顯示鍵盤時將UITextField滾動到視圖中

Question

我正在編寫針對iOS 6.1的應用程序。 我正在嘗試遵循此Apple文檔 ，以了解如何將UITextField滾動到視圖中（如果鍵盤遮擋了它）。 問題在於，Apple記錄的用於計算滾動點的算法不能很好地工作。 我計算滾動點的算法效果稍好，但減少了70個像素。 計算滾動點的正確方法是什么？

在下面您可以從左到右看到顯示鍵盤之前的視圖，使用Apple算法計算滾動點后的視圖以及使用算法計算滾動點后的視圖。 （該網格中的每個正方形都是25像素乘25像素。）

這是我正在使用的代碼。 注意#if APPLE_WAY塊。

- (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);
    self.view.contentInset = contentInsets;
    self.view.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, self.activeField.frame.origin) ) {

#if APPLE_WAY
        CGPoint scrollPoint = CGPointMake(0.0, self.activeField.frame.origin.y-kbSize.height);
#else
        CGFloat offset = self.activeField.frame.origin.y;

        //TODO: Why is this off by 70?
        offset = offset - 70;

        CGPoint scrollPoint = CGPointMake(0.0, offset);
#endif
        [self.view setContentOffset:scrollPoint animated:YES];
    }
}

Answer 1

您只需要將偏移量設置為鍵盤的高度：

CGFloat offset = kbSize.height;
CGPoint scrollPoint = CGPointMake(0.0, offset);
[self.view setContentOffset:scrollPoint animated:YES];

希望這可以幫助

Answer 2

有幾種方法可以做到這一點。 鑒於您的情況，我將執行以下操作：

- (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);
    self.scrollView.contentInset = contentInsets;
    self.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, self.activeField.frame.origin) ) {
        CGPoint scrollPoint = CGPointMake(0.0, self.activeField.frame.origin.y-kbSize.height);
        [self.scrollView setContentOffset:scrollPoint animated:YES];
    }
}

- (void)keyboardWillBeHidden:(NSNotification *)aNotification
{
    NSDictionary* info = [aNotification userInfo];
    CGSize kbSize = [[info objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue].size;

    UIEdgeInsets contentInsets = UIEdgeInsetsMake(0.0, 0.0, kbSize.height, 0.0);
    self.scrollView.contentInset = contentInsets;
    self.scrollView.scrollIndicatorInsets = contentInsets;

    CGRect aRect = self.view.frame;
    aRect.size.height -= kbSize.height;
    if (!CGRectContainsPoint(aRect, self.activeField.frame.origin) ) {
        CGPoint scrollPoint = CGPointMake(0, 0);
        [self.scrollView setContentOffset:scrollPoint animated:YES];
    }
}

然后，在您的viewDidLoad方法中：

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

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

Answer 3

當您擁有滾動視圖時，這很容易，因為您甚至不必滾動； 您所要做的就是調整contentInset和scrollIndicatorInsets使其脫離鍵盤，其余的自動發生：

- (void) keyboardShow: (NSNotification*) n {
    self->_oldContentInset = self.scrollView.contentInset;
    self->_oldIndicatorInset = self.scrollView.scrollIndicatorInsets;
    self->_oldOffset = self.scrollView.contentOffset;
    NSDictionary* d = [n userInfo];
    CGRect r = [[d objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
    r = [self.scrollView convertRect:r fromView:nil];
    CGRect f = self.fr.frame;
    CGFloat y =
        CGRectGetMaxY(f) + r.size.height -
            self.scrollView.bounds.size.height + 5;
    if (r.origin.y < CGRectGetMaxY(f))
        [self.scrollView setContentOffset:CGPointMake(0, y) animated:YES];
    UIEdgeInsets insets;
    insets = self.scrollView.contentInset;
    insets.bottom = r.size.height;
    self.scrollView.contentInset = insets;
    insets = self.scrollView.scrollIndicatorInsets;
    insets.bottom = r.size.height;
    self.scrollView.scrollIndicatorInsets = insets;
}

在本書的這一部分中，我用代碼給出了一系列不同的策略：

http://www.apeth.com/iOSBook/ch23.html#_keyboard_covers_text_field

所有這些都由可在我的github站點上獲取的可下載項目支持。