UICollectionViewLayout

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HJFlowLayout：

////  HJFlowLayout.m//  JHCircleLayout////  Created by qianfeng on 16/10/15.//  Copyright © 2016年 qianfeng. All rights reserved.//#import "HJFlowLayout.h"@implementation HJFlowLayout/* *注释: *1.边界改变是否让旧布局无效 * */-(BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds{    return YES;}/* *注释：第一步 *  1.实例化时最开始调用这个方法， *  2.布局无效之后 *  3.查询布局信息之前 *  4.如果子类覆盖（重写方法），子类应该总是调用super。invalidateLayout布局无效 *  5.在这里面一般就是写collectionView、cell。。配置信息（itemSize，间距等） */-(void)prepareLayout{    [super prepareLayout];    //滚动方向    self.scrollDirection = UICollectionViewScrollDirectionHorizontal;    //设置collectionView内边距    CGFloat insert = (self.collectionView.frame.size.width - self.itemSize.width) / 2;        self.sectionInset = UIEdgeInsetsMake(0, insert, 0, insert);}/* *注释:第二步 * *返回滚动后推荐（proposed）停止的点（偏移量），在这里要进行处理 */-(CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset withScrollingVelocity:(CGPoint)velocity{    //计算最终显示的边界    CGRect rect;    rect.origin.x = proposedContentOffset.x;    rect.origin.y = 0;    rect.size = self.collectionView.frame.size;        // 获得所有显示区域内的布局对象    NSArray *arr = [super layoutAttributesForElementsInRect:rect];    // collectionView中心点的x值 、 偏移量 + 一半宽度 = 当前collectionView的中点对应着contentView的哪一个中点    CGFloat contentCenterX = self.collectionView.frame.size.width / 2 + proposedContentOffset.x;    //存放布局对象数组中离（上面计算的）的点最小间距的布局对象的距离    CGFloat minDistance = MAXFLOAT;        for (UICollectionViewLayoutAttributes * attr in arr) {                CGFloat distance = ABS(attr.center.x - contentCenterX);                minDistance = minDistance > distance ? distance : minDistance;    }    //处理推荐的点，达到每次都停在图片中间的效果（之所以明确是➕，因为偏移一定是负数）    proposedContentOffset.x += minDistance;        return proposedContentOffset;}/* *注释：第三步：重新布局所有子控件cell * *作用相当于layoutSubViews，最后才执行的 */-(NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect{    //先布局super，只有流体布局才能使用    NSArray *arr = [super layoutAttributesForElementsInRect:rect];        //计算contentView中心点    CGFloat contentCenterX = self.collectionView.contentOffset.x + self.collectionView.frame.size.width / 2;        for (UICollectionViewLayoutAttributes *attr in arr) {        //求contentView的中心点和cell的中心点的距离[ABS:取绝对值]        CGFloat distance = ABS(attr.center.x - contentCenterX);//比不理解。。。。。。。。。。。。。。        //根据间距，计算缩放比例，        CGFloat scale = 1 - distance / self.collectionView.frame.size.width;        //设置cell的显示比例(当cell正好处于collectionView中点)        attr.transform = CGAffineTransformMakeScale(scale, scale);    }    return arr;}@end

