如何让UIScrollView滚动到UITextView的光标位置？

Question

我有一个类似于笔记应用的视图 - 即在一张纸上打字。为了使文本和纸张同时滚动，我禁用了UITextView的滚动功能，而是将UITextView和UIImageView放入UIScrollView中。

唯一的问题是，当用户键入时，文本在键盘下消失，因为显然UIScrollView不知道滚动到光标位置。

有没有简单的方法可以检索光标位置并告诉UIScrollView在那里滚动？

---编辑---

从类似的东西开始here（其中有人试图做一个UITableView类似的东西），我已经成功地使越来越多，可编辑的UITextView有固定的背景差不多完美滚动。现在唯一的问题是：

1. 如果用户键入的速度特别快，文本向上移动会有轻微抖动。
2. 如果用户隐藏键盘，选择屏幕底部的文本，然后再次显示键盘，则必须在文本再次可见之前键入几个字母 - 它不会立即向上滚动。
3. 当用户隐藏键盘时，作为滚动视图框架填充屏幕的动画不知何故感觉不太正确。

这里是代码 - 我真的很感激，如果任何人都可以进一步细化它...

#import "NoteEditViewController.h" 
#import "RLWideLabelTableCell.h" 

@implementation NoteEditViewController 
@synthesize keyboardSize; 
@synthesize keyboardHideDuration; 
@synthesize scrollView; 
@synthesize noteTextView; 

// 
// Dealloc and all that stuff 
// 
- (void)loadView 
{ 
    [super loadView]; 
    UIScrollView *aScrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds]; 
    self.scrollView = aScrollView; [aScrollView release]; 
    self.scrollView.contentSize = CGSizeMake(self.view.frame.size.width, noteTextView.frame.size.height); 
    [self.view addSubview:scrollView]; 
} 

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 

    // Get notified when keyboard is shown. Don't need notification when hidden because we are 
    // using textViewDidEndEditing so we can start animating before the keyboard disappears. 
    [[NSNotificationCenter defaultCenter] addObserver:self 
              selector:@selector(keyboardWasShown:) 
               name:UIKeyboardDidShowNotification object:nil]; 

    // Add the Done button so we can test dismissal of the keyboard  
    UIBarButtonItem *doneButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone 
     target:self 
     action:@selector(doneButton:)]; 
    self.navigationItem.rightBarButtonItem = doneButton; [doneButton release]; 

    // Add the background image that will scroll with the text 
    CGRect noteImageFrame = CGRectMake(self.view.bounds.origin.x, 
             noteTitleImageFrame.size.height, 
             self.view.bounds.size.width, 500);  

    UIView *backgroundPattern = [[UIView alloc] initWithFrame:noteImageFrame]; 
    backgroundPattern.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"Notepaper-iPhone-Line"]]; 
    [self.scrollView addSubview:backgroundPattern]; 
    [self.view sendSubviewToBack:backgroundPattern]; 
    [backgroundPattern release]; 

    // Add the textView 
    CGRect textViewFrame = CGRectMake(noteImageFrame.origin.x+27, 
             noteImageFrame.origin.y-3, 
             noteImageFrame.size.width-35, 
             noteImageFrame.size.height); 

    RLTextView *textView = [[RLTextView alloc] initWithFrame:textViewFrame]; 
    self.noteTextView = textView; [textView release]; 
    self.noteTextView.font = [UIFont fontWithName:@"Cochin" size:21]; 
    self.noteTextView.backgroundColor = [UIColor clearColor]; 
    self.noteTextView.delegate = self; 
    self.noteTextView.scrollEnabled = NO; 
    [self.scrollView addSubview:self.noteTextView]; 
} 

- (void)doneButton:(id)sender 
{ 
    [self.view endEditing:TRUE]; 
} 

// When the keyboard is shown, the UIScrollView's frame shrinks so that it fits in the 
// remaining space 
- (void)keyboardWasShown:(NSNotification*)aNotification 
{ 
    NSDictionary* info = [aNotification userInfo]; 
    CGSize kbSize = [[info objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue].size; 
    float kbHideDuration = [[info objectForKey:UIKeyboardAnimationDurationUserInfoKey] floatValue]; 
    self.keyboardHideDuration = kbHideDuration; 
    self.keyboardSize = kbSize; 
    self.scrollView.frame = CGRectMake(self.view.bounds.origin.x, 
             self.view.bounds.origin.y, 
             self.view.bounds.size.width, 
             self.view.bounds.size.height - kbSize.height);  
} 

