一個App受歡迎的程度，一方面來源于它本身為用戶提供便捷的功能，另一方面則來源于它的UI。UI是用戶體驗重要的組成部分，構成UI的的元素恰恰離不開那些看似獨立的控件。在開發的過程中，大家對UITableView應該很熟悉吧！確實UITableView在處理數據顯示方面有著很強大的功能，例如網紅們使用的微博，微信社交軟件的聊天界面等等，這種流式布局使用UITableView簡直最合適不過了；但畢竟UITableView不是萬能的，當需要顯示橫縱向的數據時它就顯得捉襟見肘了，雖然這也難不倒我們程序猿但是何必要大費周章的去定義復雜的cell呢！UICollectionView就是專門用來應付這種布局的,使用UICollectionView可以給我們帶來以下幾點優勢：1.可以高度的定制內容展示的樣式 2.高效的管理大量的數據。
首先給大家看一下這個Demo的效果圖：
iOS設備不知道現在有沒有可以屏幕錄制的app,這樣我就可以把操作的動作用gif圖片po上來了，大家如果有推薦可以告訴我哈！關于拖動，長按圖片后就可以將圖片拖到你想要的位置上，另外的圖片則會依次排序，很順暢的體驗。
在使用UICollectionView的時后，我們的類需要實現這些協議:UICollectionViewDataSource,UICollectionViewDelegateFlowLayout,
UICollectionViewDelegate,UIGestureRecognizerDelegate。
UICollectionViewDataSource：和我們在UITableView中所需要實現的UITableViewDataSource是一個道理，它里面包括以下這些API：
@protocol UICollectionViewDataSource <NSObject> @required - (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section; // The cell that is returned must be retrieved from a call to -dequeueReusableCellWithReuseIdentifier:forIndexPath: - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath; @optional - (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView; // The view that is returned must be retrieved from a call to -dequeueReusableSupplementaryViewOfKind:withReuseIdentifier:forIndexPath: - (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath; - (BOOL)collectionView:(UICollectionView *)collectionView canMoveItemAtIndexPath:(NSIndexPath *)indexPath NS_AVAILABLE_IOS(9_0); - (void)collectionView:(UICollectionView *)collectionView moveItemAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath*)destinationIndexPath NS_AVAILABLE_IOS(9_0); @end
UICollectionViewDelegateFlowLayout：UICollectionViewFlowLayout是一個專門用來管理collectionView布局的類,可以通過實現以下函數來調整我們界面的樣式：
@protocol UICollectionViewDelegateFlowLayout <UICollectionViewDelegate> @optional - (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath; - (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section; - (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section; - (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section; - (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section; - (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section; @end
UICollectionViewDelegate：和UITableViewDelegate一樣，這里就把它協議里面的的函數po出來了,通過重寫里面的函數，我們可以實現cell的點擊與拖動。
UIGestureRecognizerDelegate：由于我們還有一個拖動的功能，所以需要實現用戶手勢的協議。
好了，基礎的概念講了，現在我們就開始動手實現他吧！老樣子直接看源碼：
- (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. //設置背景色 [self.view setBackgroundColor:[UIColor colorWithPatternImage:[UIImage imageNamed:@"back.jpg"]]]; //設置數據源 self.dataSource = [[NSMutableArray alloc] initWithObjects: @"1.png",@"2.png",@"3.png", @"4.png", @"5.png", @"6.png", @"7.png", @"8.png", @"9.png", @"10.png", @"11.jpg", @"12.JPG", @"13.JPG", @"14.jpg", @"15.JPG", @"16.png", @"17.png", @"18.png", @"19.png", @"20.png", nil nil]; //初始化布局 self.flow = [[UICollectionViewFlowLayout alloc] init]; self.collect = [[UICollectionView alloc] initWithFrame:CGRectZero collectionViewLayout:self.flow]; [self.collect setBackgroundColor:[UIColor clearColor]]; //注冊cell 這一步必須要實現 [self.collect registerClass:[CustomCollectionCell class] forCellWithReuseIdentifier:@"CustomCell"]; self.collect.delegate = self; self.collect.dataSource = self; [self.collect setFrame:self.view.bounds]; //添加長按手勢 self.longPressGestureRecognizer = [[UILongPressGestureRecognizer alloc] init]; [self.longPressGestureRecognizer addTarget:self action:@selector(handleLongPressRecognizer:)]; [self.collect addGestureRecognizer:self.longPressGestureRecognizer]; [self.view addSubview:self.collect]; } 在viewDidLoad函數中，初始化了一個UICollectionViewFlowLayout布局，并且需要配合UICollectionView來使用，兩者加一起來使用才能“完美”，想比UITableView 中Cell使用的不同，在UICollectionView中必須先對Cell進行注冊(RegisterClass)，不然會在運行過程中報錯。如何使排列的圖片可以拖動呢，在這里我為UICollectionView添加了一個長按手勢UILongPressGestureRecognizer。當我們長按時會觸發handleLongPressRecognizer，代碼如下：
