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Most people do not understand the knowledge points of this article "iOS how to use UICollectionView to achieve drag and drop mobile cells", so the editor summarizes the following content, detailed content, clear steps, and has a certain reference value. I hope you can get something after reading this article. Let's take a look at this "iOS how to use UICollectionView to drag mobile cells" article.

one。 Introduction

IOS9 provides API to achieve cell sorting function, using UICollectionView and its proxy method. IOS9 has its own method to achieve this effect, only need to add long-press gesture to achieve gesture method and call iOS9 API to exchange data, iOS9 needs to write its own method to achieve this effect, in addition to adding long-press gesture, here also need to use screenshot replacement principle to manually calculate the moving position to deal with view exchange and data exchange.

two。 Methods and steps

1. Create a project and view controller, as shown in the following figure

two。 Declare objects and set up agents and data source proxies

@ interface ViewController () @ property (nonatomic, strong) NSMutableArray * dataArr;@property (nonatomic, strong) UICollectionView * collectionView;/** before selecting the screenshot of cell's NSIndexPath*/@property (nonatomic, strong) NSIndexPath* oldIndexPath;/** cell * / @ property (nonatomic, strong) UIView * snapshotView;/**, select cell NSIndexPath*/@property (nonatomic, strong) NSIndexPath* moveIndexPath; @ end

3. Initialize UICollectionView and add a long press gesture to initialize in viewDidLoad

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) / 3x 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]; / / add long press gestures UILongPressGestureRecognizer * longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector (handlelongGesture:)]; [collectionView addGestureRecognizer:longPress]

4. Instantiate the data source (50 random colors, transparency 0. 8), initialized in viewDidLoad

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

5. Two methods that must be implemented to realize UICollectionViewDataSource of UICollectionView

# 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. The key point is to realize the method of long pressing gestures.

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

Implementation after 7.iOS9

# method after pragma mark-iOS9-(BOOL) collectionView: (UICollectionView *) collectionView canMoveItemAtIndexPath: (NSIndexPath *) indexPath {/ / returns YES to allow row to move return YES;}-(void) collectionView: (UICollectionView *) collectionView moveItemAtIndexPath: (NSIndexPath *) sourceIndexPath toIndexPath: (NSIndexPath *) destinationIndexPath {/ / fetch mobile row data id color = self.dataArr [sourceIndexPath.row]; / / remove the data from the data source [self.dataArr removeObject:color] / / insert data into the target location in the data source [self.dataArr insertObject:color atIndex:destinationIndexPath.row];}-(void) iOS9_Action: (UILongPressGestureRecognizer *) longPress {switch (longPress.state) {case UIGestureRecognizerStateBegan: {/ / gesture start / / determine whether the gesture landing point is on the row NSIndexPath * indexPath = [self.collectionView indexPathForItemAtPoint: [longPress locationInView:self.collectionView]] If (indexPath = = nil) {break;} UICollectionViewCell * cell = [self.collectionView cellForItemAtIndexPath:indexPath]; [self.view bringSubviewToFront:cell]; / / iOS9 method to move cell [self.collectionView beginInteractiveMovementForItemAtIndexPath:indexPath];} break Case UIGestureRecognizerStateChanged: {/ / gesture change / / iOS9 method updates cell position at any time during movement [self.collectionView updateInteractiveMovementTargetPosition: [longPress locationInView:self.collectionView]];} break Case UIGestureRecognizerStateEnded: {/ / gesture ends / / iOS9 method closes cell movement after movement ends [self.collectionView endInteractiveMovement];} break; default: / / gesture other states [self.collectionView cancelInteractiveMovement]; break;}}

Previous implementation of 8.iOS9

# pragma mark-iOS9 previous method-(void) action: (UILongPressGestureRecognizer *) longPress {switch (longPress.state) {case UIGestureRecognizerStateBegan: {/ / gesture start / / determine whether the gesture landing point is on the row NSIndexPath * indexPath = [self.collectionView indexPathForItemAtPoint: [longPress locationInView:self.collectionView]]; self.oldIndexPath = indexPath If (indexPath = = nil) {break;} UICollectionViewCell * cell = [self.collectionView cellForItemAtIndexPath:indexPath]; / / use the screenshot feature of the system to get the screenshot view of cell UIView * snapshotView = [cell snapshotViewAfterScreenUpdates:NO]; snapshotView.frame = cell.frame; [self.view addSubview:self.snapshotView = snapshotView] / / hide the current cell cell.hidden = YES; CGPoint currentPoint = [longPress locationInView:self.collectionView] after screenshot; [UIView animateWithDuration:0.25 animations: ^ {snapshotView.transform = CGAffineTransformMakeScale (1.05,1.05); snapshotView.center = currentPoint;}];} break Case UIGestureRecognizerStateChanged: {/ / gesture change / / current finger position screenshot view position moves as the finger moves CGPoint currentPoint = [longPress locationInView:self.collectionView]; self.snapshotView.center = currentPoint / / calculate which visible cell intersects the screenshot view for (UICollectionViewCell * cell in self.collectionView.visibleCells) {/ / the currently hidden cell does not need to be exchanged, and directly continue if ([self.collectionView indexPathForCell:cell] = = self.oldIndexPath) {continue } / / calculate center distance CGFloat space = sqrtf (pow (self.snapshotView.center.x-cell.center.x, 2) + powf (self.snapshotView.center.y-cell.center.y, 2)); / / move if (space) if the intersection is halfway

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