iOS开发UICollectionView实现拖拽效果

一.介绍

iOS9提供API实现单元格排序功能，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 ()<UICollectionViewDelegate,UICollectionViewDataSource,UICollectionViewDelegateFlowLayout> @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()%128/256.0)+0.5; //0.5 到 1.0 CGFloat brightness = (arc4random()%128/256.0)+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); 您可能感兴趣的文章:Java中Collection、List、Set、Map之间的关系总结ios基于UICollectionView实现横向瀑布流JAVA集合框架工具类自定义Collections集合方法Python中collections模块的基本使用教程python的常用模块之collections模块详解Mybatis中collection和association的使用区别详解MongoDB固定集合（capped collection）的知识小结iOS Swift利用UICollectionView实现无限轮播功能（原理）详解.NetCore利用BlockingCollection实现简易消息队列collection集合体系与并发修改异常的解决方法

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