仅突出显示 UILabel 中的文本
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【中文标题】仅突出显示 UILabel 中的文本【英文标题】:Highlight just the text in a UILabel 【发布时间】:2015-07-08 13:16:51 【问题描述】:我正在尝试设置背景颜色/仅突出显示 UILabel
中的文本。问题是添加到UILabel
以保持文本居中的换行符和空格也被突出显示。
注意UILabel
中最后一行之前的间距被突出显示。此外,任何新行的开头和结尾也会突出显示。
我正在使用以下代码创建上面的示例:
-(void)createSomeLabel
// Create and position my label
UILabel *someLabel = [[UILabel alloc] initWithFrame:CGRectMake(0,
0,
self.view.frame.size.width - 40,
self.view.frame.size.height - 300)];
someLabel.center = CGPointMake(self.view.frame.size.width / 2, self.view.frame.size.height / 2);
someLabel.textAlignment = NSTextAlignmentCenter;
someLabel.textColor = [UIColor whiteColor];
someLabel.lineBreakMode = NSLineBreakByWordWrapping;
someLabel.numberOfLines = 0;
[self.view addSubview:someLabel];
// This string will be different lengths all the time
NSString *someLongString = @"Here is a really long amount of text that is going to wordwrap/line break and I don't want to highlight the spacing. I want to just highlight the words and a single space before/after the word";
// Create attributed string
NSMutableAttributedString *someLongStringAttr=[[NSMutableAttributedString alloc] initWithString:someLongString attributes:nil];
// Apply background color
[someLongStringAttr addAttribute:NSBackgroundColorAttributeName
value:[UIColor colorWithWhite:0 alpha:0.25]
range:NSMakeRange(0, someLongStringAttr.length)];
// Set text of label
someLabel.attributedText = someLongStringAttr;
我想要实现的输出是仅突出显示文本和单词之间的空格(如果只有一个空格)。文本的长度和UILabel
的大小会不断变化,所以很遗憾,硬编码解决方案不是一种选择。
【问题讨论】:
iosdevelopertips.com/user-interface/… @PavanJangid 我看不出这些示例与我提供的示例有何不同。你能详细说明一下吗? @DanielStorm 您是否尝试为每个单词的范围而不是整个字符串设置背景颜色? @Kreiri 我想到了这一点,但无法想出一种方法来从字符串中提取每个单词,两边都有空格,应用属性,然后重建字符串。我想当自动换行时,填充每个单词的空格会被拉伸,导致同样的问题? 建议使用 CoreText。一个好的开始:github.com/dineshrajas/HighlightLabel 似乎既然它计算了“真实的字母渲染”,它应该做你想做的事。不久前我在这个项目上玩了一点,如果我没记错的话,还有一些不完善的地方,还有一些改变要做。 【参考方案1】:在我看来,换行是问题所在。 我的想法是尝试知道 UILabel 何时会添加换行符,然后从突出显示的字符范围中删除该字符。
您似乎不能只询问 UILabel 换行符将在哪里,但您可以检查将 NSString 添加到标签时的大小。 使用此信息,您可以不断检查每个字符的高度,当高度发生变化时,您知道您有一个新行。
我已经做了一个例子,它采用标签的字符串并将其分成单独的行,这些行将出现在 UILabel 中。一旦我有了每一行,我只需在每一行而不是整个字符串上设置背景颜色。这消除了在换行符处设置的背景颜色。
可能有更好的解决方案,并且这个解决方案可能会进行优化以获得更好的性能,但它只是一个起点,而且似乎可行。
- (void)createSomeLabel
// Create and position my label
UILabel *someLabel = [[UILabel alloc] initWithFrame:CGRectMake(0,
0,
self.view.frame.size.width - 40,
self.view.frame.size.height - 300)];
someLabel.center = CGPointMake(self.view.frame.size.width / 2, self.view.frame.size.height / 2);
someLabel.textAlignment = NSTextAlignmentCenter;
someLabel.textColor = [UIColor whiteColor];
someLabel.lineBreakMode = NSLineBreakByWordWrapping;
someLabel.numberOfLines = 0;
[self.view addSubview:someLabel];
// This string will be different lengths all the time
NSString *someLongString = @"Here is a really long amount of text that is going to wordwrap/line break and I don't want to highlight the spacing. I want to just highlight the words and a single space before/after the word";
// Create attributed string
NSMutableAttributedString *someLongStringAttr=[[NSMutableAttributedString alloc] initWithString:someLongString attributes:nil];
// The idea here is to figure out where the UILabel would automatically make a line break and get each line of text separately.
