Scroll to bottom of UITextView erratic in iOS 7

Question

The following code will work fine in iOS < 7.0. In iOS 7 the scrolling will be choppy and erratic while the UITextView is updating. I'm not sure if this is a bug in iOS 7, or I am doing something wrong.

TestController.h

//TODO: Add UITextView in storyboard and tie to textView outlet

#define MAX_TEXT_VIEW_CHARACTERS 1000
@interface TestController : UIViewController  {
    NSMutableString *_outputText;
    NSTimer *_outputTimer;
}

@property (strong, nonatomic) IBOutlet UITextView *textView;

@end

TestController.m

@implementation TestController
@synthesize textView;

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    _outputText = [NSMutableString stringWithCapacity:MAX_TEXT_VIEW_CHARACTERS];
    _outputTimer =  [NSTimer scheduledTimerWithTimeInterval:0.01 target:self selector:@selector(outputLine:) userInfo:nil repeats:YES];
}

-(void)outputLine:(NSTimer *) theTimer {
    static int i = 0;
    //Run this 100 times
    if (i > 99) {
        [_outputTimer invalidate];
        return;
    }
    [self outputToScreen:[NSString stringWithFormat:@"Some string %d\r", ++i]];
}

-(void)outputToScreen:(NSString *)str {
    if (!str || !str.length) return;  //Nothing to output

    NSInteger outputTextSize = _outputText.length;
    [_outputText appendString:str];
    if (outputTextSize > MAX_TEXT_VIEW_CHARACTERS)
        [_outputText deleteCharactersInRange:NSMakeRange(0, outputTextSize - MAX_TEXT_VIEW_CHARACTERS)];
    self.textView.text = _outputText;

    [self scrollOutputToBottom];
}

-(void)scrollOutputToBottom {
    CGPoint p = [textView contentOffset];
    [textView setContentOffset:p animated:NO];
    [textView scrollRangeToVisible:NSMakeRange([textView.text length], 0)];
}

@end

Solution 1

This is obviously an iOS 7 bug. Here is a workaround until apple fixes it. The workaround is basically instantiates a UITextView by creating an NSTextStorage and NSLayoutManager from scratch. Apple must have forgotten to initialize something in UITextView initialization method. I filed a bug report and I hope you do too.

// ios7 bug fix
// check if the device is running iOS 7.0 or later
NSString *reqSysVer = @"7.0";
NSString *currSysVer = [[UIDevice currentDevice] systemVersion];
BOOL osVersionSupported = ([currSysVer compare:reqSysVer  options:NSNumericSearch] != NSOrderedAscending);

if (osVersionSupported) {
    NSTextStorage* textStorage = [[NSTextStorage alloc] init];
    NSLayoutManager* layoutManager = [NSLayoutManager new];
    [textStorage addLayoutManager:layoutManager];
    NSTextContainer *textContainer = [[NSTextContainer alloc] initWithSize:self.view.bounds.size];
    [layoutManager addTextContainer:textContainer];
    yourTextView = [[UITextView alloc] initWithFrame:someFrameForYourTextView
                                       textContainer:textContainer];
    // if using ARC, remove these 3 lines
    [textContainer release];
    [layoutManager release];
    [textStorage release];
}
else {
    yourTextView = [[UITextView alloc] initWithFrame:someFrameForYourTextView];
}

Solution 2

This works for me in iOS7.

-(void) scrollToBottom {
  [textView scrollRangeToVisible:NSMakeRange([textView.text length], 0)];
  [textView setScrollEnabled:NO];
  [textView setScrollEnabled:YES];
}

Solution 3

There are two problems in iOS 7 that could explain your problem:

• The contentOffset is not always up to date in iOS 7.
• scrollRangeToVisible: will not scroll to an empty line at the end of the text view.

