iOS開(kāi)發(fā)UICollectionView實(shí)現(xiàn)拖拽效果
一.介紹
iOS9提供API實(shí)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(shí)現(xiàn)該效果,只需添加長(zhǎng)按手勢(shì),實(shí)現(xiàn)手勢(shì)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(shí)現(xiàn)這效果,除了要添加長(zhǎng)按手勢(shì),這里還需要利用截圖替換原理,手動(dòng)計(jì)算移動(dòng)位置來(lái)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(xiàng)目和視圖控制器,如下圖
2.聲明對(duì)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(zhǎng)按手勢(shì),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(zhǎng)按手勢(shì) UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(handlelongGesture:)]; [collectionView addGestureRecognizer:longPress];
4.實(shí)例化數(shù)據(jù)源,(50個(gè)隨機(jī)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(shí)現(xiàn)UICollectionView的UICollectionViewDataSource的兩個(gè)必須實(shí)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(diǎn)來(lái)了,實(shí)現(xiàn)長(zhǎng)按手勢(shì)方法
#pragma mark - 長(zhǎng)按手勢(shì) - (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(shí)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(dòng) return YES; } - (void)collectionView:(UICollectionView *)collectionView moveItemAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath { //取出移動(dòng)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(biāo)位置 [self.dataArr insertObject:color atIndex:destinationIndexPath.row]; } - (void)iOS9_Action:(UILongPressGestureRecognizer *)longPress { switch (longPress.state) { case UIGestureRecognizerStateBegan: { //手勢(shì)開(kāi)始 //判斷手勢(shì)落點(diǎn)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(dòng)cell [self.collectionView beginInteractiveMovementForItemAtIndexPath:indexPath]; } break; case UIGestureRecognizerStateChanged: { // 手勢(shì)改變 // iOS9方法 移動(dòng)過(guò)程中隨時(shí)更新cell位置 [self.collectionView updateInteractiveMovementTargetPosition:[longPress locationInView:self.collectionView]]; } break; case UIGestureRecognizerStateEnded: { // 手勢(shì)結(jié)束 // iOS9方法 移動(dòng)結(jié)束后關(guān)閉cell移動(dòng) [self.collectionView endInteractiveMovement]; } break; default: //手勢(shì)其他狀態(tài) [self.collectionView cancelInteractiveMovement]; break; } }
8.iOS9之前的實(shí)現(xiàn)
#pragma mark - iOS9 之前的方法 - (void)action:(UILongPressGestureRecognizer *)longPress { switch (longPress.state) { case UIGestureRecognizerStateBegan: { // 手勢(shì)開(kāi)始 //判斷手勢(shì)落點(diǎn)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(dāng)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(shì)改變 //當(dāng)前手指位置 截圖視圖位置隨著手指移動(dòng)而移動(dòng) CGPoint currentPoint = [longPress locationInView:self.collectionView]; self.snapshotView.center = currentPoint; // 計(jì)算截圖視圖和哪個(gè)可見(jiàn)cell相交 for (UICollectionViewCell *cell in self.collectionView.visibleCells) { // 當(dāng)前隱藏的cell就不需要交換了,直接continue if ([self.collectionView indexPathForCell:cell] == self.oldIndexPath) { continue; } // 計(jì)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(dòng) if (space <= self.snapshotView.bounds.size.width / 2) { self.moveIndexPath = [self.collectionView indexPathForCell:cell]; //移動(dòng) 會(huì)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(dòng)后的起始indexPath self.oldIndexPath = self.moveIndexPath; break; } } } break; default: { // 手勢(shì)結(jié)束和其他狀態(tài) UICollectionViewCell *cell = [self.collectionView cellForItemAtIndexPath:self.oldIndexPath]; // 結(jié)束動(dòng)畫過(guò)程中停止交互,防止出問(wèn)題 self.collectionView.userInteractionEnabled = NO; // 給截圖視圖一個(gè)動(dòng)畫移動(dòng)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(kāi)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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