounds fromView:textField];
        CGRect viewRect = [self.view.window convertRect:self.view.bounds fromView:self.view];

        CGFloat midline = textFieldRect.origin.y + 0.5 * textFieldRect.size.height;
        CGFloat numerator =
        midline - viewRect.origin.y
        - MINIMUM_SCROLL_FRACTION * viewRect.size.height;
        CGFloat denominator =
        (MAXIMUM_SCROLL_FRACTION - MINIMUM_SCROLL_FRACTION)
        * viewRect.size.height;
        CGFloat heightFraction = numerator / denominator;

        if (heightFraction < 0.0)
        {
            heightFraction = 0.0;
        }
        else if (heightFraction > 1.0)
        {
            heightFraction = 1.0;
        }

        UIInterfaceOrientation orientation =
        [[UIApplication sharedApplication] statusBarOrientation];
        if (orientation == UIInterfaceOrientationPortrait)
        {
            animatedDistance = floor(PORTRAIT_KEYBOARD_HEIGHT * heightFraction);
        }
        else
        {
            animatedDistance = floor(LANDSCAPE_KEYBOARD_HEIGHT * heightFraction);
        }

        CGRect viewFrame = self.view.frame;
        viewFrame.origin.y -= animatedDistance;

        [UIView beginAnimations:nil context:NULL];
        [UIView setAnimationBeginsFromCurrentState:YES];
        [UIView setAnimationDuration:KEYBOARD_ANIMATION_DURATION];

        [self.view setFrame:viewFrame];

        [UIView commitAnimations];
    }
}

-(void) textFieldDidEndEditing:(UITextField *)textField
{
    if(UI_USER_INTERFACE_IDIOM()==UIUserInterfaceIdiomPhone)
    {
        CGRect viewFrame = self.view.frame;
        viewFrame.origin.y += animatedDistance;

        [UIView beginAnimations:nil context:NULL];
        [UIView setAnimationBeginsFromCurrentState:YES];
        [UIView setAnimationDuration:KEYBOARD_ANIMATION_DURATION];

        [self.view setFrame:viewFrame];

        [UIView commitAnimations];
    }
}
-(void)keyboardWillShow {
    // Animate the current view out of the way
    if (self.view.frame.origin.y >= 0)
    {
        [self setViewMovedUp:YES];
    }
    else if (self.view.frame.origin.y < 0)
    {
        [self setViewMovedUp:NO];
    }
}

-(void)keyboardWillHide {
    if (self.view.frame.origin.y >= 0)
    {
        [self setViewMovedUp:YES];
    }
    else if (self.view.frame.origin.y < 0)
    {
        [self setViewMovedUp:NO];
    }
}