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本文实例为大家分享了ios实现列表下拉放大效果展示的具体代码，供大家参考，具体内容如下
先看效果图
突然发现没有做出来之前都觉得蛮难的，做出来之后就觉得so easy 大家都有这样的感触吧
做这个就重写 uicollectionviewflowlayout 的几个方法就可以
oc版本
创建一个类 customcollectionviewflowlayout 继承 uicollectionviewflowlayout
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//
// customcollectionviewflowlayout.m
//
//
// created by gonghui_yj on 16/8/4.
// copyright © 2016年 yangjian. all rights reserved.
//
#import "customcollectionviewflowlayout.h"
@implementation customcollectionviewflowlayout
- (bool)shouldinvalidatelayoutforboundschange:(cgrect)newbounds
{
return yes;
}
- (nsarray *)layoutattributesforelementsinrect:(cgrect)rect {
uicollectionview *collectionview = [self collectionview];
uiedgeinsets insets = [collectionview contentinset];
cgpoint offset = [collectionview contentoffset];
cgfloat miny = -insets.top;
nsarray *attributes = [super layoutattributesforelementsinrect:rect];
if (offset.y < miny) {
cgsize headersize = [self headerreferencesize];
cgfloat deltay = fabsf(offset.y - miny);
for (uicollectionviewlayoutattributes *attrs in attributes) {
if ([attrs representedelementkind] == uicollectionelementkindsectionheader) {
cgrect headerrect = [attrs frame];
headerrect.size.height = max(miny, headersize.height + deltay);
headerrect.origin.y = headerrect.origin.y - deltay;
[attrs setframe:headerrect];
break;
}
}
}
return attributes;
}
@end
在控制器中使用 先导入头文件
// 创建collectionview customcollectionviewflowlayout *flowlayout=[[customcollectionviewflowlayout alloc] init]; [flowlayout setsectioninset:uiedgeinsetsmake(0, 0, 10, 0)]; [flowlayout setitemsize:cgsizemake(kscreenwidth / collectioncellw, kscreenwidth / collectioncellw)]; [flowlayout setheaderreferencesize:cgsizemake(kscreenwidth, userinfoimageviewh)]; [flowlayout setfooterreferencesize:cgsizemake(kscreenwidth, 83)]; [flowlayout setscrolldirection:uicollectionviewscrolldirectionvertical]; [flowlayout setminimuminteritemspacing:0.0]; [flowlayout setminimumlinespacing:0.0]; self.homecollectionview = [[uicollectionview alloc]initwithframe:cgrectmake(0, 0, kscreenwidth, kscreenheight - 44)collectionviewlayout:flowlayout]; self.homecollectionview.backgroundcolor = kviewbackgroundcolor; self.homecollectionview.alwaysbouncevertical = yes; self.homecollectionview.showsverticalscrollindicator = no; //设置代理 self.homecollectionview.delegate = self; self.homecollectionview.datasource = self; [self.view addsubview:self.homecollectionview]; // 注册表头 [self.homecollectionview registerclass:[yjheadercollectionreusableview class] forsupplementaryviewofkind:uicollectionelementkindsectionheader withreuseidentifier:kcollectionheaderview]; // 注册表尾 [self.homecollectionview registerclass:[uicollectionreusableview class] forsupplementaryviewofkind:uicollectionelementkindsectionfooter withreuseidentifier:kcollectionfooterview];
swift版
喜欢swift 不需要导入头文件那么麻烦
//
// customcollectionviewflowlayout.swift
//
//
// created by gonghui_yj on 16/8/4.
// copyright © 2016年yangjian. all rights reserved.
//
import uikit
class customcollectionviewflowlayout: uicollectionviewflowlayout {
override func shouldinvalidatelayoutforboundschange(newbounds: cgrect) -> bool {
return true
}
override func layoutattributesforelementsinrect(rect: cgrect) -> [uicollectionviewlayoutattributes]? {
let collectionview = self.collectionview
let insets = collectionview?.contentinset
let offset = collectionview?.contentoffset
let miny = -((insets?.top)!)
let attributesarray = super.layoutattributesforelementsinrect(rect)
if offset!.y < miny {
let headersize = self.headerreferencesize
let deltay = cgfloat(fabsf(float((offset?.y)! - cgfloat(miny))))
for attrs:uicollectionviewlayoutattributes in attributesarray! {
if attrs.representedelementkind == uicollectionelementkindsectionheader {
var headerrect = attrs.frame
headerrect.size.height = max(miny, headersize.height + deltay)
headerrect.origin.y = headerrect.origin.y - deltay
attrs.frame = headerrect
break
}
}
}
return attributesarray
}
}
在控制器 viewdidload方法实现
let customflowlayout = customcollectionviewflowlayout() customflowlayout.headerreferencesize = cgsizemake(kscreenwidth, 203) customflowlayout.footerreferencesize = cgsizemake(kscreenwidth, 83) customflowlayout.minimuminteritemspacing = 0 customflowlayout.minimumlinespacing = 0 customflowlayout.itemsize = cgsizemake(kscreenwidth / 3.000006, kscreenwidth / 3.00006) customflowlayout.sectioninset = uiedgeinsetsmake(0, 0, 10, 0) self.homecollectionview.setcollectionviewlayout(customflowlayout, animated: true) self.homecollectionview.backgroundcolor = kviewbackgroundcolor self.homecollectionview.alwaysbouncevertical = true let nib = uinib(nibname: "commoncollectionviewcell", bundle: nil) self.homecollectionview.registernib(nib, forcellwithreuseidentifier: cellid) // 注册表头表尾 let headernib = uinib(nibname: "headercollectionreusableview", bundle: nil) self.homecollectionview.registernib(headernib, forsupplementaryviewofkind: uicollectionelementkindsectionheader, withreuseidentifier: collectionheaderid) self.homecollectionview.registerclass(uicollectionreusableview.classforcoder(), forsupplementaryviewofkind: uicollectionelementkindsectionfooter, withreuseidentifier: collectionfooterid)
注：不要实现uicollectionviewdelegateflowlayout的代理方法了。
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