在 iOS 7 中滚动到 UITextView 不稳定的底部
以下代码在 iOS 中可以正常工作
7.0.在 iOS 7 中,当 UITextView 更新时,滚动会断断续续且不稳定.我不确定这是否是 iOS 7 中的错误,或者我做错了什么.
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", ++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
推荐答案
这显然是 iOS 7 的 bug.这是一个解决方法,直到苹果修复它.解决方法基本上是通过从头开始创建 NSTextStorage
和 NSLayoutManager
来实例化 UITextView
.苹果一定是忘记在 UITextView
初始化方法中进行初始化了.我提交了错误报告,希望你也这样做.
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];
}
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