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DraggingSort
https://github.com/HelloYeah/DraggingSort
导读拖拽排序是新闻类的App可以说是必有的交互设计，如今日头条，网易新闻等。拖拽排序是一个交互体验非常好的设计，简单，方便。
今日头条的拖拽排序界面我实现的长按拖拽排序效果实现方案1.给CollectionViewCell添加一个长按手势，通过协议把手势传递到collectionView所在的控制器中。
- (void)awakeFromNib{ self.layer.cornerRadius = 3; self.layer.masksToBounds = YES; //给每个cell添加一个长按手势 UILongPressGestureRecognizer * longPress =[[UILongPressGestureRecognizer alloc]initWithTarget:self action:@selector(longPress:)]; longPress.delegate = self; [self addGestureRecognizer:longPress]; } - (void)longPress:(UILongPressGestureRecognizer *)longPress{ if (self.delegate && [self.delegate respondsToSelector:@selector(longPress:)]) { [self.delegate longPress:longPress]; } }2.开始长按时对cell进行截图，开题报告，并隐藏cell。
- (void)longPress:(UILongPressGestureRecognizer *)longPress{ //记录上一次手势的位置 static CGPoint startPoint; //触发长按手势的cell MovingCell * cell = (MovingCell *)longPress.view; //开始长按 if (longPress.state == UIGestureRecognizerStateBegan) { [self shakeAllCell]; //获取cell的截图 _snapshotView = [cell snapshotViewAfterScreenUpdates:YES]; _snapshotView.center = cell.center; [_collectionView addSubview:_snapshotView]; _indexPath= [_collectionView indexPathForCell:cell]; _originalCell = cell; _originalCell.hidden = YES; startPoint = [longPress locationInView:_collectionView]; }3、在手势移动的时候，移动截图视图，用遍历的方法求出截图移动到哪个cell的位置，再调用系统的api交换这个cell和隐藏cell的位置，并且数据源中的数据也需要调整顺序
//手势移动的时候 else if (longPress.state == UIGestureRecognizerStateChanged){ CGFloat tranX = [longPress locationOfTouch:0 inView:_collectionView].x - startPoint.x; CGFloat tranY = [longPress locationOfTouch:0 inView:_collectionView].y - startPoint.y; //设置截图视图位置 _snapshotView.center = CGPointApplyAffineTransform(_snapshotView.center, CGAffineTransformMakeTranslation(tranX, tranY)); startPoint = [longPress locationOfTouch:0 inView:_collectionView]; //计算截图视图和哪个cell相交 for (UICollectionViewCell *cell in [_collectionView visibleCells]) { //跳过隐藏的cell if ([_collectionView indexPathForCell:cell] == _indexPath) { continue; } //计算中心距 CGFloat space = sqrtf(pow(_snapshotView.center.x - cell.center.x, 2) + powf(_snapshotView.center.y - cell.center.y, 2)); //如果相交一半且两个视图Y的绝对值小于高度的一半就移动 if (space <= _snapshotView.bounds.size.width * 0.5 && (fabs(_snapshotView.center.y - cell.center.y) <= _snapshotView.bounds.size.height * 0.5)) { _nextIndexPath = [_collectionView indexPathForCell:cell]; if (_nextIndexPath.item > _indexPath.item) { for (NSUInteger i = _indexPath.item; i < _nextIndexPath.item ; i ++) { [self.array exchangeObjectAtIndex:i withObjectAtIndex:i + 1]; } }else{ for (NSUInteger i = _indexPath.item; i > _nextIndexPath.item ; i --) { [self.array exchangeObjectAtIndex:i withObjectAtIndex:i - 1]; } } //移动 [_collectionView moveItemAtIndexPath:_indexPath toIndexPath:_nextIndexPath]; //设置移动后的起始indexPath _indexPath = _nextIndexPath; break; } }4.手势停止时，移除截图的view，显示隐藏cell
//手势停止时 }else if(longPress.state == UIGestureRecognizerStateEnded){ [self stopShake]; [_snapshotView removeFromSuperview]; _originalCell.hidden = NO; } 其他代码还可以进一步封装，写一个数据管理类dataTool，dataTool作为collectionView的数据源，开题报告，所有的数据源方法都写到dataTool类中。手势的代理方法也在里面实现，这样控制器会简洁很多，控制器就不需要关注拖拽排序的具体逻辑了。大家有空可以自己写写看，也许你们有更好的处理方案，可以评论交流一下。
