UICollectionView的基礎用法

2019-11-09 18:53:13
字體：大中小
來源：轉載
供稿：網友
UICollectionView基礎

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決定了UICollectionView如何顯示在界面上，Apple提供了一個最簡單的默認layout對象：UICollectionViewFlowLayout。
Flow Layout是一個Cells的線性布局方案，并具有頁面和頁腳。其可定制的內容如下：
itemSize屬性
設定全局的Cell尺寸，如果想要單獨定義某個Cell的尺寸，可以使用下面方法：
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
minimumLineSpacing屬性
設定全局的行間距，如果想要設定指定區內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屬性
設定全局的Cell間距，如果想要設定指定區內Cell的最小間距，可以使用下面方法：
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section;
scrollDirection屬性
設定滾動方向，有UICollectionViewScrollDirectionVertical和UICollectionViewScrollDirectionHorizontal兩個值。
headerReferenceSize屬性與footerReferenceSize屬性
設定頁眉和頁腳的全局尺寸，需要注意的是，根據滾動方向不同，header和footer的width和height中只有一個會起作用。如果要單獨設置指定區內的頁面和頁腳尺寸，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屬性
設定全局的區內邊距，如果想要設定指定區的內邊距，可以使用下面方法：
- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section;
 
然后需要實現三種類型的委托：UICollectionViewDataSource, UICollectionViewDelagate和UICollectionViewDelegateFlowLayout。
@interface ViewController : UIViewController 因為UICollectionViewDelegateFlowLayout實際上是UICollectionViewDelegate的一個子協議，它繼承了UICollectionViewDelegate，所以只需要在聲明處寫上UICollectionViewDelegateFlowLayout就行了。
 
UICollectionViewDataSource
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
返回collection view里區(section)的個數，如果沒有實現該方法，將默認返回1：
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{    return 2;} 
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
返回指定區(section)包含的數據源條目數(number of items)，該方法必須實現：
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{    return 7;} 
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
返回某個indexPath對應的cell，該方法必須實現：
- (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結構上相對比較簡單，由下至上：
首先是cell本身作為容器view然后是一個大小自動適應整個cell的backgroundView，用作cell平時的背景再其次是selectedBackgroundView，是cell被選中時的背景最后是一個contentView，自定義內容應被加在這個view上 
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString*)kind atIndexPath:(NSIndexPath *)indexPath
為collection view添加一個補充視圖(頁眉或頁腳)
 
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section
設定頁眉的尺寸
 
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section
設定頁腳的尺寸
 
- (void)registerClass:(Class)viewClass forSupplementaryViewOfKind:(NSString *)elementKind withReuseIdentifier:(NSString*)identifier
添加頁眉和頁腳以前需要注冊類和標識：
 
添加補充視圖的代碼示例：
[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 @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 
在注冊Cell和補充視圖時，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"];用這種方式注冊后，甚至可以不用新建類去綁定這個xib，直接通過viewWithTag的方式獲取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
設定指定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;
設定collectionView(指定區)的邊距
- (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
設定指定區內Cell的最小行距，也可以直接設置UICollectionViewFlowLayout的minimumLineSpacing屬性
- (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;
設定指定區內Cell的最小間距，也可以直接設置UICollectionViewFlowLayout的minimumInteritemSpacing屬性
- (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
當指定indexPath處的item被選擇時觸發
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{[self.myArray removeObjectAtIndex:indexPath.row];[collectionView deleteItemsAtIndexPaths:[NSArray arrayWithObject:indexPath]];}P.s. 當你刪除或添加元素時，一定要更新numberOfItemsInSection的返回情況。
 
- (void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath
當指定indexPath處的item被取消選擇時觸發，僅在允許多選時被調用
 
下面是三個和高亮有關的方法：
- (BOOL)collectionView:(UICollectionView *)collectionView shouldHighlightItemAtIndexPath:(NSIndexPath *)indexPath
- (void)collectionView:(UICollectionView *)collectionView didHighlightItemAtIndexPath:(NSIndexPath *)indexPath
- (void)collectionView:(UICollectionView *)collectionView didUnhighlightItemAtIndexPath:(NSIndexPath *)indexPath
 
事件的處理順序如下：
手指按下shouldHighlightItemAtIndexPath (如果返回YES則向下執行，否則執行到這里為止)didHighlightItemAtIndexPath (高亮)手指松開didUnhighlightItemAtIndexPath (取消高亮)shouldSelectItemAtIndexPath (如果返回YES則向下執行，否則執行到這里為止)didSelectItemAtIndexPath (執行選擇事件)如果只是簡單實現點擊后cell改變顯示狀態，只需要在cellForItemAtIndexPath方法里返回cell時，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;}如果要實現點擊時(手指未松開)的顯示狀態與點擊后(手指松開)的顯示狀態，則需要通過上面提到的方法來實現：
- (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]];}