// When the user presses 'done' the UIScrollView expands to the size of its superview 
// again, as the keyboard disappears. 
- (void)textViewDidEndEditing:(UITextView *)textView 
{ 
    [UIScrollView animateWithDuration:keyboardHideDuration animations:^{self.scrollView.frame = self.view.bounds;}]; 
} 

// This method needs to get called whenever there is a change of cursor position in the text box 
// That means both textViewDidChange: and textViewDidChangeSelection: 
- (void)scrollToCursor 
{ 
    // if there is a selection cursor… 
    if(noteTextView.selectedRange.location != NSNotFound) { 
     NSLog(@"selectedRange: %d %d", noteTextView.selectedRange.location, noteTextView.selectedRange.length); 

     // work out how big the text view would be if the text only went up to the cursor 
     NSRange range; 
     range.location = noteTextView.selectedRange.location; 
     range.length = noteTextView.text.length - range.location; 
     NSString *string = [noteTextView.text stringByReplacingCharactersInRange:range withString:@""]; 
     CGSize size = [string sizeWithFont:noteTextView.font constrainedToSize:noteTextView.bounds.size lineBreakMode:UILineBreakModeWordWrap]; 

     // work out where that position would be relative to the textView's frame 
     CGRect viewRect = noteTextView.frame; 
     int scrollHeight = viewRect.origin.y + size.height; 
     CGRect finalRect = CGRectMake(1, scrollHeight, 1, 1); 

     // scroll to it 
     [self.scrollView scrollRectToVisible:finalRect animated:YES]; 
    } 
} 

// Whenever the text changes, the textView's size is updated (so it grows as more text 
// is added), and it also scrolls to the cursor. 
- (void)textViewDidChange:(UITextView *)textView 
{ 
    noteTextView.frame = CGRectMake(noteTextView.frame.origin.x, 
            noteTextView.frame.origin.y, 
            noteTextView.frame.size.width, 
            noteTextView.contentSize.height); 
    self.scrollView.contentSize = CGSizeMake(self.scrollView.contentSize.width, 
              noteTextView.frame.size.height+200); 
    [self scrollToCursor]; 
} 

// The textView scrolls to the cursor whenever the user changes the selection point. 
- (void)textViewDidChangeSelection:(UITextView *)aTextView 
{ 
    [self scrollToCursor]; 
} 

// PROBLEM - the textView does not scroll until the user starts typing - just selecting 
// it is not enough. 
- (void)textViewDidBeginEditing:(UITextView *)textView 
{ 
    [self scrollToCursor]; 
} 

Answer 1

很酷，你发现我的帖子，很高兴它是有帮助的！

我相信你可能无法看到，因为这条线的底线：

CGRect finalRect = CGRectMake(1, scrollHeight, 1, 1); 

你正在创建一个1x1点框。一行文本可能是20或30个点的高度（取决于字体大小）。因此，如果您将此点滚动显示，它可能只会显示底线的顶部像素 - 使底线实际上不可见！如果您finalRect高一点，所以它涵盖了整条生产线，它可能会更好地工作：

CGRect finalRect = CGRectMake(1, scrollHeight, 1, 30); 

此外，您可以一次打电话给你scrollRectToVisible代码多次，这可能会导致“颤动”。在我的代码中，我只运行textViewDidChangeSelection中的scrollRectToVisible，并在textViewDidChange中调整UITextView的大小（如果需要）。 UIScrollView（并通过继承UITableView）内置支持将主动选择的元素滚动到可见状态，这在我测试时运行良好，只需在键入时调整UITextView的大小（但不是在通过触摸选择内部特定点时）。

Answer 2

有没有简单的方法来发现屏幕坐标中的任何文本或光标UITextView。

你应该做的是注册UIKeyboardWillShowNotification和UIKeyboardWillShowNotification。在回调中，您可以调整UIScrollView的size或contentInsets，以调整键盘的大小。

键盘的大小，甚至动画持续时间都在userInfo的通知中提供，因此您可以用一种很好的动画形式进行操作。

你会发现更多的信息和示例代码在这里：http://developer.apple.com/library/ios/#documentation/StringsTextFonts/Conceptual/TextAndWebiPhoneOS/KeyboardManagement/KeyboardManagement.html

Answer 3

不是严格意义上的回答你的问题，但这里有一个不同的方法来衬背景招调：http://www.cocoanetics.com/2010/03/stuff-you-learn-from-reverse-engineering-notes-app/

我用它和它效果很好。