Question

我使用NSTextAttachment显示占位符图像。点击此图片时，我想显示另一个图像。我在UItextView委托方法中执行此操作：

- （BOOL）textView：（UITextView *）textView shouldInteractWithTextAttachment：（NSTextAttachment *）textAttachment inRange：（NSRange）characterRange

我遇到以下问题：点击（单击）图像并已进入委托方法，但图像不会立即更改。我尝试在主队列中更改图像并调用setNeedsDisplay，但它仍然不起作用。请帮助：）

这是我的主要代码：

viewDidLoad中：

NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithString:@"This is an example by @marcelofabri_"];

[attributedString addAttribute:NSLinkAttributeName
                         value:@"username://marcelofabri_"
                         range:[[attributedString string] rangeOfString:@"@marcelofabri_"]];

//first image
NSTextAttachment *textAttachment = [[NSTextAttachment alloc] init];
textAttachment.image = [UIImage imageNamed:@"sample_image.png"];
NSAttributedString *attrStringWithImage = [NSAttributedString attributedStringWithAttachment:textAttachment];

[attributedString appendAttributedString:attrStringWithImage];

self.textView.attributedText = attributedString;
self.textView.delegate = self;
self.textView.editable = NO;

UITextView委托方法

-(BOOL)textView:(UITextView *)textView shouldInteractWithTextAttachment:(NSTextAttachment *)textAttachment inRange:(NSRange)characterRange{
UIImage *image  = textAttachment.image;

NSLog(@"width:%f , height:%f",image.size.width,image.size.height);
//change second image
  dispatch_async(dispatch_get_main_queue(), ^{                      

    textAttachment.image = [UIImage imageNamed:@"sample_image_1"];        
    [_textView setNeedsDisplay];
});

return true;
}

感谢您的帮助：）

Answer 1

经过一番挖掘后，我发现textview可以通过使布局管理器无效来重绘图像

[textView.layoutManager invalidateDisplayForCharacterRange:characterRange];

Answer 2

[textView.layoutManager invalidateDisplayForCharacterRange:characterRange];//refresh display
[textView.layoutManager invalidateLayoutForCharacterRange:characterRange actualCharacterRange:NULL];//refresh layout

更改NSTextAttachment图像即使在主队列中也不会立即生效

2 个答案: