Swift

网格UICollectionView除了使用流布局，还可以使用自定义布局。实现自定义布局需要继承UICollectionViewLayout，同时还要重载下面的三个方法：

// 这个方法返回每个单元格的位置和大小
override func layoutAttributesForItemAtIndexPath(indexPath: NSIndexPath)
    -> UICollectionViewLayoutAttributes! {
}
 
// 返回内容区域总大小，不是可见区域
override func collectionViewContentSize() -> CGSize {
}
 
// 返回所有单元格位置属性
override func layoutAttributesForElementsInRect(rect: CGRect) -> [AnyObject] {
}

下面实现一个自定义布局的例子，单元格有大小两种。网格从上到下，先是左边一个大单元格右边两个小单元格，接着左边两个小单元格右边一个大单元格，依次同上循环排列。

效果图如下：

--- 自定义布局 CustomLayout.swift ---

import UIKit
 
/**
 * 这个类只简单定义了一个section的布局
 */
class CustomLayout : UICollectionViewLayout {
     
    // 内容区域总大小，不是可见区域
    override func collectionViewContentSize() -> CGSize {
        return CGSizeMake(collectionView!.bounds.size.width,
            CGFloat(collectionView!.numberOfItemsInSection(0) * 200 / 3 + 200))
    }
     
    // 所有单元格位置属性
    override func layoutAttributesForElementsInRect(rect: CGRect) -> [AnyObject] {
         
        var attributesArray = [AnyObject]()
        let cellCount = self.collectionView!.numberOfItemsInSection(0)
        for i in 0..<cellCount {
            var indexPath =  NSIndexPath(forItem:i, inSection:0)
 
            var attributes =  self.layoutAttributesForItemAtIndexPath(indexPath)
             
            attributesArray.append(attributes)
             
        }
        return attributesArray
    }
     
    // 这个方法返回每个单元格的位置和大小
    override func layoutAttributesForItemAtIndexPath(indexPath: NSIndexPath)
        -> UICollectionViewLayoutAttributes! {
        //当前单元格布局属性
        var attribute =  UICollectionViewLayoutAttributes(forCellWithIndexPath:indexPath)
         
        //单元格外部空隙，简单起见，这些常量都在方法内部定义了，没有共享为类成员
        let itemSpacing = 2
        let lineSpacing = 5
         
        //单元格边长
        let largeCellSide:CGFloat = 200
        let smallCellSide:CGFloat = 100
         
        //内部间隙，左右5
        var insets = UIEdgeInsetsMake(2, 5, 2, 5)
         
        //当前行数，每行显示3个图片，1大2小
        var line:Int =  indexPath.item / 3
        //当前行的Y坐标
        var lineOriginY =  largeCellSide * CGFloat(line) + CGFloat(lineSpacing * line) + insets.top
        //右侧单元格X坐标，这里按左右对齐，所以中间空隙大
        var rightLargeX =  collectionView!.bounds.size.width - largeCellSide - insets.right
        var rightSmallX =  collectionView!.bounds.size.width - smallCellSide - insets.right
         
        // 每行2个图片，2行循环一次，一共6种位置
        if (indexPath.item % 6 == 0) {
            attribute.frame = CGRectMake(insets.left, lineOriginY, largeCellSide, largeCellSide)
        } else if (indexPath.item % 6 == 1) {
            attribute.frame = CGRectMake(rightSmallX, lineOriginY, smallCellSide, smallCellSide)
        } else if (indexPath.item % 6 == 2) {
            attribute.frame = CGRectMake(rightSmallX, lineOriginY + smallCellSide + insets.top,
                smallCellSide, smallCellSide)
        } else if (indexPath.item % 6 == 3) {
            attribute.frame = CGRectMake(insets.left, lineOriginY, smallCellSide, smallCellSide)
        } else if (indexPath.item % 6 == 4) {
            attribute.frame = CGRectMake(insets.left, lineOriginY + smallCellSide + insets.top,
                smallCellSide, smallCellSide)
        } else if (indexPath.item % 6 == 5) {
            attribute.frame = CGRectMake(rightLargeX, lineOriginY, largeCellSide, largeCellSide)
        }
         
        return attribute
    }
     
    /*
    //如果有页眉、页脚或者背景，可以用下面的方法实现更多效果
    func layoutAttributesForSupplementaryViewOfKind(elementKind: String!, 
        atIndexPath indexPath: NSIndexPath!) -> UICollectionViewLayoutAttributes!
    func layoutAttributesForDecorationViewOfKind(elementKind: String!, 
        atIndexPath indexPath: NSIndexPath!) -> UICollectionViewLayoutAttributes!
    */
}

--- 主页面 ViewController.swift ---

import UIKit
 
class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource
{
     
    var collectionView:UICollectionView!
    //课程名称和图片，每一门课程用字典来表示
    let courses = [
        ["name":"Swift","pic":"swift.png"],
        ["name":"OC","pic":"oc.jpg"],
        ["name":"Java","pic":"java.png"],
        ["name":"PHP","pic":"php.jpeg"],
        ["name":"JS","pic":"js.jpeg"],
        ["name":"HTML","pic":"html.jpeg"],
        ["name":"Ruby","pic":"ruby.png"]
    ]
     
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
         
        let layout = CustomLayout()
        //let layout = UICollectionViewFlowLayout()
        self.collectionView = UICollectionView(
            frame: CGRectMake(0,20,view.bounds.size.width,view.bounds.height-20),
            collectionViewLayout:layout)
        self.collectionView.delegate = self
        self.collectionView.dataSource = self
        // 注册CollectionViewCell
        self.collectionView.registerClass(UICollectionViewCell.self,
            forCellWithReuseIdentifier: "ViewCell")
        //默认背景是黑色和label一致
        self.collectionView.backgroundColor = UIColor.whiteColor()
         
        self.view.addSubview(collectionView)
    }
     
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
     
    // CollectionView行数
    func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return courses.count;
    }
     
    // 获取单元格
    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath)
        -> UICollectionViewCell {
        // storyboard里设计的单元格
        let identify:String = "ViewCell"
        // 获取设计的单元格，不需要再动态添加界面元素
        let cell = self.collectionView.dequeueReusableCellWithReuseIdentifier(
            identify, forIndexPath: indexPath) as UICollectionViewCell
        // 添加图片
        let img = UIImageView(image: UIImage(named: courses[indexPath.item]["pic"]!))
        img.frame = cell.bounds
        // 图片上面显示课程名称，居中显示
        let lbl = UILabel(frame:CGRectMake(0,5,cell.bounds.size.width,20))
        lbl.textAlignment = NSTextAlignment.Center
        lbl.text = courses[indexPath.item]["name"]
        cell.addSubview(img)
        cell.addSubview(lbl)
        return cell
    }
     
    /* 自定义布局不需要调用
    //单元格大小
    func collectionView(collectionView: UICollectionView!, 
        layout collectionViewLayout: UICollectionViewLayout!,
        sizeForItemAtIndexPath indexPath: NSIndexPath!) -> CGSize {
        let size:Float = indexPath.item % 3 == 0 ? 200 : 100
        return CGSize(size, height:size)
    }
    */
}