UICollectionView基础

惭愧惭愧，最近太懒  现在才发现本身的collectionView用的这么生疏。。。。

从基础巩固开始再来：

初始化部分：

UICollectionViewFlowLayout *flowLayout= [[UICollectionViewFlowLayout alloc]init];
self.myCollectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(20, 20, 250, 350) collectionViewLayout:flowLayout]; self.myCollectionView.backgroundColor = [UIColor grayColor]; [self.myCollectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@“myCell"]; self.myCollectionView.delegate = self; self.myCollectionView.dataSource = self; [self.view addSubview:self.myCollectionView];

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UICollectionViewLayout

UICollectionViewLayout决定了UICollectionView如何显示在界面上，Apple提供了一个最简单的默认layout对象：UICollectionViewFlowLayout。

Flow Layout是一个Cells的线性布局方案，并具备页面和页脚。其可定制的内容以下：

itemSize属性

设定全局的Cell尺寸，若是想要单独定义某个Cell的尺寸，可使用下面方法：

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath

minimumLineSpacing属性

设定全局的行间距，若是想要设定指定区内Cell的最小行距，可使用下面方法：

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section

minimumInteritemSpacing属性

设定全局的Cell间距，若是想要设定指定区内Cell的最小间距，可使用下面方法：

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section;

scrollDirection属性

设定滚动方向，有UICollectionViewScrollDirectionVertical和UICollectionViewScrollDirectionHorizontal两个值。

headerReferenceSize属性与footerReferenceSize属性

设定页眉和页脚的全局尺寸，须要注意的是，根据滚动方向不一样，header和footer的width和height中只有一个会起做用。若是要单独设置指定区内的页面和页脚尺寸，可使用下面方法：

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section

sectionInset属性

设定全局的区内边距，若是想要设定指定区的内边距，可使用下面方法：

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section;

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而后须要实现三种类型的委托：UICollectionViewDataSource, UICollectionViewDelagate和UICollectionViewDelegateFlowLayout。

@interface ViewController : UIViewController <UICollectionViewDelegateFlowLayout, UICollectionViewDataSource>

由于UICollectionViewDelegateFlowLayout其实是UICollectionViewDelegate的一个子协议，它继承了UICollectionViewDelegate，因此只须要在声明处写上UICollectionViewDelegateFlowLayout就好了。

---

 

UICollectionViewDataSource

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView

返回collection view里区(section)的个数，若是没有实现该方法，将默认返回1：

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return 2; }

 

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section

返回指定区(section)包含的数据源条目数(number of items)，该方法必须实现：

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return 7; }

 

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath

返回某个indexPath对应的cell，该方法必须实现：

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"myCell" forIndexPath:indexPath]; if(indexPath.section==0) { cell.backgroundColor = [UIColor redColor]; } else if(indexPath.section==1) { cell.backgroundColor = [UIColor greenColor]; } return cell; }

UICollectionViewCell结构上相对比较简单，由下至上：

• 首先是cell自己做为容器view
• 而后是一个大小自动适应整个cell的backgroundView，用做cell平时的背景
• 再其次是selectedBackgroundView，是cell被选中时的背景
• 最后是一个contentView，自定义内容应被加在这个view上

 

- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath

为collection view添加一个补充视图(页眉或页脚)

 

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section

设定页眉的尺寸

 

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section

设定页脚的尺寸

 

- (void)registerClass:(Class)viewClass forSupplementaryViewOfKind:(NSString *)elementKind withReuseIdentifier:(NSString *)identifier

添加页眉和页脚之前须要注册类和标识：

---

 

添加补充视图的代码示例：

[self.myCollectionView registerClass:[MyHeadView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"hxwHeader"]; [self.myCollectionView registerClass:[MyHeadView class] forSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:@"hxwHeader"]; -(CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section { CGSize size = {240,25}; return size; } -(CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section { CGSize size = {240,25}; return size; } - (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath { MyHeadView *headView; if([kind isEqual:UICollectionElementKindSectionHeader]) { headView = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"hxwHeader" forIndexPath:indexPath]; [headView setLabelText:[NSString stringWithFormat:@"section %d's header",indexPath.section]]; } else if([kind isEqual:UICollectionElementKindSectionFooter]) { headView = [collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:@"hxwHeader" forIndexPath:indexPath]; [headView setLabelText:[NSString stringWithFormat:@"section %d's footer",indexPath.section]]; } return headView; }

 

MyHeadView.h

#import <UIKit/UIKit.h>

@interface MyHeadView : UICollectionReusableView - (void) setLabelText:(NSString *)text; @end

 

