iOS 8.1仅间歇性地显示UITextView

Question

我有一个模板测验应用程序，已经在应用商店以各种形式存在了一段时间，一般来说它收到良好的评论，没有错误报告。

最近我有两个错误报告，人们使用带有iOS 8.1.2或8.1.3的iPad，并说现在我用来显示问题的UITextView是空白的。

我无法复制这个错误，但如果有人能够对它有所了解，我将不胜感激。

对象questions和userAnswer不是零，所以它肯定是一个UITextView问题。

控制器在这里：

@interface ReviewController ()
@property (strong, nonatomic) IBOutlet UITextView *output;

@end

@implementation ReviewController

- (void)viewDidLoad {
    [super viewDidLoad];

    [self setReviewText];
   // Do any additional setup after loading the view.
}

-(void)setReviewText{

    NSArray* questions = [[NSArray alloc] init];
    questions = [_manager getAllQuestions];
    NSMutableArray* userAnswer = [[NSMutableArray alloc] init];
    userAnswer = [self answersAttributed];

    if(questions == nil)
        _output.text = @"Questions Error";

    if (userAnswer == nil)
    {
        _output.text = @"Error";
    }

    NSMutableAttributedString *mutableAttString = [[NSMutableAttributedString alloc] init];

    int i = 0;
    NSAttributedString *linebreak =[[NSAttributedString alloc] initWithString:@"\n"];
    for (Question* q in questions)
    {
        if (i == [userAnswer count])
            break;

        NSAttributedString *qtext =[[NSAttributedString alloc] initWithString:q.questionText];
        NSAttributedString *ctext =[[NSAttributedString alloc] initWithString:@"Correct Answer:\n"];

        NSAttributedString *atext =[[NSAttributedString alloc] initWithString:q.answerText];
        NSAttributedString *ytext =[[NSAttributedString alloc] initWithString:@"Your Answer:\n"];
        NSAttributedString *utext =[[NSAttributedString alloc] initWithAttributedString:userAnswer[i]];
        [mutableAttString appendAttributedString:qtext];
        [mutableAttString appendAttributedString:linebreak];
        [mutableAttString appendAttributedString:ctext];
        [mutableAttString appendAttributedString:atext];
        [mutableAttString appendAttributedString:linebreak];
        [mutableAttString appendAttributedString:ytext];
        [mutableAttString appendAttributedString:utext];
        [mutableAttString appendAttributedString:linebreak];
        [mutableAttString appendAttributedString:linebreak];
        i++;
    }
    NSAttributedString* outText = [[NSAttributedString alloc] init];
    outText = [mutableAttString mutableCopy];
    _output.attributedText = outText;
    [_output setFont:[UIFont preferredFontForTextStyle:UIFontTextStyleBody]];
}


-(NSMutableArray*)answersAttributed
{
    NSMutableArray* ansAtt = [[NSMutableArray alloc] init];
    NSArray* questions = [[NSArray alloc] init];
    questions = [_manager getAllQuestions];

    NSArray* userAnswers = [[NSArray alloc] init];
    userAnswers = [_manager getAllUserAnswers];


    if ([questions count] != [userAnswers count])
    {
        return ansAtt;
    }


    int i = 0;
    for (NSString* userAnswer in userAnswers )
    {
        if([[questions[i] answerText] isEqualToString:userAnswer] )
        {
            NSDictionary *attributes = @{NSBackgroundColorAttributeName:[UIColor greenColor]};
            NSAttributedString *attrString = [[NSAttributedString alloc] initWithString:userAnswer attributes:attributes];
            [ansAtt addObject:attrString];
        }
        else
        {
            NSDictionary *attributes = @{NSBackgroundColorAttributeName:[UIColor redColor]};
            NSAttributedString *attrString = [[NSAttributedString alloc] initWithString:userAnswer attributes:attributes];
            [ansAtt addObject:attrString];

        }
        i++;
    }

    return ansAtt;
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    // Make sure your segue name in storyboard is the same as this line
    if ([[segue identifier] isEqualToString:@"review2results"])
    {
        // Get reference to the destination view controller
        ReviewController *vc = [segue destinationViewController];

        // Pass any objects to the view controller here, like...
        [vc setManager:_manager];
    }
}

Answer 1

使用自动布局时，如果您没有足够的约束来完全指定大小和位置，那么有时您会看到并且有时您不会。未指定的约束可以具有随机值，例如0高度或屏幕外位置。

检查以确保完全指定约束。

Answer 2

在我的情况下，在textview中标记为Non-Editable和Non-Selectable的Storyboard在iOS 8.1上具有相同的奇怪行为（在iOS 9+中没有问题）。

- (void)viewDidLoad {
    [super viewDidLoad];
    textview.attributedText = [[NSAttributedString alloc] initWithString:@"non-nil"]];
    value = textview.attributedText;
    //^ value is nil !!!
}

修正了这个问题：

- (void)viewDidLoad {
    [super viewDidLoad];
    textview.editable = YES;
    textview.attributedText = [[NSAttributedString alloc] initWithString:@"non-nil"]];
    textview.editable = NO;
    value = textview.attributedText;
    //^ value is @"non-nil" now !!!
}