创建可点击的“链接”在UILabel的NSAttributedString中？ [英] Create tap-able "links" in the NSAttributedString of a UILabel?
问题描述
我一直在搜索这几个小时，但我失败了。我可能甚至不知道我应该寻找什么。
I have been searching this for hours but I've failed. I probably don't even know what I should be looking for.
许多应用程序都有文本，在本文中是圆角矩形的网络超链接。当我点击它们时， UIWebView 会打开。让我感到困惑的是，他们经常有自定义链接，例如，如果单词以＃开头，它也是可点击的，应用程序通过打开另一个视图来响应。我怎样才能做到这一点？是否可以使用 UILabel 或者我需要 UITextView 还是其他什么？
Many applications have text and in this text are web hyperlinks in rounded rect. When I click them UIWebView opens. What puzzles me is that they often have custom links, for example if words starts with # it is also clickable and the application responds by opening another view. How can I do that? Is it possible with UILabel or do I need UITextView or something else?
推荐答案
一般来说，如果我们想在UILabel显示的文本中有一个可点击的链接，我们需要解决两个独立的任务：
In general, if we want to have a clickable link in text displayed by UILabel, we would need to resolve two independent tasks:
- 将部分文本的外观更改为链接
- 检测并处理链接上的触摸（打开URL是特定情况）
第一个很容易。从iOS 6开始，UILabel支持显示属性字符串。您需要做的就是创建和配置NSMutableAttributedString的实例：
The first one is easy. Starting from iOS 6 UILabel supports display of attributed strings. All you need to do is to create and configure an instance of NSMutableAttributedString:
NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithString:@"String with a link" attributes:nil];
NSRange linkRange = NSMakeRange(14, 4); // for the word "link" in the string above
NSDictionary *linkAttributes = @{ NSForegroundColorAttributeName : [UIColor colorWithRed:0.05 green:0.4 blue:0.65 alpha:1.0],
NSUnderlineStyleAttributeName : @(NSUnderlineStyleSingle) };
[attributedString setAttributes:linkAttributes range:linkRange];
// Assign attributedText to UILabel
label.attributedText = attributedString;
就是这样！上面的代码使UILabel显示字符串，其中包含链接
That's it! The code above makes UILabel to display String with a link
现在我们应该检测此链接上的触摸。我们的想法是捕获UILabel内的所有水龙头，并确定水龙头的位置是否足够接近链路。为了捕捉触摸，我们可以为标签添加点击手势识别器。确保为标签启用userInteraction，默认情况下它已关闭：
Now we should detect touches on this link. The idea is to catch all taps within UILabel and figure out whether the location of the tap was close enough to the link. To catch touches we can add tap gesture recognizer to the label. Make sure to enable userInteraction for the label, it's turned off by default:
label.userInteractionEnabled = YES;
[label addGestureRecognizer:[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTapOnLabel:)]];
现在最复杂的东西：找出点击是否显示在链接显示的位置而不是标签的任何其他部分。如果我们有单行UILabel，通过硬编码显示链接的区域边界可以相对容易地解决这个任务，但是让我们更优雅地解决这个问题，对于一般情况 - 多线UILabel没有关于链接布局的初步知识。
Now the most sophisticated stuff: finding out whether the tap was on where the link is displayed and not on any other portion of the label. If we had single-lined UILabel, this task could be solved relatively easy by hardcoding the area bounds where the link is displayed, but let's solve this problem more elegantly and for general case - multiline UILabel without preliminary knowledge about the link layout.
其中一种方法是使用iOS 7中引入的Text Kit API的功能：
One of the approaches is to use capabilities of Text Kit API introduced in iOS 7:
// Create instances of NSLayoutManager, NSTextContainer and NSTextStorage
NSLayoutManager *layoutManager = [[NSLayoutManager alloc] init];
NSTextContainer *textContainer = [[NSTextContainer alloc] initWithSize:CGSizeZero];
NSTextStorage *textStorage = [[NSTextStorage alloc] initWithAttributedString:attributedString];
// Configure layoutManager and textStorage
[layoutManager addTextContainer:textContainer];
[textStorage addLayoutManager:layoutManager];
// Configure textContainer
textContainer.lineFragmentPadding = 0.0;
textContainer.lineBreakMode = label.lineBreakMode;
textContainer.maximumNumberOfLines = label.numberOfLines;
在类的属性中保存NSLayoutManager，NSTextContainer和NSTextStorage的创建和配置实例（很可能是UIViewController的后代） ） - 我们将在其他方法中使用它们。
Save created and configured instances of NSLayoutManager, NSTextContainer and NSTextStorage in properties in your class (most likely UIViewController's descendant) - we'll need them in other methods.
现在，每次标签更改其帧时，更新textContainer的大小：
Now, each time the label changes its frame, update textContainer's size:
- (void)viewDidLayoutSubviews
{
[super viewDidLayoutSubviews];
self.textContainer.size = self.label.bounds.size;
}
最后，检测点击是否恰好在链接上：
And finally, detect whether the tap was exactly on the link:
- (void)handleTapOnLabel:(UITapGestureRecognizer *)tapGesture
{
CGPoint locationOfTouchInLabel = [tapGesture locationInView:tapGesture.view];
CGSize labelSize = tapGesture.view.bounds.size;
CGRect textBoundingBox = [self.layoutManager usedRectForTextContainer:self.textContainer];
CGPoint textContainerOffset = CGPointMake((labelSize.width - textBoundingBox.size.width) * 0.5 - textBoundingBox.origin.x,
(labelSize.height - textBoundingBox.size.height) * 0.5 - textBoundingBox.origin.y);
CGPoint locationOfTouchInTextContainer = CGPointMake(locationOfTouchInLabel.x - textContainerOffset.x,
locationOfTouchInLabel.y - textContainerOffset.y);
NSInteger indexOfCharacter = [self.layoutManager characterIndexForPoint:locationOfTouchInTextContainer
inTextContainer:self.textContainer
fractionOfDistanceBetweenInsertionPoints:nil];
NSRange linkRange = NSMakeRange(14, 4); // it's better to save the range somewhere when it was originally used for marking link in attributed string
if (NSLocationInRange(indexOfCharacter, linkRange)) {
// Open an URL, or handle the tap on the link in any other way
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"https://stackoverflow.com/"]];
}
}
这篇关于创建可点击的“链接”在UILabel的NSAttributedString中？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
