iOS UICollectionViewCell拖拽移动（配Demo下载）

iOS拖拽移动UICollectionView下载地址：http://download.csdn.net/detail/lovechris00/9587439

这个月项目用到了拖拽移动UICollectionView的位置，

实现效果：

原理如下：

拖拽方法

1、获取当前手势位置，及对应cell的indexPath

- (void)longPressGestureRecognized:(id)sender{

    UILongPressGestureRecognizer *longPress = (UILongPressGestureRecognizer *)sender;
    UIGestureRecognizerState longPressState = longPress.state;
    //手指在collectionView中的位置
    _fingerLocation = [longPress locationInView:self];
    //手指按住位置对应的indexPath，可能为nil
    _relocatedIndexPath = [self indexPathForItemAtPoint:_fingerLocation];

开始拖拽

1、设置开始时选中的Cell的位置（indexPath）为初始位置；

 //手势开始，对被选中cell截图，隐藏原cell
            _originalIndexPath = [self indexPathForItemAtPoint:_fingerLocation];

2、对被选中cell截图，隐藏原cell

originalIndexPath可能为空，需要非空判断

if (_originalIndexPath) {
                 [self cellSelectedAtIndexPath:_originalIndexPath];
            }

/**
 *  cell被长按手指选中，对其进行截图，原cell隐藏
 */
- (void)cellSelectedAtIndexPath:(NSIndexPath *)indexPath{
  
    UICollectionViewCell *cell = [self cellForItemAtIndexPath:indexPath] ;
    
    UIView *snapshot = [self customSnapshotFromView:cell];
    
    [self addSubview:snapshot];
    
    _snapshot = snapshot;
    cell.hidden = YES;
    CGPoint center = _snapshot.center;
    center.y = _fingerLocation.y;
    [UIView animateWithDuration:0.2 animations:^{
        _snapshot.transform = CGAffineTransformMakeScale(1.03, 1.03);
        _snapshot.alpha = 0.98;
        _snapshot.center = center;
    }];
}

#pragma mark - 返回一个给定view的截图.
- (UIView *)customSnapshotFromView:(UIView *)inputView {
    
    // Make an image from the input view.
    UIGraphicsBeginImageContextWithOptions(inputView.bounds.size, NO, 0);
    [inputView.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    // Create an image view.
    UIView *snapshot = [[UIImageView alloc] initWithImage:image];
    snapshot.center = inputView.center;
    snapshot.layer.masksToBounds = NO;
    snapshot.layer.cornerRadius = 0.0;
    snapshot.layer.shadowOffset = CGSizeMake(-5.0, 0.0);
    snapshot.layer.shadowRadius = 5.0;
    snapshot.layer.shadowOpacity = 0.4;
    
    return snapshot;
}

拖拽过程中

1、截图跟随手指移动

 //截图跟随手指移动
            CGPoint center = _snapshot.center;
            center.y = _fingerLocation.y;
            center.x = _fingerLocation.x ;
            _snapshot.center = center;

2、判断是否到达整个collectionView的边缘

如果到了边缘，就

判断逻辑，该截图的最小Y大于collectionView的最大Y ,就向上滚动

最大Y值小于collectionView的最小Y，就向下滚动

 if ([self checkIfSnapshotMeetsEdge]) {
                    [self startAutoScrollTimer];
                }else{
                    [self stopAutoScrollTimer];
                }

#pragma mark -  检查截图是否到达整个collectionView的边缘，并作出响应

- (BOOL)checkIfSnapshotMeetsEdge{
    CGFloat minY = CGRectGetMinY(_snapshot.frame);
    CGFloat maxY = CGRectGetMaxY(_snapshot.frame);
    if (minY < self.contentOffset.y) {
        _autoScrollDirection = RTSnapshotMeetsEdgeTop;
        return YES;
    }
    if (maxY > self.bounds.size.height + self.contentOffset.y) {
        _autoScrollDirection = RTSnapshotMeetsEdgeBottom;
        return YES;
    }
    return NO;
}

#pragma mark - timer methods
/**
 *  创建定时器并运行
 */
- (void)startAutoScrollTimer{
    if (!_autoScrollTimer) {
        _autoScrollTimer = [CADisplayLink displayLinkWithTarget:self selector:@selector(startAutoScroll)];
        [_autoScrollTimer addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
    }
}
/**
 *  停止定时器并销毁
 */
- (void)stopAutoScrollTimer{
    if (_autoScrollTimer) {
        [_autoScrollTimer invalidate];
        _autoScrollTimer = nil;
    }
}

