博客> UICollectionView基础
UICollectionView基础
2017-08-15 01:11 评论:0 阅读:198 诸葛亮倒骑小毛驴
ios UICollectionView基础

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,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

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

@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; } }

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:

  • 手指按下
  • shouldHighlightItemAtIndexPath (如果返回YES则向下执行,否则执行到这里为止)
  • didHighlightItemAtIndexPath (高亮)
  • 手指松开
  • didUnhighlightItemAtIndexPath (取消高亮)
  • shouldSelectItemAtIndexPath (如果返回YES则向下执行,否则执行到这里为止)
  • 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]]; }

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