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UICollectionView基础

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];

 

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,并具有页面和页脚。其可定制的内容如下:

itemSize属性

设定全局的Cell尺寸,如果想要单独定义某个Cell的尺寸,可以使用下面方法:

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

minimumLineSpacing属性

设定全局的行间距,如果想要设定指定区内Cell的最小行距,可以使用下面方法:

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

minimumInteritemSpacing属性

设定全局的Cell间距,如果想要设定指定区内Cell的最小间距,可以使用下面方法:

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

scrollDirection属性

设定滚动方向,有UICollectionViewScrollDirectionVerticalUICollectionViewScrollDirectionHorizontal两个值。

headerReferenceSize属性与footerReferenceSize属性

设定页眉和页脚的全局尺寸,需要注意的是,根据滚动方向不同,header和footer的width和height中只有一个会起作用。如果要单独设置指定区内的页面和页脚尺寸,可以使用下面方法:

- (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,如果想要设定指定区的内边距,可以使用下面方法:

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


 

然后需要实现三种类型的委托:UICollectionViewDataSource, UICollectionViewDelagate和UICollectionViewDelegateFlowLayout

@interface ViewController : UIViewController <UICollectionViewDelegateFlowLayout, UICollectionViewDataSource>

因为UICollectionViewDelegateFlowLayout实际上是UICollectionViewDelegate的一个子协议,它继承了UICollectionViewDelegate,所以只需要在声明处写上UICollectionViewDelegateFlowLayout就行了。


 

UICollectionViewDataSource

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView

返回collection view里区(section)的个数,如果没有实现该方法,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本身作为容器view
  • 然后是一个大小自动适应整个cell的backgroundView,用作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

 

- (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

添加页眉和页脚以前需要注册类和标识:


 

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,也可以用新建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,甚至可以不用新建类去绑定这个xib,直接通过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";

 


 

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,也可以直接设置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,也可以直接设置UICollectionViewFlowLayoutminimumInteritemSpacing属性

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

 


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,一定要更新numberOfItemsInSection的返回情况。

 

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

当指定indexPath处的item被取消选择时触发,仅在允许多选时被调用

 

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

 

事件的处理顺序如下:

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

如果只是简单实现点击后cell改变显示状态,只需要在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;}

如果要实现点击时(手指未松开)的显示状态与点击后(手指松开)的显示状态,则需要通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]];}

 

UICollectionView基础