UITextView如何将光标保持在键盘上方

Question

我有一个 ViewController，UITextView 占据了整个视图，顶部有一个导航栏。几乎像 Apple 的 "Notes" 应用程序。我想要实现的是在编辑开始或编辑时保持文本视图的光标可见。

我能够获得光标的 CGPoint，但我在计算滚动点时遇到了困难。我怎样才能做到这一点？

谢谢

当textview开始编辑时

- (void)keyboardDidShow:(NSNotification*)aNotification {

    // Keyboard
    NSDictionary *info = [aNotification userInfo];
    CGRect keyPadFrame = [[UIApplication sharedApplication].keyWindow convertRect:[[info objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue] fromView:self.view];
    CGSize keyboardSize = keyPadFrame.size;
    kbSize = keyboardSize;

    [self scrollToCursor];
}

textview 编辑时

- (void)textViewDidChange:(UITextView *)textView {
    // Scroll to cursor
    [self scrollToCursor];
}

滚动到光标方法

- (void)scrollToCursor {
    // View
    CGRect viewBounds = self.view.bounds;
    CGRect visibleViewBounds = CGRectMake(viewBounds.origin.x,
                                          viewBounds.origin.y + (self.navigationController.navigationBar.frame.size.height + [UIApplication sharedApplication].statusBarFrame.size.height),
                                          viewBounds.size.width,
                                          viewBounds.size.height - (kbSize.height + self.navigationController.navigationBar.frame.size.height + [UIApplication sharedApplication].statusBarFrame.size.height));

    // TextView
    CGPoint textViewOrigin = [self.view convertRect:self.noteTextView.frame fromView:self.noteTextView.superview].origin;

    // Cursor
    CGPoint textViewCursor = [self.noteTextView caretRectForPosition:self.noteTextView.selectedTextRange.start].origin;
    CGPoint cursorPoint = CGPointMake((textViewCursor.x + textViewOrigin.x), (textViewCursor.y - self.noteTextView.contentOffset.y));

    // Scroll to point
    if (!CGRectContainsPoint(visibleViewBounds, CGPointMake(cursorPoint.x, cursorPoint.y + 25/*25 for cursor's height*/))) {
        [self.noteTextView setContentOffset:CGPointMake(0, 0)/*How to calculate??*/ animated:YES];
    }
}

Answer 1

这根本没有经过测试，但这是我的第一次尝试。

通过监听 KeyboardWillChangeFrameNotification 获取键盘高度

CGRect keyboardFrame;
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillChange:) name:UIKeyboardWillChangeFrameNotification object:nil];
- (void)keyboardWillChange:(NSNotification *)notification {
    keyboardFrame = [notification.userInfo[UIKeyboardFrameEndUserInfoKey] CGRectValue];
    keyboardFrame = [self.view convertRect:keyboardRect fromView:nil];
}

这将为您提供键盘高度。

然后获取屏幕高度：

CGRect screenBound = [[UIScreen mainScreen] bounds];
CGSize screenSize = screenBound.size;  
CGFloat screenHeight = screenSize.height;

然后如果你知道游标的CGPoint，做这样的事情：

CGFloat keyboardTop = (screenHeight - (keyboardFrame.size.height + <padding if you want it>));
if (currentCursorPosition.y > keyboardTop)
{
 [self.noteTextView setContentOffset:CGPointMake(0, (cursorPoint.y - (viewBounds.size.height - kbSize.height)) + self.noteTextView.contentOffset.y + 25);
}

理想情况下，这应该使光标保持在键盘顶部，然后在向下移动光标时滚动。

Answer 2

为了您的理智，请使用图书馆。

这是一个很好的：https://github.com/hackiftekhar/IQKeyboardManager

迦太基：

github "hackiftekhar/IQKeyboardManager"

CocoaPods：

pod 'IQKeyboardManagerSwift', '6.3.0'

或

pod 'IQKeyboardManager', '3.3.7' #iOS7

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