- (void)handleLongPressRecognizer:(UILongPressGestureRecognizer *)gesture{ switch (gesture.state) { case UIGestureRecognizerStateBegan:{ NSIndexPath *path = [self.collect indexPathForItemAtPoint:[gesture locationInView:gesture.view]]; if(path == nil){ break; } [self.collect beginInteractiveMovementForItemAtIndexPath:path]; } break; case UIGestureRecognizerStateChanged: [self.collect updateInteractiveMovementTargetPosition:[gesture locationInView:gesture.view]]; break; case UIGestureRecognizerStateEnded: [self.collect endInteractiveMovement]; break; default: [self.collect cancelInteractiveMovement]; break; } } 好看的界面才能抓住用戶的心，這里我自定義了Cell繼承自UICollectionViewCell，cell中展示的圖片會根據自身圖片的大小進行按比例縮放，這樣我們的桌面看上去就會有橫版圖片與豎版圖片，如果不自定義的話就都是方方正正的九宮格，還是花點心思自定義一下顯示效果吧！CustomCollectionCell的的代碼如下：
#import "CustomCollectionCell.h" @implementation CustomCollectionCell @synthesize imageV = _imageV; @synthesize labelV = _labelV; @synthesize boundView = _boundView; - (id)initWithFrame:(CGRect) frame{ self = [super initWithFrame:frame]; //init attributes if(self){ [self setBackgroundColor:[UIColor clearColor]]; self.imageV = [[UIImageView alloc] initWithFrame:CGRectZero]; self.labelV = [[UILabel alloc] initWithFrame:CGRectZero]; self.boundView = [[UIView alloc] initWithFrame:CGRectZero]; [self.boundView setBackgroundColor:[UIColor whiteColor]]; [self.boundView addSubview:self.imageV]; [self addSubview:self.boundView]; [self addSubview:self.labelV]; } return self; } - (void)setImageWithText:(UIImage *)image text:(NSString *)text{ if(!image){ return; } CGFloat imgWidth = image.size.width; CGFloat imgHeight = image.size.height; CGFloat iconWidth = 0.0; CGFloat iconHeight = 0.0; if(imgWidth > imgHeight){ iconHeight = roundf(((self.frame.size.width - 16)*imgHeight)/imgWidth); iconWidth = self.frame.size.width - 16; [self.boundView setFrame:CGRectMake(0, self.frame.size.height - iconHeight - 16, iconWidth + 16, iconHeight + 16)]; [self.imageV setFrame:CGRectMake(8, 8, iconWidth, iconHeight)]; }else{ iconWidth = roundf(((self.frame.size.width - 16) *imgWidth)/imgHeight); iconHeight = self.frame.size.height - 16; [self.boundView setFrame:CGRectMake(roundf((self.frame.size.width - iconWidth)/2), 0, iconWidth + 16, iconHeight + 16)]; [self.imageV setFrame:CGRectMake(8, 8, iconWidth, iconHeight)]; } [self.imageV setImage:image]; } @end 以上這些就是構成該Demo的重要組成部分了，UICollectionView還有很多的要素在這里面沒有講到，往后我還會再研究這個控件更加高級的的使用，本篇就好比是餐前的開胃小菜吧，希望大家喜歡。附上這個例子的源碼：
@implementation ViewController @synthesize dataSource = _dataSource; @synthesize longPressGestureRecognizer = _longPressGestureRecognizer; @synthesize flow = _flow; @synthesize collect = _collect; - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. //設置背景色 [self.view setBackgroundColor:[UIColor colorWithPatternImage:[UIImage imageNamed:@"back.jpg"]]]; //設置數據源 self.dataSource = [[NSMutableArray alloc] initWithObjects: @"1.png",@"2.png",@"3.png", @"4.png", @"5.png", @"6.png", @"7.png", @"8.png", @"9.png", @"10.png", @"11.jpg", @"12.JPG", @"13.JPG", @"14.jpg", @"15.JPG", @"16.png", @"17.png", @"18.png", @"19.png", @"20.png", nil nil]; //初始化布局 self.flow = [[UICollectionViewFlowLayout alloc] init]; self.collect = [[UICollectionView alloc] initWithFrame:CGRectZero collectionViewLayout:self.flow]; [self.collect setBackgroundColor:[UIColor clearColor]]; //注冊cell 這一步必須要實現 [self.collect registerClass:[CustomCollectionCell class] forCellWithReuseIdentifier:@"CustomCell"]; self.collect.delegate = self; self.collect.dataSource = self; [self.collect setFrame:self.view.bounds]; //添加長按手勢 