IOS custom Uicollectionviewflowlayout To achieve image browsing effect _ios

Before the waterfall used to use the Uicollectionview, but at that time using the system from the Uicollectionviewflowlayout layout, read the article today, see Uicollectionviewflowlayout Custom Related things, so hands-on wrote a simple picture browsing demo, skilled some uicollectionviewflowlayout custom layout.

#import <UIKit/UIKit.h>

@interface jwcollectionviewflowlayout:uicollectionviewflowlayout

@end

Custom Uicollectionviewflowlayout, first inherit uicollectionviewflowlayout, implement a few methods

#define SCREENWIDTH [UIScreen mainscreen].bounds.size.width #define Maxchangerange #import "Jwcollectionviewflowla Yout.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 Isatrigh
   t = 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.cen
  ter.x;
  if (ABS (Itemhorizontalcenter-hcenter) < ABS (offset) {offset = Itemhorizontalcenter-hcenter;
} return Cgpointmake (Proposedcontentoffset.x + offset, proposedcontentoffset.y);

 }

Use

-(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"];
}

Demo:https://github.com/jiangtaidi/jwimagebrowsedemo.git

Run Result:

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