HJCircleLayout：

////  HJCircleLayout.m//  JHCircleLayout////  Created by qianfeng on 16/10/15.//  Copyright © 2016年 qianfeng. All rights reserved.//#import "HJCircleLayout.h"@interface HJCircleLayout ()@property(nonatomic,strong)NSMutableArray * attrsArr;@end@implementation HJCircleLayout-(NSMutableArray *)attrsArr{    if(!_attrsArr){        _attrsArr=[[NSMutableArray alloc] init];    }    return _attrsArr;}-(BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds{    return YES;}/* *注释: * * */-(void)prepareLayout{    [super prepareLayout];    [self.attrsArr removeAllObjects];    //计算出每组有多少个    NSInteger  count=[self.collectionView numberOfItemsInSection:0];    /**     * 因为不是继承流水布局 UICollectionViewFlowLayout     * 所以我们需要自己创建 UICollectionViewLayoutAttributes     */    //如果是多组的话  需要2层循环    for (int i=0; i<count; i++) {        //创建UICollectionViewLayoutAttributes        NSIndexPath * indexPath = [NSIndexPath indexPathForItem:i inSection:0];        //这里需要 告诉 UICollectionViewLayoutAttributes 是哪里的attrs        UICollectionViewLayoutAttributes * attrs=[self layoutAttributesForItemAtIndexPath:indexPath];        [self.attrsArr addObject:attrs];    }}//获得视野范围内所有cell-(NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect{    //TODO:  特别注意 在这个方法里 可以边滑动边刷新（添加） attrs 一劳永逸 如果只需要添加一次的话  可以把这些 prepareLayout方法中去    return self.attrsArr;}#pragma mark ---- 这个方法需要返回indexPath位置对应cell的布局属性/** *  //TODO:  这个方法主要用于 切换布局的时候 如果不适用该方法 就不会切换布局的时候会报错 *   reason: 'no UICollectionViewLayoutAttributes instance for -layoutAttributesForItemAtIndexPath: <NSIndexPath: 0xc000000000400016> {length = 2, path = 0 - 2}' */-(UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath{    //TODO: 主要是返回每个indexPath的attrs        //创建UICollectionViewLayoutAttributes    //这里需要 告诉 UICollectionViewLayoutAttributes 是哪里的attrs    //计算出每组有多少个    NSInteger  count=[self.collectionView numberOfItemsInSection:0];    //角度    CGFloat angle = 2* M_PI /count *indexPath.item;    //设置半径    CGFloat radius=100;    //CollectionView的圆心的位置    CGFloat Ox = self.collectionView.frame.size.width/2;    CGFloat Oy = self.collectionView.frame.size.height/2;    UICollectionViewLayoutAttributes * attrs=[UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];    attrs.center =  CGPointMake(Ox+radius*sin(angle), Oy+radius*cos(angle));    if (count==1) {        attrs.size=CGSizeMake(200, 200);    }else{        attrs.size=CGSizeMake(50, 50);    }    return attrs;}@end

