减少多行UILabel中最后一行的宽度 [英] Decrease the width of the last line in multiline UILabel

问题描述

我实现了一个阅读更多的功能，就像苹果的AppStore。但是，我使用多行 UILabel 。看看苹果的AppStore，他们如何减少最后可见的线宽度以适应更多文本，并仍然截断尾巴（见图片）？

I am implemententing a "read more" functionality much like the one in Apple's AppStore. However, I am using a multiline UILabel. Looking at Apple's AppStore, how do they decrease the last visible line's width to fit the "more" text and still truncate the tail (see image)?

推荐答案

这似乎工作，至少与我做了有限的测试。有两个公共方法。你可以使用较短的一个，如果你有多个标签都有相同的行数 - 只需更改kNumberOfLines在顶部匹配你想要的。如果您需要传递不同标签的行数，请使用更长的方法。请务必将您在IB中创建的标签类别更改为RDLabel。使用这些方法，而不是setText：。如果需要，这些方法将标签的高度扩展到kNumberOfLines，如果仍然被截断，将会展开它以适应整个字符串的触摸。目前，您可以触摸标签中的任何位置。

This seems to work, at least with the limited amount of testing I've done. There are two public methods. You can use the shorter one if you have multiple labels all with the same number of lines -- just change the kNumberOfLines at the top to match what you want. Use the longer method if you need to pass the number of lines for different labels. Be sure to change the class of the labels you make in IB to RDLabel. Use these methods instead of setText:. These methods expand the height of the label to kNumberOfLines if necessary, and if still truncated, will expand it to fit the whole string on touch. Currently, you can touch anywhere in the label. It shouldn't be too hard to change that so only touches near the ...Mer would cause the expansion.

#import "RDLabel.h"
#define kNumberOfLines 2
#define ellipsis @"...Mer ▾ "

@implementation RDLabel {
    NSString *string;
}

#pragma Public Methods

- (void)setTruncatingText:(NSString *) txt {
    [self setTruncatingText:txt forNumberOfLines:kNumberOfLines];
}

- (void)setTruncatingText:(NSString *) txt forNumberOfLines:(int) lines{
    string = txt;
    self.numberOfLines = 0;
    NSMutableString *truncatedString = [txt mutableCopy];
    if ([self numberOfLinesNeeded:truncatedString] > lines) {
        [truncatedString appendString:ellipsis];
        NSRange range = NSMakeRange(truncatedString.length - (ellipsis.length + 1), 1);
        while ([self numberOfLinesNeeded:truncatedString] > lines) {
            [truncatedString deleteCharactersInRange:range];
            range.location--;
        }
        [truncatedString deleteCharactersInRange:range];  //need to delete one more to make it fit
        CGRect labelFrame = self.frame;
        labelFrame.size.height = [@"A" sizeWithFont:self.font].height * lines;
        self.frame = labelFrame;
        self.text = truncatedString;
        self.userInteractionEnabled = YES;
        UITapGestureRecognizer *tapper = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(expand:)];
        [self addGestureRecognizer:tapper];
    }else{
        CGRect labelFrame = self.frame;
        labelFrame.size.height = [@"A" sizeWithFont:self.font].height * lines;
        self.frame = labelFrame;
        self.text = txt;
    }
}

#pragma Private Methods

-(int)numberOfLinesNeeded:(NSString *) s {
    float oneLineHeight = [@"A" sizeWithFont:self.font].height;
    float totalHeight = [s sizeWithFont:self.font constrainedToSize:CGSizeMake(self.bounds.size.width, CGFLOAT_MAX) lineBreakMode:NSLineBreakByWordWrapping].height;
    return nearbyint(totalHeight/oneLineHeight);
}

-(void)expand:(UITapGestureRecognizer *) tapper {
    int linesNeeded = [self numberOfLinesNeeded:string];
    CGRect labelFrame = self.frame;
    labelFrame.size.height = [@"A" sizeWithFont:self.font].height * linesNeeded;
    self.frame = labelFrame;
    self.text = string;
}

这篇关于减少多行UILabel中最后一行的宽度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！