The solution could be:

-(void)scrollOutputToBottom {
    CGRect caretRect = [textView caretRectForPosition:textView.endOfDocument];
    [textView scrollRectToVisible:caretRect animated:NO];
}

Solution 4

Try this:

// Don't forget to set textView's delegate 
-(void)textViewDidChangeSelection:(UITextView *)textView {
    [textView scrollRangeToVisible:NSMakeRange([textView.text length], 0)];
}

Solution 5

For those who are using Swift, I post here the same answer as RawMean (thanks again!). As I wrote this (dec. 2014), the problem still exist in iOS 8.1 and his solution work perfectly...

var textView: UITextView!
var textStorage: NSTextStorage!
var layoutManager: NSLayoutManager!
var textContainer: NSTextContainer!


override func viewDidLoad() {
    textStorage = NSTextStorage()
    layoutManager = NSLayoutManager()
    textStorage.addLayoutManager(layoutManager)

    let newTextViewRect = view.bounds
    let containerSize = CGSize(width: newTextViewRect.width, height: CGFloat.max)

    textContainer = NSTextContainer(size: containerSize)
    layoutManager.addTextContainer(textContainer)

    textView = UITextView(frame: newTextViewRect, textContainer: textContainer)

    textView.delegate = self
    view.addSubview(textView)

}

override func viewDidLayoutSubviews() {
    textView.frame = view.bounds
}

and I used the scrollRangeToVisible method to scroll smoothly at the bottom as text is added...

let length = countElements(textView.text)
let range:NSRange = NSMakeRange(length - 1, 1)
textView.scrollRangeToVisible(range)

View more solutions

Comments

[zoul]

For what it’s worth, I’m having problems even with a simple setContentOffset call. The content offset changes, but the view doesn’t scroll. The accepted answer worked.

[Mikt25]

Good point zoul. This is why I added both setContentOffset and scrollRageToVisible to show that neither method of scrolling works like it should with the new UITextView in iOS 7.

[philipkd]

Is this still an issue in iOS 10?

[Robert Atkins]

Is this still an issue in iOS 13? (It appears to be, no matter what I do I can't get the damned thing to scroll. sigh)

[Mikt25]

This code works fine in iOS 6 but has no effect in iOS 7. BTW: Do you know if contentOffset not being up to date is a bug in iOS 7?

[Mikt25]

Excellent work! To get this to work with my OP, I obviously had to change the name to textView. I also had to set some properties such as font to the same and then called [self.view addSubview:textView];

[tzer]

Solved my problem. Thanks.

[boxed]

Solved the problem for me too, thanks. And animates nicely too!

[Renjith K N]

hi welcome to so, it will be more helpfull, if you give simple explanations, along with your answer .. cheers & thank you...

[svarion]

hi my response is based on this stackoverflow.com/a/2557893/2870119 ...scrollview content offset is moved to the bottom of the content view (so I'm using its height), I'm using this solution and simply works :)

[Donald Burr]

Works for me as well. Saved me quite a lot of hair-tearing-out tonight. :)

[Duck]

+1 ... I don't know why they down voted you because this is the only answer that works for iOS 7. Thanks.

[Scott Carter]

This solved my problem also, but I switched the first 2 lines of code so that I set scrollEnabled = NO before calling scrollRangeToVisible. Though both implementations work, my version feels less like a race condition :)

[register]

This is really genius!! It takes a lot of intuition to understand that it was a bug in the sdk. By the way it has not been fixed even in 8.0. Thanks for your great contribution!!

[Allen]

This method will block scroll with doing paste action which is obvious when the content height is bigger than the textView height.

[MitchellTR]

This is still a super obnoxious iOS bug and this is the best workaround I've found anywhere online. Works like a charm.

[alexgophermix]

Amazed that this bug still exists. Reproduced on iOS 8.1 and fixed with this great piece of code.

[aramusss]

This does not work for me, it scrolls buggy for every line I add to the UITextView

[Nate]

This worked for me in iOS 7, too, but in iOS 8.?, it stopped working (scrolling was not re-enabled). I just removed the two calls to setScrollEnabled: for iOS 8.

[Nicolas Miari]

iOS 9 beta 5 here. I can confirm that this solution works.

[Mert]

On iOS8.1 observed the same thing as Nate. Removing the last two lines solved it for me too.