自定义 ---UICollectionViewLayout-正N变形居中布局

1. 自定义UICollectionLayout ---- 正三角形居中布局

 支持多个图形的自动布局

2. 自定义UICollectionLayout ---- 正方形居中布局

滚动展示的区域

3. 自定义UICollectionLayout ---- 正六边形居中布局(蜂窝布局)

等等正n变形布局，其中 正六边形支持 间距大小的改变，图形的旋转。

旋转 --

 间距

4. 核心代码 ---- 绘制正n边形 （贝塞尔曲线）

- (void)layoutSubviews
{
    [super layoutSubviews];
    // step 1: 绘制正n变形
    CGFloat X = self.contentView.frame.size.width  * 0.5;
    CGFloat Y = self.contentView.frame.size.height * 0.5;
    UIBezierPath* bezierPath = [UIBezierPath bezierPath];
    bezierPath.lineCapStyle = kCGLineCapRound;
    bezierPath.lineJoinStyle = kCGLineCapRound;
    CGFloat angle = labs(360/self.number);
    [bezierPath moveToPoint: CGPointMake(X - mm , Y)];
    for (int i = 0; i < self.number - 1; i ++) {
        CGFloat angle1 = angle *(i + 1);
        CGFloat XX = X + (mm * (COS(angle1)))*(-1);
        CGFloat YY = Y + mm * (SIN(angle1));
        [bezierPath addLineToPoint: CGPointMake(XX, YY)];
    }
    [bezierPath addLineToPoint: CGPointMake(X - mm , Y)];
    // step 2: 根据路径生成蒙板
    CAShapeLayer *maskLayer = [CAShapeLayer layer];
    maskLayer.path = [bezierPath CGPath];
    
    self.backgroundColor = [UIColor redColor];
    // step 3: 给cell添加模版
    self.layer.mask = maskLayer;
    self.titleLabel.frame = self.bounds;
}

5. 核心代码 ---  自定义Layout布局

- (void)prepareLayout
{
    [super prepareLayout];
    _itemCount = [self.collectionView numberOfItemsInSection:0];
    _attributeAttay = [[NSMutableArray alloc]init];
    for (int i = 0 ; i < _itemCount; i ++) {
        //设置第一个正六边形的中心位置
        CGFloat X = self.collectionView.frame.size.width*0.5;
        CGFloat Y = self.TopMargin;
        int num = i%3 == 2? -1:i%3;
        int num2 = i%3 == 2? 1:i%3;
        X += CST(-num)*([self judgeXWithNumber:self.number]);
        Y += ([self judgeSizeWithNumber:self.number].height + self.margin)*(i/3) + CST(num2)*([self judgeSizeWithNumber:self.number].height/2)+self.margin;
        UICollectionViewLayoutAttributes *attribute = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:[NSIndexPath indexPathForRow:i inSection:0]];
        // 设置每隔item的大小
        attribute.size = [self judgeSizeWithNumber:self.number];
        // 设置每隔item的圆心
        // 计算每个item的中心坐标
        attribute.center = CGPointMake(X, Y);
        [_attributeAttay addObject:attribute];
    }
}

// X轴方向的间隔
- (CGFloat)judgeXWithNumber:(NSInteger)xNumber
{
    if (xNumber == 3 ) {
        return mm + self.margin - COS(360/xNumber)*mm;
    }
    else if (xNumber == 4)
    {
        return mm + self.margin + COS(360/xNumber)*mm;
    }
    else if (xNumber == 5)
    {
        return mm + self.margin + SIN(360/xNumber)*mm - 5;
    }
    else if (xNumber == 6)
    {
        return mm + self.margin + COS(360/xNumber)*mm;
    }
    else if (xNumber == 7)
    {
        return mm + self.margin + SIN(360/xNumber)*mm;
    }
    else
    {
        return 2*mm + self.margin ;
    }
}

// 就算正n变形的大小
- (CGSize)judgeSizeWithNumber:(NSInteger)sNumber
{
    if (sNumber == 3 || sNumber == 6 ) {
        return CGSizeMake(2*mm,2*SIN(360/sNumber)*mm);
    }
    else
    {
        return CGSizeMake(2*(mm),2*mm);
    }
}

//设置内容区域的大小
-(CGSize)collectionViewContentSize
{
    CGFloat hh = [self judgeSizeWithNumber:self.number].height;
    CGFloat height = (hh+self.margin)*(self.itemCount/3 + 1) + self.TopMargin + 20;
    if (height > Device_height) {
        height = height;
    }
    else
    {
        height = Device_height;
    }
    
    return CGSizeMake(Device_width, height);
}

//返回设置数组
-(NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect{
    return _attributeAttay;
}