UICollectionView的拖拽重排

一.效果圖

二.核心方法

1.在iOS 9之后系統提供了一套API用於實現重排

// Support for reordering
- (BOOL)beginInteractiveMovementForItemAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(9_0); // returns NO if reordering was prevented from beginning - otherwise YES
- (void)updateInteractiveMovementTargetPosition:(CGPoint)targetPosition NS_AVAILABLE_IOS(9_0);
- (void)endInteractiveMovement NS_AVAILABLE_IOS(9_0);
- (void)cancelInteractiveMovement NS_AVAILABLE_IOS(9_0);

2.這里采用給UICollectionView添加長按手勢,結合系統API實現拖拽重排

• 給collectionView添加長按手勢

#pragma mark - 添加長按手勢
- (void)setUpLongPressGes {
    UILongPressGestureRecognizer *longPresssGes = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPressMethod:)];
    [self.collectionView addGestureRecognizer:longPresssGes]; 
}

• 監聽長按手勢,根據長按手勢狀態實現collectionView的重排方法

- (void)longPressMethod:(UILongPressGestureRecognizer *)longPressGes {
    
    // 判斷手勢狀態
    switch (longPressGes.state) {
            
        case UIGestureRecognizerStateBegan: {
            
            // 判斷手勢落點位置是否在路徑上(長按cell時,顯示對應cell的位置,如path = 1 - 0,即表示長按的是第1組第0個cell). 點擊除了cell的其他地方皆顯示為null
            NSIndexPath *indexPath = [self.collectionView indexPathForItemAtPoint:[longPressGes locationInView:self.collectionView]];
            // 如果點擊的位置不是cell,break
            if (nil == indexPath) {
                break;
            }
            NSLog(@"%@",indexPath);
            // 在路徑上則開始移動該路徑上的cell
            [self.collectionView beginInteractiveMovementForItemAtIndexPath:indexPath];
        }
            break;
            
        case UIGestureRecognizerStateChanged:
            // 移動過程當中隨時更新cell位置
            [self.collectionView updateInteractiveMovementTargetPosition:[longPressGes locationInView:self.collectionView]];
            break;
            
        case UIGestureRecognizerStateEnded:
            // 移動結束后關閉cell移動
            [self.collectionView endInteractiveMovement];
            break;
        default:
            [self.collectionView cancelInteractiveMovement];
            break;
    }
}

• 實現這個方法才能移動cell

- (void)collectionView:(UICollectionView *)collectionView moveItemAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath {
    
    
    // 取出來源組
    ClassifyItem *sourceItem = self.classifyArray[sourceIndexPath.section];
    // 取出item數據
    ClassifyDetailItem *detailItem = [sourceItem.tags objectAtIndex:sourceIndexPath.row];
    // 從資源數組中移除該數據
    [sourceItem.tags removeObject:detailItem];
    
    // 取出目標組
    ClassifyItem *destinationItem = self.classifyArray[destinationIndexPath.section];
    // 將數據插入到資源數組中的目標位置上
    [destinationItem.tags insertObject:detailItem atIndex:destinationIndexPath.row];

}