这段时间突然想到一个很久之前用到的知识-瀑布流,本来想用一个简单的方法,发现自己走入了歧途,最终只能狠下心来重写uicollectionviewflowlayout.下面我将用两种方法实现瀑布流,以及会介绍第一种实现的bug.
<1>第一种
效果图如下所示:
这种实现方法的思路:
1)首先调用随机函数,产生随机高度,并把它保存到数组中
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- (cgsize)collectionview:(uicollectionview *)collectionview layout:(uicollectionviewlayout *)collectionviewlayout sizeforitematindexpath:(nsindexpath *)indexpath { cgfloat cellw = 100; cgfloat cellh = 100 + (arc4random() % 80); [self.heightarraym addobject:@(cellh)]; return cgsizemake(cellw, cellh); } |
2)在设置cell的frame的地方,通过取余,取整确定cell的高度,并设定cell的frame
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- (uicollectionviewcell *)collectionview:(uicollectionview *)collectionview cellforitematindexpath:(nsindexpath *)indexpath { uicollectionviewcell *cell = [self.collectionview dequeuereusablecellwithreuseidentifier:id forindexpath:indexpath]; //当前处于多少行 nsinteger num1 = indexpath.row / count; //当前处于多少列 int num2 = indexpath.row % count; cgfloat cellx = num2 * 100 + (num2 + 1) * margin; cgfloat celly = 0; for (int i = 0; i < num1; i++) { nsinteger position = num2 + i * 3; celly += [self.heightarraym[position] floatvalue] + margin; } cgfloat cellw = 100; cgfloat cellh = cellheight; cell.frame = cgrectmake(cellx, celly, cellw, cellh);// cell.backgroundcolor = [uicolor redcolor]; cell.backgroundcolor = [uicolor colorwithred:(arc4random() % 250) / 250.0 green:(arc4random() % 250) / 250.0 blue:(arc4random() % 250) / 250.0 alpha:1.0]; // nslog(@"%@", nsstringfromcgrect(cell.frame)); return cell;} |
弊端 : 其实这种方法的弊端,相信从上面的动态图中可以看出来,当往上面滑的时候,由于cell的循环机制,下面的cell的会消失,但是由于高度不一致,同时撤销的是最后一行的cell,所以下面的cell在屏幕上就会消失.
下面附上第一种方法的源代码:
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#import "viewcontroller.h"#define margin 10#define count 3#define cellheight [self.heightarraym[indexpath.row] floatvalue]static nsstring * const id = @"cell";@interface viewcontroller ()<uicollectionviewdelegate, uicollectionviewdatasource, uicollectionviewdelegateflowlayout>@property (weak, nonatomic) iboutlet uicollectionview *collectionview;@property (nonatomic, strong) nsmutablearray *heightarraym;@end@implementation viewcontroller- (nsmutablearray *)heightarraym { if (_heightarraym == nil) { _heightarraym = [nsmutablearray array]; } return _heightarraym;}- (void)viewdidload { [super viewdidload]; [self.collectionview registerclass:[uicollectionviewcell class] forcellwithreuseidentifier:id]; self.collectionview.datasource = self; self.collectionview.delegate = self; //设置collectionview [self setupcollectionview];}//设置collectionview的布局- (uicollectionviewflowlayout *)setupcollectionlayout { uicollectionviewflowlayout *flowlayout = [[uicollectionviewflowlayout alloc] init]; flowlayout.minimuminteritemspacing = margin; flowlayout.minimumlinespacing = margin; flowlayout.sectioninset = uiedgeinsetsmake(margin, margin, margin, margin); return flowlayout;}//设置collectionview- (void)setupcollectionview { self.collectionview.collectionviewlayout =[self setupcollectionlayout]; }#pragma mark - uicollectionviewdatasouce- (nsinteger)collectionview:(uicollectionview *)collectionview numberofitemsinsection:(nsinteger)section { return 60;}- (uicollectionviewcell *)collectionview:(uicollectionview *)collectionview cellforitematindexpath:(nsindexpath *)indexpath { uicollectionviewcell *cell = [self.collectionview dequeuereusablecellwithreuseidentifier:id forindexpath:indexpath]; //当前处于多少行 nsinteger num1 = indexpath.row / count; //当前处于多少列 int num2 = indexpath.row % count; cgfloat cellx = num2 * 100 + (num2 + 1) * margin; cgfloat celly = 0; for (int i = 0; i < num1; i++) { nsinteger position = num2 + i * 3; celly += [self.heightarraym[position] floatvalue] + margin; } cgfloat cellw = 100; cgfloat cellh = cellheight; cell.frame = cgrectmake(cellx, celly, cellw, cellh);// cell.backgroundcolor = [uicolor redcolor]; cell.backgroundcolor = [uicolor colorwithred:(arc4random() % 250) / 250.0 green:(arc4random() % 250) / 250.0 blue:(arc4random() % 250) / 250.0 alpha:1.0]; // nslog(@"%@", nsstringfromcgrect(cell.frame)); return cell;}- (cgsize)collectionview:(uicollectionview *)collectionview layout:(uicollectionviewlayout *)collectionviewlayout sizeforitematindexpath:(nsindexpath *)indexpath { cgfloat cellw = 100; cgfloat cellh = 100 + (arc4random() % 80); [self.heightarraym addobject:@(cellh)]; return cgsizemake(cellw, cellh); }@end |
<2>下面介绍第二种(swift实现)
效果图如下所示:
这种实现方法就是比较成熟的了,我把它封装成一个类.其实主要是实现三个函数
1)重写父类的prepare方法,准备所有cell的样式
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extension waterfalllayout { // prepare准备所有cell的布局样式 override func prepare() { super.prepare() // 0.获取item的个数 let itemcount = collectionview!.numberofitems(insection: 0) // 1.获取列数 let cols = datasource?.numberofcolsinwaterfalllayout?(self) ?? 2 // 2.计算item的宽度 let itemw = (collectionview!.bounds.width - self.sectioninset.left - self.sectioninset.right - self.minimuminteritemspacing * cgfloat((cols - 1))) / cgfloat(cols) // 3.计算所有的item的属性 for i in startindex..<itemcount { // 1.设置每一个item位置相关的属性 let indexpath = indexpath(item: i, section: 0) // 2.根据位置创建attributes属性 let attrs = uicollectionviewlayoutattributes(forcellwith: indexpath) // 3.随机一个高度 guard let height = datasource?.waterfalllayout(self, indexpath: indexpath) else { fatalerror("请设置数据源,并且实现对应的数据源方法") } // 4.取出最小列的位置 var minh = colheights.min()! let index = colheights.index(of: minh)! minh = minh + height + minimumlinespacing colheights[index] = minh // 5.设置item的属性 attrs.frame = cgrect(x: self.sectioninset.left + (self.minimuminteritemspacing + itemw) * cgfloat(index), y: minh - height - self.minimumlinespacing, width: itemw, height: height) attrsarray.append(attrs) } // 4.记录最大值 maxh = colheights.max()! // 5.给startindex重新复制 startindex = itemcount }} |
2)返回设置cell样式的数组
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override func layoutattributesforelements(in rect: cgrect) -> [uicollectionviewlayoutattributes]? { return attrsarray } |
3)返回当前的contentsize
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override var collectionviewcontentsize: cgsize { return cgsize(width: 0, height: maxh + sectioninset.bottom - minimumlinespacing) } |
总结:
在下面我封装的这个类中,只需要遵守我的数据代理源协议并且实现我的协议中的两个方法,传给我对应得高度(我这里是传的随机的),可选的方法,若是不实现,会有一个默认值,就可以实现该功能.协议如下:
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@objc protocol waterfalllayoutdatasource : class { func waterfalllayout(_ layout : waterfalllayout, indexpath : indexpath) -> cgfloat @objc optional func numberofcolsinwaterfalllayout(_ layout : waterfalllayout) -> int} |
完成代码如下所示:
viewcontroller.swift中的代码:
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import uikitextension uicolor { class func randomcolor() -> uicolor { return uicolor(colorliteralred: float(arc4random_uniform(256)) / 255.0, green: float(arc4random_uniform(256)) / 255.0, blue: float(arc4random_uniform(256)) / 255.0, alpha: 1.0) }}private let kwatercellid = "kwatercellid"class viewcontroller: uiviewcontroller { var count : int = 20 override func viewdidload() { super.viewdidload() // 1.设置布局 let layout = waterfalllayout() layout.minimumlinespacing = 10 layout.minimuminteritemspacing = 10 layout.sectioninset = uiedgeinsets(top: 10, left: 10, bottom: 10, right: 10) layout.datasource = self // 2.