iOS怎么使用UICollectionView实现拖拽移动单元格

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一.介绍

iOS9提供API实现单元格排序呢功能,使用UICollectionView及其代理方法.iOS9之后有自带方法可以实现该效果,只需添加长按手势,实现手势方法和调用iOS9的API交换数据,iOS9之前需要自己写方法实现这效果,除了要添加长按手势,这里还需要利用截图替换原理,手动计算移动位置来处理视图交换和数据交换.

二.方法和步骤

1.创建工程项目和视图控制器,如下图

2.声明对象和设置代理和数据源代理

@interface ViewController () @property (nonatomic, strong) NSMutableArray *dataArr;@property (nonatomic, strong) UICollectionView *collectionView;/**之前选中cell的NSIndexPath*/@property (nonatomic, strong) NSIndexPath *oldIndexPath;/**单元格的截图*/@property (nonatomic, strong) UIView *snapshotView;/**之前选中cell的NSIndexPath*/@property (nonatomic, strong) NSIndexPath *moveIndexPath; @end

3.初始化UICollectionView,并添加长按手势,在viewDidLoad中初始化

CGFloat SCREEN_WIDTH = self.view.frame.size.width;    UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];    flowLayout.itemSize = CGSizeMake((SCREEN_WIDTH-40.0)/3, (SCREEN_WIDTH-40.0)/3);    UICollectionView *collectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(0, 50.0, SCREEN_WIDTH, (SCREEN_WIDTH-40.0)/3+20.0) collectionViewLayout:flowLayout];    collectionView.dataSource = self;    collectionView.delegate = self;    collectionView.backgroundColor = [UIColor whiteColor];    [collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"uicollectionviewcell"];    [self.view addSubview:self.collectionView = collectionView];        // 添加长按手势    UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(handlelongGesture:)];    [collectionView addGestureRecognizer:longPress];

4.实例化数据源,(50个随机颜色,透明度0.8),在viewDidLoad中初始化

self.dataArr = [[NSMutableArray alloc] init];for (NSInteger index = 0; index < 50; index ++) {        CGFloat hue = (arc4random()%256/256.0); //0.0 到 1.0        CGFloat saturation = (arc4random()8/256.0)+0.5; //0.5 到 1.0        CGFloat brightness = (arc4random()8/256.0)+0.5; //0.5 到 1.0        UIColor *color = [UIColor colorWithHue:hue saturation:saturation brightness:brightness alpha:0.5];        [self.dataArr addObject:color];    }

5.实现UICollectionView的UICollectionViewDataSource的两个必须实现的方法

#pragma mark - UICollectionViewDataSource- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{    return self.dataArr.count;} - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"uicollectionviewcell" forIndexPath:indexPath];    cell.backgroundColor = self.dataArr[indexPath.row];    return cell;}

6.重点来了,实现长按手势方法

#pragma mark - 长按手势- (void)handlelongGesture:(UILongPressGestureRecognizer *)longPress{    if ([[[UIDevice currentDevice] systemVersion] floatValue] < 9.0) {        [self action:longPress];    } else {        [self iOS9_Action:longPress];    }}

7.iOS9之后的实现

#pragma mark - iOS9 之后的方法- (BOOL)collectionView:(UICollectionView *)collectionView canMoveItemAtIndexPath:(NSIndexPath *)indexPath{    // 返回YES允许row移动    return YES;} - (void)collectionView:(UICollectionView *)collectionView moveItemAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath{    //取出移动row数据    id color = self.dataArr[sourceIndexPath.row];    //从数据源中移除该数据    [self.dataArr removeObject:color];    //将数据插入到数据源中的目标位置    [self.dataArr insertObject:color atIndex:destinationIndexPath.row];} - (void)iOS9_Action:(UILongPressGestureRecognizer *)longPress{    switch (longPress.state) {        case UIGestureRecognizerStateBegan:        { //手势开始            //判断手势落点位置是否在row上            NSIndexPath *indexPath = [self.collectionView indexPathForItemAtPoint:[longPress locationInView:self.collectionView]];            if (indexPath == nil) {                break;            }            UICollectionViewCell *cell = [self.collectionView cellForItemAtIndexPath:indexPath];            [self.view bringSubviewToFront:cell];            //iOS9方法 移动cell            [self.collectionView beginInteractiveMovementForItemAtIndexPath:indexPath];        }            break;        case UIGestureRecognizerStateChanged:        { // 手势改变            // iOS9方法 移动过程中随时更新cell位置            [self.collectionView updateInteractiveMovementTargetPosition:[longPress locationInView:self.collectionView]];        }            break;        case UIGestureRecognizerStateEnded:        { // 手势结束            // iOS9方法 移动结束后关闭cell移动            [self.collectionView endInteractiveMovement];        }            break;        default: //手势其他状态            [self.collectionView cancelInteractiveMovement];            break;    }}

