ios - 在 UITextView 中查找可见文本的范围

Question

我从之前问题的答案中找到了计算 UITextView 中可见属性文本范围的代码。它工作完美，除了在我添加任何类型的换行符以创建新段落之后。在这种情况下，代码会给出不正确的答案，直到我手动 ScrollView 。滚动后，它每次都会给出正确答案。但我需要它即使不滚动也能给出正确的答案。

下面是我的示例项目。它是一个单 View 应用程序。该程序在日志记录中报告它认为可见的文本，第一次是在 View 加载后，然后是滚动后。

ViewController.h

#import <UIKit/UIKit.h>
@interface ViewController : UIViewController <UIScrollViewDelegate> {
    UITextView *lTextView;
}
@end

ViewController.m

#import "ViewController.h"

@interface ViewController ()


@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    int statusBarHeight = 20;

    UIScrollView *scrollView;
    scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, statusBarHeight, self.view.frame.size.width * 2, self.view.frame.size.height)];
    scrollView.pagingEnabled = YES;
    scrollView.delegate = self;
    [self.view addSubview:scrollView];

    lTextView = [[UITextView alloc] initWithFrame:CGRectMake(0, 0, scrollView.frame.size.width/2, scrollView.frame.size.height)];
    lTextView.editable = NO;
    lTextView.selectable = NO;

    lTextView.attributedText = [self loremIpsum];
    [scrollView addSubview:lTextView];

    lTextView.delegate = self;

    [self report];
}

- (void)report {
    NSArray *visibleRange = [self visibleRangeOfTextView:lTextView];
    NSNumber *start = [visibleRange objectAtIndex:0];
    NSNumber *end = [visibleRange objectAtIndex:1];
    int rangeLength = (end.intValue - start.intValue);

    NSLog(@"%@", [lTextView.text substringWithRange:NSMakeRange(start.intValue, rangeLength)]);

}


-(NSArray *)visibleRangeOfTextView:(UITextView *)textView {
    CGRect bounds = textView.bounds;
    bounds.size.height -= 30.0; // to prevent including lines that can barely be seen at the bottom

    UITextPosition *start = [textView characterRangeAtPoint:bounds.origin].start;
    UITextPosition *end = [textView characterRangeAtPoint:CGPointMake(CGRectGetMaxX(bounds), CGRectGetMaxY(bounds))].end; // <<<< this gives an incorrect calculation until the user manually scrolls

    float startOffset = [textView offsetFromPosition:textView.beginningOfDocument toPosition:start];
    float endOffset = [textView offsetFromPosition:textView.beginningOfDocument toPosition:end];
    NSLog(@"startOffset: %f, endOffset %f", startOffset, endOffset);

    return [NSArray arrayWithObjects:[NSNumber numberWithFloat:startOffset], [NSNumber numberWithFloat:endOffset], nil];

}


- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    NSLog(@"scrollViewDidEndDecelerating");
    [self report];
}


- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
    NSLog(@"scrollViewDidEndDragging");
    [self report];
}


