iOS中怎么利用UICollectionView實現拖拽效果

本篇文章給大家分享的是有關iOS中怎么利用UICollectionView實現拖拽效果，小編覺得挺實用的，因此分享給大家學習，希望大家閱讀完這篇文章后可以有所收獲，話不多說，跟著小編一起來看看吧。

1.創建工程項目和視圖控制器,如下圖

2.聲明對象和設置代理和數據源代理

@interface ViewController ()<UICollectionViewDelegate,UICollectionViewDataSource,UICollectionViewDelegateFlowLayout>@property (nonatomic, strong) NSMutableArray *dataArr;@property (nonatomic, strong) UICollectionView *collectionView;/**之前選中cell的NSIndexPath*/@property (nonatomic, strong) NSIndexPath *oldIndexPath;/**單元格的截圖*/@property (nonatomic, strong) UIView *snapshotView;/**之前選中cell的NSIndexPath*/@property (nonatomic, strong) NSIndexPath *moveIndexPath;@end

3.初始化UICollectionView,并添加長按手勢,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];  // 添加長按手勢  UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(handlelongGesture:)];  [collectionView addGestureRecognizer:longPress];

4.實例化數據源,(50個隨機顏色,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.實現UICollectionView的UICollectionViewDataSource的兩個必須實現的方法

#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.重點來了,實現長按手勢方法

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

7.iOS9之后的實現

#pragma mark - iOS9 之后的方法- (BOOL)collectionView:(UICollectionView *)collectionView canMoveItemAtIndexPath:(NSIndexPath *)indexPath{  // 返回YES允許row移動  return YES;}- (void)collectionView:(UICollectionView *)collectionView moveItemAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath{  //取出移動row數據  id color = self.dataArr[sourceIndexPath.row];  //從數據源中移除該數據  [self.dataArr removeObject:color];  //將數據插入到數據源中的目標位置  [self.dataArr insertObject:color atIndex:destinationIndexPath.row];}- (void)iOS9_Action:(UILongPressGestureRecognizer *)longPress{  switch (longPress.state) {    case UIGestureRecognizerStateBegan:    { //手勢開始      //判斷手勢落點位置是否在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 移動cell      [self.collectionView beginInteractiveMovementForItemAtIndexPath:indexPath];    }      break;    case UIGestureRecognizerStateChanged:    { // 手勢改變      // iOS9方法 移動過程中隨時更新cell位置      [self.collectionView updateInteractiveMovementTargetPosition:[longPress locationInView:self.collectionView]];    }      break;    case UIGestureRecognizerStateEnded:    { // 手勢結束      // iOS9方法 移動結束后關閉cell移動      [self.collectionView endInteractiveMovement];    }      break;    default: //手勢其他狀態      [self.collectionView cancelInteractiveMovement];      break;  }}

8.iOS9之前的實現

#pragma mark - iOS9 之前的方法- (void)action:(UILongPressGestureRecognizer *)longPress{  switch (longPress.state) {    case UIGestureRecognizerStateBegan:    { // 手勢開始      //判斷手勢落點位置是否在row上      NSIndexPath *indexPath = [self.collectionView indexPathForItemAtPoint:[longPress locationInView:self.collectionView]];      self.oldIndexPath = indexPath;      if (indexPath == nil) {        break;      }      UICollectionViewCell *cell = [self.collectionView cellForItemAtIndexPath:indexPath];      // 使用系統的截圖功能,得到cell的截圖視圖      UIView *snapshotView = [cell snapshotViewAfterScreenUpdates:NO];      snapshotView.frame = cell.frame;      [self.view addSubview:self.snapshotView = snapshotView];      // 截圖后隱藏當前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:    { // 手勢改變      //當前手指位置 截圖視圖位置隨著手指移動而移動      CGPoint currentPoint = [longPress locationInView:self.collectionView];      self.snapshotView.center = currentPoint;      // 計算截圖視圖和哪個可見cell相交      for (UICollectionViewCell *cell in self.collectionView.visibleCells) {        // 當前隱藏的cell就不需要交換了,直接continue        if ([self.collectionView indexPathForCell:cell] == self.oldIndexPath) {          continue;        }        // 計算中心距        CGFloat space = sqrtf(pow(self.snapshotView.center.x - cell.center.x, 2) + powf(self.snapshotView.center.y - cell.center.y, 2));        // 如果相交一半就移動        if (space <= self.snapshotView.bounds.size.width / 2) {          self.moveIndexPath = [self.collectionView indexPathForCell:cell];          //移動 會調用willMoveToIndexPath方法更新數據源          [self.collectionView moveItemAtIndexPath:self.oldIndexPath toIndexPath:self.moveIndexPath];          //設置移動后的起始indexPath          self.oldIndexPath = self.moveIndexPath;          break;        }      }    }      break;    default:    { // 手勢結束和其他狀態      UICollectionViewCell *cell = [self.collectionView cellForItemAtIndexPath:self.oldIndexPath];      // 結束動畫過程中停止交互,防止出問題      self.collectionView.userInteractionEnabled = NO;      // 給截圖視圖一個動畫移動到隱藏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) {        // 移除截圖視圖,顯示隱藏的cell并開始交互        [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);

以上就是iOS中怎么利用UICollectionView實現拖拽效果，小編相信有部分知識點可能是我們日常工作會見到或用到的。希望你能通過這篇文章學到更多知識。更多詳情敬請關注億速云行業資訊頻道。