iOS开发之仿新闻拖拽排序，编辑删除的效果

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。

####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，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，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。github地址：https://github.com/HelloYeah/DraggingSort