- (NSAttributedString *)loremIpsum {

    NSMutableAttributedString *li = [[NSMutableAttributedString alloc] init];
    NSArray *strings = [NSArray arrayWithObjects:@"1 Lorem ipsum dolor sit amet, consectetur adipiscing elit. Aliquam congue eleifend risus eget pretium. Donec sed commodo neque, id ornare dolor.", @" 2 Vivamus vestibulum non quam et euismod. Morbi et dolor luctus velit lobortis ornare vel vel tellus. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia Curae; Aenean viverra, urna nec tempor commodo, turpis nisl rhoncus mauris, in ullamcorper justo sapien quis nulla.", @" 3 Aliquam at odio molestie, laoreet elit sed, suscipit risus. Nulla eleifend, quam eget porttitor condimentum, metus lacus lobortis ligula, accumsan tristique neque turpis non purus. Aenean malesuada tortor id elit semper, et pretium nulla viverra.", @" 4 Aliquam sollicitudin placerat massa, quis posuere est ornare vel. Nam mollis convallis risus a tincidunt. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos.", @" 5 Fusce facilisis orci nisi, vel egestas metus tristique vitae. Proin nec malesuada dolor. Donec eget felis accumsan, facilisis turpis vitae, blandit lacus.", @" 6 Pellentesque auctor nisl quis turpis commodo lacinia. In sed euismod urna. Praesent sed commodo magna.", @" 7 Ut interdum dignissim urna, nec feugiat dolor. Nulla facilisi. Donec fermentum mauris at ante tincidunt, id accumsan eros lacinia.", @" 8 Suspendisse potenti. Integer ac mattis eros, sed volutpat dui. Pellentesque vehicula turpis ut metus malesuada blandit.", @" 9 Nam laoreet dui id imperdiet pulvinar. In auctor enim ac massa feugiat adipiscing. Nam convallis neque at felis tincidunt iaculis. Maecenas dictum est ac nulla suscipit, nec condimentum metus molestie.", @" 10 Vestibulum mollis velit eu nunc eleifend egestas. Ut aliquam ultrices tellus volutpat consectetur. Morbi eget sollicitudin quam, ut imperdiet leo. Morbi sed ligula iaculis, tincidunt diam nec, pharetra ligula.", @" 11 Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos. Proin varius facilisis placerat. Fusce suscipit risus risus, in varius diam convallis quis. In hac habitasse platea dictumst. Integer non lectus non dolor fringilla venenatis eget quis nisl. Proin in pretium metus.", @" 12 Pellentesque sed tellus iaculis, bibendum neque vel, porta ante. Phasellus eu vulputate massa. Nullam venenatis lectus non nunc aliquet porta. Nunc gravida rutrum feugiat. Fusce elit nunc, facilisis non tristique placerat, tempor id orci. Mauris et massa cursus, dapibus urna a, condimentum arcu. Pellentesque vitae sagittis sapien. Ut lacus purus, suscipit at magna non, rhoncus luctus dui. Ut ipsum augue, pharetra ac ipsum sed, facilisis convallis justo.", @" 13 Ut arcu augue, hendrerit vel tincidunt vitae, aliquet ac quam. Nulla ullamcorper, dolor eu pellentesque cursus, lectus quam interdum ante, nec congue dui augue nec dolor. Sed convallis elit in enim dictum, at posuere sem mollis. Praesent in metus aliquam, ullamcorper purus tempor, mattis ipsum. Aliquam gravida, sem vitae iaculis placerat, dui velit commodo nulla, vitae ultrices lectus dolor ut mi.", @" 14 Suspendisse quis metus varius, congue turpis vitae, viverra nunc. Duis placerat, felis et laoreet pretium, nibh lorem pulvinar turpis, eu euismod arcu libero at mauris. Sed laoreet, eros in tempor accumsan, odio augue fermentum dui, a pharetra felis libero eu ligula.", @"Suspendisse ultricies pulvinar urna. Donec placerat nulla non elit vestibulum mattis.", @"Phasellus semper sem a sem dignissim tempus. Sed scelerisque sed purus interdum rhoncus. Sed gravida eros sit amet dui fermentum rutrum. Proin a arcu scelerisque, volutpat orci quis, dignissim neque. Aliquam erat volutpat. Sed eget scelerisque neque.", nil];
    for (int i = 0;  i < strings.count;  i++) {
        NSString *string = [strings objectAtIndex:i];
        if (i != 0) {
            // Comment this line and it will work perfectly:
            [li appendAttributedString:[[NSAttributedString alloc] initWithString:@"\n\n"]];
        }
        [li appendAttributedString:[[NSAttributedString alloc] initWithString:string]];
    }
    return li;
}
@end

感谢您的帮助!

