简单写了一个collectionview的拖拽效果,记录下.只是简单的实现了拖拽,其它都没有加

实现思路:

1. 首先给collectionview添加长按的手势
2. 找到当前长按的cell, 截图保存为一个view(实际拖拽过程中是拖拽的这个view) ,然后隐藏原先的cell
3. 拖拽截图的view,在拖拽的过程中和collectionview上已有的cell进行对比,交换位置,改变数据
4. 拖拽结束之后,删除截图的view,显示最开始的cell

具体代码

• 创建一个继承UICollectionViewFlowLayout 的类,你也可以直接写在viewcontroller中.(名字随便写的)

#import <UIKit/UIKit.h>

@protocol DFZFBLayoutDelegate <NSObject>

//去改变数据源
- (void)moveDataItem:(NSIndexPath*)fromIndexPath toIndexPath:(NSIndexPath*)toIndexPath;

@end

@interface DFZFBLayout : UICollectionViewFlowLayout

@property (nonatomic, assign) id<DFZFBLayoutDelegate> delegate;

@end

• .m中具体的实现
  • 这里只是简单的添加一个手势去做的,会慢慢改进.

#import "DFZFBLayout.h"

@interface DFZFBLayout ()<UIGestureRecognizerDelegate>

@property (nonatomic, strong) UILongPressGestureRecognizer *longPress;
@property (nonatomic, strong) NSIndexPath *currentIndexPath;    //当前的IndexPath
@property (nonatomic, strong) UIView *mappingImageCell;         //拖动cell的截图

@end

@implementation DFZFBLayout

- (id)initWithCoder:(NSCoder *)aDecoder{
    self = [super initWithCoder:aDecoder];
    if (self) {
        [self configureObserver];
    }
    return self;
}

- (instancetype)init{
    self = [super init];
    if (self) {
        [self configureObserver];
    }
    return self;
}

- (void)dealloc{
    [self removeObserver:self forKeyPath:@"collectionView"];
}

#pragma mark - setup

- (void)configureObserver{
    [self addObserver:self forKeyPath:@"collectionView" options:NSKeyValueObservingOptionNew context:nil];
}

- (void)setUpGestureRecognizers{
    if (self.collectionView == nil) {
        return;
    }
    _longPress = [[UILongPressGestureRecognizer alloc]initWithTarget:self action:@selector(handleLongPress:)];
    _longPress.minimumPressDuration = 0.2f;
    _longPress.delegate = self;
    [self.collectionView addGestureRecognizer:_longPress];
}

#pragma mark - observer
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
    if ([keyPath isEqualToString:@"collectionView"]) {
        [self setUpGestureRecognizers];
    }else{
        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
    }
}

- (void)handleLongPress:(UILongPressGestureRecognizer*)longPress
{
    switch (longPress.state) {
        case UIGestureRecognizerStateBegan:
        {
            CGPoint location = [longPress locationInView:self.collectionView];
            NSIndexPath* indexPath = [self.collectionView indexPathForItemAtPoint:location];
            if (!indexPath) return;

            self.currentIndexPath = indexPath;
            UICollectionViewCell* targetCell = [self.collectionView cellForItemAtIndexPath:self.currentIndexPath];
            //得到当前cell的映射(截图)
            UIView* cellView = [targetCell snapshotViewAfterScreenUpdates:YES];
            self.mappingImageCell = cellView;
            self.mappingImageCell.frame = cellView.frame;
            targetCell.hidden = YES;
            [self.collectionView addSubview:self.mappingImageCell];
            
            cellView.center = targetCell.center;
        }
            break;
        case UIGestureRecognizerStateChanged:
        {
            CGPoint point = [longPress locationInView:self.collectionView];
            //更新cell的位置
            self.mappingImageCell.center = point;
            NSIndexPath * indexPath = [self.collectionView indexPathForItemAtPoint:point];
            if (indexPath == nil )  return;
            if (![indexPath isEqual:self.currentIndexPath])
            {
                //改变数据源
                if ([self.delegate respondsToSelector:@selector(moveDataItem:toIndexPath:)]) {
                    [self.delegate moveDataItem:self.currentIndexPath toIndexPath:indexPath];
                }
                [self.collectionView moveItemAtIndexPath:self.currentIndexPath toIndexPath:indexPath];
                self.currentIndexPath = indexPath;
            }
        }
            break;
        case UIGestureRecognizerStateEnded:
        {
            UICollectionViewCell *cell = [self.collectionView cellForItemAtIndexPath:self.currentIndexPath];
            
            [UIView animateWithDuration:0.25 animations:^{
                self.mappingImageCell.center = cell.center;
            } completion:^(BOOL finished) {
                [self.mappingImageCell removeFromSuperview];
                cell.hidden           = NO;
                self.mappingImageCell = nil;
                self.currentIndexPath = nil;
            }];
        }
            break;
        default:
        {
            
        }
            break;
    }
    
    
}

@end

应用

• 在viewcontroller中代码:

 DFZFBLayout* layout = [[DFZFBLayout alloc]init];
    layout.delegate = self;
    //layout.dataSource = self;
    layout.minimumInteritemSpacing = 1;
    layout.minimumLineSpacing      = 1;
    layout.sectionInset = UIEdgeInsetsMake(1, 1, 1, 1);
    layout.headerReferenceSize = CGSizeMake(SCREEN_WIDTH, 40.f);
//    layout.footerReferenceSize = CGSizeMake(SCREEN_WIDTH, 0.f);
//    [layout setSectionInset:UIEdgeInsetsMake(0, 0,20,0)];

    
    myCollectionView = [[UICollectionView alloc]initWithFrame:CGRectZero collectionViewLayout:layout];
    myCollectionView.delegate = self;
    myCollectionView.dataSource = self;
    myCollectionView.backgroundColor = [UIColor whiteColor];
    [self.view addSubview:myCollectionView];

效果

iOS9之后 提供了API 记录下,方便以后使用

// 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);

- (void)handlelongGesture:(UILongPressGestureRecognizer *)longGesture {
    //判断手势状态
    switch (longGesture.state) {
        case UIGestureRecognizerStateBegan:{
            //判断手势落点位置是否在路径上
            NSIndexPath *indexPath = [self.collectionView indexPathForItemAtPoint:[longGesture locationInView:self.collectionView]];
            if (indexPath == nil) {
                break;
            }
            //在路径上则开始移动该路径上的cell
            [self.collectionView beginInteractiveMovementForItemAtIndexPath:indexPath];
        }
            break;
        case UIGestureRecognizerStateChanged:
            //移动过程当中随时更新cell位置
            [self.collectionView updateInteractiveMovementTargetPosition:[longGesture locationInView:self.collectionView]];
            break;
        case UIGestureRecognizerStateEnded:
            //移动结束后关闭cell移动
            [self.collectionView endInteractiveMovement];
            break;
        default:
            [self.collectionView cancelInteractiveMovement];
            break;
    }
}

- (BOOL)collectionView:(UICollectionView *)collectionView canMoveItemAtIndexPath:(NSIndexPath *)indexPath{
    //返回YES允许其item移动
    return YES;
}

- (void)collectionView:(UICollectionView *)collectionView moveItemAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath*)destinationIndexPath {
    //取出源item数据
    id objc = [_dataSource objectAtIndex:sourceIndexPath.item];
    //从资源数组中移除该数据
    [_dataSource removeObject:objc];
    //将数据插入到资源数组中的目标位置上
    [_dataSource insertObject:objc atIndex:destinationIndexPath.item];
}