HJSquareLayout：

////  HJSquareLayout.m//  JHCircleLayout////  Created by qianfeng on 16/10/15.//  Copyright © 2016年 qianfeng. All rights reserved.//#import "HJSquareLayout.h"@interface HJSquareLayout ()/** attrs的数组 */@property(nonatomic,strong)NSMutableArray * attrsArr;@end@implementation HJSquareLayout//注释:懒加载-(NSMutableArray *)attrsArr{    if(!_attrsArr){        _attrsArr=[[NSMutableArray alloc] init];    }    return _attrsArr;}- (instancetype)init{    self = [super init];    if (self) {        self.scrollDirection = UICollectionViewScrollDirectionVertical;        self.sectionInset = UIEdgeInsetsMake(10, 10, 10, 10);                    }    return self;}/* *注释：重新布局之前加载布局配置信息 * * */-(void)prepareLayout{    [super prepareLayout];    [self.attrsArr removeAllObjects];    //获得所有的cell的数量    NSInteger count =[self.collectionView   numberOfItemsInSection:0];    for (int i=0; i<count; i++) {        NSIndexPath *  indexPath =[NSIndexPath indexPathForItem:i inSection:0];        UICollectionViewLayoutAttributes * attrs=[self layoutAttributesForItemAtIndexPath:indexPath];        [self.attrsArr addObject:attrs];    }}//注释:获得显示范围内所有的cell的布局属性对象-(NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect{    return self.attrsArr;}//注释: 返回系统推荐的位置，供cell停止-(CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset{    return proposedContentOffset;}//注释：不设置这个，collectionView就不能滑动-(CGSize)collectionViewContentSize{        int count =(int)[self.collectionView numberOfItemsInSection:0];    if (self.scrollDirection == UICollectionViewScrollDirectionVertical) {        //获取视图对象数量        //行数(1-1,2-1,3-1...4-2,5-2,6-2...7-3)        int rows= (count + 2) / 3;        //行高        CGFloat rowH = self.collectionView.frame.size.width * 0.250;        //行宽        CGFloat rowW = self.collectionView.frame.size.width * 0.333;            // 2%6余2 8%6余2：纵向(第四个，会减小高度)//        if (count % 6 == 4) {//            return CGSizeMake(self.collectionView.frame.size.width, rows * rowH-rowH/2);//        }else{//            return CGSizeMake(self.collectionView.frame.size.width, rows*rowH);//        }                return CGSizeMake(self.collectionView.frame.size.width, rowH * rows);                            }else{        //列数：（1个是一列，3个也是一列）        int columns = (count + 2) / 3;        //行高        CGFloat cellH = self.collectionView.frame.size.height;        //行宽        CGFloat cellW = self.collectionView.frame.size.width;        //横向        if ( count % 6 == 4) {            return CGSizeMake(columns * cellW - cellW / 2, cellH);        }else{            return CGSizeMake(columns * cellW, cellH);        }    }}//返回每个指定item的布局属性对象，修改frame-(UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath{    //宽度,高度    CGFloat width  = self.collectionView.frame.size.width * 0.333;    CGFloat height = self.collectionView.frame.size.width * 0.250;        //通过indexpath获取对象的布局属性对象    UICollectionViewLayoutAttributes * attr = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];    NSInteger i=indexPath.item;                if (self.scrollDirection == UICollectionViewScrollDirectionVertical) {            if (i==0) {                attr.frame = CGRectMake(0, 0, width, height);            }else if (i==1){                attr.frame = CGRectMake(width, 0, width, height/2);            }else if (i==2){                attr.frame = CGRectMake(width, height/2, width, height/2);            }else if (i==3){                attr.frame = CGRectMake(0, height, width, height/2);            }else if (i==4){                attr.frame = CGRectMake(0, height+height/2, width, height/2);            }else if (i==5){                attr.frame = CGRectMake(width, height, width, height);            }else{                UICollectionViewLayoutAttributes *lastAttrs = self.attrsArr[i-6];                CGRect frame  = lastAttrs.frame;                frame.origin.y+=2 * height;                attr.frame=frame;            }            //        if (i==0) {//            attr.frame = CGRectMake(width * 0, 0, width, height);//        }else if (i==1){//            attr.frame = CGRectMake(width * 1, 0, width, height);//        }else if (i==2){//            attr.frame = CGRectMake(width * 2, 0, width, height);//        }else{//            UICollectionViewLayoutAttributes *nextAttr = self.attrsArr[i - 3];//            CGRect frame = nextAttr.frame;//            frame.origin.y += height;//            attr.frame = frame;//        }            }else{                if (i==0) {            attr.frame = CGRectMake( 0,  0, width, height);        }else if (i==1){            attr.frame = CGRectMake( width, 0, width, height/2);        }else if (i==2){            attr.frame = CGRectMake( width, height/2, width, height/2);        }else if (i==3){            attr.frame = CGRectMake(width * 2, 0, width, height);        }else if (i==4){            attr.frame = CGRectMake(width * 3, 0, width, height/2);        }else if (i==5){            attr.frame = CGRectMake(width * 3, height/2, width, height/2);        }else{            UICollectionViewLayoutAttributes *lastAttrs = self.attrsArr[i-6];            CGRect frame    = lastAttrs.frame;            frame.origin.x += 4 * height;            attr.frame=frame;        }        //        if (i==0) {//            attr.frame = CGRectMake(width * 0, 0, width, height);//        }else if (i==1){//            attr.frame = CGRectMake(width * 1, 0, width, height);//        }else if (i==2){//            attr.frame = CGRectMake(width * 2, 0, width, height);//        }else{//            UICollectionViewLayoutAttributes *nextAttr = self.attrsArr[i - 3];//            CGRect frame = nextAttr.frame;//            frame.origin.y += height;//            attr.frame = frame;//        }    }    return attr;}-(BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds {    return YES;}@end

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