#pragma mark - 开始自动滚动

- (void)startAutoScroll{
    CGFloat pixelSpeed = 4;
    if (_autoScrollDirection == RTSnapshotMeetsEdgeTop) {//向下滚动
        if (self.contentOffset.y > 0) {//向下滚动最大范围限制
            [self setContentOffset:CGPointMake(0, self.contentOffset.y - pixelSpeed)];
            _snapshot.center = CGPointMake(_snapshot.center.x, _snapshot.center.y - pixelSpeed);
        }
    }else{                                               //向上滚动
        if (self.contentOffset.y + self.bounds.size.height < self.contentSize.height) {//向下滚动最大范围限制
            [self setContentOffset:CGPointMake(0, self.contentOffset.y + pixelSpeed)];
            _snapshot.center = CGPointMake(_snapshot.center.x, _snapshot.center.y + pixelSpeed);
        }
    }
    
    /*  当把截图拖动到边缘，开始自动滚动，如果这时手指完全不动，则不会触发‘UIGestureRecognizerStateChanged’，对应的代码就不会执行，导致虽然截图在tableView中的位置变了，但并没有移动那个隐藏的cell，用下面代码可解决此问题，cell会随着截图的移动而移动
     */
//    _relocatedIndexPath = [self indexPathForRowAtPoint:_snapshot.center];
    _relocatedIndexPath = [self indexPathForItemAtPoint:_snapshot.center] ;
    if (_relocatedIndexPath && ![_relocatedIndexPath isEqual:_originalIndexPath]) {
        [self cellRelocatedToNewIndexPath:_relocatedIndexPath];
    }
}

3、判断是否进入其他cell的范围

  if (_relocatedIndexPath && ![_relocatedIndexPath isEqual:_originalIndexPath]) {
                [self cellRelocatedToNewIndexPath:_relocatedIndexPath];
                NSLog(@"elocated Success");
            }

如果到达了

1）就获取数据并更新数据源

2）把当前手势的位置作为初始位置；

3）把数据通过代理传出去；

- (void)cellRelocatedToNewIndexPath:(NSIndexPath *)indexPath{
    //更新数据源并返回给外部
    [self updateDataSource];
    //交换移动cell位置
   
    [self moveItemAtIndexPath:_originalIndexPath toIndexPath:indexPath];
   //更新cell的原始indexPath为当前indexPath
   _originalIndexPath = indexPath;

}

# pragma mark - Private methods
/**修改数据源，通知外部更新数据源*/
- (void)updateDataSource{
    
    //通过DataSource代理获得原始数据源数组
    NSMutableArray *tempArray = [NSMutableArray array];
    if ([self.adataSource respondsToSelector:@selector(originalArrayDataForcollectionView:)]) {
        [tempArray addObjectsFromArray:[self.adataSource originalArrayDataForcollectionView:self]];
    }
    
    //移动数据
    [self moveObjectInMutableArray:tempArray fromIndex:_originalIndexPath.row toIndex:_relocatedIndexPath.row];
    
    //    将新数组传出外部以更改数据源
    if ([self.adelegate respondsToSelector:@selector(collectionView:newArrayDataForDataSource:)]) {
        [self.adelegate collectionView:self newArrayDataForDataSource:tempArray];
    }
}

/**
 *  将可变数组中的一个对象移动到该数组中的另外一个位置
 *  @param array     要变动的数组
 *  @param fromIndex 从这个index
 *  @param toIndex   移至这个index
 */
- (void)moveObjectInMutableArray:(NSMutableArray *)array fromIndex:(NSInteger)fromIndex toIndex:(NSInteger)toIndex{
    
    NSInteger tempIndex = 0;
    NSMutableString *tempTitle = nil;
    
    if (fromIndex < toIndex) {
        for (NSInteger i = fromIndex; i < toIndex; i ++) {
            [array exchangeObjectAtIndex:i withObjectAtIndex:i + 1];
        }
    }else{
        for (NSInteger i = fromIndex; i > toIndex; i --) {
            [array exchangeObjectAtIndex:i withObjectAtIndex:i - 1];
        }
    }
}

拖拽结束

1、停止动画；

 [self stopAutoScrollTimer];
            [self didEndDraging];
            if ([self.adelegate respondsToSelector:@selector(cellDidEndMovingIncollectionView:)]) {
                [self.adelegate cellDidEndMovingIncollectionView:self];
            }

2、显示cell，移除截图

/**
 *  拖拽结束，显示cell，并移除截图
 */
- (void)didEndDraging{
  
    UICollectionViewCell *cell = [self cellForItemAtIndexPath:_originalIndexPath] ;
    cell.hidden = NO;
    cell.alpha = 0;
    [UIView animateWithDuration:0.2 animations:^{
        _snapshot.center = cell.center;
        _snapshot.alpha = 0;
        _snapshot.transform = CGAffineTransformIdentity;
        cell.alpha = 1;
    } completion:^(BOOL finished) {
        cell.hidden = NO;
        [_snapshot removeFromSuperview];
        _snapshot = nil;
        _originalIndexPath = nil;
        _relocatedIndexPath = nil;
    }];
}

iOS拖拽移动UICollectionView下载地址：http://download.csdn.net/detail/lovechris00/9587439

iOS UICollectionViewCell拖拽移动（配Demo下载）

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