以前瀑布流的时候使用过uicollectionview，但是那时使用的是系统自带的uicollectionviewflowlayout布局，今天看文章，看到uicollectionviewflowlayout自定义相关的东西，于是动手写了一个简单图片浏览的demo，熟练一些uicollectionviewflowlayout自定义布局。
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#import <uikit/uikit.h>
@interface jwcollectionviewflowlayout : uicollectionviewflowlayout
@end
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自定义uicollectionviewflowlayout，首先继承uicollectionviewflowlayout，实现一下几个方法
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#define screenwidth [uiscreen mainscreen].bounds.size.width
#define maxchangerange 100
#import "jwcollectionviewflowlayout.h"
@implementation jwcollectionviewflowlayout
-(void)preparelayout
{
self.scrolldirection = uicollectionviewscrolldirectionhorizontal;
self.itemsize = cgsizemake(300, 500);
}
- (bool)shouldinvalidatelayoutforboundschange:(cgrect)newbounds
{
return yes;
}
- (nullable nsarray<__kindof uicollectionviewlayoutattributes *> *)layoutattributesforelementsinrect:(cgrect)rect
{
nsarray *array = [super layoutattributesforelementsinrect:rect];
cgrect visiblerect = cgrectmake(self.collectionview.contentoffset.x, 0, self.collectionview.bounds.size.width, self.collectionview.bounds.size.height);
for (uicollectionviewlayoutattributes *attr in array)
{
if (cgrectintersectsrect(attr.frame, rect)) {
bool isatright = yes;
cgfloat distance = (attr.center.x - cgrectgetmidx(visiblerect));
if (distance<0) {
distance = -distance;
isatright = no;
}
cgfloat precent ;
if (distance < 180)
{
precent = 1.0;
}
else
{
precent = ((screenwidth / 2) - distance) / (screenwidth / 2);
}
catransform3d transform = catransform3didentity;
transform.m34 = 1.0 / 600;
if (precent < 0.5) {
precent = 0.5;
}
transform = catransform3dscale(transform, 1, precent, 1);
cgfloat p = isatright?m_pi_4:-m_pi_4;
transform = catransform3drotate(transform, p * (1 - precent), 0, 1, 0);
attr.transform3d = transform;
attr.zindex = 1;
attr.alpha = precent;
}
}
return array;
}
- (cgpoint)targetcontentoffsetforproposedcontentoffset:(cgpoint)proposedcontentoffset withscrollingvelocity:(cgpoint)velocity
{
cgfloat offset = maxfloat;
cgfloat hcenter = proposedcontentoffset.x + (cgrectgetwidth(self.collectionview.bounds) / 2.0);
cgrect currentrect = cgrectmake(proposedcontentoffset.x, 0, self.collectionview.bounds.size.width, self.collectionview.bounds.size.height);
nsarray* array = [super layoutattributesforelementsinrect:currentrect];
for (uicollectionviewlayoutattributes* layoutattributes in array)
{
cgfloat itemhorizontalcenter = layoutattributes.center.x;
if (abs(itemhorizontalcenter - hcenter) < abs(offset))
{
offset = itemhorizontalcenter - hcenter;
}
}
return cgpointmake(proposedcontentoffset.x + offset, proposedcontentoffset.y);
}
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使用
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-(void)setupui
{
jwcollectionviewflowlayout *flowlayout = [[jwcollectionviewflowlayout alloc] init];
uicollectionview *imgbrowseview = [[uicollectionview alloc] initwithframe:self.view.bounds collectionviewlayout:flowlayout];
imgbrowseview.datasource = self;
imgbrowseview.delegate = self;
imgbrowseview.backgroundcolor = [uicolor whitecolor];
[self.view addsubview:imgbrowseview];
_imgbrowseview = imgbrowseview;
[self.imgbrowseview registernib:[uinib nibwithnibname:@"custumcollectionviewcell" bundle:nil] forcellwithreuseidentifier:@"cell"];
}
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demo:https://github.com/jiangtaidi/jwimagebrowsedemo.git
运行结果：
以上就是本文的全部内容，希望对大家的学习有所帮助。