Stop UITextView from jumping when programmatically

问题:

I have to update a small amount of text in a scrolling UITextView. I'll only be inserting a character where the cursor currently is, and I'll be doing this on a press of a button on my navigation bar.

My problem is that whenever I call the setText method of the text view, it jumps to the bottom of the text. I've tried using contentOffset and resetting the selectedRange but it doesn't work! Here's my example:

// Remember offset and selection
CGPoint contentOffset = [entryTextView contentOffset];
NSRange selectedRange = [entryTextView selectedRange];
// Update text
entryTextView.text = entryTextView.text;
// Try and reset offset and selection
[entryTextView setContentOffset:contentOffset animated:NO];
[entryTextView setSelectedRange: selectedRange];

Is there any way you can update the text without any scroll movement at all... as if they'd just typed something on the keyboard?

Edit:

I've tried using the textViewDidChange: delegate method but it's still not scrolling up to the original location.

- (void)textViewDidChange:(UITextView *)textView {
    if (self.programChanged) {
        [textView setSelectedRange:self.selectedRange];
        [textView setContentOffset:self.contentOffset animated:NO];
        self.programChanged = NO;
    }
}

- (void)changeButtonPressed:(id)sender {
    // Remember position
    self.programChanged = YES;
    self.contentOffset = [entryTextView contentOffset];
    self.selectedRange = [entryTextView selectedRange];
    // Update text
    entryTextView.text = entryTextView.text;
}

回答1:

If you use iPhone 3.0 or later, you can solve this problem:

textView.scrollEnabled = NO;

//You should know where the cursor will be(if you update your text by appending/inserting/deleting you can know the selected range) so keep it in a NSRange variable.

Then update text:
textView.text = yourText;

textView.scrollEnabled = YES;
textView.selectedRange = range;//you keep before

It should work now (no more jumping)

Regards Meir Assayag

回答2:

Building on Meir's suggestion, here's code that removes the selection programmatically (yes I know there's a selection menu button that does it too, but I'm doing something a bit funky) without scrolling the text view.

NSRange selectedRange = textView.selectedRange;
textView.scrollEnabled = NO;
// I'm deleting text. Replace this line with whatever insertions/changes you want
textView.text = [textView.text
                stringByReplacingCharactersInRange:selectedRange withString:@""];
selectedRange.length = 0;
// If you're inserting text, you might want to increment selectedRange.location to be
// after the text you inserted
textView.selectedRange = selectedRange;
textView.scrollEnabled = YES;

回答3:

This decision works for iOS 8:

let offset = textView.contentOffset
textView.text = newText
textView.layoutIfNeeded()
textView.setContentOffset(offset, animated: false)

It is necessary to call exactly setContentOffset:animated: because only this will cancel animation. textView.contentOffset = offset will not cancel the animation and will not help.

回答4:

The following two solutions don't work for me on iOS 8.0.

textView.scrollEnabled = NO;
[textView.setText: text];
textView.scrollEnabled = YES;

and

CGPoint offset = textView.contentOffset;
[textView.setText: text];
[textView setContentOffset:offset];

I setup a delegate to the textview to monitor the scroll event, and noticed that after my operation to restore the offset, the offset is reset to 0 again. So I instead use the main operation queue to make sure my restore operation happens after the "reset to 0" option.

Here's my solution that works for iOS 8.0.

CGPoint offset = self.textView.contentOffset;
self.textView.attributedText = replace;
[[NSOperationQueue mainQueue] addOperationWithBlock: ^{
    [self.textView setContentOffset: offset];
}];

回答5:

No of the suggested solutions worked for me. -setContentOffset:animated: gets triggered by -setText: 3 times with animated YES and a contentOffset of the end (minus the default 8pt margin of a UITextView). I wrapped the -setText: in a guard:

textView.contentOffsetAnimatedCallsDisabled = YES;
textView.text = text;
textView.contentOffsetAnimatedCallsDisabled = NO;

In a UITextView subclass in -setContentOffset:animated: put

if (contentOffsetAnimatedCallsDisabled) return; // early return

among your other logic. Don’t forget the super call. This works.

Raphael

回答6:

In order to edit the text of a UITextView, you need to update it's textStorage field:

[_textView.textStorage beginEditing];

NSRange replace = NSMakeRange(10, 2); //enter your editing range
[_textView.textStorage replaceCharactersInRange:replace withString:@"ha ha$ "];

//if you want to edit the attributes
NSRange attributeRange = NSMakeRange(10, 5); //enter your editing attribute range
[_textView.textStorage addAttribute:NSBackgroundColorAttributeName value:[UIColor greenColor] range:attributeRange];

[_textView.textStorage endEditing];

Good luck

回答7:

in iOS 7. There seams to be a bug with sizeThatFits and having linebreaks in your UITextView the solution I found that works is to wrap it by disabling scrolling. Like this:

textView.scrollEnabled = NO;
CGSize newSize = [textView sizeThatFits:CGSizeMake(fixedWidth, MAXFLOAT)];
textView.scrollEnabled = YES;

and weird jumping has been fixed.

回答8:

Take a look at the UITextViewDelegate, I believe the textViewDidChangeSelection method may allow you to do what you need.

回答9:

Old question but I had the same issue with iOS 7 app. Requires changing the contentOffset a little bit after the run loop. Here is a quick idea.

self.clueString = [self.level clueText];
CGPoint point = self.clueText.contentOffset;
self.clueText.attributedText = self.clueString;
double delayInSeconds = 0.001; // after the run loop update
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
    [self.clueText setContentOffset:point animated:NO]; 
});

回答10:

I hit a a similar, if not the same, problem in IOS9. Changing the characteristics of some text to, say, BOLD caused the view to scroll the selection out of sight. I sorted this by adding a call to scrollRangeToVisible after the setSelectedRange:

    [self setSelectedRange:range];
    [self scrollRangeToVisible:range];

回答11:

Finally try this, checked on iOS 10

let offset = textView.contentOffset
textView.attributedText = newValue
OperationQueue.main.addOperation {
    self.textView.setContentOffset(offset, animated: false)
}

回答12:

Not so elegant solution- but it works so who cares:

- (IBAction)changeTextProgrammaticaly{
     myTextView.text = @"Some text";
     [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(rewindOffset) userInfo:nil repeats:NO];
}

- (void)rewindOffset{
    [myTextView setContentOffset:CGPointMake(0,0) animated: NO];
}

回答13:

I found a solution that works reliably in iOS 6 and 7 (and probably earlier versions). In a subclass of UITextView, do the following:

@interface MyTextView ()
@property (nonatomic) BOOL needToResetScrollPosition;
@end

@implementation MyTextView

- (void)setText:(NSString *)text
{
    [super setText:text];
    self.needToResetScrollPosition = YES;
}

- (void)layoutSubviews
{
    [super layoutSubviews];

    if (self.needToResetScrollPosition) {
        self.contentOffset = CGPointMake(0, 0);
        self.needToResetScrollPosition = NO;
    }
}

None of the other answers work in iOS 7 because it will adjust the scroll offsets at display time.