// Temporarily set the label to be that string so that we can guess where the UILabel naturally puts its line breaks.
[someLabel setText:someLongString];
// Get an array of each individual line as the UILabel would present it.
NSArray *allLines = getLinesForLabel(someLabel);
[someLabel setText:@""];
// Loop through each line of text and apply the background color to just the text within that range.
// This way, no whitespace / line breaks will be highlighted.
__block int startRange = 0;
[allLines enumerateObjectsUsingBlock:^(NSString *line, NSUInteger idx, BOOL *stop)
// The end range should be the length of the line, minus one for the whitespace.
// If we are on the final line, there are no more line breaks so we use the whole line length.
NSUInteger endRange = (idx+1 == allLines.count) ? line.length : line.length-1;
// Apply background color
[someLongStringAttr addAttribute:NSBackgroundColorAttributeName
value:[UIColor colorWithWhite:0 alpha:0.25]
range:NSMakeRange(startRange, endRange)];
// Update the start range to the next line
startRange += line.length;
];
// Set text of label
someLabel.attributedText = someLongStringAttr;
#pragma mark - Utility Functions
static NSArray *getLinesForLabel(UILabel *label)
// Get the text from the label
NSString *labelText = label.text;
// Create an array to hold the lines of text
NSMutableArray *allLines = [NSMutableArray array];
while (YES)
// Get the length of the current line of text
int length = getLengthOfTextInFrame(label, labelText) + 1;
// Add this line of text to the array
[allLines addObject:[labelText substringToIndex:length]];
// Adjust the label text
labelText = [labelText substringFromIndex:length];
// Check for the final line
if(labelText.length<length)
[allLines addObject:labelText];
break;
return [NSArray arrayWithArray:allLines];
static int getLengthOfTextInFrame(UILabel *label, NSString *text)
// Create a block for getting the bounds of the current peice of text.
CGRect (^boundingRectForLength)(int) = ^CGRect(int length)
NSString *cutText = [text substringToIndex:length];
CGRect textRect = [cutText boundingRectWithSize:CGSizeMake(label.frame.size.width, CGFLOAT_MAX)
options:NSStringDrawingUsesLineFragmentOrigin
attributes:@NSFontAttributeName : label.font
context:nil];
return textRect;
;
// Get the frame of the string for one character
int length = 1;
int lastSpace = 1;
CGRect textRect = boundingRectForLength(length);
CGFloat oneLineHeight = CGRectGetHeight(textRect);
// Keep adding one character to the string until the height changes, then you know you have a new line
while (textRect.size.height <= oneLineHeight)
// If the next character is white space, save the current length.
// It could be the end of the line.
// This will not work for character wrap.
if ([[text substringWithRange:NSMakeRange (length, 1)] isEqualToString:@" "])
lastSpace = length;
// Increment length and get the new bounds
textRect = boundingRectForLength(++length);
return lastSpace;
【讨论】:
嗨@Sam,如果我的文本是Karen Neraka
,我的行在第一行Karen
,第二行是Neraka
,会发生什么。它会崩溃吗?因为第二行更长。
嗨@KarenAnne 在突出显示标签之前计算所有内容的前期成本很小,但它应该不明显,并且取决于文本的数量。为了节省性能,您可以在后台线程上运行任何不更新标签的代码。由于线路大小,应该没有问题或崩溃。这些函数应该能够计算出正确的大小并突出显示需要的内容。
感谢@Sam 的帮助。很高兴知道它不会在性能上花费太多。
关于崩溃,我们遇到了一些索引超出范围的崩溃,我们只是修改了代码以满足我们的需要!非常感谢你的帮助! @山姆?