Answer 1

我在添加赏金的那天想出了一个解决方案，但没有发布它，以便其他人有机会发布对其他人有帮助的东西。 Bajorek 先生和 rintaro 都发布了有效的答案。我的解决方案有点不同；它更适合我在我的项目中尝试做的事情(因为我将使用多个 UITextView)。它禁用 UITextView 中的滚动，让 UIScrollView 处理滚动，并添加具有容纳所有属性文本所需的完整高度的 UITextView。这使得计算从一开始就可以正常工作。

为了以后可能阅读的其他人的利益，我在下面发布了一个完整的工作示例。我会将其标记为已接受的答案，因为这是我在发布其他解决方案之前所走的路线。

ViewController.h

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController <UIScrollViewDelegate> {
    UITextView *lTextView;
    UIScrollView *scrollView;
}
@end

ViewController.m

#import "ViewController.h"

@interface ViewController ()


@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    int statusBarHeight = 20;

    scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, statusBarHeight, self.view.frame.size.width, self.view.frame.size.height)];
    [self.view addSubview:scrollView];

    lTextView = [[UITextView alloc] init];
    lTextView.editable = NO;
    lTextView.selectable = NO;
    lTextView.scrollEnabled = NO;
    lTextView.textContainerInset = UIEdgeInsetsZero;

    lTextView.attributedText = [self loremIpsum];
    float calculatedHeight = [self heightForTextViewWithAttributedText:lTextView andWidth:scrollView.frame.size.width];
    lTextView.frame = CGRectMake(0, 0, scrollView.frame.size.width, calculatedHeight);
    [scrollView addSubview:lTextView];

    [scrollView setContentSize:CGSizeMake(scrollView.frame.size.width, calculatedHeight + 20)];
    scrollView.delegate = self;

    [self report];
}

- (void)report {
    NSArray *visibleRange = [self visibleRangeOfTextView:lTextView];
    NSNumber *start = [visibleRange objectAtIndex:0];
    NSNumber *end = [visibleRange objectAtIndex:1];
    int rangeLength = (end.intValue - start.intValue);

    NSLog(@"%@", [lTextView.text substringWithRange:NSMakeRange(start.intValue, rangeLength)]);

}


-(NSArray *)visibleRangeOfTextView:(UITextView *)textView {
    double offsetY = scrollView.contentOffset.y;
    CGPoint startingPoint = scrollView.contentOffset;
    startingPoint.y += 5; // to prevent including lines that can barely be seen at the top
    CGPoint endingPoint = CGPointMake(320, offsetY + scrollView.frame.size.height - 20);

    CGRect bounds = textView.bounds;
    bounds.size.height -= 30.0; // to prevent including lines that can barely be seen at the bottom

    UITextPosition *start = [textView characterRangeAtPoint:startingPoint].start;
    UITextPosition *end = [textView characterRangeAtPoint:endingPoint].end;

    float startOffset = [textView offsetFromPosition:textView.beginningOfDocument toPosition:start];
    float endOffset = [textView offsetFromPosition:textView.beginningOfDocument toPosition:end];

    return [NSArray arrayWithObjects:[NSNumber numberWithFloat:startOffset], [NSNumber numberWithFloat:endOffset], nil];
}


- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    NSLog(@"scrollViewDidEndDecelerating");
    [self report];
}


- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
    NSLog(@"scrollViewDidEndDragging");
    [self report];
}


