之前做使用collection做历史记录，不管sollection的怎么设置，item之间能设置最小距离，却不能设置最大距离，所以总是达不到预期效果。后来查看资料重写UICollectionViewFlowLayout方法来达到预期效果。废话不多说，上代码。
未完成效果.png
预期效果.png
一、下面是继承UICollectionViewFlowLayout写的类
import UIKit
extension UICollectionViewLayoutAttributes {
/** 每行第一个item左对齐 **/
func leftAlignFrame(sectionInset:UIEdgeInsets) {
var frame = self.frame
frame.origin.x = sectionInset.left
self.frame = frame
}
}
class UICollectionViewLeftAlignedLayout: UICollectionViewFlowLayout {
//MARK: - 重新UICollectionViewFlowLayout的方法
/** Collection所有的UICollectionViewLayoutAttributes */
override func layoutAttributesForElementsInRect(rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
let attributesToReturn = super.layoutAttributesForElementsInRect(rect)!
for attributes in attributesToReturn {
if nil == attributes.representedElementKind {
let indexPath = attributes.indexPath
attributes.frame = self.layoutAttributesForItemAtIndexPath(indexPath)!.frame
}
}
return attributesToReturn
}
/** 每个item的UICollectionViewLayoutAttributes */
override func layoutAttributesForItemAtIndexPath(indexPath: NSIndexPath) -> UICollectionViewLayoutAttributes? {
//现在item的UICollectionViewLayoutAttributes
let currentItemAttributes = super.layoutAttributesForItemAtIndexPath(indexPath)!
//现在section的sectionInset
let sectionInset = self.evaluatedSectionInset(indexPath.section)
//是否是section的第一个item
let isFirstItemInSection = indexPath.item == 0
//出去section偏移量的宽度
let layoutWidth: CGFloat = CGRectGetWidth(self.collectionView!.frame) - sectionInset.left - sectionInset.right
//是section的第一个item
if isFirstItemInSection {
//每行第一个item左对齐
currentItemAttributes.leftAlignFrame(sectionInset)
return currentItemAttributes
}
//前一个item的NSIndexPath
let previousIndexPath = NSIndexPath(forItem: indexPath.item - 1, inSection: indexPath.section)
//前一个item的frame
let previousFrame = self.layoutAttributesForItemAtIndexPath(previousIndexPath)!.frame
//为现在item计算新的left
let previousFrameRightPoint: CGFloat = previousFrame.origin.x + previousFrame.size.width
//现在item的frame
let currentFrame = currentItemAttributes.frame
//现在item所在一行的frame
let strecthedCurrentFrame = CGRectMake(sectionInset.left, currentFrame.origin.y, layoutWidth, currentFrame.size.height)
//previousFrame和strecthedCurrentFrame是否有交集，没有，说明这个item和前一个item在同一行，item是这行的第一个item
let isFirstItemInRow = !CGRectIntersectsRect(previousFrame, strecthedCurrentFrame)
//item是这行的第一个item
if isFirstItemInRow {
//每行第一个item左对齐
currentItemAttributes.leftAlignFrame(sectionInset)
return currentItemAttributes
}
//不是每行的第一个item
var frame = currentItemAttributes.frame
//为item计算新的left = previousFrameRightPoint + item之间的间距
frame.origin.x = previousFrameRightPoint + self.evaluatedMinimumInteritemSpacing(indexPath.item)
//为item的frame赋新值
currentItemAttributes.frame = frame
return currentItemAttributes
}
//MARK: - System
/** item行间距 **/
private func evaluatedMinimumInteritemSpacing(ItemAtIndex:Int) -> CGFloat {
if let delete = self.collectionView?.delegate {
weak var delegate = (delete as! UICollectionViewDelegateFlowLayout)
if delegate!.respondsToSelector(#selector(UICollectionViewDelegateFlowLayout.collectionView(_:layout:minimumInteritemSpacingForSectionAtIndex:))) {
let mini = delegate?.collectionView!(self.collectionView!, layout: self, minimumInteritemSpacingForSectionAtIndex: ItemAtIndex)
if mini != nil {
return mini!
}
}
}
return self.minimumInteritemSpacing
}
/** section的偏移量 **/
private func evaluatedSectionInset(itemAtIndex:Int) -> UIEdgeInsets {
if let delete = self.collectionView?.delegate {
weak var delegate = (delete as! UICollectionViewDelegateFlowLayout)
if delegate!.respondsToSelector(#selector(UICollectionViewDelegateFlowLayout.collectionView(_:layout:insetForSectionAtIndex:))) {
let sectionInset = delegate?.collectionView!(self.collectionView!, layout: self, insetForSectionAtIndex: itemAtIndex)
if sectionInset != nil {
return sectionInset!
}
}
}
return self.sectionInset
}
}
二、�下面在collectionView中使用这个类，我的collectionView是使用xib创建的。
/// 搜索记录
@IBOutlet weak var collectionView: UICollectionView!
/// 历史搜索类型
var historyArray = [String]()
override func awakeFromNib() {
super.awakeFromNib()
historyArray = ["关键词","iOS学习基础","牛奶","跳绳","轮滑鞋","香蕉","面包","苹果梨","苹果"]
let layout = UICollectionViewLeftAlignedLayout()
//竖向cell之间的距离
layout.minimumLineSpacing = 15
//横向cell之间的距离，没有设置0.0
layout.minimumInteritemSpacing = 10
//section的header的大小
layout.headerReferenceSize = CGSizeMake(ScreenWidth , 44);
//section的偏移量
layout.sectionInset = UIEdgeInsetsMake(0, 10, 0, 10)
//collectionView的偏移量
collectionView.contentInset = UIEdgeInsetsMake(0, 0, 5, 0)
//SearchCell:xib中item的identifier
collectionView.registerNib(UINib.init(nibName: "SearchCell", bundle: nil), forCellWithReuseIdentifier: "SearchCell")
//SearchHeaderView中sender的header的identifier
collectionView.registerNib(UINib.init(nibName: "SearchHeaderView", bundle: nil), forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, withReuseIdentifier: "SearchHeaderView")
collectionView.collectionViewLayout = layout
}
//MARK: - UICollectionViewDataSource
/** Section数 */
func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int{
if historyArray.count > 0 {
return 1
}
return 0
}
/** Items数 */
func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return historyArray.count
}
/** Items创建 */
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell{
let cell = collectionView.dequeueReusableCellWithReuseIdentifier("SearchCell", forIndexPath: indexPath) as? SearchCell
cell?.name.text = historyArray[indexPath.item]
return cell!
}
/** collection的header创建 */
func collectionView(collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, atIndexPath indexPath: NSIndexPath) -> UICollectionReusableView {
let view = collectionView.dequeueReusableSupplementaryViewOfKind(UICollectionElementKindSectionHeader, withReuseIdentifier: "SearchHeaderView", forIndexPath: indexPath) as? SearchHeaderView
return view!
}
//MARK: - UICollectionViewDelegate
/** 历史记录关键词点击 */
func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
}
//MARK: - UICollectionViewDelegateFlowLayout
/** 设置关键词大小 */
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
let name = historyArray[indexPath.item]
let size = self.boundingRectWithSize(CGSizeMake(ScreenWidth - 20, 30), options: .UsesLineFragmentOrigin, attributes: [NSFontAttributeName: UIFont.systemFontOfSize(12)], context: nil).size
let with = size.width
return CGSizeMake(with + 40, 30)
}
参考文档
http://code.cocoachina.com/view/126206
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