UICollectionView的自定义布局,在写篇文章之前，自己在方面遇到不少问题，首先感谢帮助过我的人，自己也在网上找了不少资料，如有不足之处，请多多指教。
UICollectionView 基本使用
- UICollectionView使用注意点
- 1.创建UICollectionView必须要有布局参数（UICollectionViewFlowLayout比如流水性布局,UICollectionViewLayout空白布局，需要自己写cell样式）
- 2.cell必须通过注册
- 3.cell必须自定义,系统cell没有任何子控件
//注册cell的ID
static NSString * const ID = @"cell";
- (void)viewDidLoad {
[super viewDidLoad];
// 创建布局参数
UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];
//设置 item的大小
layout.itemSize = CGSizeMake(60, 60);
//设置最小item的间距
layout.minimumInteritemSpacing = 5;
//设置最小行间距
layout.minimumLineSpacing = 5;
// 创建UICollectionView:黑色
UICollectionView *collectionView = [[UICollectionView alloc] initWithFrame:CGRectZero collectionViewLayout:layout];
collectionView.backgroundColor = [UIColor brownColor];
collectionView.center = self.view.center;
collectionView.bounds = CGRectMake(0, 0, self.view.bounds.size.width, 200);
[self.view addSubview:collectionView];
// 设置数据源
collectionView.dataSource = self;
// 注册cell
[collectionView registerNib:[UINib nibWithNibName:NSStringFromClass([PhotoCell class]) bundle:nil] forCellWithReuseIdentifier:ID];
}
#pragma mark - UICollectionViewDataSource
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return 10;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
PhotoCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:ID forIndexPath:indexPath];
NSString *imageName = [NSString stringWithFormat:@"%ld",indexPath.item + 1];
cell.image = [UIImage imageNamed:imageName];
return cell;
}
xib创建cell
#import
@interface PhotoCell : UICollectionViewCell
@property (nonatomic, strong) UIImage *image;
@end
//.m文件
#import "PhotoCell.h"
@interface PhotoCell ()
@property (weak, nonatomic) IBOutlet UIImageView *photoView;
@end
@implementation PhotoCell
- (void)awakeFromNib {
[super awakeFromNib];
}
- (void)setImage:(UIImage *)image
{
_image = image;
_photoView.image = image;
}
@end
UICollectionView基本使用.png
自定义布局
//自定义布局需要知道的几个方法
//作用：计算cell的布局
//调用：第一次布局collectionView或者collectionView刷新的时候调用
//初始化布局
- (void)prepareLayout;
/*
UICollectionViewLayoutAttributes:确定cell的尺寸
一个UICollectionViewLayoutAttributes对象就对应一个cell
拿到UICollectionViewLayoutAttributes相当于拿到cell
*/
// 返回数组中的 UICollectionViewLayoutAttributes 布局属性
/// 这个方法返回一个数组， 数组存放rect的范围内所有元素的布局属性，返回的数组决定了rect范围内所有的元素排布（frame）
- (nullable NSArray<__kindof UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect;
/**
* 当 collectionView的显示范围繁盛改变的时候，是否需要重新刷新布局
*/
- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds;
/**
* 这个方法的返回值，就决定了collectionView停止滚动时的偏移量
* proposedContentOffset 最终的偏移量
* velocity 滚动速率 这个参数可以了解到滚动的方向
*/
- (CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset withScrollingVelocity:(CGPoint)velocity;
/// 每一个item对应cell的UICollectionViewLayoutAttributes属性
- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath；
//collectionView内容大小
- (CGSize)collectionViewContentSize;
效果图.gif
自定义布局的例子-(效果如上图)
*****************控制器****************
#import "ViewController.h"
#import "CCLineLayout.h"
#import "CCCell.h"
#import "CCCircleLayout.h"
@interface ViewController ()
@property (nonatomic, strong) NSMutableArray *imageArray;
/**<#class#>*/
@property (nonatomic, weak) UICollectionView *collerView;
@end
@implementation ViewController
static NSString *const ID = @"cell";
- (NSMutableArray *)imageArray {
if (!_imageArray) {
_imageArray = [NSMutableArray array];
for (int i = 0; i< 20 ;i ++) {
[_imageArray addObject:[NSString stringWithFormat:@"%zd",i + 1]];
}
}
return _imageArray;
}
- (void)viewDidLoad {
[super viewDidLoad];
CCLineLayout *layout = [[CCLineLayout alloc] init];
layout.itemSize = CGSizeMake(100, 100);
CGFloat w = self.view.frame.size.width;
CGRect frame = CGRectMake(0, 150, w, 200);
UICollectionView *collerView = [[UICollectionView alloc] initWithFrame:frame collectionViewLayout:layout];
collerView.delegate = self;
collerView.dataSource = self;
[self.view addSubview:collerView];
self.collerView = collerView;
//注册cell
[collerView registerNib:[UINib nibWithNibName:NSStringFromClass([CCCell class]) bundle:nil] forCellWithReuseIdentifier:ID];
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
if ([self.collerView.collectionViewLayout isKindOfClass:[CCLineLayout class]]) {
[self.collerView setCollectionViewLayout:[[CCCircleLayout alloc] init] animated:YES];
} else {
CCLineLayout *layout = [[CCLineLayout alloc] init];
layout.itemSize = CGSizeMake(100, 100);