- (NSAttributedString *)loremIpsum {

    NSMutableAttributedString *li = [[NSMutableAttributedString alloc] init];
    NSArray *strings = [NSArray arrayWithObjects:@"1 Lorem ipsum dolor sit amet, consectetur adipiscing elit. Aliquam congue eleifend risus eget pretium. Donec sed commodo neque, id ornare dolor.", @" 2 Vivamus vestibulum non quam et euismod. Morbi et dolor luctus velit lobortis ornare vel vel tellus. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia Curae; Aenean viverra, urna nec tempor commodo, turpis nisl rhoncus mauris, in ullamcorper justo sapien quis nulla.", @" 3 Aliquam at odio molestie, laoreet elit sed, suscipit risus. Nulla eleifend, quam eget porttitor condimentum, metus lacus lobortis ligula, accumsan tristique neque turpis non purus. Aenean malesuada tortor id elit semper, et pretium nulla viverra.", @" 4 Aliquam sollicitudin placerat massa, quis posuere est ornare vel. Nam mollis convallis risus a tincidunt. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos.", @" 5 Fusce facilisis orci nisi, vel egestas metus tristique vitae. Proin nec malesuada dolor. Donec eget felis accumsan, facilisis turpis vitae, blandit lacus.", @" 6 Pellentesque auctor nisl quis turpis commodo lacinia. In sed euismod urna. Praesent sed commodo magna.", @" 7 Ut interdum dignissim urna, nec feugiat dolor. Nulla facilisi. Donec fermentum mauris at ante tincidunt, id accumsan eros lacinia.", @" 8 Suspendisse potenti. Integer ac mattis eros, sed volutpat dui. Pellentesque vehicula turpis ut metus malesuada blandit.", @" 9 Nam laoreet dui id imperdiet pulvinar. In auctor enim ac massa feugiat adipiscing. Nam convallis neque at felis tincidunt iaculis. Maecenas dictum est ac nulla suscipit, nec condimentum metus molestie.", @" 10 Vestibulum mollis velit eu nunc eleifend egestas. Ut aliquam ultrices tellus volutpat consectetur. Morbi eget sollicitudin quam, ut imperdiet leo. Morbi sed ligula iaculis, tincidunt diam nec, pharetra ligula.", @" 11 Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos. Proin varius facilisis placerat. Fusce suscipit risus risus, in varius diam convallis quis. In hac habitasse platea dictumst. Integer non lectus non dolor fringilla venenatis eget quis nisl. Proin in pretium metus.", @" 12 Pellentesque sed tellus iaculis, bibendum neque vel, porta ante. Phasellus eu vulputate massa. Nullam venenatis lectus non nunc aliquet porta. Nunc gravida rutrum feugiat. Fusce elit nunc, facilisis non tristique placerat, tempor id orci. Mauris et massa cursus, dapibus urna a, condimentum arcu. Pellentesque vitae sagittis sapien. Ut lacus purus, suscipit at magna non, rhoncus luctus dui. Ut ipsum augue, pharetra ac ipsum sed, facilisis convallis justo.", @" 13 Ut arcu augue, hendrerit vel tincidunt vitae, aliquet ac quam. Nulla ullamcorper, dolor eu pellentesque cursus, lectus quam interdum ante, nec congue dui augue nec dolor. Sed convallis elit in enim dictum, at posuere sem mollis. Praesent in metus aliquam, ullamcorper purus tempor, mattis ipsum. Aliquam gravida, sem vitae iaculis placerat, dui velit commodo nulla, vitae ultrices lectus dolor ut mi.", @" 14 Suspendisse quis metus varius, congue turpis vitae, viverra nunc. Duis placerat, felis et laoreet pretium, nibh lorem pulvinar turpis, eu euismod arcu libero at mauris. Sed laoreet, eros in tempor accumsan, odio augue fermentum dui, a pharetra felis libero eu ligula.", @"Suspendisse ultricies pulvinar urna. Donec placerat nulla non elit vestibulum mattis.", @"Phasellus semper sem a sem dignissim tempus. Sed scelerisque sed purus interdum rhoncus. Sed gravida eros sit amet dui fermentum rutrum. Proin a arcu scelerisque, volutpat orci quis, dignissim neque. Aliquam erat volutpat. Sed eget scelerisque neque.", nil];
    for (int i = 0;  i < strings.count;  i++) {
        NSString *string = [strings objectAtIndex:i];
        if (i != 0) {
            // Comment this line and it will work perfectly:
            [li appendAttributedString:[[NSAttributedString alloc] initWithString:@"\n\n"]];
        }
        [li appendAttributedString:[[NSAttributedString alloc] initWithString:string]];
    }
    return li;
}


- (CGFloat)heightForTextViewWithAttributedText:(UITextView *)textView andWidth:(CGFloat)width
{
    CGSize size = [textView sizeThatFits:CGSizeMake(width, FLT_MAX)];
    return size.height + 3.0;
}
@end