@KarenAnne 我也是越界异常,你还记得你改变了什么吗?【参考方案2】:
我也遇到过同样的问题,并找到了更简单的解决方案,而且没有巨大的性能成本。您可以简单地将TTTAttributedLabel 添加到您的项目中。
我的问题演示项目:
#import "TTTAttributedLabel.h"
@implementation ViewController
- (void)viewDidLoad
[super viewDidLoad];
UILabel *label1 = [UILabel new];
label1.textAlignment = NSTextAlignmentCenter;
label1.numberOfLines = 0;
label1.frame = CGRectMake(20, 0, CGRectGetWidth(self.view.frame) - 40, CGRectGetHeight(self.view.frame) / 2.0);
[self.view addSubview:label1];
TTTAttributedLabel *label2 = [TTTAttributedLabel new];
label2.textAlignment = NSTextAlignmentCenter;
label2.numberOfLines = 0;
label2.frame = CGRectMake(20, CGRectGetHeight(self.view.frame) / 2.0, CGRectGetWidth(self.view.frame) - 40, CGRectGetHeight(self.view.frame) / 2.0);
[self.view addSubview:label2];
NSDictionary *attributes = @NSBackgroundColorAttributeName:[UIColor blackColor], NSForegroundColorAttributeName:[UIColor whiteColor], NSFontAttributeName:[UIFont systemFontOfSize:32 weight:UIFontWeightBold];
NSAttributedString *string = [[NSAttributedString alloc] initWithString:@"Some very long string which can contain newlines and some other stuff" attributes:attributes];
label1.attributedText = string;
label2.text = string;
@end
【讨论】:
【参考方案3】:从 iOS 10.3 开始,有问题的相同代码现在会产生所需的结果。不确定这是错误还是新功能。
-(void)createSomeLabel
// Create and position my label
UILabel *someLabel = [[UILabel alloc] initWithFrame:CGRectMake(0,
0,
self.view.frame.size.width - 40.0,
self.view.frame.size.height - 300.0)];
someLabel.center = CGPointMake(self.view.frame.size.width / 2.0, self.view.frame.size.height / 2.0);
someLabel.textAlignment = NSTextAlignmentCenter;
someLabel.textColor = [UIColor whiteColor];
someLabel.lineBreakMode = NSLineBreakByWordWrapping;
someLabel.numberOfLines = 0;
[self.view addSubview:someLabel];
// This string will be different lengths all the time
NSString *someLongString = @"Here is a really long amount of text that is going to wordwrap/line break and I don't want to highlight the spacing. I want to just highlight the words and a single space before/after the word";
// Create attributed string
NSMutableAttributedString *someLongStringAttr = [[NSMutableAttributedString alloc] initWithString:someLongString attributes:nil];
// Apply background color
[someLongStringAttr addAttribute:NSBackgroundColorAttributeName
value:[UIColor colorWithWhite:0 alpha:0.25]
range:NSMakeRange(0, someLongStringAttr.length)];
// Set text of label
someLabel.attributedText = someLongStringAttr;
【讨论】:
错误通常不会让事情变得更好。 :) @NRitH 哈哈。我提到这更像是一个警告。到目前为止,我不会认为这是稳定的。我们需要更多时间或一些文档来确认此代码是安全的。 又回到了 iOS 11.0 之前的样子。以上是关于仅突出显示 UILabel 中的文本的主要内容,如果未能解决你的问题,请参考以下文章