[self.collerView setCollectionViewLayout:layout animated:YES];
}
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
return self.imageArray.count;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
CCCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:ID forIndexPath:indexPath];
cell.imageNmae = self.imageArray[indexPath.item];
return cell;
}
//MARK:UICollectionViewDelegate
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
[self.imageArray removeObjectAtIndex:indexPath.item];
[self.collerView deleteItemsAtIndexPaths:@[indexPath]];
}
@end
********************cell的第一个布局样式******************
计算图：
距离中心线的计算图.png
#import
@interface CCLineLayout : UICollectionViewFlowLayout
@end
#import "CCLineLayout.h"
@implementation CCLineLayout
///布局的初始化操作
- (void)prepareLayout {
self.scrollDirection = UICollectionViewScrollDirectionHorizontal;
CGFloat det = (self.collectionView.frame.size.width - self.itemSize.width)*0.5;
// 内边距
self.sectionInset = UIEdgeInsetsMake(0, det, 0, det);
}
/**
* 当 collectionView的显示范围发生改变的时候，是否需要重新刷新布局
*/
- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds {
return YES;
}
/**
* UICollectionViewLayoutAttributes
* 1.一个cell对应一个UICollectionViewLayoutAttributes对象
* 2.UICollectionViewLayoutAttributes对象决定了cell的frame
*/
/// 这个方法返回一个数组， 数组存放rect的范围内所有元素的布局属性，返回的数组决定了rect范围内所有的元素排布（frame）
- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect {
//获取布局属性数组
NSArray *array = [super layoutAttributesForElementsInRect:self.collectionView.bounds];
//更改布局属性
for (UICollectionViewLayoutAttributes *attr in array) {
//获取到cell的中心点
CGFloat cellCenterX = attr.center.x;
// del是cell中心点 距离 collectionView中心点的距离
CGFloat del = fabs((cellCenterX - self.collectionView.contentOffset.x) - self.collectionView.bounds.size.width *0.5);
//根据间距 算出比例值
CGFloat scale = 1- del/(self.collectionView.bounds.size.width *0.5) *0.25;
//缩放
attr.transform = CGAffineTransformMakeScale(scale, scale);
}
return array;
}
/**
* 这个方法的返回值，就决定了collectionView停止滚动时的偏移量
* proposedContentOffset 最终的偏移量
* velocity 滚动速率 这个参数可以了解到滚动的方向
*/
- (CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset withScrollingVelocity:(CGPoint)velocity{
CGFloat collectionViewW = self.collectionView.bounds.size.width;
//最终偏移量
CGPoint targetP = [super targetContentOffsetForProposedContentOffset:proposedContentOffset withScrollingVelocity:velocity];
//获取最终显示的区域
CGRect targetRect = CGRectMake(targetP.x, 0, collectionViewW, MAXFLOAT);
//获取布局属性数组
NSArray *arry = [super layoutAttributesForElementsInRect:targetRect];
//最小的间距
CGFloat min = MAXFLOAT;
for (UICollectionViewLayoutAttributes *arrt in arry) {
//获取距离中心点距离
CGFloat del = (arrt.center.x - targetP.x) - self.collectionView.bounds.size.width *0.5;
//找最小距离
if (fabs(min) > fabs(del)) {
min = del;
}
}
targetP.x += min;
if (targetP.x < 0) {
targetP.x = 0;
}
return targetP;
}
@end
*******************cell的第二个布局样式***************
#import
@interface CCCircleLayout : UICollectionViewLayout
@end
#import "CCCircleLayout.h"
@interface CCCircleLayout()
@property (nonatomic, strong) NSMutableArray *attArray;
@end
@implementation CCCircleLayout
- (NSMutableArray *)attArray {
if (!_attArray) {
_attArray = [NSMutableArray array];
}
return _attArray;
}
//初始化布局
- (void)prepareLayout {
[super prepareLayout];
[self.attArray removeAllObjects];
NSInteger count = [self.collectionView numberOfItemsInSection:0];
for (int i = 0; i < count; i ++) {
NSIndexPath *indexPath = [NSIndexPath indexPathForItem:i inSection:0];
UICollectionViewLayoutAttributes *atts = [self layoutAttributesForItemAtIndexPath:indexPath];
[self.attArray addObject:atts];
}
}
/// 返回数组中的 UICollectionViewLayoutAttributes 布局属性
- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect {
return self.attArray;
}
/// 每一个item对应cell的UICollectionViewLayoutAttributes属性
- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath {
NSInteger count = [self.collectionView numberOfItemsInSection:0];
//设置圆心半径
CGFloat radius = 70;
//圆心的位置
CGFloat oX = self.collectionView.frame.size.width *0.5;
CGFloat oY = self.collectionView.frame.size.height *0.5;
//创建 UICollectionViewLayoutAttributes属性
UICollectionViewLayoutAttributes *attri = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];
//设置宽高
attri.size = CGSizeMake(50, 50);
CGFloat angle = ( 2 * M_PI /count) *indexPath.item;
CGFloat centerX = oX + radius *sin(angle);
CGFloat centerY = oY + radius*cos(angle);
attri.center = CGPointMake(centerX, centerY);
return attri;
}
@end