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使用iOS控件UICollectionView生成可拖动的桌面的实例

一个App受欢迎的程度，一方面来源于它本身为用户提供便捷的功能，另一方面则来源于它的UI。UI是用户体验重要的组成部分，构成UI的的元素恰恰离不开那些看似独立的控件。在开发的过程中，大家对UITableView应该很熟悉吧！确实UITableView在处理数据显示方面有着很强大的功能，例如网红们使用的微博，微信社交软件的聊天界面等等，这种流式布局使用UITableView简直最合适不过了；但毕竟UITableView不是万能的，当需要显示横纵向的数据时它就显得捉襟见肘了，虽然这也难不倒我们程序猿但是何必要大费周章的去定义复杂的cell呢！UICollectionView就是专门用来应付这种布局的,使用UICollectionView可以给我们带来以下几点优势：1.可以高度的定制内容展示的样式 2.高效的管理大量的数据。

首先给大家看一下这个Demo的效果图：

iOS设备不知道现在有没有可以屏幕录制的app,这样我就可以把操作的动作用gif图片po上来了，大家如果有推荐可以告诉我哈！关于拖动，长按图片后就可以将图片拖到你想要的位置上，另外的图片则会依次排序，很顺畅的体验。

在使用UICollectionView的时后，我们的类需要实现这些协议:UICollectionViewDataSource,UICollectionViewDelegateFlowLayout,

UICollectionViewDelegate,UIGestureRecognizerDelegate。

UICollectionViewDataSource：和我们在UITableView中所需要实现的UITableViewDataSource是一个道理，它里面包括以下这些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是一个专门用来管理collectionView布局的类,可以通过实现以下函数来调整我们界面的样式：

@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一样，这里就把它协议里面的的函数po出来了,通过重写里面的函数，我们可以实现cell的点击与拖动。

UIGestureRecognizerDelegate：由于我们还有一个拖动的功能，所以需要实现用户手势的协议。

好了，基础的概念讲了，现在我们就开始动手实现他吧！老样子直接看源码：

- (void)viewDidLoad { 
  [super viewDidLoad]; 
  // Do any additional setup after loading the view, typically from a nib. 
   
  //设置背景色 
  [self.view setBackgroundColor:[UIColor colorWithPatternImage:[UIImage imageNamed:@"back.jpg"]]]; 
  //设置数据源 
  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]]; 
   
  //注册cell 这一步必须要实现 
  [self.collect registerClass:[CustomCollectionCell class] forCellWithReuseIdentifier:@"CustomCell"]; 
   
  self.collect.delegate = self; 
  self.collect.dataSource = self; 
   
  [self.collect setFrame:self.view.bounds]; 
   
  //添加长按手势 
  self.longPressGestureRecognizer = [[UILongPressGestureRecognizer alloc] init]; 
  [self.longPressGestureRecognizer addTarget:self action:@selector(handleLongPressRecognizer:)]; 
  [self.collect addGestureRecognizer:self.longPressGestureRecognizer]; 
   
  [self.view addSubview:self.collect]; 
}

在viewDidLoad函数中，初始化了一个UICollectionViewFlowLayout布局，并且需要配合UICollectionView来使用，两者加一起来使用才能“完美”，想比UITableView 中Cell使用的不同，在UICollectionView中必须先对Cell进行注册(RegisterClass)，不然会在运行过程中报错。如何使排列的图片可以拖动呢，在这里我为UICollectionView添加了一个长按手势UILongPressGestureRecognizer。当我们长按时会触发handleLongPressRecognizer，代码如下：

- (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户的心，这里我自定义了Cell继承自UICollectionViewCell，cell中展示的图片会根据自身图片的大小进行按比例缩放，这样我们的桌面看上去就会有横版图片与竖版图片，如果不自定义的话就都是方方正正的九宫格，还是花点心思自定义一下显示效果吧！CustomCollectionCell的的代码如下：

#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

以上这些就是构成该Demo的重要组成部分了，UICollectionView还有很多的要素在这里面没有讲到，往后我还会再研究这个控件更加高级的的使用，本篇就好比是餐前的开胃小菜吧，希望大家喜欢。附上这个例子的源码：

@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. 
   
  //设置背景色 
  [self.view setBackgroundColor:[UIColor colorWithPatternImage:[UIImage imageNamed:@"back.jpg"]]]; 
  //设置数据源 
  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]]; 
   
  //注册cell 这一步必须要实现 
  [self.collect registerClass:[CustomCollectionCell class] forCellWithReuseIdentifier:@"CustomCell"]; 
   
  self.collect.delegate = self; 
  self.collect.dataSource = self; 
   
  [self.collect setFrame:self.view.bounds]; 
   
  //添加长按手势 
  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; 
} 
 
//选中放大效果 
- (void)collectionView:(UICollectionView *)collectionView didHighlightItemAtIndexPath:(NSIndexPath *)indexPath{ 
//  CustomCollectionCell * cell = (CustomCollectionCell *)[collectionView cellForItemAtIndexPath:indexPath]; 
//   
//  [UIView animateWithDuration:1 animations:^{ 
//    cell.transform = CGAffineTransformMakeScale(2.0f, 2.0f); 
//  }]; 
} 
 
//缩小效果 
- (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); 
} 
 
/* 
 * 上左下右间距 
 */ 
- (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内容，希望对大家的学习有所帮助，也希望大家多多支持呐喊教程。

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