使用DTCoreText加载富文本以及加载图片显示问题

最近产品提出一个需求：标题+富文本+定制cell的表格显示，富文本字体大小可更改，图片可点击。
如果使用WKWebView来做，改字体比较困难，于是就想到了DTCoreText。

这里只讲解富文本这一块：

1.继承DTAttributedTextCell，创建cell

@interface EssayRichContentCell ()

@property (nonatomic, strong) NSMutableAttributedString *attributedContent;//富文本内容

@end

//MARK: -改变字体，布局
- (void)changeFontSize:(FontSize)size
{
    //默认使用中号字体大小
    if (size>0) {
        [Config currentConfig].fontSize = @(size);
    }
    UIFont *currFont = [UIFont systemFontOfSize:[Config currentConfig].fontSize.floatValue];
    //只修改内容字体大小
    NSMutableAttributedString *text = [[NSMutableAttributedString alloc] initWithAttributedString:self.attributedContent];
    [text addAttributes:[self settingAttributesWithLineSpacing:3 FirstLineHeadIndent:2*size Font:currFont TextColor:[UIColor h1Color]] range:text.rangeOfAll];
    
    //如果是图片，移除属性约束
    [self.attributedContent enumerateAttribute:NSAttachmentAttributeName inRange:NSMakeRange(0, self.attributedContent.length) options:0 usingBlock:^(id  _Nullable value, NSRange range, BOOL * _Nonnull stop) {
        if ([value isKindOfClass:[DTImageTextAttachment class]]) {
            [text removeAttribute:NSParagraphStyleAttributeName range:range];
        }
    }];
    
    self.attributedTextContextView.attributedString = text;
}

2.在控制器中创建cell

- (EssayRichContentCell *)tableView:(UITableView *)tableView preparedCellForIndexPath:(NSIndexPath *)indexPath
{
    //NSCache缓存cell
    EssayRichContentCell *cell = [self.DTTextCellCache objectForKey:kEssayAttributedTextCellId];
    if (!cell) {
        cell = [tableView dequeueReusableCellWithIdentifier:kEssayAttributedTextCellId];
        
        cell.attributedTextContextView.delegate = self;
        cell.selectionStyle = UITableViewCellSelectionStyleNone;
        [cell layoutViewWithEssayContent:self.dataArray[indexPath.section][indexPath.row]];
        [self.DTTextCellCache setObject:cell forKey:kEssayAttributedTextCellId];
    } else {
        [cell reloadContent];
    }
    
    return cell;
}
//tableview代理
//高度计算
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    CGFloat cellHeight = 0.0f;
    if (indexPath.section == 0) {
      //...
    }
    else if (indexPath.section == 1) {
       
        switch (indexPath.row) {
            case 0:
                //富文本
            {
                EssayRichContentCell *cell = [self tableView:tableView preparedCellForIndexPath:indexPath];
                cellHeight = [cell requiredRowHeightInTableView:tableView];
            }
                break;
            //...
        }
    }
    //...
    return cellHeight;
}

• 接下来就是图片加载的重点了。

#pragma mark - DTAttributedTextContentViewDelegate
- (UIView *)attributedTextContentView:(DTAttributedTextContentView *)attributedTextContentView viewForAttachment:(DTTextAttachment *)attachment frame:(CGRect)frame{
    //如果是图片，获取图片并显示，这里第一次得到的frame的宽高都为0，需要通过imageView代理计算，重新加载
    if([attachment isKindOfClass:[DTImageTextAttachment class]])
    {
        DTLazyImageView *imageView = [[DTLazyImageView alloc] initWithFrame:frame];
        // url for deferred loading
        imageView.url = attachment.contentURL;
        
        UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapImage:)];
        imageView.userInteractionEnabled = YES;
        [imageView addGestureRecognizer:tap];
        imageView.delegate = self;
        return imageView;
    }
    return nil;
}

#pragma mark - DTLazyImageViewDelegate
//MARK: - 根据获取图片size重新加载
- (void)lazyImageView:(DTLazyImageView *)lazyImageView didChangeImageSize:(CGSize)size
{
    CGFloat width = kScreenWidth - 10.5 - 13;//自己设定的宽
    CGSize imageSize = size;
    // resize image size if needed
    if (size.width > width) {
        CGFloat height = width * (size.height/size.width);
        imageSize = CGSizeMake(width, height);
    }
    
    NSURL *url = lazyImageView.url;
    NSPredicate *pred = [NSPredicate predicateWithFormat:@"contentURL == %@", url];
    
    BOOL didUpdate = NO;
    
    // update all attachments that match this URL (possibly multiple images with same size)
    EssayRichContentCell *cell = [self.DTTextCellCache objectForKey:kEssayAttributedTextCellId];
    for (DTTextAttachment *oneAttachment in [cell.attributedTextContextView.layoutFrame textAttachmentsWithPredicate:pred]) {
        // update attachments that have no original size, that also sets the display size
        if (CGSizeEqualToSize(oneAttachment.displaySize, CGSizeZero)) {
            oneAttachment.displaySize = imageSize;
            didUpdate = YES;
        }
    }
    
    if (didUpdate) {
        //获取到图片的宽高，重新加载
        [self.tableView reloadData];
    }
}