ios - 键盘出现时如何滚动 UIScrollView？

Question

我的代码有问题。当我编辑应该被键盘弹出隐藏的 UITextField 时，我正在尝试移动 UIScrollView。

我现在正在移动主框架，因为我不知道如何在代码中“向上滚动”。所以，我做了一些代码，它工作正常，但是当我编辑一个 UItextfield 并切换到另一个 UITextField 而不按“返回”按钮时，主视图会变得很远。

我用我的变量大小、距离和 textFieldRect.origin.y 做了一个 NSLog()，如下所示。当我将两个 UITextField 放在同一个位置(y 原点)并执行此特定的“开关”(不按回车键)时，我得到相同的数字，而我的代码对于第一个 UITextField 编辑但不用于第二次编辑。

看看这个:

- (void)textFieldDidBeginEditing:(UITextField *)textField {
{
    int size;
    CGRect textFieldRect = [self.view.window convertRect:textField.bounds fromView:textField];
    size = textFieldRect.origin.y + textFieldRect.size.height;
    if (change == FALSE)
    {
        size = size - distance;
    }
    if (size < PORTRAIT_KEYBOARD_HEIGHT)
    {
        distance = 0;
    }
    else if (size > PORTRAIT_KEYBOARD_HEIGHT)
    {
        distance = size - PORTRAIT_KEYBOARD_HEIGHT + 5; // +5 px for more visibility
    }
    NSLog(@"origin %f", textFieldRect.origin.y);
    NSLog(@"size %d", size);
    NSLog(@"distance %d", distance);
    CGRect viewFrame = self.view.frame;
    viewFrame.origin.y -= distance;
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationBeginsFromCurrentState:YES];
    [UIView setAnimationDuration:KEYBOARD_ANIMATION_DURATION];
    [self.view setFrame:viewFrame];
    [UIView commitAnimations];
    change = FALSE;
}

- (void)textFieldDidEndEditing:(UITextField *)textField
{
    change = TRUE;
    CGRect viewFrame = self.view.frame;
    viewFrame.origin.y += distance;
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationBeginsFromCurrentState:YES];
    [UIView setAnimationDuration:KEYBOARD_ANIMATION_DURATION];
    [self.view setFrame:viewFrame];
    [UIView commitAnimations];
}

有什么想法吗？

Answer 1

Apple 推荐的方法是更改​​ UIScrollView 的 contentInset。这是一个非常优雅的解决方案，因为您不必弄乱 contentSize。以下代码复制自 Keyboard Programming Guide ，这里解释了这个问题的处理。你应该看看它。

// Call this method somewhere in your view controller setup code.
- (void)registerForKeyboardNotifications
{
    [[NSNotificationCenter defaultCenter] addObserver:self
            selector:@selector(keyboardWasShown:)
            name:UIKeyboardDidShowNotification object:nil];
   [[NSNotificationCenter defaultCenter] addObserver:self
             selector:@selector(keyboardWillBeHidden:)
             name:UIKeyboardWillHideNotification object:nil];
}

// Called when the UIKeyboardDidShowNotification is sent.
- (void)keyboardWasShown:(NSNotification*)aNotification
{
    NSDictionary* info = [aNotification userInfo];
    CGSize kbSize = [[info objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size;
    UIEdgeInsets contentInsets = UIEdgeInsetsMake(0.0, 0.0, kbSize.height, 0.0);
    scrollView.contentInset = contentInsets;
    scrollView.scrollIndicatorInsets = contentInsets;

    // If active text field is hidden by keyboard, scroll it so it's visible
    // Your application might not need or want this behavior.
    CGRect aRect = self.view.frame;
    aRect.size.height -= kbSize.height;
    if (!CGRectContainsPoint(aRect, activeField.frame.origin) ) {
        CGPoint scrollPoint = CGPointMake(0.0, activeField.frame.origin.y-kbSize.height);
        [scrollView setContentOffset:scrollPoint animated:YES];
    }
}

// Called when the UIKeyboardWillHideNotification is sent    
- (void)keyboardWillBeHidden:(NSNotification*)aNotification
{
    UIEdgeInsets contentInsets = UIEdgeInsetsZero;
    scrollView.contentInset = contentInsets;
    scrollView.scrollIndicatorInsets = contentInsets;
}

Swift 版本:

func registerForKeyboardNotifications() {
    NotificationCenter.default.addObserver(self, selector: #selector(onKeyboardAppear(_:)), name: NSNotification.Name.UIKeyboardDidShow, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(onKeyboardDisappear(_:)), name: NSNotification.Name.UIKeyboardDidHide, object: nil)
}

// Don't forget to unregister when done
deinit {
    NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIKeyboardDidShow, object: nil)
    NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIKeyboardDidHide, object: nil)
}

@objc func onKeyboardAppear(_ notification: NSNotification) {
    let info = notification.userInfo!
    let rect: CGRect = info[UIKeyboardFrameBeginUserInfoKey] as! CGRect
    let kbSize = rect.size

    let insets = UIEdgeInsetsMake(0, 0, kbSize.height, 0)
    scrollView.contentInset = insets
    scrollView.scrollIndicatorInsets = insets

    // If active text field is hidden by keyboard, scroll it so it's visible
    // Your application might not need or want this behavior.
    var aRect = self.view.frame;
    aRect.size.height -= kbSize.height;

    let activeField: UITextField? = [addressTextView, servicePathTextView, usernameTextView, passwordTextView].first { $0.isFirstResponder }
    if let activeField = activeField {
        if !aRect.contains(activeField.frame.origin) {
            let scrollPoint = CGPoint(x: 0, y: activeField.frame.origin.y-kbSize.height)
            scrollView.setContentOffset(scrollPoint, animated: true)
        }
    }
}

@objc func onKeyboardDisappear(_ notification: NSNotification) {
    scrollView.contentInset = UIEdgeInsets.zero
    scrollView.scrollIndicatorInsets = UIEdgeInsets.zero
}