第七章

去年今日此门中，人面桃花相映红。人面不知何处去，桃花依旧笑春风。

CoreText使用教程(五)

本篇文章为CoreText教程系列的第五篇，也是最后一篇。

本文实现了在纯文本排版时，监听用户的点击，并把识别到的点击内容通过NSLog打印出来。

实现的思路主要是给控件添加手势点击并进行监听，在用户点击时拿到点击的位置，并在手势识别结束后用CoreText遍历每一个CTLine，判断点击的位置是否在识别的特定字符串（比如人名或者连续的数字串）内，如果是则找出该字符串。使用CTLineGetStringIndexForPosition函数来找出点击的字符位于整个字符串的位置。

完整的代码放在了github的仓库。

运行效果为：

大部分代码与之前一致，主要增加了使用正则表达式来检测特定的字符串，以及监听用户的点击，进行遍历找出用户点击的字符。

本文使用了正则表达式监测“@”开头空格结尾的人名和一串连续的数字。

检测的格式为:

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NSString *kAtRegularExpression = @"@[^\\s@]+?\\s{1}";
NSString *kNumberRegularExpression = @"\\d+[^\\d]{1}";

给控件添加手势监听:

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self.longPressGesture = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPressed:)];

self.longPressGesture.minimumPressDuration = 0.01;

self.longPressGesture.delegate = self;

[self addGestureRecognizer:self.longPressGesture];

手势识别的方法为:

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#pragma mark - 手势识别相关
- (void)longPressed:(UIGestureRecognizer *)gesture
{
    if (gesture.state == UIGestureRecognizerStateBegan)
    {

    } else if (gesture.state == UIGestureRecognizerStateChanged)
    {

    } else if (gesture.state == UIGestureRecognizerStateCancelled)
    {

    } else if (gesture.state == UIGestureRecognizerStateEnded)
    {

        if (self.pressRange.location != 0 && self.pressRange.length != 0)
        {
            NSLog(@"识别到点击");

            NSString *clickStr = [self.text substringWithRange:self.pressRange];

            NSLog(@"点击了 %@",clickStr);
        }

    }
}

需要实现手势识别的两个代理方法

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#pragma mark - UIGestureRecognizerDelegate
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
{

    if (gestureRecognizer == self.longPressGesture)
    {
        // 点击处在特定字符串内才进行识别
        BOOL gestureShouldBegin = NO;

        CGPoint location = [gestureRecognizer locationInView:self];

        CGFloat lineHeight = self.font.pointSize * kPerLineRatio;

        int lineIndex = location.y/lineHeight;

        NSLog(@"点击了第 %d 行",lineIndex);

        // 把点击的坐标转换为CoreText坐标系下
        CGPoint clickPoint = CGPointMake(location.x, self.textHeight-location.y);

        CFArrayRef lines = CTFrameGetLines(self.ctFrame);

        if (lineIndex < CFArrayGetCount(lines))
        {
            CTLineRef clickLine = CFArrayGetValueAtIndex(lines, lineIndex);

            // 点击处的字符位于总字符串的index
            CFIndex strIndex = CTLineGetStringIndexForPosition(clickLine, clickPoint);

            NSLog(@"strIndex = %ld",strIndex);

            NSMutableAttributedString *mutableAttributed = [[NSMutableAttributedString alloc] initWithString:self.text];
            NSArray *checkResults = [self recognizeSpecialStringWithAttributed:mutableAttributed];

            for (NSValue *value in checkResults)
            {
                NSRange range = [value rangeValue];

                if (strIndex >= range.location && strIndex <= range.location + range.length)
                {
                    self.pressRange = range;
                    gestureShouldBegin = YES;
                    NSLog(@"pressRange = %@",NSStringFromRange(range));
                }

            }
        }


        return gestureShouldBegin;
    }


    return YES;
}

// 该方法可实现也可不实现，取决于应用场景
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRequireFailureOfGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    if ([otherGestureRecognizer isKindOfClass:[UIPanGestureRecognizer class]])
    {
        return YES; // 避免应用在UITableViewCell上时，挡住拖动tableView的手势
    }

    return NO;
}

一个识别特定字符串的工具方法为：

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#pragma mark - 识别特定字符串并改其颜色，返回识别到的字符串所在的range
- (NSMutableArray *)recognizeSpecialStringWithAttributed:(NSMutableAttributedString *)attributed
{
    NSMutableArray *rangeArray = [NSMutableArray array];

    // 识别@人名
    NSRegularExpression *atRegular = [NSRegularExpression regularExpressionWithPattern:kAtRegularExpression options:NSRegularExpressionCaseInsensitive error:nil];

    NSArray *atResults = [atRegular matchesInString:self.text options:NSMatchingWithTransparentBounds range:NSMakeRange(0, self.text.length)];

    for (NSTextCheckingResult *checkResult in atResults)
    {
        if (attributed)
        {
            [attributed addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:NSMakeRange(checkResult.range.location, checkResult.range.length -1)];
        }

        [rangeArray addObject:[NSValue valueWithRange:checkResult.range]];
    }


    // 识别连续的数字
    NSRegularExpression *numberRegular = [NSRegularExpression regularExpressionWithPattern:kNumberRegularExpression options:NSRegularExpressionCaseInsensitive|NSRegularExpressionUseUnixLineSeparators error:nil];

    NSArray *numberResults = [numberRegular matchesInString:self.text options:NSMatchingWithTransparentBounds range:NSMakeRange(0, self.text.length)];

    for (NSTextCheckingResult *checkResult in numberResults)
    {
        if (attributed)
        {
            [attributed addAttribute:NSForegroundColorAttributeName value:[UIColor blueColor] range:NSMakeRange(checkResult.range.location, checkResult.range.length-1)];
        }

        [rangeArray addObject:[NSValue valueWithRange:NSMakeRange(checkResult.range.location, checkResult.range.length -1)]];
    }


    return rangeArray;
}

本次教程是我在自己学习的过程中，边学边写的。一来检查自己的学习效果，而来分享学习心得也可顺便帮助其他初学者。

CoreText学习起来并不难，只是其属于偏底层的实现，需要花费多一些的时间。