iOS流布局UICollectionView系列七——三维中的球型布局

一、引言

通过6篇的博客，从平面上最简单的规则摆放的布局，到不规则的瀑布流布局，再到平面中的圆环布局，我们突破了线性布局的局限，在后面，我们将布局扩展到了空间，在Z轴上进行了平移，我们实现了一个类似UIPickerView的布局模型，其实我们还可以再进一步，类比于平面布局，picKerView只是线性排列布局在空间上的旋转与平移，这次，我们更加充分了利用一下空间的尺寸，来设计一个圆球的布局模型。以下是前几篇博客地址：

1.初识与简单实用UICollectionView：http://my.oschina.net/u/2340880/blog/522613

2.UICollectionView的代理方法：http://my.oschina.net/u/2340880/blog/522682

3.实用FlowLayout进行更灵活布局：http://my.oschina.net/u/2340880/blog/522748

4.自定义FlowLayout进行瀑布流布局：http://my.oschina.net/u/2340880/blog/522806

5.平面圆环布局的实现：http://my.oschina.net/u/2340880/blog/523064

6.将布局从平面应用到空间：http://my.oschina.net/u/2340880/blog/523341

二、将布局扩展为空间球型

在viewController中先实现一些准备代码：

- (void)viewDidLoad {[super viewDidLoad];// Do any additional setup after loading the view, typically from a nib.MyLayout * layout = [[MyLayout alloc]init];UICollectionView * collect  = [[UICollectionView alloc]initWithFrame:CGRectMake(0, 0, 320, 400) collectionViewLayout:layout];collect.delegate=self;collect.dataSource=self;//这里设置的偏移量是为了无缝进行循环的滚动，具体在上一篇博客中有解释collect.contentOffset = CGPointMake(320, 400);[collect registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"cellid"];[self.view addSubview:collect];
}-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{return 1;
}
//我们返回30的标签
-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{return 30;
}
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{UICollectionViewCell * cell  = [collectionView dequeueReusableCellWithReuseIdentifier:@"cellid" forIndexPath:indexPath];cell.backgroundColor = [UIColor colorWithRed:arc4random()%255/255.0 green:arc4random()%255/255.0 blue:arc4random()%255/255.0 alpha:1];UILabel * label = [[UILabel alloc]initWithFrame:CGRectMake(0, 0, 30, 30)];label.text = [NSString stringWithFormat:@"%ld",(long)indexPath.row];[cell.contentView addSubview:label];return cell;
}- (void)didReceiveMemoryWarning {[super didReceiveMemoryWarning];// Dispose of any resources that can be recreated.
}
//这里对滑动的contentOffset进行监控，实现循环滚动
-(void)scrollViewDidScroll:(UIScrollView *)scrollView{if (scrollView.contentOffset.y<200) {scrollView.contentOffset = CGPointMake(scrollView.contentOffset.x, scrollView.contentOffset.y+10*400);}else if(scrollView.contentOffset.y>11*400){scrollView.contentOffset = CGPointMake(scrollView.contentOffset.x, scrollView.contentOffset.y-10*400);}if (scrollView.contentOffset.x<160) {scrollView.contentOffset = CGPointMake(scrollView.contentOffset.x+10*320,scrollView.contentOffset.y);}else if(scrollView.contentOffset.x>11*320){scrollView.contentOffset = CGPointMake(scrollView.contentOffset.x-10*320,scrollView.contentOffset.y);}
}

这里面的代码比较上一篇博客中的并没有什么大的改动，只是做了横坐标的兼容。

在我们的layout类中，将代码修改成如下：

-(void)prepareLayout{[super prepareLayout];}
//返回的滚动范围增加了对x轴的兼容
-(CGSize)collectionViewContentSize{return CGSizeMake( self.collectionView.frame.size.width*([self.collectionView numberOfItemsInSection:0]+2), self.collectionView.frame.size.height*([self.collectionView numberOfItemsInSection:0]+2));
}
-(BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds{return YES;
}-(UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath{UICollectionViewLayoutAttributes * atti = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];//获取item的个数int itemCounts = (int)[self.collectionView numberOfItemsInSection:0];atti.center = CGPointMake(self.collectionView.frame.size.width/2+self.collectionView.contentOffset.x, self.collectionView.frame.size.height/2+self.collectionView.contentOffset.y);atti.size = CGSizeMake(30, 30);CATransform3D trans3D = CATransform3DIdentity;trans3D.m34 = -1/900.0;CGFloat radius = 15/tanf(M_PI*2/itemCounts/2);//根据偏移量 改变角度//添加了一个x的偏移量float offsety = self.collectionView.contentOffset.y;float offsetx = self.collectionView.contentOffset.x;//分别计算偏移的角度float angleOffsety = offsety/self.collectionView.frame.size.height;float angleOffsetx = offsetx/self.collectionView.frame.size.width;CGFloat angle1 = (float)(indexPath.row+angleOffsety-1)/itemCounts*M_PI*2;//x，y的默认方向相反CGFloat angle2 = (float)(indexPath.row-angleOffsetx-1)/itemCounts*M_PI*2;//这里我们进行四个方向的排列if (indexPath.row%4==1) {trans3D = CATransform3DRotate(trans3D, angle1, 1.0,0, 0);}else if(indexPath.row%4==2){trans3D = CATransform3DRotate(trans3D, angle2, 0, 1, 0);}else if(indexPath.row%4==3){trans3D = CATransform3DRotate(trans3D, angle1, 0.5,0.5, 0);}else{trans3D = CATransform3DRotate(trans3D, angle1, 0.5,-0.5,0);}trans3D = CATransform3DTranslate(trans3D, 0, 0, radius);atti.transform3D = trans3D;return atti;
}-(NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect{NSMutableArray * attributes = [[NSMutableArray alloc]init];//遍历设置每个item的布局属性for (int i=0; i<[self.collectionView numberOfItemsInSection:0]; i++) {[attributes addObject:[self layoutAttributesForItemAtIndexPath:[NSIndexPath indexPathForItem:i inSection:0]]];}return attributes;
}

布局效果如下：

滑动屏幕，这个圆球是可以进行滚动的。

TIP：这里我们只平均分配了四个方向上的布局，如果item更加小也更加多，我们可以分配到更多的方向上，使球体更加充实。