UITextView标签中的占位符不会消失

我知道这里有很多关于UITextView占位符的链接，我尝试了为我工作的那个，但我不工作。即使当我开始在textView中输入时，他们的占位符文本仍然存在。任何人有任何想法，为什么？下面粘贴了我的代码。UITextView标签中的占位符不会消失

AddExerciseViewController.m

#import "AddExerciseViewController.h" 

@implementation AddExerciseViewController 
@synthesize nameTextField = _nameTextField; 
@synthesize descriptionTextView = _descriptionTextView; 
@synthesize placeholderLabel = _placeholderLabel; 

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil 
{ 
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; 
    if (self) {  
    } 
    return self; 
} 

- (void)viewDidLoad 
{ 
    _descriptionTextView.layer.borderWidth = 3.0f; 
    _descriptionTextView.layer.borderColor = [[UIColor grayColor ] CGColor]; 
    _descriptionTextView.layer.cornerRadius = 5; 
    _descriptionTextView.clipsToBounds = YES; 

    _placeholderLabel = [[UILabel alloc] initWithFrame:CGRectMake(10.0, 0.0,   _descriptionTextView.frame.size.width - 20.0, 34.0)]; 
    [_placeholderLabel setText: @"FooBar"]; 

    // placeholderLabel is instance variable retained by view controller 
    [_placeholderLabel setBackgroundColor:[UIColor clearColor]]; 
    [_placeholderLabel setTextColor:[UIColor lightGrayColor]]; 

    [_descriptionTextView addSubview:_placeholderLabel]; 
    [super viewDidLoad]; 
} 

- (void) textViewDidChange:(UITextView *)theTextView 
{ 
    if(![_descriptionTextView hasText]) { 
    [_descriptionTextView addSubview:_placeholderLabel]; 
    [UIView animateWithDuration:0.15 animations:^{ 
     _descriptionTextView.alpha = 1.0; 
    }]; 
} else if ([[_descriptionTextView subviews] containsObject:_placeholderLabel]) { 

    [UIView animateWithDuration:0.15 animations:^{ 
     _placeholderLabel.alpha = 0.0; 
    } completion:^(BOOL finished) { 
     [_placeholderLabel removeFromSuperview]; 
    }]; 
} 
} 


- (void)textViewDidEndEditing:(UITextView *)theTextView 
{ 
    if (![_descriptionTextView hasText]) { 
     [_descriptionTextView addSubview:_placeholderLabel]; 
     [UIView animateWithDuration:0.15 animations:^{ 
      _placeholderLabel.alpha = 1.0; 
     }]; 
    } 
} 

- (void)viewDidUnload 
{ 
    [self setDescriptionTextView:nil]; 
    [self setNameTextField:nil]; 
    [super viewDidUnload]; 
}

@end

来源

2012-03-21 Niels Sønderbæk

我相信textViewDidChange:被编辑完成后才能调用。您可能想要改为在textViewDidBeginEditing:上隐藏占位符。

来源

2012-03-21 22:31:08 MechEthan

我不确定你的意思是什么？ – 2012-03-21 22:52:12

您粘贴的代码在用户将文本输入到UITextView时不会工作。 ' - （void）textViewDidChange：（UITextView *）theTextView {...}'只有在选择另一个字段或隐藏键盘之后才会被调用。 'textViewDidBeginEditing：'将在用户开始输入时立即调用UITextView的。 – MechEthan 2012-03-21 23:25:22

这很有道理。我想通过另一种方式来做到这一点。我只是添加了一个观察者'UITextViewTextDidBeginEditingNotification'，并且这个函数删除了占位符，一旦该通知被调用:) – 2012-03-21 23:34:16

UITextView标签中的占位符不会消失

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