创建uicollectionview let collectionview = uicollectionview(frame: view.bounds, collectionviewlayout: layout) collectionview.datasource = self collectionview.register(uicollectionviewcell.self, forcellwithreuseidentifier: kwatercellid) view.addsubview(collectionview) } }extension viewcontroller : uicollectionviewdatasource { func collectionview(_ collectionview: uicollectionview, numberofitemsinsection section: int) -> int { return count } func collectionview(_ collectionview: uicollectionview, cellforitemat indexpath: indexpath) -> uicollectionviewcell { let cell = collectionview.dequeuereusablecell(withreuseidentifier: kwatercellid, for: indexpath) cell.backgroundcolor = uicolor.randomcolor() if indexpath.item == count - 1 { count += 20 collectionview.reloaddata() } return cell }}extension viewcontroller : waterfalllayoutdatasource { func waterfalllayout(_ layout: waterfalllayout, indexpath: indexpath) -> cgfloat { return cgfloat(arc4random_uniform(80) + 100) } func numberofcolsinwaterfalllayout(_ layout: waterfalllayout) -> int { return 3 }} |
封装自定义布局中的waterfalllayout.swift代码如下:
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import uikit@objc protocol waterfalllayoutdatasource : class { func waterfalllayout(_ layout : waterfalllayout, indexpath : indexpath) -> cgfloat @objc optional func numberofcolsinwaterfalllayout(_ layout : waterfalllayout) -> int}class waterfalllayout: uicollectionviewflowlayout { // mark: 对外提供属性 weak var datasource : waterfalllayoutdatasource? // mark: 私有属性 fileprivate lazy var attrsarray : [uicollectionviewlayoutattributes] = [uicollectionviewlayoutattributes]() fileprivate var totalheight : cgfloat = 0 fileprivate lazy var colheights : [cgfloat] = { let cols = self.datasource?.numberofcolsinwaterfalllayout?(self) ?? 2 var colheights = array(repeating: self.sectioninset.top, count: cols) return colheights }() fileprivate var maxh : cgfloat = 0 fileprivate var startindex = 0}extension waterfalllayout { // prepare准备所有cell的布局样式 override func prepare() { super.prepare() // 0.获取item的个数 let itemcount = collectionview!.numberofitems(insection: 0) // 1.获取列数 let cols = datasource?.numberofcolsinwaterfalllayout?(self) ?? 2 // 2.计算item的宽度 let itemw = (collectionview!.bounds.width - self.sectioninset.left - self.sectioninset.right - self.minimuminteritemspacing * cgfloat((cols - 1))) / cgfloat(cols) // 3.计算所有的item的属性 for i in startindex..<itemcount { // 1.设置每一个item位置相关的属性 let indexpath = indexpath(item: i, section: 0) // 2.根据位置创建attributes属性 let attrs = uicollectionviewlayoutattributes(forcellwith: indexpath) // 3.随机一个高度 guard let height = datasource?.waterfalllayout(self, indexpath: indexpath) else { fatalerror("请设置数据源,并且实现对应的数据源方法") } // 4.取出最小列的位置 var minh = colheights.min()! let index = colheights.index(of: minh)! minh = minh + height + minimumlinespacing colheights[index] = minh // 5.设置item的属性 attrs.frame = cgrect(x: self.sectioninset.left + (self.minimuminteritemspacing + itemw) * cgfloat(index), y: minh - height - self.minimumlinespacing, width: itemw, height: height) attrsarray.append(attrs) } // 4.记录最大值 maxh = colheights.max()! // 5.给startindex重新复制 startindex = itemcount }}extension waterfalllayout { override func layoutattributesforelements(in rect: cgrect) -> [uicollectionviewlayoutattributes]? { return attrsarray } override var collectionviewcontentsize: cgsize { return cgsize(width: 0, height: maxh + sectioninset.bottom - minimumlinespacing) }} |
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。
原文链接：http://www.cnblogs.com/muzichenyu/p/6108040.html
