iOS - UICollectionView 长按拖拽单元格

一、先上gif效果图，DEMO链接：https://gitee.com/xudongxiang/DragDropCollectionView.git

二、代码实现细节

1. 初始化collectionView，以及遵守UICollectionViewDelegate、UICollectionViewDataSource ，并且注册cell等一波常规操作

    UICollectionViewFlowLayout *collectionFlowLayout = [[UICollectionViewFlowLayout alloc] init];
    collectionFlowLayout.scrollDirection = UICollectionViewScrollDirectionVertical;
    self.collectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(0, 0, 375, 667) collectionViewLayout:collectionFlowLayout];
    self.collectionView.backgroundColor = [UIColor whiteColor];
    [self.collectionView registerClass:[CollectionViewCell class] forCellWithReuseIdentifier:@"cell"];
    self.collectionView.dataSource = self;
    self.collectionView.delegate = self;
    [self.view addSubview:self.collectionView];

2. 为collectionView添加长按手势

// 添加长按抖动手势
[self addRecognize];

- (void)addRecognize
{
    UILongPressGestureRecognizer *recognize = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPressGestureAction:)];
    
    //设置长按响应时间为0.5秒
    recognize.minimumPressDuration = 0.5;   
    
    [self.collectionView addGestureRecognizer:recognize];
}

3. 实现长按后collectionView的抖动效果，并且为collectionView添加拖动手势

// 长按抖动手势方法
- (void)longPressGestureAction:(UILongPressGestureRecognizer *)longGesture {
    switch (longGesture.state) {
        case UIGestureRecognizerStateBegan: {
        
            // 移除长按手势
            [self.collectionView removeGestureRecognizer:longGesture];
            
            // 为collectionView添加拖动手势
            [self addGesture];
            
             // 用一个BOOL类型的全局变量，记录collectionView是否为抖动状态，YES：抖动，NO：停止抖动
            _isItemShake = YES; 
            [self.collectionView reloadData];
        }
            break;
        case UIGestureRecognizerStateChanged: {}
            break;
        case UIGestureRecognizerStateEnded: {}
            break;
        default:
            break;
    }
}

- (void)addGesture
{
    UILongPressGestureRecognizer *longGesture = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(handlelongGesture:)];
    longGesture.minimumPressDuration = 0;
    [self.collectionView addGestureRecognizer:longGesture];
}

4. 实现collectionView的拖动效果，下面会使用iOS9的新特性实现拖拽，必须调用UICollectionView的下面两个方法

// 开始移动的时候调用此方法，可以获取相应的datasource方法设置特殊的indexpath 能否移动,如果能移动返回的是YES ,不能移动返回的是NO
- (BOOL)beginInteractiveMovementForItemAtIndexPath:(NSIndexPath *)indexPath

// 更新移动过程的位置
- (void)updateInteractiveMovementTargetPosition:(CGPoint)targetPosition 

// 长按抖动手势方法
- (void)handlelongGesture:(UILongPressGestureRecognizer *)longGesture {
    switch (longGesture.state) {
        case UIGestureRecognizerStateBegan:{
        
            // 通过手势获取点，通过点获取点击的indexPath， 移动该cell
            NSIndexPath *aIndexPath = [self.collectionView indexPathForItemAtPoint:[longGesture locationInView:self.collectionView]];
            [self.collectionView beginInteractiveMovementForItemAtIndexPath:aIndexPath];
            
        }
            break;
        case UIGestureRecognizerStateChanged:{
        	
            // 通过手势获取点，通过点获取拖动到的indexPath， 更新该cell位置
            [self.collectionView updateInteractiveMovementTargetPosition:[longGesture locationInView:self.collectionView]];
            
        }
            break;
        case UIGestureRecognizerStateEnded:{
        
            // 移动完成关闭cell移动
            [self.collectionView endInteractiveMovement];

	    // 移除拖动手势
            [self.collectionView removeGestureRecognizer:longGesture];

            // collectionView停止抖动
            _isItemShake = NO;
            
            // 为collectionView添加拖动手势
            [self addRecognize];
            
            NSArray *cellArray = [self.collectionView visibleCells];
            for (CollectionViewCell *cell in cellArray ) {
                // 调用cell停止抖动方法
                [cell stopShake];
            }
        }
            break;
        default:
            [self.collectionView endInteractiveMovement];
            [self.collectionView removeGestureRecognizer:longGesture];
            _isItemShake = NO;
            [self addRecognize];
            NSArray *cellArray = [self.collectionView visibleCells];
            for (CollectionViewCell *cell in cellArray ) {
                [cell stopShake];
            }
            break;
    }
}

5. 实现UICollectionViewDelegate、UICollectionViewDataSource

- (BOOL)collectionView:(UICollectionView *)collectionView canMoveItemAtIndexPath:(NSIndexPath *)indexPath
{
    return YES;
}

- (void)collectionView:(UICollectionView *)collectionView moveItemAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath
{
    // 删除数据源中初始位置的数据
    id objc = [self.colorArray objectAtIndex:sourceIndexPath.item];
    [self.colorArray removeObject:objc];

    // 将数据插入数据源中新的位置，实现数据源的更新
    [self.colorArray insertObject:objc atIndex:destinationIndexPath.item];
    
    NSArray *cellArray = [self.collectionView visibleCells];
    for (CollectionViewCell *cell in cellArray ) {
        [cell stopShake];
    }
}

//配置cell大小
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    return CGSizeMake(167, 167);
}

//配置行间距
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section
{
    return 15;
}

//配置每组上下左右的间距
- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
    return UIEdgeInsetsMake(0, 13, 15, 13);
}

#pragma mark - UICollectionViewDataSource
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return 1;
}

//配置每个组里面有多少个cell
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return self.colorArray.count;
}
//配置cell，并且通过_isItemShake控制cell是否抖动
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    CollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"cell" forIndexPath:indexPath];
    [cell loadWithModel:self.colorArray[indexPath.row] ];
    if (_isItemShake) {
    
	// 调用cell开始抖动方法
        [cell beginShake];
        
    }else{
    
        // 调用cell停止抖动方法
        [cell stopShake];
        
    }
    return cell;
}

6. 在CollectionViewCell.m文件中实现cell的抖动和停止抖动方法

// 实现cell抖动方法
- (void)beginShake
{
    CAKeyframeAnimation *anim = [CAKeyframeAnimation animation];
    anim.keyPath = @"transform.rotation";
    anim.duration = 0.2;
    anim.repeatCount = MAXFLOAT;
    anim.values = @[@(-0.03),@(0.03),@(-0.03)];
    anim.removedOnCompletion = NO;
    anim.fillMode = kCAFillModeForwards;
    [self.layer addAnimation:anim forKey:@"shake"];
}

// 实现cell停止抖动方法
- (void)stopShake
{
    [self.layer removeAllAnimations];
}