MyHeadView.m

#import "MyHeadView.h" @interface MyHeadView() @property (strong, nonatomic) UILabel *label; @end @implementation MyHeadView - (id)initWithFrame:(CGRect)frame { self = [super initWithFrame:frame]; if (self) { self.label = [[UILabel alloc] init]; self.label.font = [UIFont systemFontOfSize:18]; [self addSubview:self.label]; } return self; } - (void) setLabelText:(NSString *)text { self.label.text = text; [self.label sizeToFit]; } @end

 

在注册Cell和补充视图时，也能够用新建xib文件的方式：

[self.myCollectionView registerNib:[UINib nibWithNibName:@"MyCollectionCell" bundle:nil] forCellWithReuseIdentifier:@"hxwCell"]; [self.myCollectionView registerNib:[UINib nibWithNibName:@"MySupplementaryView" bundle:nil] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"hxwHeader"]; [self.myCollectionView registerNib:[UINib nibWithNibName:@"MySupplementaryView" bundle:nil] forSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:@"hxwFooter"];

用这种方式注册后，甚至能够不用新建类去绑定这个xib，直接经过viewWithTag的方式获取xib里的控件：

UICollectionReusableView *view =  [collectionView dequeueReusableSupplementaryViewOfKind :kind withReuseIdentifier:@"hxwHeader" forIndexPath:indexPath]; UILabel *label = (UILabel *)[view viewWithTag:1]; label.text = @"empty";

 

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UICollectionViewDelegateFlowLayout

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath

设定指定Cell的尺寸

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    if(indexPath.section==0 && indexPath.row==1) { return CGSizeMake(50, 50); } else { return CGSizeMake(75, 30); } }

 

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section;

设定collectionView(指定区)的边距

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
    if(section==0) { return UIEdgeInsetsMake(35, 25, 15, 25); } else { return UIEdgeInsetsMake(15, 15, 15, 15); } }

 

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section

设定指定区内Cell的最小行距，也能够直接设置UICollectionViewFlowLayout的minimumLineSpacing属性

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section
{
    if(section==0) { return 10.0; } else { return 20.0; } }

 

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section;

设定指定区内Cell的最小间距，也能够直接设置UICollectionViewFlowLayout的minimumInteritemSpacing属性

- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section
{
    if(section==0) { return 10.0; } else { return 20.0; } }

 

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UICollectionViewDelegate

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath

当指定indexPath处的item被选择时触发

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath { [self.myArray removeObjectAtIndex:indexPath.row]; [collectionView deleteItemsAtIndexPaths:[NSArray arrayWithObject:indexPath]]; }

P.s. 当你删除或添加元素时，必定要更新numberOfItemsInSection的返回状况。

 

- (void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath

当指定indexPath处的item被取消选择时触发，仅在容许多选时被调用

 

下面是三个和高亮有关的方法：

- (BOOL)collectionView:(UICollectionView *)collectionView shouldHighlightItemAtIndexPath:(NSIndexPath *)indexPath

- (void)collectionView:(UICollectionView *)collectionView didHighlightItemAtIndexPath:(NSIndexPath *)indexPath

- (void)collectionView:(UICollectionView *)collectionView didUnhighlightItemAtIndexPath:(NSIndexPath *)indexPath

 

事件的处理顺序以下：

1. 手指按下
2. shouldHighlightItemAtIndexPath (若是返回YES则向下执行，不然执行到这里为止)
3. didHighlightItemAtIndexPath (高亮)
4. 手指松开
5. didUnhighlightItemAtIndexPath (取消高亮)
6. shouldSelectItemAtIndexPath (若是返回YES则向下执行，不然执行到这里为止)
7. didSelectItemAtIndexPath (执行选择事件)

若是只是简单实现点击后cell改变显示状态，只须要在cellForItemAtIndexPath方法里返回cell时，指定cell的selectedBackgroundView：

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"myCell" forIndexPath:indexPath]; UIView* selectedBGView = [[UIView alloc] initWithFrame:cell.bounds]; selectedBGView.backgroundColor = [UIColor blueColor]; cell.selectedBackgroundView = selectedBGView; return cell; }

若是要实现点击时(手指未松开)的显示状态与点击后(手指松开)的显示状态，则须要经过上面提到的方法来实现：

- (BOOL)collectionView:(UICollectionView *)collectionView shouldHighlightItemAtIndexPath:(NSIndexPath *)indexPath
{
    return YES; } - (void)collectionView:(UICollectionView *)colView didHighlightItemAtIndexPath:(NSIndexPath *)indexPath { UICollectionViewCell* cell = [colView cellForItemAtIndexPath:indexPath]; [cell setBackgroundColor:[UIColor purpleColor]]; } - (void)collectionView:(UICollectionView *)colView didUnhighlightItemAtIndexPath:(NSIndexPath *)indexPath { UICollectionViewCell* cell = [colView cellForItemAtIndexPath:indexPath]; [cell setBackgroundColor:[UIColor yellowColor]]; }