[英]Scroll to bottom of UITextView erratic in iOS 7
The following code will work fine in iOS < 7.0. 以下代码在iOS <7.0中可以正常工作。 In iOS 7 the scrolling will be choppy and erratic while the UITextView is updating.
在iOS 7中,当UITextView正在更新时,滚动将变得不稳定且不稳定。 I'm not sure if this is a bug in iOS 7, or I am doing something wrong.
我不确定这是否是iOS 7中的错误,或者我做错了什么。
TestController.h
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
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
This works for me in iOS7. 这适用于iOS7。
-(void) scrollToBottom {
[textView scrollRangeToVisible:NSMakeRange([textView.text length], 0)];
[textView setScrollEnabled:NO];
[textView setScrollEnabled:YES];
}
This is obviously an iOS 7 bug. 这显然是iOS 7的错误。 Here is a workaround until apple fixes it.
这是一个解决方法,直到苹果修复它。 The workaround is basically instantiates a
UITextView
by creating an NSTextStorage
and NSLayoutManager
from scratch. 解决方法基本上是通过从头创建
NSTextStorage
和NSLayoutManager
来实例化UITextView
。 Apple must have forgotten to initialize something in UITextView
initialization method. Apple必须忘记在
UITextView
初始化方法中初始化一些东西。 I filed a bug report and I hope you do too. 我提交了一份错误报告,我希望你也这样做。
// 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];
}
There are two problems in iOS 7 that could explain your problem: iOS 7中有两个问题可以解释您的问题:
The solution could be: 解决方案可能是:
-(void)scrollOutputToBottom {
CGRect caretRect = [textView caretRectForPosition:textView.endOfDocument];
[textView scrollRectToVisible:caretRect animated:NO];
}
Try this: 尝试这个:
// Don't forget to set textView's delegate
-(void)textViewDidChangeSelection:(UITextView *)textView {
[textView scrollRangeToVisible:NSMakeRange([textView.text length], 0)];
}
For those who are using Swift, I post here the same answer as RawMean (thanks again!). 对于那些使用Swift的人,我在这里发布与RawMean相同的答案(再次感谢!)。 As I wrote this (dec. 2014), the problem still exist in iOS 8.1 and his solution work perfectly...
正如我写的那样(2014年12月),问题仍然存在于iOS 8.1中,他的解决方案完美地工作......
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... 我使用scrollRangeToVisible方法在文本添加时在底部平滑滚动...
let length = countElements(textView.text)
let range:NSRange = NSMakeRange(length - 1, 1)
textView.scrollRangeToVisible(range)
Basically setScrollEnabled = YES need to be set before layoutSubviews get called. 基本上setScrollEnabled = YES需要在调用layoutSubviews之前设置。 It worked for me.
它对我有用。
That works for me. 这对我行得通。 Reference: UITextView setText should not jump to top in ios8
参考: UITextView setText不应该跳转到ios8的顶部
self.textView.layoutManager.allowsNonContiguousLayout = NO;
self.textView.text = fileContent;
if(fileContent.length > 1)
{
NSRange range = NSMakeRange(self.textView.text.length - 1, 1);
[self.textView scrollRangeToVisible:range];
}
Swift 2.0 - IOS 8 Swift 2.0 - IOS 8
This is basically a Swift 2.0 version of dklt's answer above. 这基本上是上面dklt的答案的Swift 2.0版本。 Previously I was using the same method without the 2 lines of
scrollEnabled
. 以前我使用相同的方法没有2行
scrollEnabled
。 Most of the time it works fine. 大多数时候它工作正常。 However, when
scrollToBottom()
is called in quick succession at almost the same time, it doesn't works sometimes. 但是,当几乎同时快速连续调用
scrollToBottom()
时,它有时不起作用。
The 2 lines of scrollEnabled
doesn't makes much sense, but after adding them the method works consistently ! scrollEnabled
的两行没有多大意义,但在添加它们之后,该方法始终如一 !
Note: I have tried to put the 2 lines of scrollEnabled
in various position before or after the scrollRangeTovisible
, as was suggested in dklt's answer's comments... 注:我试图把2线
scrollEnabled
在不同位置的前面或后面scrollRangeTovisible
,如dklt的答复的意见建议......
ONLY dklt's original solution works for me. 只有dklt的原始解决方案适合我。 The rest doesn't.
其余的没有。
func scrollToBottom()
{
let range:NSRange = NSMakeRange(self.textView.text.characters.count - 1, 1)
self.textView.scrollRangeToVisible(range)
self.textView.scrollEnabled = false
self.textView.scrollEnabled = true
}
please try this solution 请试试这个解决方案
-(void) scrollToBottom {
[textView setContentOffset:CGPointMake(0.0, textView.contentSize.height) animated:YES];
}
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