為 UITableViewCell 的 NSTextAttachment 加載圖像異步

Question

在異步線程或圖像緩存庫（如 SDwebimage）中動態加載圖像。 下面的代碼是我嘗試過的，從網絡獲取圖像后它不會重新繪制。

    let mutableAttributedString = NSMutableAttributedString()

    if let _img = newsItem.img {
        var attachment = NSTextAttachment()
        attachment.bounds = CGRectMake(4, 4, expectedWidth, expectedWidth * _img.ratio)

        dispatch_async(dispatch_get_main_queue(), { () -> Void in
            attachment.image = UIImage(data: NSData(contentsOfURL: NSURL(string: _img.src)!)!)
        })

        mutableAttributedString.appendAttributedString(NSAttributedString(attachment: attachment))
    }

Answer 1

后image的NSTextAttachment設置，您需要強制的刷新textView內容。 為此，您可以使用textView.layoutManager's方法invalidateDisplayCharacterRange ，其中range - 是您的 NSTextAttachement 子字符串的范圍

Answer 2

您可以使用這個來顯示帶有屬性字符串的遠程圖像： https : //github.com/namanhams/RemoteImageTextAttachment

Answer 3

@Raniys 我正在使用

NSTextAttachment *attachment = [[NSTextAttachment alloc] init];


                dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0ul);


                dispatch_async(queue, ^{


                    NSURL *url = [NSURL URLWithString:[[NSString stringWithFormat:@"%@%@", [ServerURL stringByReplacingOccurrencesOfString:@"/api" withString:@""], iconsArr[i][@"icon"]] stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];


                    SDWebImageManager *manager = [SDWebImageManager sharedManager];


                    [manager downloadImageWithURL:url options:0 progress:NULL completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {


                        attachment.image = image;


                        [cell.descL setNeedsDisplay];
                    }];
                });


                attachment.bounds = CGRectMake(0, -3, 12, 12);


                NSAttributedString *attachmentString = [NSAttributedString attributedStringWithAttachment:attachment];


                NSMutableAttributedString *myString = [[NSMutableAttributedString alloc] initWithAttributedString:attachmentString];


                NSAttributedString *myText = [[NSMutableAttributedString alloc] initWithString:[NSString stringWithFormat:@" %@ \n", iconsArr[i][@"title"]]];


                [myString appendAttributedString:myText];


                [descStr appendAttributedString:myString];