self.longPressGestureRecognizer = [[UILongPressGestureRecognizer alloc] init]; [self.longPressGestureRecognizer addTarget:self action:@selector(handleLongPressRecognizer:)]; [self.collect addGestureRecognizer:self.longPressGestureRecognizer]; [self.view addSubview:self.collect]; } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } - (void)handleLongPressRecognizer:(UILongPressGestureRecognizer *)gesture{ switch (gesture.state) { case UIGestureRecognizerStateBegan:{ NSIndexPath *path = [self.collect indexPathForItemAtPoint:[gesture locationInView:gesture.view]]; if(path == nil){ break; } [self.collect beginInteractiveMovementForItemAtIndexPath:path]; } break; case UIGestureRecognizerStateChanged: [self.collect updateInteractiveMovementTargetPosition:[gesture locationInView:gesture.view]]; break; case UIGestureRecognizerStateEnded: [self.collect endInteractiveMovement]; break; default: [self.collect cancelInteractiveMovement]; break; } } #pragma mark UICollectionViewDataSource - (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{ return self.dataSource.count; } - (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{ return 1; } - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{ CustomCollectionCell * cell = (CustomCollectionCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"CustomCell" forIndexPath:indexPath]; UIImage *image = [UIImage imageNamed:[self.dataSource objectAtIndex:indexPath.row]]; [cell setImageWithText:image text:@""]; return cell; } - (BOOL)collectionView:(UICollectionView *)collectionView canMoveItemAtIndexPath:(NSIndexPath *)indexPath{ return YES; } - (void)collectionView:(UICollectionView *)collectionView moveItemAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath*)destinationIndexPath{ id item = [self.dataSource objectAtIndex:sourceIndexPath.item]; [self.dataSource removeObject:item]; [self.dataSource insertObject:item atIndex:destinationIndexPath.item]; } #pragma mark UICollectionViewDelegate - (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{ TestViewController *test = [[TestViewController alloc] initWithNibName:@"TestViewController" bundle:nil]; NSString *imageName = [self.dataSource objectAtIndex:indexPath.row]; test.imageName = imageName; [self.navigationController pushViewController:test animated:YES]; } - (BOOL)collectionView:(UICollectionView *)collectionView shouldHighlightItemAtIndexPath:(NSIndexPath *)indexPath{ return YES; } //選中放大效果 - (void)collectionView:(UICollectionView *)collectionView didHighlightItemAtIndexPath:(NSIndexPath *)indexPath{ // CustomCollectionCell * cell = (CustomCollectionCell *)[collectionView cellForItemAtIndexPath:indexPath]; // // [UIView animateWithDuration:1 animations:^{ // cell.transform = CGAffineTransformMakeScale(2.0f, 2.0f); // }]; } //縮小效果 - (void)collectionView:(UICollectionView *)collectionView didUnhighlightItemAtIndexPath:(NSIndexPath *)indexPath{ // CustomCollectionCell * cell = (CustomCollectionCell *)[collectionView cellForItemAtIndexPath:indexPath]; // // [UIView animateWithDuration:1 animations:^{ // cell.transform = CGAffineTransformMakeScale(1.0f, 1.0f); // }]; } #pragma mark UICollectionViewDelegateFlowLayout - (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath{ return CGSizeMake(100, 100); } /* * 上左下右間距 */ - (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section{ return UIEdgeInsetsMake(15, 15, 15, 15); } /* * item space */ - (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section{ return 8; } /* * 行距 20 */ - (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section{ return 10; } 以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持武林網。
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