8.12 CollectionView

import UIKit

class ViewController: UIViewController, UICollectionViewDataSource,UICollectionViewDelegateFlowLayout {

    var collectionView: UICollectionView!

    override func viewDidLoad() {

        super.viewDidLoad()

        //1. 系统默认提供布局方式： 多行多列布局

        let layout = UICollectionViewFlowLayout()

//        //2. 设置Cell的大小

//        layout.itemSize = CGSize(width: self.view.bounds.size.width, height: 200)

//        //3. 滚动方向

        layout.scrollDirection = .Horizontal

////        layout.sectionInset = UIEdgeInsets(top: 10, left: 10, bottom: 10, right: 10)

//        //cell的最小间距

//        layout.minimumInteritemSpacing = 0

//        //行间距

//        layout.minimumLineSpacing = 0

       
        let rect = CGRect(x: 0, y: 0, width: self.view.bounds.size.width, height:self.view.bounds.size.height)

        collectionView = UICollectionView(frame: rect, collectionViewLayout: layout)

        collectionView.backgroundColor = UIColor.whiteColor()

        collectionView.showsHorizontalScrollIndicator = false

//        collectionView.contentOffset

//        collectionView.scrollToItemAtIndexPath(<#T##indexPath: NSIndexPath##NSIndexPath#>, atScrollPosition: <#T##UICollectionViewScrollPosition#>, animated: <#T##Bool#>)

        

        //分页显示

        collectionView.pagingEnabled = true

        //注册cell

        collectionView.registerClass(UICollectionViewCell.self, forCellWithReuseIdentifier: "cell")

        //注册section header/footer

        collectionView.registerClass(UICollectionReusableView.self, forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, withReuseIdentifier:"header")

        collectionView.registerClass(UICollectionReusableView.self, forSupplementaryViewOfKind: UICollectionElementKindSectionFooter, withReuseIdentifier:"footer")

        collectionView.dataSource = self
        collectionView.delegate = self
        self.view.addSubview(collectionView)
        
//        NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: #selector(didTimer(_:)), userInfo: nil, repeats: true)
    }

    func didTimer(timer: NSTimer) {

        //两种表示方法
        //NSIndexPath
        //位置: frame.origin
        //获取内容的偏移量
        let offset = collectionView.contentOffset
        //根据位置获取Cell
        let indexPath = collectionView.indexPathForItemAtPoint(CGPoint(x: offset.x, y:0))
        if indexPath!.item == 4 {
            //滚动某个Cell到可见区域
            collectionView.scrollToItemAtIndexPath(NSIndexPath(forItem: 0, inSection:0), atScrollPosition: .Left, animated: false)
       collectionView.scrollToItemAtIndexPath(NSIndexPath(forItem: 1, inSection:0), atScrollPosition: .Left, animated: true)
        }
        else {
           collectionView.scrollToItemAtIndexPath(NSIndexPath(forItem: indexPath!.item + 1, inSection: 0), atScrollPosition: .Left, animated: true)
        }
    }

//    func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
//        return 4
//    }

    //Section中Cell的个数

    func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 5
    }

    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {

        let cell = collectionView.dequeueReusableCellWithReuseIdentifier("cell", forIndexPath: indexPath)

        if indexPath.item % 2 == 0 {
            cell.contentView.backgroundColor = UIColor.redColor()
        }
        else {
            cell.contentView.backgroundColor = UIColor.blueColor()
        }
        return cell
    }

    func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
        print("\(indexPath.section):\(indexPath.item)")
    }

    //section header
    //section footer

    func collectionView(collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, atIndexPath indexPath: NSIndexPath) ->UICollectionReusableView {
        //header
        if kind == UICollectionElementKindSectionHeader {
            let header = collectionView.dequeueReusableSupplementaryViewOfKind(UICollectionElementKindSectionHeader, withReuseIdentifier: "header", forIndexPath: indexPath)
            header.backgroundColor = UIColor.blueColor()
            return header
        }
        else {
            let footer = collectionView.dequeueReusableSupplementaryViewOfKind(UICollectionElementKindSectionFooter, withReuseIdentifier: "footer", forIndexPath: indexPath)
            footer.backgroundColor = UIColor.cyanColor()
            return footer
        }
    }

    //cell大小

    func collectionView(collectionView: UICollectionView, layout collectionViewLayout:UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
        return CGSize(width: 10 * (indexPath.item + 1), height: 10 * (indexPath.item +1))
    }

    func collectionView(collectionView: UICollectionView, layout collectionViewLayout:UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
        return CGSize(width: 100, height: 200)
    }

    func collectionView(collectionView: UICollectionView, layout collectionViewLayout:UICollectionViewLayout, referenceSizeForFooterInSection section: Int) -> CGSize {
        return CGSize(width: 100, height: 200)
    }
}