最近看了看YY微博的實現(xiàn)渗勘，用小本子記了記筆記。
先上一個簡略的流程圖：

圖1.png

• 首先后臺線程異步的去請求數(shù)據(jù)（從JSON文件取）张惹，初始化WBStatusLayout類來接受數(shù)據(jù)，然后根據(jù)數(shù)據(jù)計算好業(yè)務(wù)所需要的布局信息（這個類就是核心類）岭洲，這個工作結(jié)束后回到主線程刷新UITableView宛逗。
  dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
  for (int i = 0; i <= 7; i++) {
  NSData *data = [NSData dataNamed:[NSString stringWithFormat:@"weibo_%d.json",i]];
  WBTimelineItem *item = [WBTimelineItem modelWithJSON:data];
  for (WBStatus *status in item.statuses) {
  WBStatusLayout *layout = [[WBStatusLayout alloc] initWithStatus:status style:WBLayoutStyleTimeline];
  [_layouts addObject:layout];
  }
  }

    // 復(fù)制一下，讓列表長一些盾剩，不至于滑兩下就到底了
    [_layouts addObjectsFromArray:_layouts];
    
    dispatch_async(dispatch_get_main_queue(), ^{
        self.title = [NSString stringWithFormat:@"Weibo (loaded:%d)", (int)_layouts.count];
        [indicator removeFromSuperview];
        self.navigationController.view.userInteractionEnabled = YES;
        [_tableView reloadData];
    });
  

  });

• 下面這個方法就是WBStatusLayout類根據(jù)存儲圖片數(shù)據(jù)的個數(shù)來布局“9宮格圖片雷激。WBStatusLayout會計算出每個 cell的高度和相關(guān)布局信息緩存下來。這樣再次滑動UITableView直接從緩存里面提取就好了彪腔，并不會再次計算侥锦。

   - (void)_layoutPicsWithStatus:(WBStatus *)status isRetweet:(BOOL)isRetweet {
   if (isRetweet) {
    _retweetPicSize = CGSizeZero;
    _retweetPicHeight = 0;
   } else {
    _picSize = CGSizeZero;
    _picHeight = 0;
   }
    if (status.pics.count == 0) return;

     CGSize picSize = CGSizeZero;
     CGFloat picHeight = 0;

     CGFloat len1_3 = (kWBCellContentWidth + kWBCellPaddingPic) / 3 - kWBCellPaddingPic;
     len1_3 = CGFloatPixelRound(len1_3);
     switch (status.pics.count) {
    case 1: {
        WBPicture *pic = _status.pics.firstObject;
        WBPictureMetadata *bmiddle = pic.bmiddle;
        if (pic.keepSize || bmiddle.width < 1 || bmiddle.height < 1) {
            CGFloat maxLen = kWBCellContentWidth / 2.0;
            maxLen = CGFloatPixelRound(maxLen);
            picSize = CGSizeMake(maxLen, maxLen);
            picHeight = maxLen;
        } else {
            CGFloat maxLen = len1_3 * 2 + kWBCellPaddingPic;
            if (bmiddle.width < bmiddle.height) {
                picSize.width = (float)bmiddle.width / (float)bmiddle.height * maxLen;
                picSize.height = maxLen;
            } else {
                picSize.width = maxLen;
                picSize.height = (float)bmiddle.height / (float)bmiddle.width * maxLen;
            }
            picSize = CGSizePixelRound(picSize);
            picHeight = picSize.height;
        }
    } break;
    case 2: case 3: {
        picSize = CGSizeMake(len1_3, len1_3);
        picHeight = len1_3;
    } break;
    case 4: case 5: case 6: {
        picSize = CGSizeMake(len1_3, len1_3);
        picHeight = len1_3 * 2 + kWBCellPaddingPic;
    } break;
    default: { // 7, 8, 9
        picSize = CGSizeMake(len1_3, len1_3);
        picHeight = len1_3 * 3 + kWBCellPaddingPic * 2;
    } break;
   }

    if (isRetweet) {
    _retweetPicSize = picSize;
    _retweetPicHeight = picHeight;
    } else {
    _picSize = picSize;
    _picHeight = picHeight;
   }
   }

• 通過下面協(xié)議方法去給Cell相關(guān)信息。非常簡潔德挣。
  - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
  NSString *cellID = @"cell";
  WBStatusCell *cell = [tableView dequeueReusableCellWithIdentifier:cellID];
  if (!cell) {
  cell = [[WBStatusCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellID];
  cell.delegate = self;
  }
  [cell setLayout:_layouts[indexPath.row]];
  return cell;
  }

YY的代碼真心寫的非常的漂亮恭垦。特別是把Cell所有的事件通過WBStatusCellDelegate代理進行統(tǒng)一的管理，提高了代碼的可讀性格嗅。

  /// 點擊了 Cell
  - (void)cellDidClick:(WBStatusCell *)cell;
  /// 點擊了 Card
  - (void)cellDidClickCard:(WBStatusCell *)cell;
  /// 點擊了轉(zhuǎn)發(fā)內(nèi)容
  - (void)cellDidClickRetweet:(WBStatusCell *)cell;
  /// 點擊了Cell菜單
  - (void)cellDidClickMenu:(WBStatusCell *)cell;
  /// 點擊了關(guān)注
  - (void)cellDidClickFollow:(WBStatusCell *)cell;
  /// 點擊了轉(zhuǎn)發(fā)
  - (void)cellDidClickRepost:(WBStatusCell *)cell;
  /// 點擊了下方 Tag
  - (void)cellDidClickTag:(WBStatusCell *)cell;
  /// 點擊了評論
  - (void)cellDidClickComment:(WBStatusCell *)cell;
 /// 點擊了贊
  - (void)cellDidClickLike:(WBStatusCell *)cell;
  /// 點擊了用戶
 - (void)cell:(WBStatusCell *)cell didClickUser:(WBUser *)user;
  /// 點擊了圖片
- (void)cell:(WBStatusCell *)cell didClickImageAtIndex:(NSUInteger)index;
/// 點擊了 Label 的鏈接
- (void)cell:(WBStatusCell *)cell didClickInLabel:(YYLabel *)label textRange:(NSRange)textRange;

在這里我只是簡略的去做了一個梳理番挺。如果您有興趣可以去github上下載下來讀讀源碼。
YYkit github : https://github.com/ibireme/YYKit