iOS開發(fā)UICollectionView實現(xiàn)拖拽效果

更新時間：2019年01月23日 14:34:51 作者：夕陽下的守望者

這篇文章主要為大家詳細介紹了iOS開發(fā)UICollectionView實現(xiàn)拖拽效果，具有一定的參考價值，感興趣的小伙伴們可以參考一下

一.介紹

iOS9提供API實現(xiàn)單元格排序功能，使用UICollectionView及其代理方法。iOS9之后有自帶方法可以實現(xiàn)該效果，只需添加長按手勢，實現(xiàn)手勢方法和調(diào)用iOS9的API交換數(shù)據(jù)，iOS9之前需要自己寫方法實現(xiàn)這效果，除了要添加長按手勢，這里還需要利用截圖替換原理，手動計算移動位置來處理視圖交換和數(shù)據(jù)交換。

二.方法和步驟

1.創(chuàng)建工程項目和視圖控制器,如下圖

2.聲明對象和設(shè)置代理和數(shù)據(jù)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(shù)據(jù)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(xiàn)UICollectionView的UICollectionViewDataSource的兩個必須實現(xiàn)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(xiàn)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(xiàn)

#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(shù)據(jù)
  id color = self.dataArr[sourceIndexPath.row];
  //從數(shù)據(jù)源中移除該數(shù)據(jù)
  [self.dataArr removeObject:color];
  //將數(shù)據(jù)插入到數(shù)據(jù)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(jié)束
      // iOS9方法 移動結(jié)束后關(guān)閉cell移動
      [self.collectionView endInteractiveMovement];
    }
      break;
    default: //手勢其他狀態(tài)
      [self.collectionView cancelInteractiveMovement];
      break;
  }
}

8.iOS9之前的實現(xiàn)

#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(tǒng)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(diào)用willMoveToIndexPath方法更新數(shù)據(jù)源
          [self.collectionView moveItemAtIndexPath:self.oldIndexPath toIndexPath:self.moveIndexPath];
          //設(shè)置移動后的起始indexPath
          self.oldIndexPath = self.moveIndexPath;
          break;
        }
      }
    }
      break;
    default:
    { // 手勢結(jié)束和其他狀態(tài)
      UICollectionViewCell *cell = [self.collectionView cellForItemAtIndexPath:self.oldIndexPath];
      // 結(jié)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);

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