ios - 在 UIScrollVIew 中确定 UITextView 的滚动偏移量

Question

我在 UIScrollView 中的 textView 下方和之后有 UITextView 和其他 View 。当用户输入文本时，我更改 textView.contentSize.height 上的 textView 框架高度。这个想法是为用户保留查看所有文本和其他元素的可能性。我有一些问题。当用户点击时，我想滚动到这一行。这看起来一定是这样的:

我无法确定如何计算偏移量并始终滚动到当前插入符号。

我的初始屏幕:

所有 View 都是 UIScrollView 的 subview 。每次当用户输入 @"\n" 时，我都会更改 UITextView 框架:

CGRect textViewFrame = textView.frame;
CGSize textViewContentSize = textView.contentSize;
NSLog(@"textView content size: %@", NSStringFromCGSize(textViewContentSize));
textViewFrame.size.height = textViewContentSize.height;
[textView setFrame:textViewFrame];

然后我增加 UIScrollView contentSize。我的问题 - 我不明白如何在键盘下滚动到 textView 的 CURSOR。我尝试做一些事情:

CGPoint cursorPosition = [textView caretRectForPosition:textView.selectedTextRange.start].origin;

CGPoint relativeCursorPoint = [textView convertPoint:cursorPosition toView:scrollView];

if(textView.isFirstResponder && relativeCursorPoint.y >= scrollViewFrame.size.height + scrollView.contentOffset.y)
{
    int offset = relativeCursorPoint.y - scrollViewFrame.size.height + 18.0f;
    //int offset = textViewRect.origin.y - scrollViewFrame.size.height + 18.0f;
    [scrollView setContentOffset:CGPointMake(0, offset) animated:YES];
}

但是没有用。

Answer 1

A.) 为了实现与 Apple Notes 滚动 + 键盘关闭类似的效果，我首先在 UIScrollView 中添加了一个 UITextView。

B.) 然后将自己添加为键盘变化的观察者:

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textViewDidBeginEditing:) name:UITextViewTextDidBeginEditingNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self  selector:@selector(keyboardWillChangeFrame:) name:UIKeyboardWillChangeFrameNotification object:nil];

C.) 然后当用户点击 TextView /文本字段时，将调用下面的方法。您获取键盘的开始高度和结束高度，并将名为 keyboardHeight 的变量设置为 endHeight 值(稍后使用)。

下面计算的“差异”用于在用户上下移动自动更正/建议栏时上下移动文本。如果您不想这样做，您可以将 textView 上的“autocorrectionType”设置为 false。

-(void)keyboardWillChangeFrame:(NSNotification *)n {

    float beginHeight = [[n.userInfo valueForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size.height;
    float endHeight = [[n.userInfo valueForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue].size.height;
    float difference = beginHeight-endHeight;
    keyBoardHeight = endHeight; //set the var

    //animate change
    if (difference != 0){ //animate frame change in your textview }
}

D.) 在 textViewDidBegin 方法中，将 UIScrollview 移动到屏幕顶部，因此 textview 与顶部齐平 (setContentOffset)。

您计算 TextView 的高度，因为它应该在 View 顶部和键盘顶部之间，在下面称为“initialTVHeight”。

您应该强制 TextView 启用滚动，因此将 textView.contentSize 设置为最小尺寸 (initialTVHeight) + 一个像素 - 这会强制滚动。

-(void)textViewDidBeginEditing:(UITextView *)textView {

    //need to move the tv up to the top
    float yOff = 0;
    yOff += durationCell.frame.size.height;
    yOff += reminderCell.frame.size.height;
    yOff += fixedCell.frame.size.height;
    yOff += repeatCell.frame.size.height;
    [mainScroller setContentOffset:CGPointMake(0, yOff) animated:true];

    //resize the textview to meet the top of the keyboard
    float padding = 0; //padding between keyboard and last line in the textview
    initialTVHeight = h - 60 - keyBoardHeight - padding; //the height when text does not overflow
    textTV.frame = CGRectMake(0, textTV.frame.origin.y, w, initialTVHeight); //set the frame to that size

    //if smaller than minimum, increase (if editing existing text)
    if (textTV.contentSize.height < initialTVHeight){
       textTV.contentSize = CGSizeMake(w, initialTVHeight+1); //force initial scroll
    }
}

E.) 此方法将 textView contentSize 更新为最小高度以确保启用滚动(即，如果只有两行文本，用户仍然可以反弹滚动)。在 textView 内容比初始大小长的地方，让它自然增长。

-(void)textViewDidChange:(UITextView *)textView {
    //require minimum height for scroll
    if (textTV.contentSize.height < initialTVHeight){ //content height comes in under, force scroll
        textTV.contentSize = CGSizeMake(w, initialTVHeight+1); //adding one forces scroll
    }
}

F.) 添加这些方法，确保键盘仅在用户拖动时关闭(而不是在用户输入新行时)

-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    if ([scrollView isEqual:textTV]){
        enableDragDismiss = true;
    }
}
-(void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{
    if ([scrollView isEqual:textTV]){
        enableDragDismiss = false;
    }
}

G.) 最后，添加这个方法，如果用户拖动到键盘高度以下，它会关闭键盘。

-(void)scrollViewDidScroll:(UIScrollView *)scrollView {

    if (enableDragDismiss && [scrollView isEqual:textTV]){

        float y = [textTV.panGestureRecognizer locationInView:self.view].y;
        float keyboardY = h-keyBoardHeight;

        if (y > keyboardY){
            enableDragDismiss = false; //allow only once
            [textTV resignFirstResponder];
            [UIView animateWithDuration:0.5f
                                  delay:0.0f
                 usingSpringWithDamping:1.0f
                  initialSpringVelocity:0.8f
                                options:UIViewAnimationOptionCurveEaseOut
                             animations:^{
                                 mainScroller.contentOffset = CGPointMake(0, 0);
                                 textTV.contentOffset = CGPointMake(0, 0);
                             }
                             completion:^(BOOL finished){
                             }];

            float yOff = 60;
            yOff += durationCell.frame.size.height;
            yOff += reminderCell.frame.size.height;
            yOff += fixedCell.frame.size.height;
            yOff += repeatCell.frame.size.height;
            textTV.frame = CGRectMake(0, textTV.frame.origin.y, w, h-yOff);
        }
    }
}