8.iOS9之前的实现

#pragma mark - iOS9 之前的方法- (void)action:(UILongPressGestureRecognizer *)longPress{    switch (longPress.state) {        case UIGestureRecognizerStateBegan:        { // 手势开始            //判断手势落点位置是否在row上            NSIndexPath *indexPath = [self.collectionView indexPathForItemAtPoint:[longPress locationInView:self.collectionView]];            self.oldIndexPath = indexPath;            if (indexPath == nil) {                break;            }            UICollectionViewCell *cell = [self.collectionView cellForItemAtIndexPath:indexPath];            // 使用系统的截图功能,得到cell的截图视图            UIView *snapshotView = [cell snapshotViewAfterScreenUpdates:NO];            snapshotView.frame = cell.frame;            [self.view addSubview:self.snapshotView = snapshotView];            // 截图后隐藏当前cell            cell.hidden = YES;                        CGPoint currentPoint = [longPress locationInView:self.collectionView];            [UIView animateWithDuration:0.25 animations:^{                snapshotView.transform = CGAffineTransformMakeScale(1.05, 1.05);                snapshotView.center = currentPoint;            }];        }            break;        case UIGestureRecognizerStateChanged:        { // 手势改变            //当前手指位置 截图视图位置随着手指移动而移动            CGPoint currentPoint = [longPress locationInView:self.collectionView];            self.snapshotView.center = currentPoint;            // 计算截图视图和哪个可见cell相交            for (UICollectionViewCell *cell in self.collectionView.visibleCells) {                // 当前隐藏的cell就不需要交换了,直接continue                if ([self.collectionView indexPathForCell:cell] == self.oldIndexPath) {                    continue;                }                // 计算中心距                CGFloat space = sqrtf(pow(self.snapshotView.center.x - cell.center.x, 2) + powf(self.snapshotView.center.y - cell.center.y, 2));                // 如果相交一半就移动                if (space <= self.snapshotView.bounds.size.width / 2) {                    self.moveIndexPath = [self.collectionView indexPathForCell:cell];                    //移动 会调用willMoveToIndexPath方法更新数据源                    [self.collectionView moveItemAtIndexPath:self.oldIndexPath toIndexPath:self.moveIndexPath];                    //设置移动后的起始indexPath                    self.oldIndexPath = self.moveIndexPath;                    break;                }            }        }            break;        default:        { // 手势结束和其他状态            UICollectionViewCell *cell = [self.collectionView cellForItemAtIndexPath:self.oldIndexPath];            // 结束动画过程中停止交互,防止出问题            self.collectionView.userInteractionEnabled = NO;            // 给截图视图一个动画移动到隐藏cell的新位置            [UIView animateWithDuration:0.25 animations:^{                self.snapshotView.center = cell.center;                self.snapshotView.transform = CGAffineTransformMakeScale(1.0, 1.0);            } completion:^(BOOL finished) {                // 移除截图视图,显示隐藏的cell并开始交互                [self.snapshotView removeFromSuperview];                cell.hidden = NO;                self.collectionView.userInteractionEnabled = YES;            }];        }            break;    }}

三.iOS9之后添加的API如下

// 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);

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