objective-c - 当焦点和键盘隐藏文本字段时滚动到文本字段

Question

我有多个文本字段，当我关注文本框时，它会自动向上滚动并且键盘隐藏文本字段。

知道如何在单击时将文本字段滚动到焦点字段吗？

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

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

}
- (void)textFieldDidBeginEditing:(UITextField *)textField
{
    activeField = textField;
}

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

Answer 1

我认为您发布的代码片段来自 Apple 的文档，它假定一个基本的 View 层次结构，其中包含一个 UIScrollView(或其子类之一，如 UITableView)填充整个屏幕。如果您的 View 布局更复杂，或者您需要支持多个方向，文本字段将不会滚动到可见，因为矩形计算将是错误的。您需要稍微调整一下代码，我的建议是您以这种方式解决问题:

ScrollView 的新 contentInsent 高度应等于键盘和 ScrollView 之间的交叉矩形的高度。

在代码中:

- (void)keyboardWasShown:(NSNotification*)aNotification
{
    CGRect kbRawRect = [[info objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];    
    CGRect scrollViewFrame = [self.scrollView.window convertRect:self.scrollView.frame fromView:self.scrollView.superview];

    // Calculate the area that is covered by the keyboard
    CGRect coveredFrame = CGRectIntersection(scrollViewFrame, kbRawRect);
    // Convert again to window coordinates to take rotations into account
    coveredFrame = [self.scrollView.window convertRect:self.scrollView.frame fromView:self.scrollView.superview];

    UIEdgeInsets contentInsets = UIEdgeInsetsMake(0.0, 0.0, coveredFrame.size.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
    CGRect activeFieldRect = [self.activeField convertRect:self.activeField.bounds toView:self.scrollView];
   [self.scrollView scrollRectToVisible:activeFieldRect animated:YES];
}

请注意，我使用了方便的 UIScrollView 的 scrollRectToVisible函数尽可能抽象最终的滚动操作。